October is Breast Cancer Awareness Month. The month aims to promote 
screening and prevention, and invariably includes both information and misinformation about diet and breast cancer. In today’s blog we take a look at what the science tells us.
We should start by saying that contrary to some claims, there aren’t specific foods that can increase survival. Rather, there is considerable evidence that dietary patterns can make a significant difference for women fighting breast cancer. Let’s take a look at some of these.
Dietary fat intake
Much has been written about the potential health benefits of eating a high fat/very low carbohydrate diet. But what does the science tell us? In one study, the Women’s Intervention Nutrition Study (WINS), R.T. Chlebowski and colleagues demonstrated that when women reduced their fat intake to 20% or less, they reduced their risk of breast cancer recurrence by an average of 24%! A different study, though not specific to breast cancer, showed that reducing saturated fat intake to under 10% reduced cancer mortality by 45%! And yet, according to the CDC, women eating the Standard American Diet consume an average of 36.1% of their daily calories from fat! We have to assume this number is even higher for women following a high fat/low carb diet. This is very concerning for anyone battling breast cancer, and certainly not advisable, based on what the science is telling us.
Carbohydrates
As previously mentioned, one very popular diet recommends consuming a diet very low in carbohydrates. Meaning all carbohydrates, which suggests that this recommendation doesn’t distinguish between refined carbohydrates (pastries, white bread, white rice), which we should all limit or avoid, from complex carbohydrates (unrefined whole grains, legumes, oats), which are nutritious and actually help stabilize glucose. As those of you familiar with Life Over Cancer already know, simple and refined carbs can lead to glycemia and insulinemia, both of which can drive cancer growth! On the other hand, complex carbs do not raise blood glucose and insulin. In fact, the research demonstrates that controlling glycemia and insulin levels through the use of complex carbohydrates not only reduces the risk of cancer recurrence, but also reduces mortality!
Vegetables and fruits
Vegetables and fruits are fundamental to any healthy diet, and are part of nutritious dietary recommendations for the prevention of cancer as well as other diseases. As it relates to breast cancer, Cheryl Rock and colleagues assessed carotenoid levels of patients in a breast cancer diet trial and found that those in the top 2/3 of carotenoid levels over the course of the study were 33% less likely to have a breast cancer recurrence or new breast cancer. Carotenoids are found in both vegetables and fruits; yellow and orange fruits and vegetables and dark green leafy vegetables are particularly good sources. Dark green vegetables also contain lutein, including kale, collards, spinach and Swiss chard. Other high carotenoid vegetables and fruits include carrots, sweet potatoes, pumpkins, winter squash, apricots, mangoes, cantaloupe, and tomatoes. As far as fruit juices, while it’s OK to occasionally enjoy some of these fruits as juices, we generally recommend eating them as whole fruits. However, if you choose to drink juices, you might consider diluting them with water by 25% – 50% in order to reduce the sugar load. Eating whole fruit provides extra fiber and helps control calories as well as excess fructose consumption. As it relates to breast cancer, it’s important to note that high fiber intake is associated with lower overall mortality in breast cancer patients, including both breast cancer deaths and deaths from other causes. Foods high in fiber include raspberries, pears, barley, whole wheat spaghetti, brown rice (as opposed to white rice), beans (all types, e.g. split peas, lentils, kidney beans, black beans), green peas, broccoli, cauliflower, and turnip greens.
Dairy
Several studies have shown that high-fat dairy intake is significantly related to higher breast cancer mortality as well as mortality from other diseases. Low fat dairy did not demonstrate a direct correlation to breast cancer mortality. So, if you’re going to use dairy products, choose low-fat varieties of milk, yogurt or cheese. Better still – and what we recommend to our patients at the Block Center – consider some of the dairy alternatives available today, including unsweetened soy milk, almond milk (available in low-fat and unsweetened), and rice or oat milk.
Fish and Fish Oil
High intake of omega-3 fatty acids from fish in the diet has been correlated with reduced breast cancer events (recurrences, new breast cancers) and reduced overall deaths from breast cancer and other causes. Fish that are high in omega-3 fats include salmon, sardines, anchovies, tuna, cod, haddock, Atlantic mackerel, halibut and other fish from northern oceans. We recommend reducing or avoiding tropical fish, like tilapia, or farmed catfish, which are not high in omega-3s.
Soy
There has long been controversy as to whether an estrogen-sensitive breast cancer patient might worsen their disease by consuming soy products. In fact, a few leading breast cancer specialists have railed against the consumption of soy, raising worries of its safety. At the same time, breast cancer research at the Block Center demonstrated enhanced outcomes among patients consuming increased levels of soy. And now, emerging science from both the laboratory and from large scale epidemiological studies have confirmed what our early data suggested. Bottom line, soy is not harmful for breast cancer patients, and may, in fact, be quite helpful. When you add soy foods to your diet, emphasize the relatively un-processed types of soy, such as tofu, edamame, miso and tempeh. These are healthier and less caloric than highly processed soy meat substitutes. Additionally, when used as a substitute for meat, soy may be helpful in controlling weight, since it’s lower in calories.
In addition to these dietary recommendations, it is important to mention that there is research demonstrating that both obesity and weight gain following a breast cancer diagnosis can lower the chances of survival, as pointed out in a 2019 review article. If your weight is not ideal, a plan for weight loss that incorporates sound nutritional choices and exercise is a powerful way to improve your outcome.