Each of the macronutrients, carbohydrate, protein and fat, has a unique set of properties that influence health, but all are a source of energy. The optimal balance of their contribution to the diet has been a long-standing matter of debate. Over the past half century, there has been a progression of thinking regarding the mechanisms by which each may contribute to energy balance. At the beginning of this time period, the emphasis was on metabolic signals that initiated eating events (i.e., determined eating frequency). This was followed by an orientation to gut endocrine signals that purportedly modulate the size of eating events (i.e., determined portion size). Most recently, research attention has been directed to the brain where the reward signals elicited by the macronutrients are viewed as potentially problematic (i.e., contribute to disordered eating). At this point the predictive power of the macronutrients for energy intake remains limited.

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The racial and ethnic disparities in diet-related chronic diseases are major concerns. This systematic review examines the extent to which diet-induced changes in health outcomes such as cardiometabolic, inflammation, cancer, bone health, kidney function outcomes etc., have been reported and discussed by race or ethnicity in randomized trials with 2 or more diet arms that recruited both minority and non-Hispanic White groups. Databases i.e., PubMed, Cochrane library and Web of Science were searched up to August 2021. Thirty-four studies that discussed effects of defined dietary interventions on health outcomes by racial or ethnic minority group vs. non-Hispanic Whites were included in the systematic review (PROSPERO registration number: CRD42021229256). Acute trials and those with one diet arm that accounted for race or ethnicity in their analyses, and studies that focused on a single racial or ethnic group were discussed separately. Most studies were conducted in Black vs. White adults testing effects of energy restriction, macronutrient modification, sodium reduction, or variations of the Dietary Approaches to Stop Hypertension (DASH) diet on cardiometabolic outcomes. There was limited focus on other minority groups. Evidence suggests greater blood pressure reduction for Black adults compared to Whites particularly on DASH (or similar) diets. Overall, there was limited consideration for group-specific eating patterns and diet acceptability. Overall risk of bias was low. With emerging precision nutrition initiatives that aim to optimize metabolic responses in population subgroups through tailored approaches, it is imperative to ensure adequate representation of racial and ethnic subgroups for addressing health disparities. Factors that help explain variability in responses such as socioecological context should be included and adequately powered. Given the racial and ethnic disparities in chronic diseases, studying the adoption, maintenance, and effectiveness of dietary interventions on health outcomes among different groups is critical for developing approaches that can mitigate diet-related health disparities.

There is a disproportionate increase in the incidence of diet-related cardiometabolic disorders in racial and ethnic minority groups. This systematic review examines the extent to which diet-induced changes in health outcomes have been discussed by race or ethnicity in randomized controlled trials recruiting both minority and non-Hispanic White groups. Databases i.e. PubMed, Cochrane library and Web of Science were searched up to November 2019. Studies that discussed effects of defined dietary interventions on health outcomes by racial or ethnic minority group vs. non-Hispanic Whites (n=29) were included in the review. Most studies were conducted in Black vs. White people testing effects of energy restriction, macronutrient modification, sodium reduction, or variations of the Dietary Approaches to Stop Hypertension (DASH) diet on cardiometabolic outcomes. There was limited focus on other minority groups. Evidence suggests greater blood pressure reduction for Black people compared to Whites particularly on DASH (or similar) diets. Overall, there was limited consideration for group-specific eating patterns and diet acceptability in most studies. Adequately powered studies are needed for accurate interpretation of race by diet effects. With emerging precision nutrition initiatives, it is imperative to ensure adequate representation of racial and ethnic subgroups for addressing nutrition-related health disparities.

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