A vegetarian diet has been advocated by everyone from philosophers such as Plato and Nietzsche, to political leaders such as Benjamin Franklin and Gandhi, to modern pop icons such as Paul McCartney and Bob Marley. Science is also on the side of vegetarianism. A multitude of studies have proven the health benefits of a vegetarian diet to be remarkable.
"Vegetarian" is defined as avoiding all animal flesh, including fish and poultry. Vegetarians who avoid flesh, but do eat animal products such as cheese, milk, and eggs, are ovo-lacto-vegetarians (ovo = egg; lacto = milk, cheese, etc.). The ranks of those who eschew all animal products are rapidly growing; these people are referred to as pure vegetarians or vegans. Scientific research shows that ovo-lacto-vegetarians are healthier than meat-eaters, and vegans are the healthiest overall.
Only 20% of Americans eat at least the recommended 5 servings per day of fruits and vegetables. In it's statement of position on the vegetarian diet , the American Dietetic Association states:
Many contemplating conversion to a vegan diet (one completely free of animal products) are concerned about its viability and safety, particularly for children. Given the many health benefits of such a diet, does the evidence show that vegan diets do indeed meet nutritional needs? The answer is clearly yes. According to the American Dietetic Association's position paper on vegetarian diets  "Appropriately planned vegan and lacto-ovo-vegetarian diets satisfy nutrient needs of infants, children, and adolescents and promote normal growth."
In one study, pediatric developmental tests in vegetarian children indicated mental age advanced over a year beyond chronological age, and mean IQ was well above average (with an average of 116 points), providing reassurance that brain development is normal. Questions about the adequacy of plant-based diets were raised by Dagnelie  and Dwyer  who observed poor growth in children following a strict macrobiotic diet. The feeding practices of macrobiotic families can vary greatly from those of vegan families. Some very strict macrobiotic diets may lack adequate calories due to fat restrictions, and these diets have been modified more recently to permit the inclusion of somewhat more fat, such as is found in seeds and nuts.
Most parents find it easy to plan a vegan diet that is adequate in protein, calories, vitamins and minerals. Following a vegan diet has been made easier in recent years since vegetarian products fortified with calcium, vitamin D, and vitamin B12 are available in most food stores: vegetarian hot dogs, burgers, fortified soy and rice milks, vegetarian deli slices, and other meat analogs are readily available. Calorie, protein, and all other nutrient needs can be easily met by a vegan diet, supplemented with vitamin B12.
Vegan foods, which can be bought at health food stores and many other places, are made without any animal products, such as eggs or milk. Be careful to read the labels of soy cheeses, though. They may say "milk-free," but they could contain milk protein. For your sweet tooth, soy- or rice-based frozen desserts, sorbets, and puddings are good substitutes for ice cream, as are ice pops. For baking, milk substitutes work as well as milk and some even come out better. Dairy-free margarine works as well as butter for recipes and spreading on a bagel. You might also want to look for foods labeled "parve" or "pareve": they are usually made without milk products according to kosher dietary laws. Kosher foods that are marked with a "D" are dairy and shouldn't be eaten. Those marked with "D.E." were made using dairy equipment and shouldn't be risked either.
Many of the diet and lifestyle changes recommended against allergies are a natural consequence of adhering to a more animal-free lifestyle: avoiding saturated fats (meats and dairy products), eggs, shellfish; consuming fresh fruits and vegetables (be careful of citrus in particular though), whole grains, nuts, seeds, and fresh juices; using synthetic materials such as acrylic instead of animal products such as wool.
A low-fat, low-cholesterol diet is recommended, as is an increase fiber (especially water-soluble fibers), fruits, vegetables, and vegetarian sources of protein.
Important dietary changes for preventing atherosclerosis (and, consequently, intermittent claudication) include avoiding meat and dairy fat, increasing fiber, and possibly avoiding foods containing trans fatty acids.
August, 2017: A dietary review of 49 observational and controlled studies found that plant-based vegetarian diets – especially vegan diets – are associated with lower levels of total cholesterol, including lower levels of HDL and LDL cholesterol, compared to omnivorous diets.
Numerous earlier studies also found that cholesterol levels are much lower in vegetarians [1-4]. Vegetarian diets reduce serum cholesterol levels to a much greater degree than is achieved with the National Cholesterol Education Program Step Two diet [5-8]. In one study published in The Lancet  total cholesterol in those following a vegetarian diet for 12 months decreased by 24.3%.
The ratio of HDL- to total-cholesterol has been shown to be significantly lower in vegans as compared to lacto-ovo-vegetarians. The recommended minimum ratio of HDL total cholesterol is below 5, optimal being below 3.5 according to the American Heart Association.
Permanent weight control is difficult to achieve. Between 95% and 98% of repeat dieters fail, regaining the weight that they initially lose. What about the other 2-5%? In her book "Eating Thin for Life," award winning journalist and dietician Anne Fletcher delved into the habits of a few hundred people who had not only lost an average of 64 pounds but also maintained that loss for an average of 11 years. What did she find? "Basically, they're eating the opposite of a high-protein, low carbohydrate diet," Fletcher reported. When she asked them to describe their eating habits, the top response was "low-fat" followed by "eating less meat." These dieters with long-term success also told her they ate "more fruits and vegetables."
