On October 16, the World Cancer Research Fund (WCRF), a highly regarded non-profit organization dedicated to preventing cancer, released a comprehensive update of research on lifestyle for breast cancer survivors. This update reviewed epidemiological studies that examined links between diet, physical activity and breast cancer survival. It was an update of a 2007 report that found limited evidence of links between lifestyle and survival after a breast cancer diagnosis. This new study included studies that had been published since the previous report. This is not a study of randomized trials, since there have been all too few randomized trials of lifestyle and breast cancer. But, in some ways, epidemiological studies can be more revealing than randomized trials. These studies assess large populations to see what their lifestyle is, follow them for many years, and then evaluate how patients with their specific lifestyle characteristics are doing. Since randomized trials tend to enlist patients who are healthier than average, and who may have lifestyles that differ from most breast cancer patients, the picture they provide is actually somewhat biased in comparison to epidemiological studies.
What new data did the WCRF researchers find about breast cancer? To begin with, the report cautions that, despite their real relevance to breast cancer patients, there are limitations to epidemiological data. Epidemiological studies have to adjust data to account for differences among women who have different outcomes. For instance, it would be ideal to adjust the data for the doses of chemotherapy that women receive, since overweight women sometimes receive a lower dose of chemotherapy than they actually should. This may, in fact, be part of the reason why they tend to not do as well as healthy weight women. But it’s not always possible to get all the data one would need to make these adjustments, and it’s important to keep in mind that this can limit the accuracy of conclusions that researchers make.
This report makes conclusions in three general areas, body weight, diet and physical activity. Here are the conclusions they were able to make, along with our comments about them:
- Although the evidence has limitations, it suggests that breast cancer patients who have a healthy body mass index, both before and after breast cancer diagnosis, have better survival overall. An important reminder: A healthy body mass index isn’t only relevant to breast cancer, it’s also quite relevant to cardiovascular disease. And, considering that half of all breast cancer patients actually die of cardiovascular disease, breast cancer patients should be proactive in lowering their risks for heart disease also (maintaining a healthy weight will contribute to this). Both diet and exercise habits can be helpful in achieving and maintaining a healthy weight.
- Women who eat more foods containing fiber, both before and after diagnosis, have better survival overall than those who eat low-fiber diets. Important dietary sources of fiber are beans, whole grains, vegetables, fruits and nuts, and we suggest that you include all of these in your diet. Do note that if you are trying to increase your whole grain consumption, we do not recommend that you binge on whole grain flour products, many of which are quite processed or may contain unhealthy sugars. We recommend actual whole grains: think brown rice, barley, quinoa and millet, which are just a few of the options.
- Women who eat more foods containing soy after their diagnosis have better survival overall than those who eat less soy. This conclusion was welcome, and may come as a bit of a surprise to some people, given all the negative press about phytoestrogens in soy (the Block Center staff have been aware of this trend in the research for a few years now). The conclusion is based on studies that found that women had better survival when they ate diets that are rich in soy foods, as well as diets that are rich in isoflavones. The phytoestrogen components of soy have chemical structures that are called isoflavones. The main sources of isoflavones in our diet are soy foods (though some processed soy foods might not have high isoflavone contents, and are likely to contain GMOs, which should be avoided). Other beans also contain isoflavones as well. We thus recommend soy foods and a variety of other beans as a regular part of your diet. What we don’t recommend – if you are a breast cancer survivor – are isoflavone supplements. These may have stronger estrogenic effects than soy foods, which may compromise their safety. We also don’t recommend making soy the main protein source of your diet, or drinking 7 glasses a day of soymilk, which one oddly designed study recently found had estrogenic effects on the breast.
- Women who eat diets high in fat, and especially high in saturated fat, before developing breast cancer have an increased risk of dying if they develop the disease. This finding means we really cannot recommend high fat diets for women, especially those who may be at an elevated risk of breast cancer (for instance, women who drink more than a glass of wine or a beer a day, who had children later in life or not at all, who are not physically active or who have pre-breast cancer conditions). Of course, as current proponents of high fat diets would point out, the women who eat high fat diets might also be eating a lot of sugar or refined flour, or might tend to be overweight. However, most studies of nutrition that examine fat intake will adjust for the amount of carbohydrates that patients eat, as well as for their weight, in order to rule out exactly this type of effect. Mediterranean diet proponents will point out that these studies don’t include a lot of women who eat very high amounts of olive oil or almonds, and we do acknowledge that olive oil and almonds are healthier-fat foods. They are also, notably, low in saturated fat. If you feel you must follow a high-fat dietary pattern for your health, do at least take into account the advice to avoid saturated fat by keeping the amount of red meat and other saturated fat sources in your diet to a minimum.
The overall recommendation of the WCRF for breast cancer survivors is to follow their 10 cancer prevention guidelines, all of which are based on a thorough analysis of the scientific literature, as this study was. We can support all of these. You probably have heard most of them already, but just so you keep them in mind, here they are once again:
- Be as lean as you can without being underweight.
- Be physically active for at least 30 minutes a day.
- Limit consumption of energy-dense (high-calorie) foods.
- Eat a variety of vegetables, fruits, whole grains and beans.
- Limit red meat, and avoid processed meat (hot dogs, baloney, sausages etc).
- If you drink alcohol, have no more than 1 drink a day if you are a woman, or 2 drinks if you are a man.
- Limit salt intake and avoid moldy grains and cereals.
- Don’t rely on supplements to prevent cancer: thinking that you can overcome the ill effects of an unhealthy lifestyle and diet with vitamin pills will get you nowhere!
- If you are a mom who’s just had a baby, try to breastfeed exclusively for 6 months.
- Cancer survivors should follow cancer prevention guidelines.
These recommendations are suitable for reducing risk for most kinds of cancers. There are, of course, other risk-reduction suggestions that are not based on diet or physical activity, such as not smoking. The great thing about these suggestions is that not only are they suitable for preventing cancer, they also will help in preventing heart disease, which is the leading cause of death in this country.
If you are looking for support to implement these cancer preventing and cancer fighting lifestyle recommendations, or have questions relevant to your specific situation, you may want to consider scheduling a consultation with one of our registered dietitians. You may schedule an appointment by calling the Center at 847-492-3040.