Oats and Cholesterol

 

    After reading the recent blog on "Two Apples a Day may Lower Cholesterol", one of my friends asked if oats also had cholesterol-lowering property and if any reports on it. My answer was that "foods that contain a good amount of fibers, such as oats, have cholesterol-lowering benefits, and there had been many studies on oats". I said that I would write my next blog about oats and cholesterol.

 

    Indeed, there had been many studies on oats and cholesterol that I found 100+ published clinical studies on PubMed. I have to pick just a few to illustrate the cholesterol-lowering benefits of oats in this short blog.

 

    In a randomized, double-blind study, 74 healthy and mild hypercholesterolemic subjects either consumed 100 g of oat noodles (the experimental group with 3.12 g of β -glucan) or wheat noodles (placebo group) by replacing one or two meals/day for 10 weeks. Consumption of oat noodles by replacing staple food for 10 weeks significantly reduced the levels of total cholesterol (- 17.46%), LDL-cholesterol (-19.03%), and blood pressure (systolic blood pressure; -11.09% and diastolic blood pressure; -7.48%)(P<0.05 for all) in both healthy and mildly hypercholesterolemic subjects, while the lipid and blood pressure parameters were not significantly changed in the placebo group (1).

 

    In a 6-week randomized controlled trial (2), 87 mildly hypercholesterolaemic men and women were assigned to one of three diet treatments with a base diet that contained energy content of 25 % protein; 45 % carbohydrate; and 30 % fat, at energy requirements for weight maintenance: 1) minimal β -glucan (control); 2) low-dose oat β-glucan (1·5 g β -glucan; oats low – OL) or 3) higher dose oat β -glucan (3·0 g β -glucan; oats high – OH). Total cholesterol reduced significantly in all groups 27·8 ± 13·8 %, 27·2 ±12·4 %, and 25·5 ±9·3 % in the OH, OL, and control groups, as did LDL-cholesterol 28·4 ± 18·5 %, 28·5 ± 18·5 % and 25·5 ± 12·4 % in the OH, OL and control groups, but between-group differences were not significant. The study results suggested that following a weight-maintaining diet by itself could result in significant total cholesterol and LDL-cholesterol reduction, the addition of 1.5 -3 g/day β -glucan oat foods could result in ~3% extra reduction for the cholesterol (2).

 

    A randomized, controlled, parallel study was conducted in people with mild to moderate hypercholesterolemia. The oat group (n=85) consumed 100 g of instant oat cereal, while the control group (n=81) consumed 100 g of wheat flour-based noodles daily for 6 weeks. Compared to those of the control group, total-cholesterol (-6.2% vs. -2.3%), LDL-cholesterol (-8.4% vs. -3.5%) and waist circumference (-1.27 cm vs. +0.85 cm) decreased significantly in the oat group (3).

 

    Free-living, overweight and obese adults (n=204, body mass index 25 to 45) with baseline LDL cholesterol levels 130 to 200 mg/dL (3.4 to 5.2 mmol/L) were randomized in a paralleled controlled study for 12 weeks (4). Two portions per day of whole-grain ready-to-eat oat cereal (3 g/day oat β-glucan) or energy-matched low-fiber foods (control), as part of a reduced energy ( approximately 500 kcal/day deficit) dietary program that encouraged limiting consumption of foods high in energy and fat, portion control, and regular physical activity.

 

    LDL-cholesterol level was reduced significantly more with whole-grain ready-to-eat oat cereal vs. control (-8.7±1.0 vs. -4.3±1.1%, P<0.05). Total cholesterol (-5.4±0.8 vs. -2.9±0.9%, P<0.05) and non-high-density lipoprotein-cholesterol (-6.3±1.0 vs. -3.3±1.1%, P<0.05) were also lowered significantly more with whole-grain ready-to-eat oat cereal, whereas high-density lipoprotein and triglyceride responses did not differ between groups. Weight loss was not different between groups (-2.2±0.3 vs. -1.7±0.3 kg, P=0.325), but waist circumference decreased more (-3.3±0.4 vs. -1.9±0.4 cm, P<0.05) with whole-grain ready-to-eat oat cereal. The more reductions in LDL-cholesterol, total cholesterol, and non-high-density lipoprotein cholesterol levels and waist circumference were evident as early as week 4 in the whole-grain ready-to-eat oat cereal group. This study showed that a whole-grain, ready-to-eat oat cereal containing viscous fiber, as part of a dietary program for weight loss, could lower LDL cholesterol levels and improve cardiovascular disease risk markers more than a dietary program alone (4).

