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Exploring the effect of oats on risk factors for heart disease

This meta-analysis examined the effect of oats on cardiovascular disease risk factors in 3 contexts: adding oats to the usual diet, adding oats to a restricted diet, and comparing oats with another food. In all contexts oats reduced total and LDL (“bad”) cholesterol, with additional benefits seen depending on the context.

Background

Some evidence suggests eating oats may improve biomarkers related to the risk of cardiovascular disease (CVD), including lowering low-density lipoprotein (LDL) cholesterol and improving blood sugar control, possibly due to oats’ fiber content. However, it was not clear if the context in which oats are consumed influences their effect.

The study

This systematic review and meta-analysis of 74 randomized controlled trials examined the effect of oats on CVD risk factors. The trials included 4,937 people and ranged from 2 to 26 weeks (median length of 8 weeks). Of the trials, 56 were conducted on people with a metabolic health disorder (e.g., high cholesterol, type 2 diabetes, high blood pressure), and 18 were conducted on healthy people. The forms of oats used were primarily oat bran, oatmeal, oat porridge, and oat beta-glucan–containing products.

The outcomes assessed were serum lipids, body composition, blood sugar control, inflammation markers, oxidative stress markers, and blood pressure. Meta-analyses looked at the effects of oats on these outcomes in 3 contexts: oats compared with no oats when the diet was otherwise unchanged (12 trials); oats compared with no oats in the context of dietary restriction (e.g., calorie restriction, fat restriction; 12 trials); and oats compared with another food (e.g., rice, wheat, eggs, non-oat fiber; 35 trials). Meta-analyses were not possible for inflammation and oxidative stress markers, so the effect of oats on these outcomes in available trials was summarized.

The results

When added to the usual diet, oats reduced body mass index (BMI), body weight, waist circumference, total cholesterol, LDL, and fasting blood sugar.

In the context of dietary restriction, oats reduced BMI, total cholesterol, LDL, high-density lipoprotein (HDL) cholesterol, hemoglobin A1c (HbA1c; the average blood sugar over the past 3 months), and diastolic blood pressure.

When compared with another food, oats reduced total cholesterol, LDL, triglycerides, and apolipoprotein B, which helps carry fat and cholesterol through the body and is important in the development of heart disease.

In 1 trial oats decreased inflammatory markers but had no effect on those markers in 3 trials. One trial supplementing with compounds found in oats (avenanthramides) had mixed effects on markers of oxidative stress.

In risk of bias assessment, 60 trials had a moderate risk of bias, 10 had a high risk of bias, and 4 had a low risk of bias.

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