Latest Research News
- Long-known to lower LDL cholesteral, a new study shows oats also impact other markers that may be better measures of cardiovascular risk for those with diabetes or metabolic syndrome.
- An experimental study shows that whole grain foods significantly lower blood pressure compared to eating the equivalent refined grain foods.
- A review of population studies shows that the more whole grains you eat, the lower your risk of cardiovascular disease.
Eating oats lowers cholesterol on 3 markers
It’s long been known that eating oats can lower cholesterol levels, but the research focus has been on the effect on LDL cholesterol. However, there is growing evidence that two other markers provide an even more accurate assessment of cardiovascular risk:
- non-HDL cholesterol (total cholesterol minus HDL cholesterol)
- apolipoprotein B (apoB) — a lipoprotein that carries LDL cholesterol through the blood.
This is especially true for people with metabolic syndrome and Type 2 diabetes, since they typically don't have elevated LDL cholesterol levels.
In light of this, it’s good to see a review and meta-analysis of 58 clinical trials has concluded that eating oat fibre can reduce all three markers.
The reason is thought to lie in beta-glucan, a viscous soluble fibre, for which oats are a rich source. Oat bran contains twice as much as oat meal.
The review found that overall, LDL cholesterol was reduced by 4.2%, non-HDL cholesterol by 4.8% and apoB by 2.3%.
Whole grain diet reduces cardiovascular disease risk
A study involving 33 overweight and obese adults who followed a whole grain diet for eight weeks and a refined grain diet during another eight week period, found that those on the whole grain diet saw a more than three-fold improvement in diastolic blood pressure compared to the refined grain diet.
This improvement equates to reducing the risk of death from heart disease by almost one-third, and the risk of death from a stroke by two-fifths.
Participants were under 50. Before age 50, an elevated diastolic blood pressure is associated with increased cardiovascular disease risk (diastolic is the bottom number, when you’re given a blood pressure reading).
Overall, there were substantial reductions in body weight, fat loss, systolic blood pressure, total cholesterol, and LDL cholesterol during both diet periods, but these differences were due to the people changing their normal dietary habits to carefully controlled diets. The order of diets was randomized, and there was a ten week period between them. The 33 participants included 6 men and 27 women.
The finding is supported by a meta-analysis of 45 different population studies that investigated whole grain intake in relation to risk of future illness or death due to specific causes. The review found that eating three more portions of whole grain foods a day was associated with a lower risk for all cardiovascular diseases and for dying of cancer, diabetes, and respiratory and infectious diseases. Three servings would be, say, two slices of whole-grain bread and one bowl of whole-grain cereal.
The benefits were dose-dependent, with the lowest risk found among those with the highest intake of whole-grain products: 7 to 7 ½ servings of whole grain products a day. This corresponds to 210-225 grams of whole grain products in fresh weight and about 70-75 grams of whole grains in dry weight.
Ho, H., Sievenpiper, J., Zurbau, A., Blanco Mejia, S., Jovanovski, E., Au-Yeung, F., . . . Vuksan, V. (2016). The effect of oat β-glucan on LDL-cholesterol, non-HDL-cholesterol and apoB for CVD risk reduction: A systematic review and meta-analysis of randomised-controlled trials. British Journal of Nutrition, 116(8), 1369-1382. doi:10.1017/S000711451600341X
Kirwan, J. P., Malin, S. K., Scelsi, A. R., Kullman, E. L., Navaneethan, S. D., Pagadala, M. R., … Ross, A. B. (2016). A Whole-Grain Diet Reduces Cardiovascular Risk Factors in Overweight and Obese Adults: A Randomized Controlled Trial. The Journal of Nutrition, 146(11), 2244–2251. https://doi.org/10.3945/jn.116.230508
Aune Dagfinn, Keum NaNa, Giovannucci Edward, Fadnes Lars T, Boffetta Paolo, Greenwood Darren C et al. Whole grain consumption and risk of cardiovascular disease, cancer, and all cause and cause specific mortality: systematic review and dose-response meta-analysis of prospective studies BMJ 2016; 353 :i2716 http://www.bmj.com/content/353/bmj.i2716
Data from 3,349 participants in the PREDIMED Study who were free of diabetes at baseline but at high cardiovascular risk, has found that those who consumed higher amounts of saturated fatty acids and animal fat had a twofold higher risk of developing type 2 diabetes over 4.5 years than those with a lower intake of saturated and animal fat. 266 participants developed diabetes during the period.
They also found that those who had a higher intake of legumes (lentils, chickpeas, beans and peas) had a 35% lower risk of developing type 2 diabetes compared to those eating the least amount. The main benefit came from lentils, with chickpeas running second. Those with a higher intake consumed at least 28.75 grams/day (equivalent to 3.35 servings/week).
There was also a positive benefit when half a serving per day of foods rich in protein or carbohydrates (such as eggs, bread, rice and baked potato) was replaced with a similar amount of legumes.
Legumes are rich in B vitamins, with beneficial minerals such as calcium, potassium and magnesium. They have long been thought to protect against type 2 diabetes.
Guasch-Ferré, M. et al. 2017. Total and subtypes of dietary fat intake and risk of type 2 diabetes mellitus in the Prevención con Dieta Mediterránea (PREDIMED) study. Total and subtypes of dietary fat intake and risk of type 2 diabetes mellitus in the Prevención con Dieta Mediterránea (PREDIMED) study Am J Clin Nutr 2017 105: 3 723-735; First published online February 15, 2017. doi:10.3945/ajcn.116.142034
Becerra-Tomás N, Díaz-López A, Rosique-Esteban N, Ros E, Buil-Cosiales P, Corella D, Estruch R, Fitó M, Serra-Majem Ll, Arós F, Lamuela-Raventós R.M, Fiol M, Santos-Lozano J.M, Diez-Espino J, Portoles O, Salas-Salvadó J, PREDIMED study investigators. "Legume consumption is inversely associated with type 2 diabetes incidence in adults: a prospective assessment from the PREDIMED study". Clinical Nutrition (2017). http://dx.doi.org/10.1016/j.clnu.2017.03.015.
