Atherosclerosis

The most important dietary changes to make in protecting arteries from atherosclerosis include avoiding sources of saturated fat, such as meat and dairy products. A decrease in atherosclerosis resulting from a pure vegetarian diet (no meat, poultry, dairy or eggs), combined with exercise and stress reduction, has been proven by medical research. So-called “Mediterranean” diets (high in beans and peas, fish, fruit, vegetables, bread, and cereals; and low in meat, dairy fat, and eggs) have also had remarkable effects in reducing the risk of dying from heart disease.

Cancer

Research suggests that consumption of meat and other animal products may increase the risk of colon cancer, particularly if the meat is overcooked. Compared with meat eaters, most, but not all, studies have found vegetarians are less likely to be diagnosed with cancer. Female vegetarians have been reported to have lower estrogen levels compared with meat-eating women, possibly explaining a lower incidence of uterine and breast cancers.

The following two possibilities are both strongly supported by research findings:

Some foods consumed by vegetarians may protect against cancer.

Eating meat may increase the risk of cancer.

Breast and Colon Cancer (in relation to how meat is cooked)

Most, but not all, studies show meat-eaters have a high risk of colon and breast cancers. In some colon-cancer studies, the association has been limited to consumption of sausage or other processed meats.

The association between cancer and consumption of meat depends in part on how well the meat is cooked. Well-done meat contains more carcinogenic material than does lightly cooked meat. Recent evidence from preliminary studies shows that people who eat well-done, fried, or heavily browned meat have a high risk of colon and breast cancers.

However, not every report has found that exposure to carcinogens found in well-done meat leads to an increased risk of cancer. Some studies may have failed to find this link because they did not consider the effect of genetics. Susceptibility to the colon cancer-causing effects of well-cooked meat appears to be genetically determined. Genetics may also determine whether eating well-done meat increases the risk of breast cancer. As with colon cancer, genetic testing to determine which consumers of well-done meat are at high risk of breast cancer is rarely done except in research trials.

Most doctors tell people wishing to reduce their risk of breast and colon cancers to stop eating meat, or at least significantly reduce consumption, and to limit intake to meat that is rare or medium-cooked. Removing all meat from the diet may be the safest option, because consumption of even rare or medium-cooked meat has been associated with at least some increase in risk.

Prostate Cancer (in relation to how meat is cooked)

Meat contains high amounts of arachidonic acid. Some by-products of arachidonic acid have promoted prostate cancer in animals. Preliminary reports have suggested that frequently eating well-done steak or cured meats may also increase the risk of prostate cancer in men, although the association between prostate cancer and other meats has not been consistently reported.

Lung Cancer (in relation to how meat is cooked)

Consumption of fried and well-done red meat was associated with an elevated risk of lung cancer in one report. Consumption of red meat in general, as well as fried meat, correlated with a high risk of lung cancer in another study. People who cook with fat taken from meat (such as bacon fat and lard) may also be at high risk of lung cancer, according to preliminary research.

In one report, high consumption of hot dogs was associated with an almost tenfold increase in the risk of childhood leukemia when compared with low consumption. In another report, maternal consumption of hot dogs and childhood consumption of hamburgers or hot dogs at least once per week were associated with a doubling of the risk of cancers in children. A review of nine studies found an association between consumption by pregnant women of cured meat and the risk of brain cancer in their offspring. These associations do not yet constitute proof that eating hot dogs or hamburgers causes cancer in children, and evidence linking cured meat consumption to childhood cancers remains somewhat inconsistent.

In the report studying the effects of eating hot dogs and hamburgers, the association between meat eating and leukemia was weakest among children who took vitamin supplements, suggesting that these supplements may have had a protective effect. Processed meats such as hot dogs contain nitrates and nitrites—precursors to carcinogens. Antioxidants found in multivitamins keep nitrates and nitrites from converting into those carcinogens. Therefore, the association between vitamin consumption in children and protection against childhood cancers remains plausible, though unproven.