 

    In a randomized crossover design, 27 volunteers with Type 2 diabetes (range from 46 to 71 years of age, 18 males, 9 females), managed on diet and lifestyle only, were studied for two consecutive 8-week periods following either the oats-enriched diet or re-enforced standard dietary advice. After testing at the start of the study, at which point they were following their habitual diet, the subjects then were asked to substitute part of the carbohydrate content at each meal with an oat-based product, to include 60–100 g/day of oats during the 8-weeks of the oat-enriched diet treatment period. The oat-enriched diet had a modest impact on lipid-lowering but did not impact on oxidative stress or inflammation in these study volunteers with diabetes. Total cholesterol (5.1±1.0 vs. 4.9±0.8 mmol/L, P<0.05) levels declined following the oat-enriched diet compared with that of re-enforced standard dietary advice (5).

 

    A total of 260 Type 2 diabetic patients between 50 and 65 years of age participated in a single-blinded, 30-day centralized management of a dietary program in China. Participants in the program were randomly assigned into one of the four study groups: usual care group (control group, only basic health advice), diet group (systematic diet plans and intensive education), 50 g organic naked oat with whole germ group (ONOG) and 100 g-organic naked oats with whole germ group (daily ONOG replacement boiled into porridge based on diet group) (6).

 

    Compared with the usual care control group, diet group and 50–100 g/day ONOG additional supplements to structured dietary intervention significantly reduced HbA1c, plasma glucose, and total cholesterol with a dose-effect. The 100 g-ONOG group showed significant reductions in all the study parameters (P <0.05 for all) compared to those of the usual care control group, including HbA1c (-2.22 vs. -0.22%), fasting plasma glucose (-1.91 vs. -0.22 mmol/L), insulin resistance (-0.33 vs. -0.11 mU mol/L2 ), total cholesterol (-0.59 vs. -0.01 mmol/L), LDL-cholesterol (-0.31 vs. 0.02 mmol/L), triglyceride (-0.53 vs. -0.08 mmol/L), weight (-1.17 vs. -0.37 kg), and waist circumference (-2.68 vs. -1.22 cm), respectively. The nutrient composition of 100 g ONOG was 1623 kJ energy, 13.7 g protein, 63.5 g carbohydrates, 7.6 g fat, 8.7 g fiber, of which 5.0 g was b-glucan (6).

 

    A double-blind, randomized, crossover study was conducted in 24 young healthy adults (age 25.2±2.7 years; body mass index: 24.9±2.9 kg/m2), who completed two 2-week dietary intervention periods: low-fiber diet (control) and an oat bran (control +102 g oat bran/day) diet. Total cholesterol decreased by 14% during the oat bran period compared with 4% during the control period (P<0.001). Non-high-density lipoprotein (HDL) cholesterol decreased by 16% in the oat bran period compared with 3% in the control period (P<0.01), as did total triglyceride (21 vs. 10%, P<0.05). Fecal volume and dry matter were greater when consuming the oat bran diet compared with the control (P<0.001), and energy excretion was increased by 37% (1014 vs 638 kJ/day, P<0.001); however, changes in body weight did not differ (oat bran:-0.3±0.5 kg; control: 0.0±0.7 kg). The addition of oat bran (6 g soluble fiber/day) to a low-fiber diet lowered total and non-HDL cholesterol (7).

 

    The effects of 3 different β-glucan sources, incorporated into a beverage and yogurt, on blood lipids and fecal endpoints were investigated in 14 young healthy subjects in a randomized, crossover, single-blinded study with four 3-week periods: control and 3.3 g/day oats, barley, and barley mutant β-glucans of similar molecular mass. Treatment did not affect changes in total, LDL, and HDL cholesterol compared with control; however, consumption of 3.3 g/d of oat β-glucans for 3 weeks resulted in greater decreases in total cholesterol (-0.29 ± 0.09 mmol/L, P < 0.01), LDL-cholesterol (-0.23 ± 0.07 mmol/L, P < 0.01), and HDL-cholesterol (-0.05 ± 0.03 mmol/L, P < 0.05) cholesterol compared with baseline. Decreases in fasting triglyceride were substantially greater after oat β-glucan treatment compared with control (P <0.05). Fecal dry and wet weight, stool frequency, fecal pH, and energy excretion were unaffected. The differences compared with baseline underlined the importance of elusive structural β-glucan features from oats for beneficial physiologic effects presumably due to its higher solubility and viscosity (8).

