Vegan Diets: The Pros and Cons
Author: Winston Craig, MPH, PhD, RD.
Increasingly, people are concerned today about the health of the environment. Some are very concerned about the inappropriate treatment of farm animals. For many others, the concern is about their health and what changes they can make to promote a better quality of life. Because of these concerns, many are making the switch to a plant-based diet.
About two to three million adult Americans have chosen to go totally vegetarian and eliminate all animal products from their diet. If one eats only plant foods, are there really any additional health benefits? What about risks? The research studies point to a better quality of health for the total vegetarian, or vegan.
Although research studies on vegans are few in number, there are some things that have been clearly shown. It is observed that vegans are significantly thinner, their blood pressure levels are lower, and they have lower blood cholesterol and LDL cholesterol levels than other vegetarians and much lower levels than those who eat meat (omnivores). These factors all translate into a lower risk of cardiovascular disease. The lower body weight would also be associated with a lower risk of cancer and diabetes.
These health advantages can be partly explained by the fact that vegan diets are richer in dietary fiber, higher in potassium and magnesium, folic acid, the antioxidant vitamins C and E, and the health-promoting phytochemicals. Fruits and vegetables, whole grains, legumes, and nuts have all shown protective characteristics against the major chronic diseases.
Those who consume high levels of these plant foods show lower levels of heart disease, stroke, diabetes, osteoporosis, and some cancers, compared with those who consume low levels of the plant foods. In addition, the use of spices such as turmeric, ginger, garlic, and onions to flavor food protects the consumer against cancer, stroke and heart disease.
Eliminating meat from the diet may not lower your saturated fat and cholesterol intake if a considerable use is made of milk, eggs and cheese. However, if one uses non-fat dairy products and egg whites (without the yolk), then the saturated fat and cholesterol intake will be considerably reduced. The dairy products can carry a slight risk of Listeriosis and Salmonella poisoning as well as allergies from milk protein and antibiotic residues in the milk. On the other hand, eggs carry a risk of salmonellosis and must be thoroughly cooked before consumption. The elderly, pregnant women and children are particularly vulnerable to improperly cooked eggs due to their partially compromised immune system.
Is There a Downside to Eating a Vegan Diet?
There are always questions about calcium and vitamin D intakes and the impact these have upon risk of bone fractures in vegans. Eliminating dairy from the diet does remove a good source of calcium from the diet. Vegans can get their daily needs of calcium from dark green leafy vegetables (such as broccoli, Brussels sprouts, kale, and bok choy), calcium-fortified soy and rice beverages, and cereals, and calcium-fortified orange and apple juices. Tofu, oranges, tahini, figs, and sweet potatoes also provide useful amounts of calcium.
A large study in the United Kingdom showed that common bone fractures were no more common in vegans provided they consumed over 525 mg calcium a day. In addition to calcium, other components of a plant-based diet that are believed to protect the integrity of bone structure are potassium, magnesium, vitamin K, soy, and certain culinary herbs, such as thyme, sage, and rosemary.
The potassium- and magnesium-rich fruits and vegetables provide an alkaline residue which protects against bone loss. This alkaline residue is especially important to the aging kidney which has a problem with handling excess acid. Vitamin K-rich leafy vegetables facilitate the formation of the essential bone protein osteocalcin. Women with a higher vitamin K intake (a green leafy vegetable at least once a day) had a 45 percent reduced risk of hip fractures compared to those women with a low intake (eating a leafy vegetable less than once a week).
Soy is particularly useful in protecting against loss of bone mineral density especially in post-menopausal women. The isoflavones in soy are also reported to significantly promote bone formation and inhibit bone loss. Two servings of soy per day provides the optimal effect.
Vitamin D that is required for calcium metabolism can be obtained from vitamin D-fortified cereals, margarines, and soy beverages. During the winter months, vitamin D –rich foods are essential since very little, if any, vitamin D is synthesized by the body during the winter months for those living north of Denver and Washington DC.
Iron deficiency is a worldwide concern for everyone, especially women of child-bearing age. Eliminating dairy from the diet has no impact on iron status since milk is a very poor source of iron. Furthermore, the iron in egg is not readily bioavailable. Hence, the vegan is not considered to be at any greater risk of iron deficiency compared with other vegetarians.
A major concern for those who subsist solely on plant foods has been vitamin B12. While meat, milk and eggs have ample vitamin B12 , plants contain none. Vitamin B12 deficiency can have serious consequences such as early dementia, lack of coordination, forgetfulness, nerve dysfunction, memory loss, disorientation, difficulty with concentration, and difficulty with one’s balance when walking.
It is important for vegans to daily consume foods fortified with vitamin B12 such as fortified soy and rice beverages, some cereals and meat analogs. Reading labels is important to ensure one has an adequate intake. In fact, all persons who are fifty years of age and above should consume foods that are fortified with vitamin B12 since they may have decreased stomach acid to digest the vitamin B12 in animal foods.
Long chain omega-3 fatty acids are important for cardiovascular health as well as brain and eye function. The fatty acids can be obtained from fish. The vegetarian can now obtain the omega-3 fatty acid DHA from microalgae supplements. In addition, the body can convert alpha-linolenic acid to the long chain fatty omega-3 fatty acid DHA, although this is a fairly inefficient process. Alpha-linolenic acid can be obtained from a variety of vegetable sources, including flax seed, canola oil, walnuts, tofu, soy beverages, and soy products.
By appropriate food selections a vegetarian can chose to eliminate all animal products from their diet and still have a nutritionally adequate diet. An unwise selection of foods can leave one short of certain nutrients and may induce deficiency symptoms and adverse health outcomes. Following a plant-based diet lowers the risk of age-related problems such as overweight, high blood pressure, and heart disease.
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While some studies show a decrease in total and LDL cholesterol levels other studies fail to show any beneficial effect of soy isoflavones on lipid profiles. In most studies, beneficial effects could not be attributed with certainty to the isoflavones. If these components have any health-promoting effect in humans, it is small compared with the effect of soy protein itself.