Vegetarian diet protects against cancer

In this Article (Index)

• The Vegetarian Diet's Anticancer Effects
• Cancer Protective effects of a Vegetarian Diet
• Vegetarians and Cancer Protection
• How Does a Vegetarian Protect Against Cancer?
• Stomach Cancer
• Breast and Prostate Cancers
• Immunity
• Specific Anticancer Foods

The Vegetarian Diet's Anticancer Effects

A recent paper, published this month(1) analyzed the cancer-preventive effects of a vegetarian diet.

It is known that vegetarian diets are associated with a lower risk of some types of cancer, but, this is the first paper to conduct a strict statistical analysisi using data from large, long-term studies.

It used information from 79,468 participants of the North American Seventh-day Adventists that were initially cancer-free. The data spanned five years, from 2002 to 2007. The authors then looked into the types of cancer that appeared in this cohort, and their correlation with diet.

Dietary classification

The participants were classified into five different dietary groups. The first three groups were considered Vegetarians, and if they ingested animal products, did so infrequently:

• Vegans, or strict vegetarians. They did not consume any type of animal product.
• Lacto-ovo-vegetarians. These did not consume any flesh (fish or meat), however, they consumed dairy products and eggs.
• Pesco-vegetarians. Similar to the previous group, but, they ate fish.
• Semi-vegetarians. This group consumed differnt types of flesh (between, less than once a week, but more than once a month).
• Nonvegetarians. Similar to the previous group, but with a more frequent intake (more than once a week).

Cancer Protective effects of a Vegetarian Diet

The study reported that all vegetarians, compared with nonvegetarians had the following risk reductions:

• 12% for overall cancers
• 18% for medium frequency cancers

The risk reduction for specific cancers was the following:

• 21% for colorectal cancer
• 45% for stomach cancer
• 25 % for lymphoproliferative cancer

The risk for breast cancer, lymphoma, all lymphoproliferative cancers, prostate cancer, colorectal cancers, medium frequency cancers and for all cancers combined was also proved using another statistical tool.

Vegetarians and Cancer Protection

Nonvegetarians have a higher risk for cancer in comparison to vegetarians, but between the different types of vegetarians, there were also some different protective effects.

Vegans had lower rates of "breast and prostate cancers at younger ages."

Pesco-vegetarians had lower rates of " colorectal cancer and breast cancer at older ages.."

Vegans and lacto-ovo-vegetarians had lower rates of " medium-frequency cancers, lymphomas (also when combined with lymphoid leukemias as lymphoproliferative)."

How Does a Vegetarian Protect Against Cancer?

The paper studied some associations between diet, food types, and cancer, and mentions previous findings on the matter.

Stomach Cancer

Processed meats are a risk factor, absent in vegetarians.

Eating fruits, and especially citrus, grilled vegetables, fish and meats are also linked with stomach cancer.

Other risk factors are obesity, and chemicals linked to meat and processed meats such as nitrites, nitrates, heme iron, polycyclic aromatic hydrocarbons (or PAHS) which are carcinogens and found in fatty processed meats like sausages, ham, beef jerky, smoked fish, and bacon, and heterocyclic amines (mutagenic compounds found in cooked and especially in well-done meat).

Breast and Prostate Cancers

Both of these cancers have a strong association with dairy products, and in particular, milk.

In Pisco-vegetarians (who ingest some fish), there may be a protective effect from the healthy omega-3 (omega;-3) fatty acids in fish (not the plant-based ω3, but the marine ω-3).

Immunity

Improved immunity due to a vegetarian diet may be the cause behind its cancer protective effect against lymphoproliferative cancers which have been linked to viral stimulation ("Burkitt’s lymphoma and HIV, Eppstein Barr virus")

Other studies have suggested that the vegetarian diet reduces the risk of lupus and may be helpful in treating rheumatoid arthritis.

Specific Anticancer Foods

The protective effect of the Vegetarian diet may stem from specific food groups that are excluded from this diet: Lack of red meats, dairy foods, fish, grilled meats may have preventive activity.

The inclusion of other foods may also exert a protective effect: dietary fiber, cruciferous vegetables (arugula, broccoli, Brussels sprouts, cabbage, cauliflower, kale, radishes, turnips), allium veggies (garlic, onions, leeks, scallions, chives, and shallots), plant-based sources of omega-3 fats (which exert an anti-inflamatory effect), and soy phytoestrogens which could have an effect on cancers mediated by hormones.

Important

Of course, as with all observational studies (see more here: What are Clinical Trials?) there are factors that confound the findings. Perhaps those who eat a vegetarian diet alos have healthier lifestyles (don't smoke, drink alcohol, exercise more, sleep better, are slimmer), which could have a cancer protective effect.