Initial findings from the Walnuts and Healthy Aging (WAHA) study indicate that daily walnut consumption positively impacts blood cholesterol levels without adverse effects on body weight among older adults.
The study involved 707 healthy older adults of whom some were told to add significant daily amounts of walnuts (~15% of caloric intake) to their usual diet. They were not given any advice on what they should be eating, apart from that.
After a year, a comparison of the two groups found that those eating the walnuts were not any heavier than those who hadn't included walnuts in their diet, but the walnut-diet resulted in significant reductions in LDL cholesterol. There was minimal effect on triglycerides and HDL cholesterol.
Another study reported at the conference found that daily consumption of 1.5 ounces of walnuts significantly affected the bacteria in the human gut in a way that was favorable to decreasing inflammation and cholesterol. This was a small study involving only 18 healthy adults. However, a 2015 study with rats similarly found that a diet with walnuts had a significant effect on gut bacteria communities.
Walnuts are unique among nuts in being primarily composed of polyunsaturated fat. This includes alpha-linolenic acid (ALA), the plant-based omega-3 fatty acid, which is known to reduce inflammation. Walnuts are the only nut that contain a significant amount of alpha-linolenic acid.
Walnuts are also said to be an excellent source of antioxidants — indeed, second only to blackberries.
Ros E, Rajaram S, Sala-Vila A, et al. Effect of a 1-Year Walnut Supplementation on Blood Lipids among Older Individuals: Findings from the Walnuts and Healthy Aging (WAHA) study [abstract]. FASEB J. 2016;30(Supp 1)293.4. Available at: http://www.fasebj.org/content/30/1_Supplement/293.4.abstract
Guetterman HM, Swanson KS, Novotny JA, et al. Walnut Consumption Influences the Human Gut Microbiome [abstract]. FASEB J. 2016;30(Supp 1)406.2. Available at: http://www.fasebj.org/content/30/1_Supplement/406.2.abstract
Vinson, JA & Cai, Y. (2012) Nuts, especially walnuts, have both antioxidant quantity and efficacy and exhibit significant potential health benefits. Food & Function, 3(2), 134-140 . http://pubs.rsc.org/en/Content/ArticleLanding/2012/FO/C2FO10152A#!divAbstract
A new meta-analysis supports the link between intake of EPA and DHA omega-3 fatty acids, and reduction in major depressive disorder (MDD).
The meta-analysis only included studies in adult patients with MDD assessed using standardized clinical interviews, and excluded studies that specifically studied perinatal/perimenopausal or comorbid MDD, in order to get a more homogenous population. Studies not applying a randomized placebo-controlled trial design were also excluded. This criteria resulted in 13 studies with a total of 1233 participants (out of an original pool of 1955 studies).
The analysis of these studies showed a benefit for these omega-3 acids that was comparable to effects reported in meta-analyses of antidepressants. The effect was greater in studies supplementing higher doses of EPA and performed in patients already on antidepressants.
Mocking, R. J. T., Harmsen, I., Assies, J., Koeter, M. W. J., Ruhe, H. G., & Schene, A. H. (2016). Meta-analysis and meta-regression of omega-3 polyunsaturated fatty acid supplementation for major depressive disorder. Transl Psychiatry, 6, e756. Retrieved from http://dx.doi.org/10.1038/tp.2016.29
A pilot study involving 14 overweight or obese adults (average age 56) on a calorie-restricted diet, found that those whose diet had higher levels of protein showed greater improvements in their sleep score, regardless of the source of the protein.
In a follow-up study, 44 overweight or obese participants followed a normal-protein or a higher-protein weight loss diet (either 0.8 or 1.5 kg of protein for each kg of body weight) for 16 weeks. Sleep quality improved for those on the high-protein diet, but not for those on the normal-protein diet.
Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) questionnaire.
The sources of protein were beef and pork, or soy and legume.
Higher protein intake has also been linked to promoting body fat loss, retention of lean body mass and improvements in blood pressure.
Zhou, J., Kim, J. E., Armstrong, C. L., Chen, N., & Campbell, W. W. (2016). Higher-protein diets improve indexes of sleep in energy-restricted overweight and obese adults: results from 2 randomized controlled trials. The American Journal of Clinical Nutrition, 103(3), 766–774. http://doi.org/10.3945/ajcn.115.124669
A small, Israeli study involving 48 overweight and obese older adults with Type 2 diabetes (average age 59) has found that those who ate a large breakfast containing whey protein managed their diabetes better.
Participants in the study were randomly alloted to one of three diets that contained the same number of calories, and followed the pattern: large breakfast, medium-sized lunch and small dinner. They followed this diet for 23 months. The groups varied in the type of breakfast: primarily whey protein; other proteins such as eggs, soy and tuna; a meal high in carbohydrates or starch.
After 12 weeks, the group on whey protein lost the most weight: 7.6 kg (16.7 pounds), compared to 6.1 kg (13.4 pounds) for those on the other proteins, and 3.1 kg (6.8 pounds) for those in the carbohydrate group. Those on whey protein were also more satiated and less hungry throughout the day, with lower glucose spikes after meals compared to the other two diets, and their HbA1C also decreased more than with the other two diets.
For two years, 70 obese postmenopausal women with normal fasting plasma glucose levels ate either a Paleolithic-type diet or a “prudent” diet. The Paleolithic-type diet was based on lean meat, fish, eggs, vegetables, fruits, nuts and berries, with rapeseed, olive oils and avocado as additional fat sources. The diet excluded dairy products, cereals, added salt and refined fats and sugar. 30% of the calories were supposed to come from protein, 30% from carbohydrates, and 40% from fats with high unsaturated fatty acid content. The prudent control diet had a markedly different target: 15% in protein, 30% in fat, and 55% in carbohydrates.
Both groups took part in 12 group sessions led by a dietitian, and kept ongoing records of their food intake.
