On December 7, 2015, 91-year-old Jimmy Carter told the world that his recent brain scans showed that he is clear of the melanoma cancer that had spread to his liver and brain. He took the FDA-approved immune-stimulator drug, pembrolizumab (brand name Keytruda). This is the first drug that has been found to treat melanoma cancers that have already spread to other parts of the body. It stimulates your own immune system to recognize, attack and kill cancers. It costs tens of thousands of dollars a month.

The hottest research on cancer now lies in ways to stimulate your immune system to kill cancer cells the same way that it attacks and kills germs. Cancers are currently treated with radiation and chemotherapy, but these treatments do not kill just cancer cells and leave normal cells alone; they kill all types of cells. The new research aims at developing drugs that stimulate your own immunity to attack and kill cancer cells in the same way that it kills invading germs, without harming normal cells.

Gut Bacteria to Help Stimulate Your Immunity to Kill Cancer Cells
To function properly, your immunity depends on the tens of trillions of bacteria in your intestines. The new cancer treatments rely on gut bacteria to help stimulate the immune system to kill cancers such as lymphomas in the blood and melanomas in the skin. If you give antibiotics that kill gut bacteria before you give these cancer drugs, the cancer drugs do not work at all (Science, Nov 22, 2013:342(6161):971-976).

Two recent papers show that changing colon bacteria is a possible future treatment to help your own immunity control cancer:

• University of Chicago researchers gave mice good bacteria called Bifidobacterium, that normally resides in human healthy gastrointestinal tracts, and found it as effective as the immunotherapy that is currently used to control skin cancers. Giving Bifidobacterium together with drugs to stimulate the immune system cured some cancers (Science, November 27, 2015;350(6264):1084-9).

• French researchers gave mice the same type of good Bifidobacterium bacteria to stimulate an immune response that successfully killed melanoma cancers (Science, November 27, 2015;350(6264):1079-84).

Giving a cocktail of several chemicals to stimulate the immune system to attack cancer cells shrank cancers and prolonged the lives of mice with cancers. However, giving antibiotics prior to giving the cocktail prevented the benefits. The anti-cancer drug cyclophosphamide did not work at all when mice were given antibiotics beforehand (OncoImmunology, Jan 17, 2014;3(1)) Two natural intestinal bacteria called Lactobacillus johnsonii and Lactobacillus murinus made the cyclphosphamide more effective in killing cancer cells.

What is Cancer?
Normal cells have a programmable death called apoptosis. They divide a certain number of times and then die.
• Skin cells live 28 days and then die,
• Cells inside your mouth live for 48 hours and then die,
• red blood cells live 120 days and then die, and so forth.
In cancer, cells have lost their programmed death and try to live forever. Cancer cells rarely kill a person if they remain in a single location, but when they become so numerous that they leave the original site, they invade and destroy other parts of the body. For example, breast cancer does not kill as long as it remains in the breast, but when the cancer cells leave the breast, they can invade the lungs and the person smothers to death, or they invade the brain to stop it from functioning, and so forth.

How Your Immunity Tries to Protect You from Cancer
Your body makes new cells every day, guided by the genetic material inside each cell. Each day, mutations occur in some cells that turn these once-normal cells into millions of cancer cells that try to live forever. To protect you from developing cancer, your immunity searches out and kills these cancer cells in the same way that it kills germs that try to invade your body.

When a germ gets into your body, your immunity recognizes that the germ cells have proteins on their outer surfaces that are different from your body's own cells. Your immunity produces cells and proteins that attack and kill these invading bacteria. In the same way, your immunity notices that cancer cells have proteins that are different from those on your normal cells, so it attacks and kills the cancer cells and removes them from your body. A cancer spreads only when your immunity fails to keep the proliferating cancer cells under control.

The Future of Gut Bacteria
The trillions of bacteria in your colon have many functions that are not yet fully understood. It now appears that they may help to determine whether you are fat or skinny, they can determine your ability to kill invading germs, and they can make your immunity overactive which may lead to "auto-immune" diseases such as rheumatoid arthritis and lupus. This new research shows that intestinal bacteria are necessary for some treatments for cancer to be effective.

Many studies show that obesity is a risk factor for several types of cancer including colon, post-menopausal breast, endometrial and aggressive prostate cancers (Cancer Epidemiology, Biomarkers & Prevention, April 23, 2013). Other studies have shown that obese people often have a much narrower variety of bacteria in their colons. We do not yet know whether there is a connection.

In the future, doctors may give specific intestinal bacteria to treat or prevent cancers, but at this time we do not know which bacteria to give or how to give them. You cannot sustain a change in colon bacteria just by taking bacteria in pills or in foods. For example, if you eat yogurt that contains lactobacillus, that beneficial bacteria will be found in your colon, but if you stop eating the yogurt the lactobacillus disappears. The bacteria in your colon eat the same food that you do, so the foods that you eat regularly determine which types of bacteria colonize successfully and which types disappear.

My Recommendations
So far, studies on which types of gut bacteria are beneficial and which are harmful are showing that a high-plant diet grows more of the healthful types. Based on this early research, I recommend that you:
• Eat a plant-based diet that includes plenty of vegetables, fruits, whole grains, beans, nuts and other seeds
• Restrict ultra-processed foods that are low in nutrients and high in added sugars
• Restrict red meat, processed meats, sugared drinks, sugar-added foods and fried foods
You do not need to be a vegetarian, but plants should form a large part of what you eat. The type of diet that is being recommended to grow beneficial bacteria in your colon, and possibly to help prevent cancer or to treat cancer patients, is the same diet that is recommended to prevent heart attacks, strokes and diabetes.