Abstract
Recently, vegetarian diets have experienced an increase in popularity. A vegetarian diet is associated with many health benefits because of its higher content of fiber, folic acid, vitamins C and E, potassium, magnesium, and many phytochemicals and a fat content that is more unsaturated. Compared with other vegetarian diets, vegan diets tend to contain less saturated fat and cholesterol and more dietary fiber. Vegans tend to be thinner, have lower serum cholesterol, and lower blood pressure, reducing their risk of heart disease. However, eliminating all animal products from the diet increases the risk of certain nutritional deficiencies. Micronutrients of special concern for the vegan include vitamins B-12 and D, calcium, and long-chain n-3 (omega-3) fatty acids. Unless vegans regularly consume foods that are fortified with these nutrients, appropriate supplements should be consumed. In some cases, iron and zinc status of vegans may also be of concern because of the limited bioavailability of these minerals. Am J Clin Nutr 2009;89(suppl):1627S-33S.
Generated Summary
This document is a review article that explores the health effects of vegan diets, comparing them with other vegetarian diets and omnivorous diets. The study uses data from various sources, including the Adventist Health Study, and other large population studies, to analyze the nutritional and health status of vegans. The review aims to discuss the nutritional concerns and advantages of vegan diets, providing practical dietary recommendations for individuals following a vegan lifestyle. The methodology involves synthesizing existing research to summarize current knowledge on the health effects of vegan diets, focusing on cardiovascular disease, cancer, and bone health. It also addresses potential nutritional shortfalls and the importance of appropriate food choices.
Key Findings & Statistics
- A nationwide poll in April 2006 indicated that 1.4% of the American population identifies as vegan.
- Vegans tend to have lower serum cholesterol and blood pressure.
- Vegans consume substantially greater quantities of fruit and vegetables compared to omnivores.
- Data from the Adventist Health Study showed that non-vegetarians had a substantially increased risk of both colorectal and prostate cancer compared to vegetarians.
- Vegans consume considerably more legumes, total fruit and vegetables, tomatoes, allium vegetables, fiber, and vitamin C than do omnivores.
- Vegans may have a lower risk of cardiovascular disease (CVD), obesity, type 2 diabetes, and some cancers.
- Plasma total and LDL cholesterol were 32% and 44% lower among vegans than among omnivores.
- In the Adventist Health Study, plasma lipids were lower among vegetarians than among omnivores, with the lowest reported among vegans.
- Data from the Adventist Health Study showed that consumption of soy milk by vegetarians protected them against prostate cancer (36), whereas in other studies the use of dairy was associated with an increased risk of prostate cancer (25, 37-39).
- The risk of hip fracture was decreased 45% for ≥1 servings/d of green leafy vegetables.
- In the Framingham Heart Study, elderly men and women in the highest quartile of vitamin K intake had a 65% decreased risk of hip fracture.
- Data from the EPIC-Oxford study provide good evidence that the risk of bone fractures for vegetarians was similar to that of omnivores (46).
- In Finland, the dietary intake of vitamin D in vegans was insufficient to maintain serum 25-hydroxyvitamin D and parathyroid hormone concentrations within normal ranges during the winter.
- Throughout the year serum 25-hydroxyvitamin D concentrations were lower and parathyroid hormone higher in vegan women than in omnivores.
Other Important Findings
- Vegan diets tend to be higher in dietary fiber, magnesium, folic acid, vitamins C and E, iron, and phytochemicals.
- Vegans tend to have a lower risk of heart disease.
- Eliminating all animal products from the diet increases the risk of certain nutritional deficiencies, including vitamins B-12 and D, calcium, and omega-3 fatty acids.
- Vegan diets are usually higher in fiber, magnesium, folic acid, vitamins C and E, iron, and phytochemicals.
- Vegan diets tend to be lower in calories, saturated fat, and cholesterol.
- Vegan diets appear to be useful for increasing the intake of protective nutrients and phytochemicals.
- Vegans consume considerably more legumes, total fruit and vegetables, tomatoes, allium vegetables, fiber, and vitamin C than do omnivores.
- A low vitamin D status is often reported in vegan populations and is associated with an increased risk of cancers.
- Vegans can obtain DHA from microalgae supplements containing DHA, as well as from foods fortified with DHA.
- Vegans should be able to easily reach the n-3 fatty acid requirements by including regular supplies of ALA-rich foods in their diet and also DHA-fortified foods and supplements.
- Vegans tend to have lower plasma vitamin B-12 concentrations, higher prevalence of vitamin B-12 deficiency, and higher concentrations of plasma homocysteine.
Limitations Noted in the Document
- The bioavailability of phytochemicals may be an important determining factor in the observed differences between vegetarians and nonvegetarians.
- Population studies have not shown more pronounced differences in cancer incidence or mortality rates between vegetarians and nonvegetarians.
- Further research is needed to explore the relation between consuming plant-based diets and the risk of cancer.
- The vegan studies that do exist often involve only a small number of subjects.
- More studies are needed with long-term vegans.
- The evidence for a risk-reducing effect of consuming whole grains was assessed as possible for colorectal cancer and probable for type 2 diabetes and CVD.
- The evidence for a risk-reducing effect of consuming nuts was assessed as probable for CVD.
Conclusion
The review concludes that vegan diets offer several health benefits, including a lower risk of heart disease, lower serum cholesterol, and blood pressure. Vegan diets tend to be higher in beneficial nutrients such as fiber, vitamins, and phytochemicals. However, the elimination of animal products can lead to nutritional deficiencies, particularly in vitamins B-12 and D, calcium, and omega-3 fatty acids. The article underscores the need for careful planning and the consumption of fortified foods or supplements to address these potential shortfalls. While vegans may experience a lower risk of certain chronic diseases, the article emphasizes the importance of ongoing research to understand the long-term health effects of vegan diets fully. The document highlights that vegans should regularly consume vitamin B-12-fortified foods or supplements, ensure adequate calcium intake through fortified foods, and maintain sufficient vitamin D levels. Overall, the review emphasizes the importance of a well-planned vegan diet for optimal health, while also recognizing the need for further research in this area. The findings show the importance of incorporating a variety of plant foods, and fortified options, to achieve a nutritionally complete diet. The review reinforces the idea that while there are potential advantages to a vegan diet, careful attention to nutrient intake is essential to avoid deficiencies. The document suggests that a well-structured and informed approach is crucial for individuals considering or following a vegan lifestyle to ensure their long-term health and well-being. The conclusion highlights the potential for vegan diets to promote health, but also stresses the importance of informed choices and ongoing monitoring.