Recent research supports this notion. One research study showed that significant weight loss can be triggered by just feeding people extra fruit – 3 added apples or pears a day [Nutrition 19 (2003): p.253]. Harvard studied 75,000 women for a decade and the results suggest that the more fruits and vegetables women eat the less likely they will become obese [American Journal of Clinical Nutrition 70 (1999): p.412]. A 2004 review of the available research suggests that in general "increasing fruit and vegetable intake may be an important strategy for weight loss." [Nutrition Reviews 62 (2004): p.1]
The results of the biggest study on diet and obesity to date was released in 2003, comparing over a thousand vegans to tens of thousands of meat-eaters, and lacto-ovo vegetarians [International Journal of Obesity 27 (2003): p.728]. The meat-eaters were on average significantly heavier than the vegetarians, who were significantly heavier than the vegans. Even after controlling for exercise and smoking and other nondietary factors, vegans came out slimmest in every age group: fewer than 2% of vegans were obese. In a snapshot of the diets of 10,000 Americans, those eating vegetarian were slimmest whereas those eating the fewest carbs in the sample weighed the most. [Journal of the American Dietetics Association 1010 (2001): p.411]
Researchers at the National Cancer Institute followed over 75,000 people for ten years to find out which behaviors were associated with weight loss and weight gain. The one dietary behavior most associated with an expanding waistline was high meat consumption and the dietary behavior most strongly associated with a loss of abdominal fat was high vegetable consumption. Even after controlling for other factors, men and women who ate more than a serving of meat per day seemed to be 50% more likely to suffer an increase in abdominal obesity than those who ate meat just a few times a week. The researchers conclude: "Our analysis has identified several easily described behaviors [such as reducing meat intake to less than three servings per week and jogging a few hours every week] that, if widely adopted, might help reverse recent increases in adult overweight... Increases in vegetable consumption might reduce abdominal obesity even further." [American Journal of Public Health 87 (1997): p.747]
Obesity is a major contributor to many serious illnesses, and is much less common among vegetarians, compared to the general population. Vegetarians are, on average, about 10% leaner than omnivores.
A study published in the January, 2001 edition of the American Journal of Clinical Nutrition examined the diets of 1,035 women, particularly focusing on the protein intake from animal and vegetable sources. Deborah Sellmeyer, M.D., found that animal protein increases bone loss. In her study, women with a high animal-to-vegetable protein ratio experienced an increased rate of femoral neck bone loss, and an increased risk of hip fracture.
Dr. Sellmeyer stated: "Sulfur-containing amino acids in protein-containing foods are metabolized to sulfuric acid. Animal foods provide predominantly acid precursors. Acidosis stimulates osteoclastic activity and inhibits osteoblast activity."
A 1994 report in the American Journal of Clinical Nutrition showed that when volunteers are switched from a typical American diet to a diet eliminating animal proteins, calcium losses were reduced to less than half of baseline values. [Remer T, Manz F. Estimation of the renal net acid excretion by adults consuming diets containing variable amounts of protein. Am Clin Nutr 1994;59: pp.1356-61]
Researchers in one study found that participants who ate the greatest number of servings of cooked vegetables were about 75% less likely to develop rheumatoid arthritis than those who reported eating the fewest servings. [American Journal of Clinical Nutrition: November 1999;70: pp.1077-82]
"... 43 patients with rheumatoid arthritis, those assigned to a vegan diet... had improvement in rheumatoid arthritis symptoms." [British J Rheumatology, 36(1) 1997]
Preferably no meat should be eaten as it is rich in uric acid forming components. Raw fruit, vegetables, grains, seeds and nuts are highly recommended.
Reuters, July 27, 2006: "People who ate a low-fat vegan diet, cutting out all meat and dairy, lowered their blood sugar more and lost more weight than people on a standard American Diabetes Association diet... They lowered their cholesterol more and ended up with better kidney function, according to the report published in Diabetes Care, a journal published by the American Diabetes Association."
Dr. Neal Barnard's team and colleagues at George Washington University, the University of Toronto and the University of North Carolina tested 99 people with type-2 diabetes, assigning them randomly to either a low-fat, low-sugar vegan diet or the standard American Diabetes Association diet. After 22 weeks on the diet, 43% of those on the vegan diet and 26% of those on the standard diet were either able to stop taking some of their drugs such as insulin or glucose-control medications, or lowered the doses. The vegan dieters lost 14 pounds (6.5kg) on average while the diabetes association dieters lost 6.8 pounds (3.1kg). An important level of glucose control called a1c fell on average by 1.23 points in the vegan group and by 0.38 in the group on the standard diet.
After removal of the gallbladder, a healthy low-fat, plant-food based (high-fiber) diet is very important.
A low protein diet is important in reducing the processing responsibilities of compromised kidneys.
