By Dr. Laura Vater, MD, Oncologist (IG: @doclauravater)
Cancer is one of the leading causes of death worldwide. Preventing and delaying cancer through adopting a healthy lifestyle can expand the span and quality of life. Healthy habits that help prevent cancer include getting adequate sleep, engaging in regular physical activity, avoiding tobacco products, and eating a diet consisting mainly of plants.
Researchers estimate that approximately one-third of cancers diagnosed in the U.S. and Canada could be prevented with diet and nutrition alone.
Phytochemicals in plants
Many plants contain cancer-fighting components called phytochemicals (also called phytonutrients). They are found in all plant foods, so eating a variety of fruits, vegetables, nuts, seeds, beans, and whole grains is important. These phytochemicals can help prevent DNA damage and assist with DNA repair, slow cancer cell growth, reduce inflammation, and bolster the immune system.
Some of the phytochemicals found in plants include curcumin from turmeric, genistein from soybeans, tea polyphenols from green tea, resveratrol from grapes, sulforaphane from broccoli, isothiocyanates from cruciferous vegetables, diallyl sulfide from garlic, lycopene from tomatoes, rosmarinic acid from rosemary, apigenin from parsley, and gingerol from gingers, among many others.
While supplements may claim to capture the phytonutrients from plants, it is best to eat whole foods.
Fiber and reduced risk for cancer
Eating foods high in fiber has been shown in a number of studies to reduce the risk of colon cancer, and possibly breast, ovarian and endometrial cancers. It is ideal to eat plants as a fiber source rather than taking a fiber supplement or eating processed foods that have been supplemented with fiber.
Meat and cancer
Population-level research studies have found an association between eating processed meat and developing cancer, including colorectal, stomach, pancreatic, and prostate cancer. Processed meat includes meat that has been preserved by salting, smoking, curing, or adding preservatives such as nitrates and nitrites. This includes bacon, hot dogs, bologna, ham, salami, and pastrami, among others.
Cooking meats at high temperatures (including grilling) produces chemicals linked to colorectal cancer, including heterocyclic amines and polycyclic aromatic hydrocarbons.
The World Health Organization (WHO) has classified processed meat as a Group 1 carcinogen, meaning there is convincing evidence it causes cancer. Red meat is classified as a Group 2A carcinogen, meaning it likely causes colorectal cancer.
Dairy and cancer
Dairy products are a wide group of foods, and the composition of dairy varies widely. This makes studying the association with cancer more difficult. Associations between dairy intake and cancer have been inconsistent. Some studies have suggested a reduced risk of colorectal cancer. Others have shown an increased risk of prostate cancer.
A recent study conducted by Loma Linda researchers found that even moderate consumption of dairy milk was associated with up to 80% increased risk for breast cancer in a cohort of 53,000 women. The authors concluded that drinking dairy milk (or some other factor closely associated with ingesting dairy milk) increased the risk of breast cancer. Proposed mechanisms for increased risk were: 1) the estrogen and progesterone found in dairy milk that may lead to growth of estrogen-sensitive breast cancer, and 2) higher blood levels of insulin-like growth factor-1 (IGF-1) after consuming dairy. IGF-1 is a growth factor that may promote the growth of certain cancers.
Take home points
To reduce your risk of cancer, eat mostly plants, including a variety of fruits, vegetables, beans, nuts, seeds, and whole grains. Plants contain phytonutrients that protect your body from cancer. Reduce your intake of meat, and try to eliminate processed meat from your diet. Lastly, choose to eat plants rather than taking supplements.
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