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The plethora of different ways of reporting whole grains in clinical trials has led to great difficulty in directly comparing different studies. This, in turn, hampers meta‐analyses pooling data from different studies to increase the statistical power for finding differences due to dietary interventions that include whole grains. Reports of whole grain intake may be as basic as people who report “eating more brown bread” through to a detailed breakdown of the gram amounts of different cereal types in the diet.

As scientists working in the field struggle to reconcile the consistent and strong evidence that whole grains reduce disease risk with the mixed intervention‐study evidence, it is clear that few studies offer both a clear idea of exactly which specific grains people were eating and in what amount, and whether the subjects were actually eating what they reported. One study using dietary biomarkers found major discrepancies between what people reported eating in an intervention study and what they plausibly ate based on an unbiased biomarker measurement of intake,⁽²⁷⁾ which raises questions about other studies where compliance was not rigorously cross‐checked. Another large study found that although average biomarker concentrations increased, individual variation suggested that a large proportion of subjects were likely not compliant, in spite of major efforts to ensure compliance using suitably packaged food and questionnaires.⁽²⁸⁾ In essence, the entire field has a cloud of uncertainty over it due to the fact that there are several different ways that intake of whole grains is reported, and we cannot confirm whether study volunteers are actually eating the products they are supposed to. Of some comfort is the observation that generally those studies where overall compliance has been judged to have been good based on biomarker measurements, have also been those where effects on risk markers have been observed.^{(29,30, 31,32)}

These issues led to recommendations for reporting whole grain intake in both intervention and population‐based studies.⁽³³⁾ The proposed guidelines for reporting whole grains in foods and whole grain intake are as follows:

 Report whole grain intake as grams of whole grain ingredients rather than absolute amounts of a particular food or poorly defined measures such as servings.

 Note which definition is being used to define whole grain ingredients – for example, the AACCI or HealthGrain definition.

 State the proportion of different cereal grains that have been provided or are consumed so that it is possible to separate effects of, for example, whole grain wheat or oats.

 For intervention studies, describe the type of processing the intervention foods have undergone, including the structure of the flour (e.g., fine or coarse flour).

 If bran or germ are of interest, clearly state what is added bran or germ versus bran and germ coming from whole grain flour.

 Use an appropriate control group in intervention studies, such as an equivalent amount of similar foods based on refined flour. Avoid situations that may lead to the “addition” of intervention foods, rather than replacement of normal foods with intervention foods.

 If possible, use a biomarker of whole grain intake to improve estimates of compliance or intake.

These recommendations aim to standardize reporting of whole grain intake and also allow greater nuances to be applied to our understanding of the effects of whole grains on health – in particular, around the different types of cereals and cereal processing. The requirement to report on food processing also increases the requirement for scientists running such trials to have some knowledge about food processing, or to include food scientists when designing and preparing for such studies.