In the debate over whether dietary fat increases breast cancer risks, only one fact is indisputable: women in countries that consume high amounts of meat and dairy fat have a high risk of breast cancer, while women in countries that mostly consume rice, soy, vegetables and fish (instead of meat and dairy fat) have a low risk of breast cancer.

Cardiovascular Disease

A diet high in fish appears protective against heart disease, while a high intake of saturated fat (found in meat) may contribute to heart disease. A large study of male healthcare professionals found that those men eating mostly a “prudent” diet (high in fruits, vegetables, legumes, whole grains, fish, and poultry) had a 30 percent lower risk of heart attacks compared to men who ate the fewest foods in the “prudent” category. In contrast, men who ate the highest percentage of their foods from the “typical American diet” category (high in red meat, processed meat, refined grains, sweets, and desserts) had a 64 percent increased risk of heart attack, compared to men who ate the fewest foods in that category.

Crohn’s Disease

As with many other health conditions, it may be beneficial for persons with this condition to eat less meat and dairy fat and more fruits and vegetables.

Diabetes

Vegetarians have been reported to have a low risk of type 2 diabetes. When people with diabetic nerve damage switch to a vegan diet (no meat, dairy, or eggs), improvements have been reported after several days. In one trial, pain completely disappeared in 17 of 21 people. Fats from meat also cause heart disease, the leading killer of people with diabetes. Vegetarians eat less protein than do meat eaters. Reducing protein intake has lowered kidney damage caused by diabetes, and may also improve glucose tolerance. Diets high in fat, especially saturated fat, worsen glucose tolerance and increase the risk of type 2 diabetes. Worldwide, children whose energy comes primarily from a diet high in dairy (or meat) products have a significantly higher chance of developing type 1 diabetes than do children whose energy comes primarily from a diet high in vegetable sources.

Diverticular Disease

One study of food intake revealed a 50 percent increase in incidence of diverticular disease in persons eating a diet high in meat and low in vegetables relative to those eating a high-vegetable and low-meat diet.

Fibrocystic Breast Disease (FBD)

Fibrocystic disease has been linked to estrogen imbalance in the body. When women with fibrocystic disease eat a low-fat diet, their estrogen levels decrease. After three to six months, the pain and lumpiness of FBD also decreases, according to some research. The link between fat and FBD symptoms appears to be most strongly related to saturated fat, which is high in meat.

Gallstones

In some trials, vegetarians had only half the risk of developing gallstones compared with meat eaters. Vegetarians often eat fewer calories and less cholesterol. They also tend to weigh less than meat eaters. All of these differences may reduce gallstone incidence.

Gout

Restricting purine intake can reduce the risk of a gout attack in people susceptible to gout. Foods high in purines include protein-rich foods, such as sweetbreads, liver, and other organ meats, and red meat.

Halitosis

Access by oral bacteria to sulfur-containing amino acids enhances the production of the sulfur gases partially responsible for bad breath. Cleaning the mouth after eating sulfur-rich food, including meat, may help remove the food for these bacteria.

Heart Attack

Dietary fat consumption increases heart attack risk. The Nurses’ Health Study found that eating foods high in saturated fats (meat and dairy fat) was directly associated with more nonfatal heart attacks and deaths from coronary heart disease than eating lower amounts of these foods. Other studies report a direct association between frequent consumption of meat and butter and heart attacks. Making positive dietary changes immediately following a heart attack is likely to decrease one’s chance of having a second heart attack. In one study, people began eating more vegetables and fruits, and substituted fish, nuts, and legumes for meat and eggs 24 to 48 hours after a heart attack. Six weeks later, the diet group had significantly fewer fatal and nonfatal heart attacks than a similar group who did not make these dietary changes. Many doctors tell people trying to reduce their risk of heart disease to avoid all meat and dairy fat. Fish is often suggested instead of meat. People eating a “Mediterranean” diet (high in beans and peas, fish, fruit, vegetables, bread, and cereals; and low in meat, dairy fat, and eggs) for two years had a remarkable 70 percent reduced risk of dying from heart disease compared with people not eating the diet. Similar results were also confirmed after almost four years.

