摘要
Intake of wholegrain foods has been associated in large prospective cohort studies with decreased rates of diseases such as type 2 diabetes, ischaemic heart disease and hypertension. Multiple mechanisms for the protectiveness of wholegrain foods have been reported. Health authorities in western countries recommend wholegrains as one of the major food sources in a healthy diet, otherwise rich in vegetables, legumes and low-fat dairy. However, the existing evidence for the intake of wholegrains is highly subject to confounding. Many of the results seen in the prospective cohort studies have not been borne out in randomised controlled trials or good-quality meta-analyses. The recommended intake of wholegrains suggested in some countries is well above what there is evidence for. Products labelled wholegrain have variable quantities of the intact grain and differ widely in their effect on blood glucose. Excessive quantities may add to glycaemic load, and anti-nutrients in wholegrains may have adverse health consequences. With the rate of diabetes and obesity increasing, some researchers have questioned the role of grains as part of a healthy diet. Palaeolithic diets, those that are more in keeping with our evolutionary legacy, contain no grains or dairy, but are rich in vegetables, meat, fish and eggs, with the inclusion of some tubers. Smaller trials in animals and humans comparing a palaeolithic diet to a grain-based diet show improved metabolic profiles in the former.
Intake of wholegrain foods has been associated in large prospective cohort studies with decreased rates of diseases such as type 2 diabetes, ischaemic heart disease and hypertension. Multiple mechanisms for the protectiveness of wholegrain foods have been reported. Health authorities in western countries recommend wholegrains as one of the major food sources in a healthy diet, otherwise rich in vegetables, legumes and low-fat dairy. However, the existing evidence for the intake of wholegrains is highly subject to confounding. Many of the results seen in the prospective cohort studies have not been borne out in randomised controlled trials or good-quality meta-analyses. The recommended intake of wholegrains suggested in some countries is well above what there is evidence for. Products labelled wholegrain have variable quantities of the intact grain and differ widely in their effect on blood glucose. Excessive quantities may add to glycaemic load, and anti-nutrients in wholegrains may have adverse health consequences. With the rate of diabetes and obesity increasing, some researchers have questioned the role of grains as part of a healthy diet. Palaeolithic diets, those that are more in keeping with our evolutionary legacy, contain no grains or dairy, but are rich in vegetables, meat, fish and eggs, with the inclusion of some tubers. Smaller trials in animals and humans comparing a palaeolithic diet to a grain-based diet show improved metabolic profiles in the former.
