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
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
Data from 4.1 million British adults who were free of diabetes and cardiovascular disease at the start of the study has found that those with high blood pressure were almost 60% more likely to develop type 2 diabetes.
The strength of the association declined with increasing body mass index and age.
The finding strengthens previous research indicating that you are more at risk of diabetes if you have had high blood pressure, a heart attack or a stroke.
Emdin CA, Anderson SG, Woodward M, Rahimi K. Usual Blood Pressure and Risk of New-Onset Diabetes: Evidence From 4.1 Million Adults and a Meta-Analysis of Prospective Studies. J Am Coll Cardiol. 2015;66(14):1552-1562. doi:10.1016/j.jacc.2015.07.059.
Sleep apnea is common among overweight and obese individuals, and many people with prediabetes have untreated sleep apnea, although few of them are aware of it.
A study involving 39 middle-aged, overweight or obese volunteers with prediabetes and sleep apnea has found that those who received two weeks of CPAP treatment improved their blood sugar control and the ability of insulin to regulate their blood sugar, and also had lower blood pressure and lower levels of the stress hormone norepinephrine.
Two-thirds of the volunteers received continuous positive airway pressure (CPAP) for eight hours during the night; the other 13 received a placebo to be taken before bedtime. They were told the study would compare the two treatments. All participants slept in the sleep laboratory and were closely monitored.
Sushmita Pamidi, Kristen Wroblewski, Magdalena Stepien, Khalid Sharif-Sidi, Jennifer Kilkus, Harry Whitmore, and Esra Tasali "Eight Hours of Nightly Continuous Positive Airway Pressure Treatment of Obstructive Sleep Apnea Improves Glucose Metabolism in Patients with Prediabetes. A Randomized Controlled Trial", American Journal of Respiratory and Critical Care Medicine, Vol. 192, No. 1 (2015), pp. 96-105. doi: 10.1164/rccm.201408-1564OC
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.
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 Greek study involving 386 middle aged patients (average age 61) with arterial hypertension has found that those who had a midday nap had lower systolic BP than those who didn't. Their average systolic BP readings were 4% lower when they were awake (5 mmHg) and 6% lower while they slept at night (7 mmHg) than non-midday sleepers .
Moreover, midday sleepers had pulse wave velocity levels that were 11% lower and left atrium diameter was 5% smaller — suggesting there is less damage in the arteries and heart. Additionally, midday sleepers had greater dips in blood pressure during the night (which is a good thing), and they took fewer antihypertensive medications.
Longer naps were better than shorter.
The research was presented at the 2015 ESC Congress.
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 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
A four-year study involving 1,502 healthy older adults (50+) has found that the frequency of negative interactions with family members (not partners or children) and friends was associated with an increased risk of developing hypertension in women (but not in men). Each increase in the total average negative social interaction score was associated with a 38% increased chance of developing hypertension. Younger older women (51-64) were more affected than those 65 or older.
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.
Brain scans of 61 older adults (65-90), of whom 30 were cognitively healthy, 24 cognitively impaired and 7 diagnosed with dementia, found that, across all groups, both memory and executive function correlated negatively with brain infarcts, many of which had been clinically silent. The level of amyloid in the brain did not correlate with either changes in memory or executive function, and there was no evidence that amyloid interacted with infarcts to impair thinking.
Bottom line: vascular brain injury was far more important than amyloid burden for memory and executive function. The finding highlights the role of vascular injury in mild cognitive impairment.
(2013). The aging brain and cognition: Contribution of vascular injury and aβ to mild cognitive dysfunction.
JAMA Neurology. 1 - 8.