Both groups lost significant body weight and had significantly less abdominal obesity, but the women eating the Paleolithic-type diet also had significantly lower levels of specific fatty acids associated with insulin resistance, compared with those on the prudent control diet. Presumably this reflects the marked change in the types of fats eaten. At the end of the two years, the women eating the Paleolithic-type diet reported that their intake of saturated fatty acids decreased by 19%, while monounsaturated fatty acids increased by 47% and polyunsaturated fatty acids by 71%.
A Finnish study involving 2,189 healthy men aged 42-60 found that over 19 years, 417 men (19%) were diagnosed with type 2 diabetes. Those with high omega-6 polyunsaturated fatty acid concentrations in their blood were 46% less likely to develop diabetes. When analyzed, it turned out that this association depended on linoleic and arachidonic acid concentrations only; high serum gamma-linolenic and dihomo-γ-linolenic acid concentrations were linked to a higher risk.
The serum linoleic acid concentration is determined by the person's diet, and the main sources of linoleic acid are vegetable oils, nuts and seeds. Arachidonic acid is present in meat and eggs; however, the human body can also make arachidonic acid from linoleic acid.
Gamma-linolenic acid and dihomo-γ-linolenic acid are mainly formed in the human body from linoleic acid, but their concentrations in serum are very low.
Linoleic acid is the most common omega-6 fatty acid, and has been linked to a reduced risk of cardiovascular diseases as well as type 2 diabetes.
Teymoor Yary, Sari Voutilainen, Tomi-Pekka Tuomainen, Anu Ruusunen, Tarja Nurmi, Jyrki K Virtanen 2016. Serum n-6 polyunsaturated fatty acids, delta-5- and delta-6-desaturase activities and risk of incident type 2 diabetes in men: The Kuopio Ischaemic Heart Disease Risk Factor Study. American Journal of Clinical Nutrition, Published online March 24, 2016 http://ajcn.nutrition.org/content/early/2016/03/23/ajcn.115.128629.abstract
Lower salt generally lowers blood pressure, but it turns out this may not apply in all instances. A mouse study suggests that a low-salt diet can increase the risk of hypertension if you have a disrupted circadian rhythm. Sleep disorders, shift work, disease, and aging are all potential signs of or triggers for circadian dysfunction.
A 24-hour blood pressure check may reveal that blood pressure is not falling, as it should, during the night. Nondipping blood pressure is estimated as high as 53% in patients being treated for hypertension. It may be that, for those with a disrupted circadian rhythm, the timing of antihypertensive medication should be different.
Pati, P., Fulton, D. J. R., Bagi, Z., Chen, F., Wang, Y., Kitchens, J., … Rudic, R. D. (2016). Low-Salt Diet and Circadian Dysfunction Synergize to Induce Angiotensin II–Dependent Hypertension in Mice. Hypertension, 67(3), 661–668. http://doi.org/10.1161/HYPERTENSIONAHA.115.06194
A review of recent neutral studies questioning the benefits of omega-3s for heart health suggests that the findings may have been due to a number of design issues, rather than a lack of substantiated clinical benefits in cardiovascular disease. The issues include such things as:
- aggressive cardiovascular drug treatment overshadowing the benefits of long-chain omega-3s
- high background long-chain omega-3 intake at study initiation
- too few subjects in the study
- treatment duration too short
- insufficient LC omega-3 dosage
- increase in omega-6 fatty acid intake during the study
- failure to assess the LC omega-3 status of the subjects prior to and during treatment
- lack of clarity concerning which mechanisms were expected to produce benefits
The existing body of gold-standard research showing omega-3s may reduce cardiovascular death risk, maintain healthy blood pressure and improve triglyceride levels also makes it difficult to conclude that EPA and DHA consumption does not contribute to a healthy heart.
Rice, H. B., Bernasconi, A., Maki, K. C., Harris, W. S., von Schacky, C., & Calder, P. C. (2016). Conducting omega-3 clinical trials with cardiovascular outcomes: Proceedings of a workshop held at ISSFAL 2014. Prostaglandins, Leukotrienes and Essential Fatty Acids (PLEFA), 107, 30–42. http://doi.org/10.1016/j.plefa.2016.01.003
Telomeres are the protective caps at the ends of chromosomes that affect how quickly cells age. With age, they shorten, and as their structural integrity weakens, the cells age and die quicker. Telomere length thus is a biomarker of cellular age. Stress is also thought to shorten telomere length.
A year-long study that looked at the effects of three healthy behaviors in 239 post-menopausal, non-smoking women has found that women who engaged in lower levels of healthy behaviors showed a significantly greater telomere shortening for every major life stressor that occurred. However, stress didn't lead to greater shortening in those women who maintained active lifestyles, healthy diets, and good quality sleep.
Shorter telomeres have become associated with a broad range of aging-related diseases, including stroke, vascular dementia, cardiovascular disease, obesity, osteoporosis diabetes, and many forms of cancer.
Puterman, E., Lin, J., Krauss, J., Blackburn, E. H., & Epel, E. S. (2015). Determinants of telomere attrition over 1 year in healthy older women: stress and health behaviors matter. Molecular Psychiatry, 20(4), 529–535. http://doi.org/10.1038/mp.2014.70
In a study involving 52 sedentary, overweight, middle-aged men and women (aged 45-65), both exercise and calorie restriction had positive — and equal — effects on insulin sensitivity, but a combination of both had twice as much benefit for glucoregulation as either single approach. All three programs were designed to achieve about the same amount of weight loss (6-8%).
The study also indicated that both exercise and calorie restriction improve regulation of glucose levels through weight loss, but also through mechanisms that are independent of weight loss.
What all this suggests is that, even if you're maintaining a healthy weight, how much you eat, and whether you exercise, are factors that have health implications.
Weiss, E. P., Albert, S. G., Reeds, D. N., Kress, K. S., Ezekiel, U. R., McDaniel, J. L., … Villareal, D. T. (2015). Calorie Restriction and Matched Weight Loss From Exercise: Independent and Additive Effects on Glucoregulation and the Incretin System in Overweight Women and Men. Diabetes Care, 38(7), 1253–1262. http://doi.org/10.2337/dc14-2913
A very small Israeli study, involving eight men and 10 women aged 30-70 with type 2 diabetes, has found that a big breakfast and a small dinner helped control blood sugar levels through the day.
