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6 | Spring 13 | The Digest


Research on Nuts Supports Current Global Dietary Recommendations,


The Growing Evidence Base Demonstrates Multiple Health Benefits


Connie Diekman, MEd, RD, LD, FADA and Penny M. Kris-Etherton, PhD, RD, FAHA, FNLA ABSTRACT


Dietary recommendations have been made for nuts on the basis of an impressive evidence base demonstrating many health benefits. This article reviews the current research that supports dietary recommendations for nuts. In addition, we discuss the PREDIMED Prevencion con Dieta Mediterranea Trial, a landmark primary prevention intervention study that evaluated the inclusion of nuts in a Mediterranean- style diet on cardiovascular disease. This trial showed a 30% reduction in risk of cardiovascular disease events, and a 49% reduction in risk of stroke in the Mediterranean diet supplemented with mixed nuts group compared to the low-fat group. Research on nuts is moving at a fast pace, and the dietetic community needs to keep abreast of the emerging findings to be best positioned to respond to patient, colleague, and media inquiries.


INTRODUCTION


The Global Burden of Disease Study (2010), largely funded by the Gates Foundation and conducted in concert with the World Health Organization (WHO), recently reported the world’s top health problems.1 Ischemic heart disease (IHD) was ranked as the number one health problem in the world, and stroke was number three. In 1990, IHD and stroke were ranked number 4 and 5, respectively, indicating that the burden of cardiovascular disease (CVD), a non-communicable, chronic disease, is growing globally.


Of interest to the nutrition community is that the top ranked (presented in parentheses below) nutrition-related risk factors causing the greatest “loss of health” include: low fruit consumption (# 5), high sodium intake (#11), low intake of nuts and seeds (#12), iron deficiency (#13), low intake of whole grains (#16), vegetables (#17), and omega-3 fatty acids (#18), high processed meat intake (# 22), low fiber intake (# 24), vitamin A deficiency (#29), and zinc deficiency (# 31). Other ranked risk factors related to poor nutrition practices include high blood pressure, alcohol use, high body mass index, high fasting plasma glucose, childhood underweight, suboptimal breast feeding, high total cholesterol, lead, and non-potable water. In a ranking of dietary risk factors that affect IHD, a diet low in nuts and seeds was ranked at the top, contributing 40% of disability- adjusted life years.2


In recognition of the importance of a heart healthy diet as one strategy to decrease CVD by 20% by the year 2020, the American Heart Association has recommended ≥ 4 servings/week of nuts, legumes, and seeds.3 Likewise, because of their many health benefits, the 2010 Dietary Guidelines for Americans recommends choosing a variety of protein foods, including unsalted nuts and seeds, in the list of foods and nutrients to increase.4


In this article we review the research that supports the current dietary recommendations for nuts, specifically related to major chronic diseases. In addition, we summarize the very exciting research from the


PREDIMED Trial, a large intervention trial evaluating the effects of two Mediterranean-style diets, one that recommends daily nut consumption or olive oil compared with a lower- fat prudent diet on CVD and other diseases and conditions.5


Nuts and CVD


Four epidemiologic studies conducted in the United States (Adventist Health Study, Iowa Women’s Health Study, Nurses’ Health Study, Physicians’ Health Study) demonstrate a dose-response decrease in coronary heart disease (CHD) risk with increasing nut comsumption.6 Participants who consumed nuts > 5 times/week had an approximate 40% reduction in CHD risk. Consuming nuts 1-4 times/week was associated with about a 30% decrease in CHD risk. In a comprehensive pooled analysis of 25 feeding trials with 1284 data points, Sabate and colleagues reported a dose-response decrease in total cholesterol, LDL-cholesterol (LDL-C), the LDL-C/HDL-C ratio, and triglycerides (TG) with increasing calories from nuts in the diet (10%, 12% and 20% of calories).7 The consistent evidence showing benefits of nut consumption on lipids and lipoproteins is one widely accepted mechanism to explain the cardioprotective benefits of nuts. Interestingly, many studies have shown a greater cholesterol lowering effect of nuts than would be predicted from their fatty acid profile.8 The conclusion that emerged from this is that there are other bioactive factors in nuts that contribute to their cholesterol- lowering effects beyond their


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