Journal of the American College of Nutrition, Vol. 17, No. 5, 407-408 (1998)
Published by the American College of Nutrition
Vegan Diets and Cardiovascular Health
Gene A. Spiller, PhD, CNS, FACN and
Bonnie Bruce, DrPH, RD, FACN
Health Research and Studies Center and Sphera Foundation, Los Altos, CA
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INTRODUCTION
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Expanding evidence continues to confirm the positive nutritional attributes of plant-based eating patterns. Several international studies have demonstrated that a plant-based diet is linked to a much lower risk of death from ischemic heart disease when compared to the general population [1–4]. Yet the American public continues to consume a modern diet that is primarily meat-centered and which relies heavily on refined foods.
It is well established that dietary intake influences plasma lipids, and that elevated blood cholesterol increases risk of heart disease. Consumption of a diet consisting of whole grains, fruits, vegetables, nuts and seeds has been associated with more favorable lipoprotein profiles in both observational and clinical studies. This was shown by Thorogood et al in their cross-sectional study of the effects of eating patterns on plasma cholesterol in British subjects, which found that plasma cholesterol of lacto-ovo vegetarians was 14% higher than vegans [5]. In their clinical study, Jenkins and colleagues demonstrated that a vegan diet resulted in highly significant reductions in plasma lipoproteins that were greater than what would have been predicted by differences in dietary fat and cholesterol [6].
The cross-sectional study by Toohey et al in this issue of the Journal adds further support for the salutary effects of plant-based eating patterns by reporting on the improved heart disease risk profile in African-American vegans. This is a particular important contribution, since African-Americans have higher blood pressure and increased risk of death from coronary disease than Caucasians or Hispanics [7], and thus shows that this population group can also benefit from a plant-based diet. Their vegan subjects exhibited similar dietary patterns as vegans in general, with higher carbohydrate and fiber intakes, and lower total fat and saturated fat intakes than African-American lacto-ovo vegetarians.
Several dietary factors have been identified as contributing to these benefits, including higher complex carbohydrate and fiber intakes from whole and unrefined foods, which have been linked with favorable lipoprotein profiles and reduced coronary disease risk. Vegans generally consume 50% to 100% more fiber than the general population [8], and soluble fibers from legumes, fruits, vegetables, nuts, and seeds appears to reduce risk by lowering plasma cholesterol [9]. Fruits and vegetables, especially leafy greens and some legumes, are abundant in folic acid, which has been shown to help lower homocysteine levels. Elevated levels of blood homocysteine are strongly associated with increased risk of heart disease [10]. Many whole and unrefined plant foods are also important sources of minerals, such as copper, and magnesium, both of which may protect against cardiovascular disease.
In addition, vegans have a lower saturated fat intake and do not consume animal protein. The link between elevated cholesterol concentrations and saturated fat is well accepted. However, the relation between a high consumption of animal proteins and heart disease remains speculative. This may be due in part to an underappreciation of their favorable amino acid profiles relative to their effects on lipids. Plant foods, such as nuts, have a distinctive amino acid profile that is high in arginine, a precursor of nitric oxide, which is a potent vasodilator [11].
Until recently, rarely discussed were potential contributions by the wide variety of phytochemicals in unrefined plant foods that has been linked to reduced risk of chronic disease. In vitro and human studies have indicated that the wealth of dietary constituents found naturally in plant foods play important roles in maintaining desirable lipid concentrations. In one study, subjects placed on whole food, vegan eating regimens after being on a typical meat-centered Westernized diet showed significant, favorable changes in lipoprotein profiles [12]. Protective phytochemicals in plants include phytosterols, saponins, carotenoids, phenolics and flavonoids which are found abundantly in whole grains, legumes, and fruits and vegetables. These factors, among the plethora of beneficial dietary constituents present in their natural packages in whole plant foods, help to underscore the important of striving to encourage individuals toward health-improving, plant-based eating patterns.
Notwithstanding the many positive aspects of vegan diets, two major problems may arise for individuals used to consuming either non-vegetarian or lacto-ovo vegetarian diets. One problem is that proteins may be of poor biological value unless unrefined foods—such as whole grains—are chosen and protein foods properly combined, such as whole grains with beans, nuts and other oil seeds such as sesame. The second problem is the risk of vitamin B12 deficiency, a typical vitamin of animal origin: a B12 supplement appears advisable. Furthermore, as the world around us is not a vegan world, a vegan has more difficulty finding proper foods in restaurants and when travelling, which could lead to a variety of problems. But as the risks of protein and B12 deficiency can be easily prevented with minimal knowledge, there appears to be a clear advantage in moving toward a vegan diet or at least a diet based on plant food.
Received July 1, 1998.
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INTRODUCTION
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