Patients were randomly assigned to follow either a “B diet”, in which breakfast contained 2946 kilojoules, lunch 2523 kj, and dinner 858kj, or a “D diet”, which involved a 858 kj breakfast, 2523 kj lunch, and 2946 kj dinner. In other words, the same total amount of calories, in the same foods, was eaten by both groups, and lunch was the same for both, but the 'breakfast' and 'dinner' meals swapped timing.
After six days on the diet, patients ate their meals on the 7th day at the lab, where glucose levels were repeatedly tested during the day. After a break of two weeks, each patient was put on the alternate diet, and the same procedure was followed.
It was found that blood glucose levels rose 23% less after the lunch preceded by a large breakfast.
Jakubowicz, D., Wainstein, J., Ahrén, B., Bar-Dayan, Y., Landau, Z., Rabinovitz, H. R., & Froy, O. (2015). High-energy breakfast with low-energy dinner decreases overall daily hyperglycaemia in type 2 diabetic patients: a randomised clinical trial. Diabetologia, 58(5), 912–919. http://doi.org/10.1007/s00125-015-3524-9
Mouse and human immune cells have demonstrated that a compound produced by the body when dieting or fasting (β-hydroxybutyrate — BHB) directly inhibits a protein, NLRP3, which is part of a complex set of proteins that drive the inflammatory response in several disorders, including autoimmune diseases, type 2 diabetes, Alzheimer's disease, atherosclerosis, and autoinflammatory disorders.
BHB is produced in response to fasting, high-intensity exercise, caloric restriction, or consumption of the low-carbohydrate ketogenic diet.
The finding helps explain why calorie restriction reduces inflammation.
Youm, Y.-H., Nguyen, K. Y., Grant, R. W., Goldberg, E. L., Bodogai, M., Kim, D., … Dixit, V. D. (2015). The ketone metabolite β-hydroxybutyrate blocks NLRP3 inflammasome-mediated inflammatory disease. Nature Medicine, 21(3), 263–269. http://doi.org/10.1038/nm.3804
Studies have found that low levels of magnesium increases the chance that you will develop type 2 diabetes, but a large study shows that this association is modified by genetic variations in magnesium-related ion channel genes. So, for example, among Hispanic American women with high magnesium intake, those with one particular variant had a 35% lower risk of developing type 2 diabetes.
The study involved 7,287 black women and 3,285 Hispanic women aged 50-79.
Chan, K. H. K., Chacko, S. A., Song, Y., Cho, M., Eaton, C. B., Wu, W.-C. H., & Liu, S. (2015). Genetic Variations in Magnesium-Related Ion Channels May Affect Diabetes Risk among African American and Hispanic American Women. The Journal of Nutrition, 145(3), 418–424. http://doi.org/10.3945/jn.114.203489
A review of studies investigating lifestyle interventions that can delay or prevent the onset of type 2 diabetes in people with prediabetes and focusing specifically on ones that looked at gender differences, found that both men and women benefited equally from the interventions. The review of 12 studies found that those who received lifestyle interventions (including diet and exercise) were 40% less likely to progress to type 2 diabetes after 1 year, and 37% less likely to progress after 3 years.
People involved in lifestyle interventions also experienced greater weight reductions, and greater reductions of fasting plasma glucose.
Glechner, A., Harreiter, J., Gartlehner, G., Rohleder, S., Kautzky, A., Tuomilehto, J., … Kautzky-Willer, A. (2014). Sex-specific differences in diabetes prevention: a systematic review and meta-analysis. Diabetologia, 58(2), 242–254. http://doi.org/10.1007/s00125-014-3439-x
A new class of lipids produced in human and mouse fat has been discovered, and these ones seem to be good for you. Following the discovery that diabetes-resistant mice had dramatically higher levels of these “fatty acid hydroxy fatty acids (FAHFAs)”, levels were found to be low in pre-diabetic humans. Moreover, when mice with the equivalent of type 2 diabetes were given this lipid, blood sugar levels dropped and insulin levels rose. FAHFAs also seem to reduce inflammation.
FAHFAS are found in low levels in a wide range of vegetables, fruits and other foods, as well as being (unlike omega-3 fatty acids) produced and broken down inside the body.
Yore, M. M., Syed, I., Moraes-Vieira, P. M., Zhang, T., Herman, M. A., Homan, E. A., … Kahn, B. B. (2014). Discovery of a Class of Endogenous Mammalian Lipids with Anti-Diabetic and Anti-inflammatory Effects. Cell, 159(2), 318–332. http://doi.org/10.1016/j.cell.2014.09.035
Oregano and rosemary turn out to be packed with healthful compounds that may work in much the same way as prescription anti-diabetic medication in keeping their blood-sugar level in check. While greenhouse-grow herbs contained more polyphenols and flavonoids compared to the equivalent commercial dried herbs, commercial extracts of Greek oregano, Mexican oregano and rosemary were better inhibitors of the enzyme, required to reduce risk of type-2 diabetes.
Bower, A. M., Real Hernandez, L. M., Berhow, M. A., & de Mejia, E. G. (2014). Bioactive Compounds from Culinary Herbs Inhibit a Molecular Target for Type 2 Diabetes Management, Dipeptidyl Peptidase IV. Journal of Agricultural and Food Chemistry, 62(26), 6147–6158. http://doi.org/10.1021/jf500639f
A Canadian study involving 141 people with Type 2 diabetes, who ate either a low glycemic index diet that included bread made with canola oil, or a whole wheat diet known to reduce the risk of cardiovascular disease, found that those on the canola bread diet experienced both a reduction in blood glucose levels and a significant reduction in LDL, or "bad," cholesterol. Moreover, the canola bread diet seemed to have the most significant impact on people who needed help the most — those whose HbA1c test measuring blood glucose over the previous two or three months was highest.
