Page 18 - Nutrinsight-2

NutrInsight • Whole grain and health: new evidence
2.8 Large scale intervention studies to study changes in risk factors for heart health
While the observational evidence described above is a powerful indicator of the inverse correlation between whole grain intake and CVD risk, this evidence does not demonstrate causality. Evidence from controlled dietary intervention studies with large numbers of subjects showing clear benefit of increased consumption of whole grain foods on markers of disease risk is needed. However, two such recent studies have produced conflicting results.
The WHOLEheart study [Brownlee et al., 2010] involved a total of 316 participants (aged 18–65 years; BMI = 25 kg/m2) consuming 30 g WG/d who were randomly assigned to three groups: control (no dietary change), intervention 1 (60 g WG/d for 16 weeks), and intervention 2 (60 g WG/d for 8 weeks followed by 120 g WG/d for 8 weeks). Markers of CVD risk, measured at 0 (baseline), 8, and 16 weeks, were BMI, percentage body fat, waist circumference; fasting plasma lipid profile, glucose and insulin; and indicators of inflammatory, coagulation, and endothelial function. Results showed that consuming whole grains had no effect on:
• Insulin sensitivity,
• Fasting lipid profile,
• Endothelial functions,
• Anthropometric measures (no weight gain despite WG group consuming more energy during the intervention).
Explanations for the lack of effect could be that a period of 4 months may be insufficient to change the lifelong disease trajectory associated with CVD or that compliance in the high whole grain groups had not been good enough to show an effect. Any beneficial effects may also have been masked by the higher food consumption in the high whole grain consumers.
The GrainMark study [Seal et al., unpublished] was another intervention study over 4 weeks comparing 0, 3, and 6 servings of whole grain rye vs. whole grain wheat. In this study better compliance than WHOLEheart was achieved, possibly by telling subjects that the investigators were measuring markers of whole grain intake. In this study a significant dose response reduction in LDL cholesterol was seen with both types of whole grain.
• The strongest relationships between whole grain intake and disease risk have been found for cardiovascular diseases.
• Strongrelationshipshavebeenfoundfortype2diabetes,symptomsofthemetabolic syndrome, and several cancer types, particularly those of the gastrointestinal tract.
• Whole grain intakes are associated with improved gastrointestinal health in general.
• Possible active components are increased intake of soluble and insoluble fibre, resistant starch and prebiotic components, bio-active compounds associated with the bran and germ fractions such as plant lignans, phyto-oestrogens, phytates and phenolics.
• Possible mechanisms include lowered inflammatory status, improved insulin response, and maybe improved vascular function.
• Further research will strengthen the evidence base to develop health promotion strategies, so that whole grain intake is increased across all population groups.
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Key Points