- 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