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Whole grain and health: new evidence • NutrInsight
2 WHATEvIDENCEDOWEHAvEFORRELATIONSHIPS BETWEEN WHOLE GRAIN INTAKE AND CHRONIC DISEASE?
There is general agreement that whole grains are good for you, but what do we mean by this? Good for what? How do we know? How do they do this? To try to answer these questions, Professor Chris Seal (Professor of Food & Human Nutrition, Newcastle University, UK) gave an overview of the literature on whole grains and health.
2.1 Types of evidence for whole grain and health
Hierarchy of evidence
Scientists and policy makers tend to judge the evidence according to a hierarchy of evidence. In this, consensus reports from authoritative bodies and intervention trial evidence rate highest, “observational comparison” studies come next and animal studies and other in vitro studies are lowest (although these are very important for establishing mechanisms).
Whole grain and health
The fact that whole grains have been eaten in traditional diets since before the industrial revolution is an important testament to their safety, but this does not feature on this hierarchy of evidence. Most of the scientific evidence for the benefits of whole grain comes from “observational” studies which have associated its consumption in different population groups with reduced disease risk or death from the disease. However, the obvious question follows: does this positive association only exist because whole grain consumers have healthier lifestyles? (lifestyles which relate not only to types of diet, but to drinking and smoking habits and to levels of physical activity).
Currently, there is much less supporting evidence for whole grains from intervention studies and the results are more variable. Nevertheless, the overall benefits of whole grains are difficult to argue against and several authoritative bodies have recognized a beneficial effect of whole grain consumption.
Hierarchy of evidence for whole grains and health
• Consensus reports from National and International Expert panels and authoritative statements: yes, for CVD (and cancer).
• Human intervention studies: mixed outcome, expanding.
• Observation/Ecological studies: extensive, mostly convincing.
• Animal and in vitro studies: some, mechanistic value.
• Evidence of traditional and experience of use: yes.
Examples of authorised statements about whole grain
“Diets rich in whole grain foods and other plant foods and low in total fat, saturated fat and cholesterol may reduce the risk of heart disease and some cancers.”
“People with a healthy heart tend to eat more whole grain foods as part of a healthy lifestyle.”
“A healthy lifestyle and a well balanced diet rich in whole grain products reduces the risk for (coronary) heart disease. The product X is rich in whole grains (contains Y% of wholegrain).”
(Food and Drug Administration, 1999)
(Joint Health Claims Initiative, 2002)
(Swedish Nutrition Foundation, 2004)
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