16 Diet Tips for Cancer Prevention

The role of diet in the development of cancer has been researched since the 1940s. In Western nations about a third of all cancers have been estimated to be directly or indirectly linked to dietary factors. Cancers that are believed to be particularly sensitive to dietary factors include esophageal, gastrointestinal, breast, bladder, lung, prostate, and cervical cancers. In this section of healwithfood.org's Cancer Prevention Guide, you will find a collection of diet tips for cancer prevention. After getting familiar with the tips provided in this article, be also sure to check out the list of the best cancer fighting foods.

Note: The information on this page and elsewhere on this website is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or a qualified health care professional for any questions you may have regarding any medical condition, including cancer.

#1: Include Allicin-Containing Foods in Your Diet

Since 1950s, several studies have linked allicin to tumor inhibition. Allicin is a compound that is found in garlic and other members of the Allium family, such as onions and shallots, when the plant is crushed or chopped. Allicin, which gives garlic its distinctive odor and flavor, has been shown to slow and prevent certain types of cancer, particularly prostate and stomach cancer, when consumed regularly. Population studies have also found that countries with a high consumption of garlic (e.g. China, Japan, France) have a reduced risk of stomach, breast, colon, pancreatic, and esophageal cancer. To fully benefit from the health-promoting effects of garlic, allow crushed garlic sit for 10 minutes before eating or cooking — this leaves enough time for allicin to form after crushing.

#2: Avoid Excess Protein

More than hundred years ago John Beard, a Scottish doctor, discovered that the body's primary defense against proliferating cancer cells is pancreatin, a mix of enzymes that are also involved in the digestion of proteins. In case of a high protein diet, the pancreatic enzymes are constantly occupied with digesting protein and are left with little time to do their other job, the eradication of cancer. While a certain amount of protein is necessary for the proper functioning of the body, excessive amounts of protein should be avoided. It may also be a good idea to skip protein at one or two meals a day. Indeed, some experts suggest that the body needs a protein-free period of approximately 12 hours a day if it is to combat cancer efficiently.

Carotenoid-rich foods, such as tomatoes, may guard against lung cancer and other cancers.

#3: Get Enough Vitamin A and Carotenoids

Evidence suggests that there is an inverse relationship between the risk of cancer and the consumption of foods rich in vitamin A and its precursors, the carotenoids. Carotenoids are pigments that give fruits and vegetables such as carrots, cantaloupe, sweet potato, kale, spinach, and collard greens their orange, yellow, and green colors. The most common carotenoids in the Western diet include beta-carotene, lycopene, lutein and zeaxanthin. The protective effect of these nutrients has been shown to be particularly strong for lung cancer, but also the risk of gastrointestinal, pancreas, prostate, skin, and breast cancers may be significantly reduced by including a variety of carotenoid-rich foods in diet.

#4: Avoid Foods That May Be Contaminated with Aflatoxins

Carcinogenic substances can occur in foods when certain types of fungus grow on food and produce toxins during processing, storage, or transport. These toxins include the remarkably potent aflatoxins which have been shown to cause cancer, particularly liver cancer. Peanuts and other legumes are particularly susceptible to contamination with aflatoxins, but also many other types of foods, including whole nuts, spices, and grains, may be contaminated with aflatoxins. Aflatoxins are resistant to cooking and freezing, but care in selecting your foods can greatly reduce your risk of exposure to these toxins:

• Select fresh seeds, nuts, legumes, and grains (or at least avoid nuts and grains from last year's harvest)
• Look for signs of proper storage and avoid foods from countries that have substandard storage requirements
• Discard nuts that taste stale or look suspicious
• Eat green vegetables that are rich in chlorophyll to further reduce the risk of harmful impacts of aflatoxins; chlorophyll has been shown to reduce aflatoxins levels

#5: Reduce Fat Intake, Especially From Animal Fat

A high dietary intake of animal fat has been associated with an increased risk of cancer. One particular compound that seems to play a major role in this context is arachidonic acid, found primarily in fatty red meats, egg yolks and organ meats. This omega-6 fatty acid has been shown to enhance cancer growth and to facilitate its spread within the body, and some evidence suggests that arachidonic acid is also able destroy cells of the immune system involved in the protection against cancer.

In contrast, omega-3 fatty acids, found in fatty fish such as salmon and mackerel and in a few other foods including flaxseed and walnuts, are believed to have a protective effect against cancer. However, even then it is wise to limit the total intake of fat to approximately 20% of total caloric intake because all dietary fat stimulates the production of bile, which in turn increases the apocholic acid and lithocholic acid in the gut, both of which are known to have carcinogenic properties.

#6: Consume Plenty of Foods Rich in Quercetin

Consume foods that contain quercetin. Quercetin is a bioflavonoid that has anti-cancer, anti-fungal, anti-bacterial, and anti-inflammatory properties and that is concentrated in red and yellow onions. According to one study, half an onion a day could reduce the risk of stomach cancer by 50%. In addition to yellow and red onions, good dietary sources of quercetin include capers, apples, lovage, broccoli, red grapes, cherries, citrus fruits, tea, and many berries, including raspberries, lingonberries, and cranberries.

#7: Push Up Your Vitamin C and Vitamin E Levels

Vitamins C and E are potent antioxidants which help neutralize cancer-causing free radicals and boost the immune system, and may therefore help lower your risk of developing cancer. In addition, vitamin C and vitamin E can inhibit the formation of nitrosamine, a potentially carcinogenic substance. However, the impact of vitamin C on nitrosamine formation might be relevant only if there is no fat in the stomach: A group of researchers replicated the chemical conditions of the upper stomach and measured the impact of vitamin C on the production of nitrosamines, both when fat was present in the stomach and when it was absent. Without fat, vitamin C decreased the levels of nitrosamines, but when 10% fat was added, vitamin C actually boosted the formation of nitrosamines.

#8: Ensure a Sufficient Intake of Selenium

Several population studies suggest that the risk of death from cancer, including lung, colorectal, and prostate cancers, is lower among people with a higher intake of the trace mineral selenium. Death rates from cancer are significantly lower in areas of the world where selenium is abundant in the soil than in areas where selenium levels are low. Selenium is believed to reduce cancer risk in two ways: First, selenium is an important constituent of glutathione peroxidase, an enzyme with antioxidant properties which can help protect the body from damaging effects of free radicals. Second, selenium is believed to prevent tumor growth by boosting the immune system and by inhibiting the development of blood vessels to the tumor. It is recommended that you get your selenium intake through diet rather than through supplements, as high-dose selenium supplements can be risky due to the narrow margin between safe and toxic doses of selenium.

#9: Step Up Your Zinc Intake

Zinc is a trace mineral vital to the production of more than 200 essential enzymes in the body, one of them being superoxide dismutase (SOD). SOD is an important antioxidant which helps protect the body from the damaging effects of free radicals, and may thus slow or possibly prevent cancer. In addition, zinc may also reduce the risk of cancer by helping the immune system to destroy abnormal or worn out cells before they multiply themselves and become potentially cancerous. While the body benefits from sufficient levels of dietary zinc, large doses of supplemental zinc may exert unwanted effects: according to some studies, zinc supplementation may stimulate tumor growth and shorten life span.