On the other hand, those on the whole wheat diet seemed to have better blood flow after 12 weeks than those on the canola bread diet.
Jenkins, D. J. A., Kendall, C. W. C., Vuksan, V., Faulkner, D., Augustin, L. S. A., Mitchell, S., … Leiter, L. A. (2014). Effect of Lowering the Glycemic Load With Canola Oil on Glycemic Control and Cardiovascular Risk Factors: A Randomized Controlled Trial. Diabetes Care, 37(7), 1806–1814. http://doi.org/10.2337/dc13-2990
A trial in which 163 overweight adults with elevated blood pressure were given one of four complete diets that contained all their food for five weeks has found that a low glycemic diet did not improve insulin sensitivity, lipid levels or blood pressure. But it's important to note than all diets were based on a healthful DASH-type diet, varying only in their glycemic index and carbohydrate proportions.
So, the trial found that a healthy diet with low–glycemic index carbohydrate-containing foods didn't improve insulin sensitivity, HDL cholesterol levels, LDL cholesterol levels, or systolic blood pressure any more than the healthy diet with high–glycemic index foods It did reduce plasma triglyceride levels slightly more.
In fact, the low–glycemic index with high-carbohydrate diet was worse than the high–glycemic index, high-carbohydrate diet — decreasing insulin sensitivity and increasing LDL cholesterol and LDL apolipoprotein B levels. This finding was unexpected and inconsistent with other research. However, a meta-analysis of 28 trials found that lowering glycemic index did not affect HDL cholesterol or triglyceride levels and lowered LDL cholesterol level only if fiber content was also increased.
In line with the researchers' previous findings, the DASH diet had slightly better effects when its carbohydrate content was reduced. When the same calories were instead supplied by unsaturated fat and protein, triglycerides and VLDL levels were substantially lowered and diastolic blood pressure slightly lowered.
As in previous trials, all the DASH-type diets lowered blood pressure and LDL cholesterol levels.
Previous research has shown inconsistent results on whether low glycemic index helped people lose weight.
Sacks FM, Carey VJ, Anderson CM, et al. Effects of High vs Low Glycemic Index of Dietary Carbohydrate on Cardiovascular Disease Risk Factors and Insulin Sensitivity: The OmniCarb Randomized Clinical Trial. JAMA. 2014;312(23):2531-2541. doi:10.1001/jama.2014.16658.
Goff LM, Cowland DE, Hooper L, Frost GS. Low glycaemic index diets and blood lipids: a systematic review and meta-analysis of randomised controlled trials. Nutr Metab Cardiovasc Dis. 2013;23(1):1-10.
A meta-analysis of 61 controlled trials has concluded that consuming tree nuts, such as walnuts, lowers total cholesterol, triglycerides, LDL cholesterol, and ApoB, the primary protein found in LDL cholesterol. Walnuts were investigated in 21 of the 61 trials, more than any other nut reviewed.
Consuming at least two servings (two ounces) per day of tree nuts had stronger effects on total cholesterol and LDL. The evidence also suggests that tree nut consumption may be particularly important for lowering the risk of heart disease in individuals with type 2 diabetes.
Walnuts have also been shown to reduce inflammation, and improve arterial function.
Del Gobbo, L., Falk, M.C., Feldman, R., Lewis, K., Mozaffarian, D. Effects of tree nuts on blood lipids, apolipoproteins, and blood pressure: systematic review, meta-analysis and dose-response of 61 controlled intervention trials. Am J Clin Nutr.2015; doi: 10.3945/ajcn.115.110965.
Kris-Etherton P. Walnuts decrease risk of cardiovascular disease: a summary of efficacy and biologic mechanisms. J Nutr. 2014; 10.39:2S-8S.
Zhao G, Etherton TD, Martin KR, et al. Dietary alpha-linolenic acid reduces inflammatory and lipid cardiovascular risk factors in hypercholesterolemic men and women. J Nutr 2004; 134: 2991-2997.
Further analysis of data from a 2011 study on the effect of the 'portfolio diet' on cholesterol has found that it also lowered blood pressure by an average 2% more than the DASH diet, a diet specifically designed to reduce hypertension, which is associated with a 5-10 mm blood pressure improvement.
The Canadian study involved 241 participants with hyperlipidemia, of whom 82 were randomly assigned to a DASH-type diet (control group) and 159 to the portfolio diet. Compared to the control, the portfolio diet reduced systolic, diastolic and mean arterial blood pressure by 2.1 mm Hg, 1.8 mm Hg and 1.9 mm Hg, respectively. Blood pressure reductions were small at 12 weeks and only reached significance at 24 weeks.
The portfolio diet includes foods that have been shown to lower cholesterol including mixed nuts, soy protein, plant sterols (found in vegetable oils and leafy vegetables) and viscous or soluble fiber. Viscous fiber is found only in plant-based food; rich sources include asparagus, Brussels sprouts, sweet potatoes, turnips, apricots, mangoes, oranges, legumes and oat bran.
However, the DASH diet did have higher compliance rates.
Jenkins, D.J.A. et al. 2015. The effect of a dietary portfolio compared to a DASH-type diet on blood pressure. Nutrition, Metabolism and Cardiovascular Diseases, 25 (12), 1132-1139. http://dx.doi.org/10.1016/j.numecd.2015.08.006
A British study involving 165 healthy nonsmoking adults (aged 40–70) has found that a diet based on UK health guidelines could reduce risk of a heart attack or a stroke by up to a third, compared to a traditional British diet
The predicted risk of cardiovascular disease over the next 10 years for the participants was estimated to be about 8% in the men and 4% in the women. Participants followed their diets for 12 weeks. Those on the modified diet ate oily fish once a week, more fruit and vegetables, replaced refined with wholegrain cereals, swapped high-fat dairy products and meats for low-fat alternatives, and restricted their intake of added sugar and salt. Participants were asked to replace cakes and cookies with fruit and nuts and were also supplied with cooking oils and spreads high in monounsaturated fat.