High Cholesterol

Significant amounts of saturated fat are found in beef, pork, and veal. Avoiding these foods reduces cholesterol levels and has even been reported to reverse existing heart disease. Vegetarians have lower cholesterol and less heart disease than meat eaters, in part because they avoid animal fat. Vegans (people who eat no meat, dairy, or eggs) have the lowest cholesterol levels, and switching from a standard diet to a vegan diet has been reported to reverse heart disease.

High Homocysteine

People with high-homocysteine levels are typically advised to reduce their consumption of meat and saturated fat, because these dietary changes lower the risk of heart disease. Since homocysteine is produced from the amino acid methionine, intake of large amounts of methionine increases homocysteine levels. Foods high in methionine that have also been linked with an increased risk of heart disease include meat and eggs. The extent to which consumption of these foods affects the risk of heart disease as a result of their methionine content remains unknown.

High Triglycerides

People with high triglycerides are typically advised to reduce their weight and limit the consumption of meat and saturated fats. Many doctors recommend a diet low in saturated fat (meaning avoidance of red meat and all dairy except nonfat dairy) to reduce triglycerides and the risk of heart disease.

Hives

Allergy to foods and food additives is a common cause of hives, especially in chronic cases. Cured meat is among the foods most commonly reported as a trigger for hives.

Intermittent Claudication

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.

Iron Deficiency

The most absorbable form of iron, called “heme” iron, is found in meat, poultry, and fish.

Kidney Stones

Increased levels of urinary calcium also increase the risk of stone formation. Consumption of animal protein from meat, dairy, poultry, or fish increases urinary calcium.

Morning Sickness

In a Harvard study, women with a high intake of saturated fat (found mainly in meat and dairy) during the year prior to pregnancy had a much higher risk of severe morning sickness than did women eating less saturated fat.

Osteoarthritis (OA)

From the 1950s through the 1970s, Dr. Max Warmbrand used a diet free of meat, poultry, dairy, chemicals, sugar, eggs, and processed foods for people with rheumatoid arthritis (RA) and OA, claiming significant anecdotal success. He reported that clinical results took at least six months to develop. The Warmbrand diet has never been properly tested in clinical research. Moreover, although the diet is healthful and should reduce the risk of being diagnosed with many other diseases, it is difficult for most people to follow. This difficulty, plus the lack of published research, leads many doctors who are aware of the Warmbrand diet to use it only if other approaches have failed.

Parasites

Undercooked meat and poultry can contain parasites.

Phenylketonuria (PKU)

A PKU diet is one that is low in protein, providing no more than the minimum amount of phenylalanine needed by the body. All high-protein foods, such as meats and poultry, are usually eliminated.

Premenstrual Syndrome (PMS)

Several studies suggest that diets low in fat may help to reduce symptoms of PMS. Many doctors recommend diets very low in meat and dairy fat and high in fruit, vegetables, and whole grains for women with PMS.

Rheumatoid Arthritis (RA)

From the 1950s through the 1970s, Max Warmbrand, a naturopathic doctor, used a very low-fat diet to treat people with RA. He recommended a diet free of meat, dairy, chemicals, sugar, eggs, and processed foods. See Osteoarthritis (above).

Systemic Lupus Erythematosus (SLE)

An isolated case of someone with SLE improving significantly after the introduction of a vegetarian diet has been reported. In Japan, women who frequently ate fatty meats, such as beef and pork, were reported to be at higher risk for SLE compared with women eating little of these foods. Consuming fewer calories, less fat, and foods low in phenylalanine and tyrosine (prevalent in high-protein foods such as meat and dairy) might be helpful, according to animal and preliminary human studies.

Weight Loss

For weight loss, foods with a high proportion of calories from fat should be eliminated from the diet, or consumed only in limited amounts; these include red meat, poultry skins, and dark poultry meat.

Wilson’s Disease

Most foods contain at least some copper, so it is not possible to avoid the metal completely. Foods high in copper, such as organ meats, should be eliminated from the diet.