Oats Cut Cholesterol, But Evidence for Whole Grains Lags

April 24, 2007

MIDDLESBROUGH, England -- Whole-grain oats can carry the lipid-lowering banner higher than other whole grains -- but not too high.

MIDDLESBROUGH, England, April 24 -- Whole-grain oats can carry the lipid-lowering banner higher than other whole grains -- but not too high.

So found a Cochrane review by Sarah Kelly, Ph.D., of the University of Teesside here, and colleagues. They reported that observational studies have made the case for the beneficial effects of whole grains against coronary heart disease risk factors, but clinical trials have lagged behind.

The trials have provided evidence for LDL reduction only by whole-grain oats, and even then only in the short term, the Cochrane group found in a meta-analysis.

Whole-grain oats significantly lowered total (-0.20 mmol/L, P=0.0001) and low-density lipoprotein cholesterol (-0.18 mmol/L, P

In 2003 the Atherosclerosis Risk in Communities (ARIC) study showed whole grain consumption reduced risk of overall mortality and coronary artery disease incidence. And in 2002, the Framingham Offspring Study found diets rich in whole grains inversely associated with total cholesterol, LDL cholesterol and body mass index.

Dr. Kelly and colleagues undertook their meta-analysis to evaluate evidence from randomized controlled trials assessing the effects of whole-grain foods or diets containing whole grains on total mortality from coronary heart disease, coronary events or morbidity, and risk factors.

Among the 10 trials meeting their criteria, however, none looked at mortality, coronary heart disease events, or morbidity. All 914 adult participants had existing heart disease or at least one major risk factor for it, typically high cholesterol.

Eight studies looked at whole-grain oats, of which three used Cheerios cereal as the oat product, compared with a refined grain food. One examined a diet containing a variety of whole-grain foods and snacks. Another looked at whole-grain rye bread as part of the usual diet.

All the studies had similar carbohydrate, fat, protein, and energy intake between intervention and control groups without aiming for weight loss. Study durations ranged from four to eight weeks.

All 10 studies had some methodological weaknesses earning them low marks in quality and "a high risk of bias." Most of the studies were at least partly funded by commercial sources, primarily the Quaker Oats Company or General Mills.

Among the end-of-study results the researchers reported (weighted mean difference between intervention and control):

  • Total cholesterol was reduced in the whole-grain oat groups (-0.19 mmol/L, 95% CI -0.30 to -0.08, P=0.0005) and when combined with the rye study results, which added little to the effect (-0.20, 95% CI -0.31 to -0.10, P=0.0001).
  • LDL cholesterol fell with diets containing oatmeal (-0.18 mmol/L, 95% CI -0.28 to -0.09, P