The average body weight in the group on the modified diet fell by 1.3 kg; that in the control group rose by 0.6 kg. Waist circumference was 1.7 cm lower in the dietary group compared to the control group. There were also significant falls in systolic blood pressure/diastolic blood pressure (4.2/2.5 mm Hg for daytime and 2.9/1.9 mm Hg for night time) and average heart rate. Cholesterol fell by 8%. High-sensitivity C-reactive protein (a marker for inflammation) was 36% lower. There was no significant change in markers for insulin sensitivity. Much of the fall in blood pressure could be accounted for by the drop in sodium.
Reidlinger, D. P., Darzi, J., Hall, W. L., Seed, P. T., Chowienczyk, P. J., & Sanders, T. A. (2015). How effective are current dietary guidelines for cardiovascular disease prevention in healthy middle-aged and older men and women? A randomized controlled trial. The American Journal of Clinical Nutrition, 101(5), 922–930. http://doi.org/10.3945/ajcn.114.097352
A small 12-week clinical trial involving 52 overweight, middle-aged adults with high total and LDL cholesterol has found that those who ate a daily snack of almonds significantly improved a number of cardiovascular risk factors compared to those who ate a banana muffin.
Specifically, they decreased total cholesterol, LDL-cholesterol non-HDL-cholesterol and remnant lipoproteins, and reduced abdominal fat mass, waist circumference and leg fat mass (not total weight or fat mass — this is about distribution).
The muffin and the 1.5 oz (42g) of whole natural almonds had the same number of calories. Otherwise, the participants ate the same balanced diet. Participants followed each diet for six weeks, with a two-week “washout” period in between. Adherence to the diets was 85%.
Berryman CE, West SG, Fleming JA, Bordi PL, Kris-Etherton PM. Effects of Daily Almond Consumption on Cardiometabolic Risk and Abdominal Adiposity in Healthy Adults with Elevated LDL-Cholesterol: A Randomized Controlled Trial. Journal of the American Heart Association 2015; 4:e000993 DOI: 10.1161/JAHA.114.000993.
A small study involving 45 healthy, overweight or obese adults aged 21-70 has found that a diet including a daily Hass avocado was more effective than other cholesterol-reducing diets. Participants followed each of three diets for five weeks: one containing 24% fats and two containing 34% fats, one of which included an avocado and the other a comparable amount of high oleic acid oils (e.g. olive oil). There was a two-week break between each diet.
The avocado diet decreased bad cholesterol by 13.5 mg/dL, while LDL was decreased by 8.3 mg/dL on the moderate-fat diet and by 7.4 mg/dL on the low-fat diet.
Wang, L., Bordi, P. L., Fleming, J. A., Hill, A. M., & Kris Etherton, P. M. (2015). Effect of a Moderate Fat Diet With and Without Avocados on Lipoprotein Particle Number, Size and Subclasses in Overweight and Obese Adults: A Randomized, Controlled Trial. Journal of the American Heart Association, 4(1), e001355. http://doi.org/10.1161/JAHA.114.001355
A small study involving 48 post-menopausal women with pre- and stage 1 hypertension found that daily consumption of freeze-dried blueberry powder for eight weeks improved blood pressure and arterial stiffness. The amount of powder (22g) equated to one cup of fresh blueberries.
The improvement is thought to occur partly by helping nitric oxide-mediated vasodilation. Nitric oxide bioavailability is believed to increase endothelial-dependent vasodilation, leading to lower blood pressure.
After eight weeks those taking the blueberry powder showed a mean systolic blood pressure that was lower by 7 mmHg (5.1%) and mean diastolic blood pressure lower by 5 mmHg (6.3%), with no corresponding lowering in those taking a placebo. Nitric oxide measurements were significantly increased (68.5%) in the blueberry group. Arterial stiffness, measured by brachial ankle pulse wave velocity was significantly reduced (6.5%) after eight weeks in the blueberry-treated group, with, again, no changes in the control group. Aortic stiffness, measured by the carotid-femoral pulse wave velocity, did not change in either group, suggesting that peripheral arteries may be more responsive to dietary interventions than central arteries.
Among all fruits, blueberries are one of the richest sources of phenolic compounds. While previous studies have found positive effects on cardiovascular risk factors, they have all used large amounts of blueberry powder. These findings suggest that regular consumption of blueberries in quite moderate amounts could prevent or delay the progression of prehypertension to hypertension.
Johnson, S. A., Figueroa, A., Navaei, N., Wong, A., Kalfon, R., Ormsbee, L. T., … Arjmandi, B. H. (2015). Daily Blueberry Consumption Improves Blood Pressure and Arterial Stiffness in Postmenopausal Women with Pre- and Stage 1-Hypertension: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial. Journal of the Academy of Nutrition and Dietetics, 115(3), 369–377. http://doi.org/10.1016/j.jand.2014.11.001
Following on from the evidence that Alzheimer’s brains show higher levels of metals such as iron, copper, and zinc, a mouse study has found that amyloid plaques in Alzheimer’s-like brains with significant neurodegeneration have about 25% more copper than those with little neurodegeneration. This is consistent with a human study showing very high levels of copper in Alzheimer’s plaques.
Iron, though doubled in Alzheimer’s brains compared to controls, was not significantly different as a function of neurodegeneration, and zinc showed very little difference.
The findings suggest that the cellular control of copper is altered in some way in Alzheimer’s brains, while the increase in oxidized iron suggests it might be useful as a biomarker for the early diagnosis of Alzheimer’s.
(2013). Elevated copper in the amyloid plaques and iron in the cortex are observed in mouse models of Alzheimer's disease that exhibit neurodegeneration.
Biomedical Spectroscopy and Imaging. 2(2), 129 - 139.
Data from the very large U.S. National Health and Nutrition Examination Survey (NHANES), involving 23,168 people, has found a significant association between low dietary fiber intake and risk of metabolic syndrome, cardiovascular inflammation, and obesity.
Dietary fiber intake was also consistently below recommended intake levels: 38g per day for men aged 19-50 years, 30g per day for men 50 and over, 25g for women aged 19-50 years, and 21g per day for women over 50. Mean dietary fiber intake was only 16.2g per day across all groups.
