Ask the Diet Doctor: Can a Vegan Diet Prevent Cancer?
The answer is more complicated that you'd guess
Q: Is going vegan the best diet to prevent cancer?
A: Unfortunately science has yet to show us any specific diet that will prevent cancer. One of the main issues with the diet-cancer connection is that it is very complex. A cancer that impacts a particular area, like breast cancer, can be driven by several biological mechanisms so that while it is breast cancer, the diet or treatments that that particular breast cancer responds to could be very different.
During my brief stint as a medical student (before leaving to study nutrition full time), I had a professor who was in oncologic pathology. He always talked about "cancer bingo" in that there are a set number of things that will influence most cancers: genetics (a big one), diet, environmental exposures, and more. It wasn't necessarily each individual component that would cause a given cancer but instead the coming together of several specific components that would then yield cancer.
This makes it very hard to study. If you are concerned with developing or are fighting a particular type of cancer, then it is important to look at that cancer specifically and what treatments it responds to.
For example, certain kinds of breast cancers are insulin sensitive, and thus eating a lot of carbohydrates (ironically like in a vegan diet) would cause your body to produce lots of insulin, making this an inefficacious strategy in reducing risk for those particular kinds of cancer.
Other researchers believe that very low-carb diets may be a key treatment strategy for fighting brain tumors in the future, as certain brain tumors rely heavily on glucose to fuel their uncontrolled growth and unlike regular brain cells do not function very well when ketones are the only fuel source available (like in a very low carbohydrate diet).
As for protein, one Hawaiian study looked at the impact between red meat consumption and cancer. They found a very large increase in associated risk of intestinal cancer when an individual had specific genes and ate red meat well done, while the association greatly diminished or went away when one or neither of those factors were present.
Regardless of your genetic profile, the following guidelines can help reduce your risk of any cancer.
1. Don't smoke. Obvious but worth mentioning.
2. Eat 2 to 3 cups of vegetables a day. This is the recommendation from the American Cancer Society; I would say eat more. Two cups isn't that much, and more is better in this situation so you can pack in as many powerful antioxidants in your diet as possible.
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3. Have one alcoholic drink daily (or less). There is definitely a sweet spot for alcohol consumption and health. For women, one drink per day is the maximum you'd want to average before it begins to stop being a positive factor in your overall health and wellness program.
4. Limit your consumption of processed meats. High fat, highly preserved meats cooked or charred over an open flame is never a good idea. This makes many people only think of red meat, but research shows that the same pro-carcinogenic compounds can be formed when poultry fat (i.e. chicken skin or other visible fat) is exposed to direct flames and high heats.
5. Stay active and get lean. I recommend that weight-loss clients get at least five hours of exercise a week, and this is a good benchmark to shoot for even if you are not trying to lose weight since it will make maintaining your weight much easier. Overweight and obesity are thought to contribute to 14 to 20 percent of cancer-associated mortality in America.
I don't think that there is a "best" diet for fighting cancer, as you can achieve the above list by following a multitude of eating plans. The key is to create a situation where you can follow these principles consistently, especially late into life as your risk for numerous cancers increases.