A more vegetarian diet is naturally lower in saturated fats (meat and dairy products) and higher in grains, vegetables, fruits, vegetable proteins (legumes such as soy), and essential fatty acids (cold-water fish, nuts, and seeds) that are all recommended for Hepatitis. Foods that support the liver are beets, artichokes, yams, onions, garlic, green leafy vegetables, apples, and lemons.
A long-term trial of a vegan diet (elimination of all animal products) provided significant improvement in 92% of the 25 patients who completed the study. Drinking water was limited to spring water (chlorinated tap water was prohibited), and coffee, tea, chocolate, sugar and salt were excluded. [Journal of Asthma 1985; 22:44, p.13]
Diets high in vitamin C and beta-carotene provide significant protection against Parkinson's disease. American researchers have concluded that a high intake of animal fats is associated with a five-fold increase risk.
A low incidence of cerebrovascular disease was associated with geographical regions where fresh fruit and vegetable consumption (and therefore increased potassium) was high. [Low fruits and vegetables, high-meat diet increase cerebrovascular event risk. Medical Tribune March 10, 1997:26]
Constipation is one of the leading causes of varicose veins, although it may initially be hard to see the connection. Constipation may restrict the blood as it returns to the torso through the deep veins in the legs. Straining to have a bowel movement closes off these veins. As the blood backs up it takes another course through superficial veins, thus the blue streaks in the legs. A diet low in fat and high in fiber is best for promoting regularity: reorganize your diet to include plenty of low-fat foods, grains, fresh fruit and vegetables. A diet tending towards vegan/raw-food generally satisfies all these requirements; vegetarians should watch their fat intake.
Eating a low-fat plant-based diet in small frequent meals is one of the best ways to reduce heartburn.
In a study of nurses who ate spinach or other leafy greens at least 5 times a week, it was found they had a 47-65% lower risk of cataracts.
A study in July, 2004 showed that consumption of fresh fruits and green vegetables was associated with decreased risk of developing endometriosis, and preventing re-occurrence.
In a study published in the British Medical Journal, it was shown that vegetarian women had a much lower incidence of gallstones than non-vegetarian women. Of the 632 non-vegetarians, overall occurrence of gallstones was 25%. Vegetarians had only half as many gallstone problems, with 12% being found to have gallstones.
An October, 2001 study by Yale School of Medicine researchers found that a diet high in cholesterol, animal protein and vitamin B12 is linked to increased risk of a specific type of esophageal and stomach cancer, known as adenocarcinoma of the esophagus and gastric cardia, that has been increasing rapidly. The number of cases increased by 300% between the mid-1970s and 2000, according to lead author Susan Mayne, associate professor in the Department of Epidemiology and Public Health at Yale School of Medicine, and associate director of the Yale Cancer Center.
"We found that many animal-based nutrients found in foods of animal origin are strongly associated with risk of developing these types of cancers and we were able to identify nutrients that presumably would be protective," said Mayne. "We also found that regular users of vitamin C supplements were at significantly lower risk of stomach cancer."
"Our results suggest that prevention strategies for these cancers should emphasize increased consumption of plant foods, decreased consumption of foods of animal origin with the possible exception of dairy products, and control of obesity."
The intake of vegetable fiber, but not of fruit or cereal fiber, was found to be negatively associated with risk of ovarian cancer, with a 37% decrease in the odds for each 10gm per day addition. [Am J Epidemiol 139(11): S37, 1994]
Consumption of foods containing beta-carotene by 71 women with epithelial cancer of the ovary and 141 matched controls was investigated. Consumption of carrots was found to decrease risk. [Nutr Cancer 15: pp.239-47, 1991]
Cancer rates for vegetarians are 25 to 50% below population averages, even after controlling for smoking, body mass index, and socioeconomic status.[1,2] Vegans show even better results. One study found that people who include generous amounts of fruits and vegetables in their daily diets have lower rates of cancers of the lung, breast, colon, bladder, stomach, mouth, larynx, esophagus, pancreas, and cervix compared to people who avoid such foods.
Fruits and vegetables contain antioxidant substances, such as vitamin C, vitamin E, and carotenoids, which protect cells against oxidative damage, which is related to cancer risk and other health problems. The multitude of phytochemicals found in various fruits, vegetables, grains, legumes, and nuts are thought to protect against heart disease and cancer.
"35 percent of cancer deaths may be related to diet." [The National Cancer Institute booklet "Diet, Nutrition, & Cancer Prevention: A Guide to Food Choices"]
In the Nurses' Health Study, beta carotene proved protective against breast cancer for more than 87,000 women. Beta carotene both in supplement form and in foods such as fresh fruits and vegetables should be included in your diet if you are interested in breast cancer prevention.
Regarding children, plant-based diets may encourage a later menarche (beginning of the menstrual function), which has been shown to be associated with reduced risk of breast cancer in epidemiologic studies.[1, 2]
Diets high in fiber-rich foods may reduce the risk of cancers of the colon and rectum. [The National Cancer Institute booklet "Diet, Nutrition, & Cancer Prevention: A Guide to Food Choices"]
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