A study involving 12 rhesus macaques, of whom some were given access to alcohol, has found that those who drank moderately showed enhanced responses to a smallpox vaccine (compared with the control group of monkeys who drank sugar water), indicating a bolstered immune system, while heavy drinkers showed greatly diminished vaccine responses.
A mouse study suggests that resveratrol—a compound abundant in red wine—may moderate some of a high-fat diet’s negative effects on the immune system.
A study involving 74 older adults (70+), of whom 3 had mild dementia, 33 were cognitively normal and 38 had mild cognitive impairment, has found that high levels of "good" cholesterol and low levels of "bad" cholesterol correlated with lower levels of the amyloid-beta plaques in the brain (a hallmark of Alzheimer's disease).
A review of research from 1957 to the present has concluded that a whole diet approach, and specifically Mediterranean-style diets, has more evidence for reducing cardiovascular risk than strategies that focus exclusively on reduced dietary fat.
A Swedish study has found that those who ate poor breakfasts as year 9 students had a higher incidence of metabolic syndrome 27 years later, compared with those who ate more substantial breakfasts.
A study involving 39 young adult men and women of normal weight, who ate 750 extra calories in the form of muffins every day for seven weeks, found that those whose muffins were made with palm oil built significantly more fat and less muscle than those whose muffins were made with sunflower oil. Moreover, the palm oil group developed the fat in more dangerous places — in the liver and abdomen. The groups gained the same amount of weight.
A study in which 23 healthy volunteers ate half a kilo of strawberries every day for a month has found that their levels of bad cholesterol and triglycerides reduced significantly.
"Sprouted" garlic — old garlic bulbs with bright green shoots emerging from the cloves — have been found to have even more heart-healthy antioxidant activity than fresh garlic.
A study involving 44 middle-aged overweight men who consumed 70 grams of dark chocolate per day over two periods of four weeks, has found that dark chocolate helps restore flexibility to arteries while also preventing white blood cells from sticking to the walls of blood vessels. Both arterial stiffness and white blood cell adhesion are known factors that play a significant role in atherosclerosis.
A Finnish study has found that people who increased their intake of fatty fish to a minimum of 3–4 weekly meals had more large HDL cholesterol in their blood than people who were less frequent eaters of fish. Large HDL particles are believed to protect against cardiovascular diseases.
A large long-running study has found that eating a diet rich in animal proteins during middle age makes you four times more likely to die of cancer than a low-protein diet (a mortality risk factor comparable to smoking), 74% more likely to die of any cause within the 20-year study period, and five times more likely to die of diabetes. Even those eating a moderate amount of protein had much higher levels of mortality risk.
However, a high or moderate protein diet is helpful for those over 65, when levels of the growth hormone IGF-I drop off dramatically.
Plant-based proteins didn’t seem to have the same mortality effects as animal proteins.
The findings support recommendations from several leading health agencies to consume about 0.8 grams of protein per kilogram of body weight every day in middle age.
A "high-protein" diet derives at least 20% of calories from protein; a "moderate" protein diet includes 10-19% of calories from protein; a "low-protein" diet includes less than 10% protein.
Middle-aged Japanese men living in Japan had lower incidence of coronary artery calcification, a predictor of heart disease, than middle-aged white men living in the United States, after accounting for risk factors such as smoking, cholesterol, alcohol consumption, diabetes and high blood pressure.
It’s suggested that the mixed results from studies looking at the effect of fish oil on cardiovascular health are due to the substantially lower intake of omega-3 fatty acids than that found in Japanese. The average dietary intake of fish by Japanese people living in Japan is nearly 100 grams each day, compared to the average American intake of 7-13 grams a day (about one serving a week).
Japanese-Americans had levels of coronary artery calcification higher than that of the rest of the US population.
A new study from the Women's Health Initiative has found that calcium and vitamin D supplements after menopause can improve women's cholesterol profiles, with much of that effect tied to raising vitamin D levels. Taking the calcium and vitamin D supplements was especially helpful in raising vitamin D levels in women who were older, women who had a low intake, women who had levels first measured in the winter, and women who didn’t smoke and who drank less alcohol.
A study involving 362 children with reading problems has found that 16 weeks of daily 600 mg supplements of omega-3 DHA from algal sources improved their sleep. According to a sleep questionnaire filled out by parents, 40% of these children had significant sleep problems. Monitoring of 43 of the poor sleepers found that children taking daily supplements of omega-3 had nearly one hour (58 minutes) more sleep and seven fewer waking episodes per night compared with children taking a placebo.
Data from 11 different cohort studies, involving more than 600,000 people from around the world, has found that:
- men with waists 43 inches (114 cm) or greater in circumference had a 50% higher mortality risk than men with waists less than 35 inches (89 cm), giving them about a three-year lower life expectancy after age 40.
- women with a waist circumference of 37 inches (94 cm) or greater had about an 80% higher mortality risk than women with a waist circumference of 27 inches or less (68.5 cm), giving them about a five-year lower life expectancy after age 40.
Risk increased in a linear fashion such that for every 2 inches of greater circumference, mortality risk went up about 7% in men and about 9% in women. The association was observed regardless of BMI.
A meta-analysis of 72 studies with over 600,000 participants from 18 nations has concluded that total saturated fatty acid, whether measured in the diet or in the bloodstream as a biomarker, was not associated with coronary disease risk. Nor was there any significant association between consumption of total monounsaturated fatty acids, long-chain omega-3 and omega-6 polyunsaturated fatty acids, and cardiovascular risk.
However, there were some significant associations between specific fatty acids. Eicosapentaenoic and docosahexaenoic acids (two main types of long-chain omega-3 polyunsaturated fatty acids), and arachidonic acid (an omega-6 fat) were each associated with lower coronary risk, while palmitic and stearic acids (found largely in palm oil and animal fats, respectively) were associated with higher risk, and margaric acid (a dairy fat) with lower risk.
