There is a certain amount of tug of war in nutrition as it relates to cancer. On the one hand there are frequent “discoveries” of chemicals founds in foods that seem to be helpful in “fighting” cancer. Often the chemical in question is just one of many found in a particular plant and it is studied in isolation. This information is very exciting, and often provides support for the general recommendation to “Eat more fruits, vegetables, beans, nuts and whole grains”. On the other hand, these discoveries can lead to confusion about what exactly to do with this information. Exactly how much broccoli should someone every day? What about turmeric, green tea, blueberries, walnuts, red wine, spinach, apples, onion, oregano? What about the even more exotic foods that are not often a part of our diets such as acai, noni, goji, or miyake mushrooms? Will people really benefit from taking these foods as powders or supplements?
Is there a “best diet” or are there “best foods”? These terms are used a lot on magazines and on short news segments and are often based on recent research into certain chemicals found in foods. It is difficult however to put into more relevant terms what the terms “best foods” mean. When people ask me, “What are the best foods”, I think they mean “What is the combination of foods that will assure me the very lowest risk possible of ever getting cancer, or lowest possible risk of a recurrence?” The truth is, even with all the exciting research that goes on in the area, I just don’t know. I don’t really have a comprehensive way to rank foods over one another. Is broccoli better than walnuts? Broccoli does have more Vitamin C and a particular chemical called indole-3-carbinol which is often studied for breast cancer prevention, but walnuts have protein, omega-3 fats and a chemical called resveratrol, which also may fight breast cancer, but in a different way. Are onions more potent at fighting cancer than garlic? If someone doesn’t like green leafy vegetables or beans, is there some other way for that person to get the known benefits from these foods. Is drinking one soda bad? What about one soda every day?
The bottom line is that the scientific community knows some very specific things, such as how certain detoxifying systems in the body are affected by particular chemicals in broccoli, and we know some very general things, such as eating lots of fruits and vegetables seems to help reduce someone’s risk for developing certain cancers. The area in the middle however, is very great. So far, the best advice I’ve seen is from Micheal Pollan: “Eat food, not too much, mostly from plants.” As an added step, you can see how many different kinds of plants you are eating in a day, or a week. I may not know if broccoli is better than walnuts, but I know they both have chemicals that have been shown to be healthy. Instead of trying to figure out which is better, I recommend including them both, along with many other fruits, vegetables, beans, whole grains and nuts. That way, when the next “best food” comes along, you’ll already be eating it!
There was a facebook post asking about serving size. Here is Karen’s response:
Serving size is a whole other confusing issue and certainly one of those gray areas that we don’t have perfect information about! The USDA specifies recommended “serving sizes” for most foods, such as ½ cup cooked for vegetables, including broccoli, or 1 ounce of nuts (usually about ¼ cup). For more information about these serving sizes, please visit http://www.choosemyplate.gov/. These serving sizes can be different than what people eat. Besides the difference between recommended serving sizes and what people actually eat, there is the issue of what concentrations of healthy plant chemicals that are being used in research. Usually when scientists are doing experiments in labs, they are using concentrated extracts of vegetables, and sometimes just one extracted chemical from hundreds that are in a vegetable. To stay with broccoli for instance, to ingest the amount of indole-3-carbinol (I3C) used in laboratory studies, you may have to eat more than 10 pounds of broccoli every day. However, we also have some data from long term nutrition studies that people who eat ½ – 1 cup of brassica vegetables daily (this vegetable family includes broccoli, but also, cauliflower, cabbage, kale, Brussels sprouts and others) seem to have a lower risk of breast and possible prostate cancer. So again, this is a perfect example of how we have some very specific information about what a concentrated extract of a chemical from broccoli will do in a cell culture, and we have some data that eating foods with this chemical seems to have some benefit, at least in some populations, but the grey area in the middle is very big. With awareness of the limits of making such recommendations, having at least 1 serving (1/2 cup or more) of vegetables from the brassica family each day is a reasonable goal for most people. Brassica vegetables can interact with the medication Coumadin, however, so if you are on Coumadin or Warfarin, please talk with your doctor before making dietary changes. For more information on research into specific plant chemicals including I3C, please visit http://www.AICR.org in the ‘Foods that Fight Cancer’ section.