Submitted to: Journal of Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/14/2010
Publication Date: 11/1/2011
Citation: Mckeown, N., Troy, L.M., Jacques, P.F., Hoffman, U., O'Donnell, C.J., Fox, C. 2011. Whole- and refined-grain intakes are differentially associated with abdominal visceral and subcutaneous adiposity in healthy adults: The Framingham Heart Study. Journal of Nutrition. 141:1011S-1022S. Interpretive Summary: The prevalence of obesity continues to increase as one in three people in the United States are currently classified as obese. However, the extent of obesity alone may not determine the metabolic consequences of excess body fat. Location of the fat deposits appears to be critical to its health effects. Body fat stored in the abdominal cavity, referred to as visceral adipose tissue (VAT), is more strongly associated with risk of developing health problems such as coronary heart disease, diabetes and stroke than fat located underneath the skin, subcutaneous adipose tissue (SAT). Waist circumference is a common method of estimating abdominal adiposity, but it is a composite of both the SAT and VAT compartments. Therefore, more direct measures of VAT and SAT using computed tomography (CT) imaging provide better estimates of regional fat deposits and are better for estimating risks associated with abdominal adiposity. Many lifestyle behaviors may impact total body fat and its distribution. One important dietary factor associated with body fat is consumption of whole-grain foods. Observational studies have found that people who eat more whole-grain foods have lower body mass index (a measure of total body fat) and waist circumference measures if they consume 3 or more servings of whole-grains per day. Few observational studies however have examined the relationship between whole- and refined- grain intakes to adipose tissue compartments. In this study, we used the gold standard, multidetector computed tomography, to measure VAT and SAT in a large sample of healthy adults. We found that people who ate more whole grain foods had a lower VAT and SAT compared to those people who ate less whole grain foods. In contrast, people who ate more refined grains had higher VAT and SAT compared to people who ate fewer refined grains. When both VAT and SAT were considered together in the statistical modes, VAT remained strongly associated with whole-grain intake, but SAT did not. Thus, the potential health benefits observed with higher intakes of whole-grains on cardiometabolic risk factors observed in other studies may be due, in part, to lower volumes of VAT.
Technical Abstract: Different aspects of diet may be differentially related to body fat distribution. The purpose of this study was to assess associations between whole- and refined- grain intake and abdominal subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT). We examined the cross-sectional associations between whole- and refined- grain intakes waist circumference and abdominal SAT and VAT volumes were examined in 2,834 Framingham Heart Study participants (49.4% women; age range 32-83 y). Dietary information was assessed using a semi-quantitative food frequency questionnaire. Whole-grain intake was inversely associated with SAT (2882 cm**3 vs. 2509 cm**3 in the lowest compared to highest quintile category, P- trend <0.001) and VAT (1882 cm**3 vs. 1538 cm**3 , P- trend <0.001), after adjustment for age, sex, smoking status, total energy and alcohol intake. In contrast, refined-grain intake was positively associated with SAT (2768 cm**3 vs. 2978 cm**3, P-trend=0.004) and VAT (1722 cm**3 vs. 1937 cm**3, P-trend<0.001) in multivariable models. When SAT and VAT were evaluated jointly, the p-value for SAT was attenuated (p=0.12 for whole-grains and p=0.81 for refined grains), whereas VAT remained associated with both whole-grains (p<0.001) and refined-grains (p =0.001. In conclusion, higher intake of whole-grains is differentially associated with SAT as compared to VAT. Further research is required to elicit the potential mechanisms whereby whole-grain foods influence body fat distribution and associated cardiometabolic risk.