Data from AREDS2, involving 4,203 older adults with age-related macular degeneration, has found that daily dietary supplements of either omega-3 polyunsaturated fatty acids (also found in fish) or lutein and zeaxanthin (nutrients found in green leafy vegetables) were not associated with reduced risk for cardiovascular disease (CVD).
A review of 19 studies involving over 162,000 people has found that adherence to the Mediterranean diet was associated with a 21% reduced risk of diabetes, with a greater effect (27%) for those at high risk for cardiovascular disease. The association was found in both European and non-European groups.
The research was presented at the American College of Cardiology's 63rd Annual Scientific Session.
A study involving healthy men and women fed a baseline diet containing 550 mg choline/day (the adequate intake level set by the Institute of Medicine) for 10 days, then put on a low choline diet (50 mg choline/day) for up to 42 days, has found that the "right" amount of choline depends on many factors, including gender, age, and ethnicity.
A very large Italian study provides more evidence that the Mediterranean diet reduces inflammation, with their finding that those with a greater adherence to such a diet had significantly lower levels of platelets and white blood cells. These are both inflammatory markers: high platelet counts are associated with both vascular disease and non-vascular conditions such as cancer, and a high white blood cell count is a predictor of ischemic vascular disease.
A 25-year study of diet and aging in 76 rhesus monkeys shows a significant reduction in mortality and in age-associated diseases among those on calorie-restricted diets.
These findings contradict an earlier primate study, perhaps because the current study reduced the diet of the experimental group by 30% based on what the adults wanted to eat. In the earlier study, both experimental and control animals were given diets based on a standardized food intake chart — meaning that the controls may have been on a restricted diet too (an idea supported by their weight, which was at all times less than that of the controls in the current study). Moreover, the earlier study, although reported as showing calorie restriction is ineffective, had 4 of the 10 experimental group achieve the unusual age of 40+, as did 1 of the 10 controls.
The current study also saw diabetes occurring in the control group, who were allowed to eat what they wanted.
Mice given decaffeinated green tea and regular exercise lost weight and improved their health after 16 weeks. Specifically, they reduced body mass by 27% (on average), reduced abdominal fat by 37%; reduced blood glucose level by 17%, plasma insulin level by 65%, and insulin resistance by 65%..
Neither green tea alone, nor exercise alone, produced such significant changes. The amount of green tea was a lot: the equivalent of 8-10 cups a day. Decaffeination may not be important; it was done to keep the effects of caffeine out of the study.
Green tea is thought to affect genes related to energy metabolism.
A mouse study suggests that merely changing meal times could have a significant effect on the levels of triglycerides in the liver. Levels of triglycerides followed a circadian rhythm, with levels peaking about eight hours after sunrise (note that mice are nocturnal). Mice generally eat 20% of their food during the day, and 80% at night. Mice lacking a functional body clock eat constantly during the day. When normal mice were given the same amount of food, but had to eat it only at night, there was a quick and dramatic 50% decrease in overall liver TAG levels.
A small trial involving seven older adults with insomnia has found that when they consumed 8 ounces of tart cherry juice twice daily for two weeks, they were able to sleep more than an hour longer each night (averaging 84 minutes) compared to when they took the placebo, and their sleep tended to be more efficient.
Montmorency tart cherries are a natural source of melatonin, a hormone that helps regulate the sleep-wake cycle. The juice also helped to increase the availability of tryptophan, an essential amino acid and a precursor to serotonin that helps with sleep.
A study involving 61 women, of whom 33 were chronically stressed caring for a spouse or parent with dementia, has found that highly stressed people who ate a lot of high-fat, high-sugar food were likely to have:
- a larger waistline,
- more truncal fat,
- higher oxidative damage, and
- more insulin resistance.
This association was not found among the low-stress women who ate the same amount of unhealthy food.
The findings are consistent with animal studies.
A 2-year trial involving 59 patients with type 2 diabetes has found that those on a low-carbohydrate diet showed lower levels of inflammation compared with those on a traditional low-fat diet. Weight loss was similar in both groups.
Contradicting some earlier studies, new research using data from the very large and long-running Nurses' Health Study has found that calcium supplement intake was not associated with a higher risk of cardiovascular disease in women.
Preliminary studies have demonstrated that grape skin extract exerts a novel inhibitory activity on hyperglycemia and could be developed to aid in diabetes management.
An Italian study has found that older adults with the highest concentration of resveratrol metabolites were no less likely to have died of any cause than those with no resveratrol found in their urine. The concentration of resveratrol was not associated with inflammatory markers, cardiovascular disease, or cancer rates. The finding indicates that whatever health benefits red wine, blueberries and dark chocolate have, it is not due to this antioxidant.
Given that the participants were from Tuscany, where consumption of red wine is the norm, I do wonder if the same result would have been found if people with very low consumption of resveratrol had been included. Perhaps there are no benefits over a certain level, but this is not to say there are no benefits for those below that level. But this is mere speculation on my part.
A review and meta-analysis of all international studies that compared the effects of higher versus lower added sugar consumption on blood pressure and lipids (blood fats or cholesterol) has uncovered evidence that sugar has a direct effect on risk factors for heart disease, and is likely to impact on blood pressure, independent of weight gain.
Two studies help explain why kidney disease increases the risk of cardiovascular diseases such as high blood pressure and vascular calcification. The mediator seems to be a hormone called FGF23, which is sensitive to the level of phosphates in the body.
Phosphate rich foods include processed cheese, Parmesan, cola, baking powder and most processed foods.
A finding that free radicals promote longevity in the roundworm challenges the theory that free radicals (oxidants) are damaging and cause aging.
Analysis of eight studies on diet and stroke published between 1990 and 2012 has found that risk of first-time stroke dropped with every 7g increase in total daily fibre. That amount of fibre is contained in a bowl of wholewheat pasta plus two servings of fruit or vegetables.
Insufficient data is available to say whether soluble or insoluble fibre is better. The studies came from the United States, northern Europe, Australia, and Japan.
(2013). Dietary Fiber Intake and Risk of First Stroke A Systematic Review and Meta-Analysis.