Many people are skeptical about incorporating nuts and seeds into their diet because of high calorie content. However, these foods come with some health benefits, and the new Dietary Guidelines for Americans encourage the inclusion of these foods in the diet (1). Research is currently underway to investigate just what these health effects are, and if these effects are noteworthy enough to recommend nuts and seeds in lifestyle counseling to alleviate metabolic syndrome symptoms.
Metabolic syndrome is classified as a group of risk factors, including central obesity, dyslipidemia, elevated blood pressure, and hyperglycemia, which increase risk for heart disease and type II diabetes. Metabolic syndrome has become a major threat in China, so lifestyle and diet modification strategies need to be established to help control this epidemic.
Hongyu Wu et al. conducted a 3-arm, randomized, controlled study among 283 participants (158 men and 125 women) diagnosed with metabolic syndrome to investigate the effects of including flaxseeds and walnuts in peoples’ diets (2). In addition to supplementation, subjects attended healthy lifestyle counseling (LC) on the management of metabolic syndrome for men and women living in China. Individuals were included if they met at least 3 of the following criteria: 1) waist circumference ≥ 90 cm for men or ≥ 80 cm for women 2) triglycerides ≥ 1.7 mmol/L 3) HDL cholesterol < 1.03 mmol/L for men or < 1.30 mmol/L for women 4) blood pressure ≥ 130/85 mmHg 5) fasting glucose ≥ 5.6 mmol/L; and 6) LDL cholesterol ≥ 3.4 mmol/L. All three groups received lifestyle counseling based on the American Heart Association guidelines. In addition to counseling, the flaxseed (LCF) and walnut (LCW) groups were given bread containing 30g/day of flaxseeds or walnuts, respectively, to replace staple foods in the diet, such as rice or bread. Flaxseeds and walnuts were chosen because these are high in omega-3 polyunsaturated fats and fiber. The lifestyle counseling urged participants to consume a low-fat diet, limit intake of red or processed meat, decrease salt intake, increase consumption fruit and vegetables, quit smoking, and limit alcohol. At the end of the 12-week intervention, total energy intakes decreased from baseline (P < 0.02 for within-group differences). Participants in all 3 groups consumed more protein and fat, while carbohydrate intake decreased. The LCF and LCW groups consumed more polyunsaturated fats and fiber compared to the LC group. The percentage of people classified as having metabolic syndrome decreased in all 3 groups from baseline (P < 0.005 with a decrease of 16.9 percent in the LC group, 20.2 percent in the LCF group, and 16.0 percent in the LCW group). Central obesity decreased more in the LCF and LCW groups compared to the LC group. Serum glucose was also lower in the LCF group. Although flaxseed and walnuts contain a significant amount of calories, all three groups lost weight.
These results show a low-intensity LC program can help alleviate the prevalence of metabolic syndrome among the Chinese population. Further, supplementing with flaxseed and/or walnuts can help reverse some characteristics of metabolic syndrome even more, especially central obesity. This is especially important in the Asian population because this is a population that is more likely to have metabolic syndrome compared to Caucasians, even under normal weight conditions (3,4). There is speculation that the presence of the polyunsaturated fats in flaxseed and walnuts may help regulate body fat deposition and reduce the accumulation of fat around the abdomen. Although supplementing with flaxseed and walnuts did not improve blood lipid ratios, these foods helped reduce central obesity, an important risk factor for metabolic syndrome and other diseases. Nutrition education is an important tool for preventative medicine, and should be taken full advantage of with programs that include lifestyle counseling.
References:
U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2010. 7th Edition, Washington, DC: U.S. Government Printing Office, December 2010.
Wu H, Pan A, Yu Z, et al. Lifestyle Counseling and Supplementation with Flaxseed or Walnuts Influence the Management of Metabolic Syndrome. J Nutr; 2010; 140(11): 1937-1942.
Lutsey PL, Steffen LM, Stevens J. Dietary intake and the development of the metabolic syndrome: The Atherosclerosis Risk in Communities Study. Circulation; 2008; 117(6): 754–61.
Chan JCN, Malik V, Jia W, et al. Diabetes in Asia: epidemiology, risk factors, andpathophysiology. J Am Med Assoc; 2009; 301(20): 2129–40.
Deborah Fetter, Department of Nutrition, University of California, Davis.