Location: Obesity and Metabolism ResearchTitle: Impact of an 8-week controlled feeding trial based on the Dietary Guidelines for Americans on cardiometabolic health indices
|KRISHNAN, SRIDEVI - UNIVERSITY OF CALIFORNIA, DAVIS|
|ADAMS, SEAN - ARKANSAS CHILDREN'S NUTRITION RESEARCH CENTER (ACNC)|
|BURNETT, DUSTIN - UNIVERSITY OF CALIFORNIA, DAVIS|
|WITBRACHT, MEGAN - UNIVERSITY OF CALIFORNIA, DAVIS|
|WELCH, LUCAS - UNIVERSITY OF CALIFORNIA, DAVIS|
|QUE, EXCEL - UNIVERSITY OF CALIFORNIA, DAVIS|
Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2018
Publication Date: 8/7/2018
Citation: Krishnan, S., Adams, S.H., Allen, L.H., Laugero, K.D., Newman, J.W., Stephensen, C.B., Burnett, D.J., Witbracht, M.G., Welch, L.C., Que, E.S., Keim, N.L. 2018. Impact of an 8-week controlled feeding trial based on the Dietary Guidelines for Americans on cardiometabolic health indices. American Journal of Clinical Nutrition. 108(2):266-278. https://doi.org/10.1093/ajcn/nqy113.
Interpretive Summary: The Dietary Guidelines for Americans (DGA) outlines food and nutrition recommendations for the general public and is considered an authoritative source that serves as the basis for nutritional policy in the U.S. However, the recommendations set forth in the Guidelines are largely based on studies of individual foods or nutrients tested in isolation, or on population studies that lack clarity and accuracy of actual food intake. In fact, the food and nutrient recommendations of the DGA, as a complete diet pattern, have not been tested in a controlled, intervention trial. We evaluated the impact of a DGA-based diet compared with a representative typical American diet (TAD) on measures of blood glucose control in women who were generally healthy but had increased risk of developing chronic disease related to diabetes or cardiovascular disease. After consuming the controlled diets for 8 weeks, we observed no improvement in measures of blood glucose control, but total cholesterol and HDL-cholesterol decreased in both groups. By design, study volunteers maintained weight during the study. Therefore, in the absence of weight loss, consuming either a DGA or TAD diet pattern for 8 weeks did result in the anticipated improvement in blood glucose control.
Technical Abstract: Background: The 2010 Dietary Guidelines for Americans (DGA) recommended that nutrient needs be met by increasing fruit, vegetable, and whole grain intake, using low or fat-free dairy products, and reducing sodium, solid fats, and added sugars. However, the DGA, as a diet pattern, has not been tested in an intervention trial. Objective: To evaluate the impact of a DGA-based diet compared with a representative typical American diet (TAD) on measures of glucose homeostasis in individuals at risk for cardiometabolic disease. Design: A randomized double-blind controlled eight-week intervention was conducted in overweight or obese women selected on indices of insulin resistance and/or dyslipidemia. Women were randomly assigned to the DGA or TAD group (n = 22/group). The TAD diet was based on average adult intake from the National Health and Nutrition Examination Survey (NHANES) 2009 - 2010. The DGA and TAD diets had respective Healthy Eating Scores of 98 and 62. All foods and beverages were provided during the intervention. Oral glucose tolerance and fasting lipids were evaluated at 0, 2 and 8 weeks of intervention. Insulin resistance/sensitivity was estimated using clinical surrogates (e.g. HOMA-IR). Results: By design, study volunteers maintained weight during the intervention. No changes were observed in fasting insulin, glucose, oral glucose tolerance tests, or indices of insulin resistance between weeks 0, 2, and 8. Total cholesterol and HDL-c decreased in both groups (p<0.05). Exploratory analysis comparing volunteers entering the study with insulin resistance and dyslipidemia, versus only dyslipidemia, did not reveal an effect of pre-existing condition on glucose tolerance or fasting lipid outcomes. Conclusions: In the absence of weight loss, consuming either a DGA or TAD diet pattern for 8 weeks did not reduce fasting insulin, glucose, or indices of insulin resistance. Total and HDL cholesterol were reduced in response to both diet pattern interventions.