 

    Elevated cholesterol level is a risk factor for cardiovascular diseases. Studies have shown that hypercholesterolemia can be modifiable by altering lifestyle through a balanced diet with high dietary fibers. Consumption of cereals like oats, which are rich in fibers could considerably lower the lipid/cholesterol levels which have been shown in people with hypercholesterolemia, people with diabetes, and even in healthy young people, that they can reduce the risk of cardiovascular diseases. The major contributor to the lipid-lowering activity of oat is β -glucan, which is a viscous soluble fiber that aids in lipid excretion owing to its structural and fermentable property. US Food and Drug Administration (FDA) has recommended a dose of 3 g/day (β -glucan) is sufficient to elite its biological properties. The estimate is that every 1% reduction in total cholesterol may result in a 2% reduction in cardiovascular disease risk (1). Yes, oats can lower cholesterol and is good for your heart.

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References:

1. Liao, M.-Y., Shen, Y.-C., Chiu, H.-F., Ten, S.-M., Lu, Y.-Y., Han, Y.-C., Venkatakrishnan, K., Yang, S.-F., Wang, C.-K. (2018). Down-regulation of partial substitution for staple food by oat noodles on blood lipid levels: A randomized, double-blind, clinical trial. Journal of Food and Drug Analysis. doi:10.1016/j.jfda.2018.04.001

2. Charlton, K. E., Tapsell, L. C., Batterham, M. J., O'Shea, J., Thorne, R., Beck, E., & Tosh, S. M. (2011). Effect of 6 weeks' consumption of β-glucan-rich oat products on cholesterol levels in mildly hypercholesterolaemic overweight adults. British Journal of Nutrition, 107(07), 1037–1047.

3. Zhang, J., Li, L., Song, P., Wang, C., Man, Q., Meng, L., Cai, J., Kurilich, A. (2012). Randomized controlled trial of oatmeal consumption versus noodle consumption on blood lipids of urban Chinese adults with hypercholesterolemia. Nutrition Journal, 11(1). doi:10.1186/1475-2891-11-54

4. Maki, K. C., Beiseigel, J. M., Jonnalagadda, S. S., Gugger, C. K., Reeves, M. S., Farmer, M. V., Kaden, V. N., Rains, T. M. (2010). Whole-Grain Ready-to-Eat Oat Cereal, as Part of a Dietary Program for Weight Loss, Reduces Low-Density Lipoprotein Cholesterol in Adults with Overweight and Obesity More than a Dietary Program Including Low-Fiber Control Foods. Journal of the American Dietetic Association, 110(2), 205–214.

5. McGeoch, S. C., Johnstone, A. M., Lobley, G. E., Adamson, J., Hickson, K., Holtrop, G., Fyfe, C., Clark, L. F., Pearson, D. W. M., Abraham, P., Megson, I. L., MacRury, S. M. (2013). A randomized crossover study to assess the effect of an oat-rich diet on glycaemic control, plasma lipids and postprandial glycaemia, inflammation and oxidative stress in Type 2 diabetes. Diabetic Medicine, 30(11), 1314–1323.

6. Ma, X., Gu, J., Zhang, Z., Jing, L., Xu, M., Dai, X., Jiang, Y., Bao, L., Cai, X., Ding, Y., Wang, J., Li, Y. (2013). Effects of Avena nuda L. on metabolic control and cardiovascular disease risk among Chinese patients with diabetes and meeting metabolic syndrome criteria: secondary analysis of a randomized clinical trial. European Journal of Clinical Nutrition, 67(12), 1291–1297.

7. Kristensen, M., & Bügel, S. (2011). A diet rich in oat bran improves blood lipids and hemostatic factors and reduces apparent energy digestibility in young healthy volunteers. European Journal of Clinical Nutrition, 65(9), 1053–1058.

8. Ibrügger, S., Kristensen, M., Poulsen, M. W., Mikkelsen, M. S., Ejsing, J., Jespersen, B. M., Dragsted, L. O., Engelsen, S. B., Bügel, S. (2013). Extracted Oat and Barley β-Glucans Do Not Affect Cholesterol Metabolism in Young Healthy Adults. The Journal of Nutrition, 143(10), 1579–1585.