David Servan-Schreiber, MD, PhD
University of Pittsburgh School of Medicine
At any given time, the average person might have thousands of cancer cells in his/her body. Individually, these abnormal cells are harmless, but any one of them could potentially proliferate and form a mass of cells (a tumor) that damages normal tissues and can spread to other parts of the body. About one-third of us eventually will get full-fledged cancer.
Often people who get cancer have created impairments in their natural defenses, allowing cancer cells to survive and proliferate. About 85% of all cancers are caused by environmental and lifestyle factors. We can’t always control our environments, but we can control what we eat. Diet is one key factor that determines who gets cancer and who doesn’t.
Example: Asian men have just as many precancerous microtumors in the prostate gland as American men, yet they are as much as 60 times less likely to develop prostate cancer. It’s not a coincidence that their diets are far healthier, on average, than those consumed by men in the US. Asian men eat far more fruits and vegetables than Americans and relatively little red meat. They also tend to eat more fish and soy foods, and they drink more tea, especially green tea. These and other dietary factors allow their immune systems and other natural defenses to prevent cancer cells from proliferating.
My story: I was a physician in Pittsburgh when I was first diagnosed with a brain tumor in 1992. With the benefit of hindsight — and years of research into the origins and development of cancer — I have come to understand that my previous lifestyle, particularly my poor diet, fostered a procancer environment. For example, a typical lunch for me was chili con carne, a plain bagel and a can of Coke.
CAUSES OF CANCER
It can take years for cancer cells to turn into tumors — assuming that they ever do. This lag time means that we have many opportunities to create an anticancer environment in our bodies.
There are three main factors that promote the development of cancer…
- Weakened immunity. The immune system normally patrols the body for bacteria and viruses, as well as for cancer cells. When it spots something foreign, it dispatches a variety of cells, including natural killer cells, to destroy the foreign substance. In people who eat an unhealthy diet — not enough produce, too much alcohol, very little fish and so on — the immune system works less efficiently. This means that cancer cells can potentially slip under the radar and eventually proliferate.
- Inflammation. Millions of Americans have subclinical chronic inflammation. It doesn’t cause symptoms, but it can lead to heart disease and cancer. Chronic inflammation can be caused by infection, a diet low in antioxidant nutrients and even emotional stress. It’s accompanied by the release of cytokines and other inflammatory chemicals. Inflammation also prevents the immune system from working efficiently.
- Angiogenesis. Cancer cells, like other cells in the body, need blood and nourishment to survive. They send out chemical signals that stimulate the growth of blood vessels that carry blood to and from the cancer.
This process is called angiogenesis — and it can be strongly influenced by what we eat.
Example: People who eat no more than 12 ounces of red meat weekly can reduce their overall risk for cancer by 30%. Red meat stimulates the release of inflammatory chemicals that inhibit apoptosis, the genetically programmed cell death that prevents uncontrolled growth.
CANCER FIGHTERS
The best cancer-fighting foods…
- Fatty fish. The omega-3 fatty acids in fish reduce inflammation. Oncologists in Scotland have measured inflammatory markers in the blood of cancer patients since the 1990s. They have found that patients with the lowest levels of inflammation are twice as likely to live through the next several years as patients who have more inflammation.
Laboratory studies indicate that a high-fish diet can reduce the growth of lung, breast, colon, prostate and kidney cancers. And naturally, people who eat more fish tend to eat less red meat.
Important: The larger fatty fish, such as tuna, are more likely to be contaminated with mercury and other toxins. The best sources of omega-3s are smaller fatty fish, such as sardines, anchovies and small mackerel.
- Low-glycemic carbohydrates. The glycemic index measures the effects of the carbohydrates in foods on blood glucose levels. Foods with a high-glycemic index, such as white bread and table sugar, cause a rapid rise in insulin as well as a rise in insulin-like growth factor (IGF). IGF stimulates cell growth, including the growth of cancer cells. Both insulin and IGF also promote inflammation.
Data from the Harvard Nurses’ Health Study indicate that people who eat the most high-glycemic foods (these same people tend to be sedentary and overweight) are 260% more likely to get pancreatic cancer and 80% more likely to get colorectal cancer.
Recommended: Unprocessed carbohydrates that are low on the glycemic scale, such as whole-grain breakfast cereals and breads (with whole wheat, barley, oats, flaxseeds, etc.)… cooked whole grains, such as millet, quinoa and barley… and vegetables, such as broccoli and cauliflower.
Also important: Reduce or eliminate refined sugar as well as honey.
Better: Agave nectar, available at most health-food stores. Extracted from cactus sap, it’s sweeter than sugar or honey, yet it has a glycemic index four to five times lower. You can use agave nectar just as you would sugar or honey — by adding it to cereals, tea and so on. Because of the liquid content of the syrup, you’ll generally want to reduce the amount of other liquids in baked goods. Substitute three-quarter cup of agave nectar per one cup of any other sweetener.
- Green tea. Between three and five cups daily can significantly reduce your cancer risk. A chemical in green tea, epigallocatechin gallate (EGCG), inhibits angiogenesis. Green tea also contains polyphenols and other chemical compounds that reduce inflammation and activate liver enzymes that break down and eliminate potential carcinogens. In men who already have prostate cancer, consuming five cups or more of green tea daily has been associated with reduced risk of progressing to advanced cancer by 50%. In women with certain types of breast cancer, three cups daily reduced relapses by 30%. Because black tea is fermented, it has a lower concentration of polyphenols and is less protective than green tea.
- Soy foods. The isoflavones in tofu, soy milk, edamame (green soybeans) and other soy foods help prevent breast cancer, particularly in women who started eating soy early in life. These compounds, known as phytoestrogens, have estrogen-like effects. They occupy the same cellular receptors as the body’s estrogen yet are only about one-hundredth as active. This means that they may slow the development of estrogen-dependent tumors.
Recommended: Three servings of soy per week — but only for women who are cancer-free. Avoid soy if you have or had cancer — there’s some concern that the estrogen-like compounds in soy might promote tumor growth in women who have a type of breast cancer that is sensitive to estrogen’s effects.
- Turmeric. No other food ingredient has more powerful anti-inflammatory effects. In laboratory studies, the active ingredient curcumin in the spice turmeric inhibits the growth of many different cancers. It helps prevent angiogenesis and promotes the death of cancer cells.
In India, people consume an average of one-quarter to one-half teaspoon of turmeric daily. They experience one-eighth as many lung cancers as Westerners of the same age… one-ninth as many colon cancers… and one-fifth as many breast cancers.
- Asian mushrooms, such as shiitake, maitake and enokitake. They’re available in most supermarkets and gourmet stores and are one of the most potent immune system stimulants. Among people who eat a lot of these mushrooms, the rate of stomach cancer is 50% lower than it is among those who don’t eat them. One to two half-cup servings weekly probably is enough to have measureable effects.
- Berries. Berries contain ellagic acid, which strongly inhibits angiogenesis. Aim for one-half cup per day.
- Dark chocolate. One ounce contains twice as many polyphenols as a glass of red wine and almost as much as a cup of green tea. Laboratory studies indicate that these compounds slow the growth of cancer cells. Look for a chocolate with more than 70% cocoa. The “lighter” milk chocolates don’t contain adequate amounts of polyphenols — and the dairy component of milk chocolate blocks the absorption of polyphenols.