Four Studies Representative of Frank Hu’s Work from Harvard’s Nurses Studies Showing a Protective Dietary Model for Heart Disease and Obesity

By Joel Fuhrman, M.D.

Hu FB. Plant-based foods and prevention of cardiovascular disease: an overview. Am J Clin Nutr 2003 Sep;78(3 Suppl):544S-551S.

Evidence from prospective cohort studies indicates that a high consumption of plant-based foods such as fruit and vegetables, nuts, and whole grains is associated with a significantly lower risk of coronary artery disease and stroke. The protective effects of these foods are probably mediated through multiple beneficial nutrients contained in these foods, including mono- and polyunsaturated fatty acids, n-3 fatty acids, antioxidant vitamins, minerals, phytochemicals, fiber, and plant protein. In dietary practice, healthy plant-based diets do not necessarily have to be low in fat. Instead, these diets should include unsaturated fats as the predominant form of dietary fat (e.g., fats from natural liquid vegetable oils and nuts), whole grains as the main form of carbohydrate, an abundance of fruit and vegetables, and adequate n-3 fatty acids. Such diets, which also have many other health benefits, deserve more emphasis in dietary recommendations to prevent chronic diseases.

He K, Hu FB, Colditz GA, et al. Changes in intake of fruits and vegetables in relation to risk of obesity and weight gain among middle-aged women. Int J Obese Relat Metab Disord 2004 Dec;28(12):1569-1574.

OBJECTIVE: To examine the changes in intake of fruits and vegetables in relation to risk of obesity and weight gain among middle-aged women.
DESIGN: Prospective cohort study with 12 y of follow-up conducted in the Nurses' Health Study.
SUBJECTS: A total of 74,063 female nurses aged 38-63 y, who were free of cardiovascular disease, cancer, and diabetes at baseline in 1984.
MEASUREMENTS: Dietary information was collected using a validated food frequency questionnaire, and body weight and height were self-reported.
RESULTS: During the 12-y follow-up, participants tended to gain weight with aging, but those with the largest increase in fruit and vegetable intake had a 24% of lower risk of becoming obese (BMI> or =30 kg/m2) compared with those who had the largest decrease in intake after adjustment for age, physical activity, smoking, total energy intake, and other lifestyle variables (relative risk (RR), 0.76; 95% confidence interval (CI), 0.69-0.86; P for trend <0.0001). For major weight gain (> or =25 kg), women with the largest increase in intake of fruits and vegetables had a 28% lower risk compared to those in the other extreme group (RR, 0.72; 95% CI, 0.55-0.93; P=0.01). Similar results were observed for changes in intake of fruits and vegetables when analyzed separately.
CONCLUSIONS: Our findings suggest that increasing intake of fruits and vegetables may reduce long-term risk of obesity and weight gain among middle-aged women.

Hu FB, Willett WC. Optimal diets for prevention of coronary heart disease. JAMA 2002 Nov 27;288(20):2569-2578.

CONTEXT: Coronary heart disease (CHD) remains the leading cause of mortality in industrialized countries and is rapidly becoming a primary cause of death worldwide. Thus, identification of the dietary changes that most effectively prevent CHD is critical.
OBJECTIVE: To review metabolic, epidemiologic, and clinical trial evidence regarding diet and CHD prevention.
DATA SOURCES AND STUDY SELECTION: We searched MEDLINE through May 2002 for epidemiologic and clinical investigations of major dietary factors (fat, cholesterol, omega-3 fatty acids, trans-fatty acids, carbohydrates, glycemic index, fiber, folate, specific foods, and dietary patterns) and CHD. We selected 147 original investigations and reviews of metabolic studies, epidemiologic studies, and dietary intervention trials of diet and CHD.
DATA EXTRACTION: Data were examined for relevance and quality and extracted by 1 of the authors.
DATA SYNTHESIS: Compelling evidence from metabolic studies, prospective cohort studies, and clinical trials in the past several decades indicates that at least 3 dietary strategies are effective in preventing CHD: substitute nonhydrogenated unsaturated fats for saturated and trans-fats; increase consumption of omega-3 fatty acids from fish, fish oil supplements, or plant sources; and consume a diet high in fruits, vegetables, nuts, and whole grains and low in refined grain products. However, simply lowering the percentage of energy from total fat in the diet is unlikely to improve lipid profile or reduce CHD incidence. Many issues remain unsettled, including the optimal amounts of monounsaturated and polyunsaturated fats, the optimal balance between omega-3 and omega-6 polyunsaturated fats, the amount and sources of protein, and the effects of individual phytochemicals, antioxidant vitamins, and minerals.
CONCLUSIONS: Substantial evidence indicates that diets using nonhydrogenated unsaturated fats as the predominant form of dietary fat, whole grains as the main form of carbohydrates, an abundance of fruits and vegetables, and adequate omega-3 fatty acids can offer significant protection against CHD. Such diets, together with regular physical activity, avoidance of smoking, and maintenance of a healthy body weight, may prevent the majority of cardiovascular disease in Western populations.

Hu FB, Stampfer MJ. Nut consumption and risk of coronary heart disease: a review of epidemiologic evidence. Curr Atheroscler Rep 1999 Nov;1(3):204-209.

Traditionally nuts have been perceived as an unhealthy food because of their high fat content. However, recent accumulative evidence suggests that frequent consumption of nuts may be protective against coronary heart disease (CHD). So far, five large prospective cohort studies (the Adventist Health Study, the Iowa Women Health Study, the Nurses' Health Study, the Physicians' Health Study, and the CARE Study) have examined the relation between nut consumption and the risk of CHD and all have found an inverse association. In addition, several clinical studies have observed beneficial effects of diets high in nuts (including walnuts, peanuts, almonds, and other nuts) on blood lipids. The beneficial effects of nut consumption observed in clinical and epidemiologic studies underscore the importance of distinguishing different types of fat. Most fats in nuts are mono- and polyunsaturated fats that lower low-density lipoprotein cholesterol level. Based on the data from the Nurses' Health Study, we estimated that substitution of the fat from 1 ounce of nuts for equivalent energy from carbohydrate in an average diet was associated with a 30% reduction in CHD risk and the substitution of nut fat for saturated fat was associated with 45% reduction in risk. Given the strong scientific evidence for the beneficial effects of nuts, it seems justifiable to move nuts to a more prominent place in the United States Department of Agriculture Food Guide Pyramid. Regular nut consumption can be recommended in the context of a healthy and balanced diet.