Dietary Patterns and Breast Cancer: What Every Patient Needs To Know By: Keith I. Block, MD

I am often asked if there are specific foods that can boost cancer survival. For Breast Cancer Awareness Month, I thought I’d address this question as it relates to breast cancer.
Existing research doesn’t support the notion that there are specific foods that can increase survival. However, 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 patterns.

In the Women’s Intervention Nutrition Study (WINS), R.T. Chlebowski and colleagues organized a large-scale randomized trial that included women with early-stage breast cancer who reduced their fat intake to 20% or less, following dietary counseling, as well as a control group who did not reduce their dietary fat. The low-fat diet group started showing better results early in their follow-up, with a reduction in breast cancer recurrence of 24% after the groups had been followed for only a few years. As published in May of 2020, after nearly 20 years of tracking these women, a 15% reduction in deaths from all causes and a 20% reduction in deaths specifically from breast cancer was documented. Evidence from a well-conducted randomized trial with long-term tracking is as good as it gets in medical research, and this is a result that patients should listen to. I know there are several other cancer diets that have been proposed since the WINS study started, but it must be noted that they have only very preliminary trials to back them up. My staff and I have been recommending a low-fat diet to our patients in the 40 years that I have been treating them; we also recommend they use healthful fat sources such as olive oil and nuts, rather than less healthful options such as corn oil.
Several currently popular diets hyped as being good for all of us are high in fat, rich in animal proteins and low in carbohydrates, because the assumption is that all carbohydrates are unhealthy. However – and, contrary to popular opinion – these diets are not good for any of us and, in fact, can be the recipe for a bad outcome for breast cancer patients! Why? Because all carbohydrates are NOT created equal. 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. One study in women, for instance, found that a low-glycemic and low-fat, mostly vegetarian diet based on legumes such as lentils, split peas, chickpeas and other beans, lowered insulin levels better than a standard cholesterol-lowering diet that included meat and dairy. It’s not surprising that whole grains and beans, along with vegetables and fruits, are among the dietary guidelines for cancer patients of the World Cancer Research Foundation and the American Institute of Cancer Research (WCRF/AICR). A recent review of studies that graded healthy people on how well they followed these guidelines showed reduced breast cancer risk in patients who followed them the most consistently. A study mentioned in the review, which looked at how well breast cancer patients followed the guidelines, found a nearly 40% reduction in risk of dying from breast cancer among those whose diet and lifestyle were most in line with the recommendations.

Vegetables and fruits are fundamental to any healthy diet, and are part of healthy 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 diagnosis. 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, which also contain lutein, include 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, and to eat a protein source, such as seeds, nuts, or hummus on a cracker. The protein will help buffer a possible glycemic surge. Eating whole fruit helps control calories as well as excess fructose consumption, and provides extra fiber. Extra fiber is important because a 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.

A recent study found that high-fat dairy intake was 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. High long-term consumption of regular milk products was associated with higher risk of breast cancers that were positive for estrogen and progesterone receptors in a newly published Swedish study, although fermented milk products like yogurt did not increase risk So, if you’re going to use dairy products, choose low-fat varieties of milk, yogurt or cheese, and consider fermented products. Or, better still – and what I recommend to our patients – consider some of the dairy alternatives available today, including unsweetened soy milk, almond milk, rice or oat milk.

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. However, be aware that most fish oil supplements are of the ratios optimal for heart disease and arthritis, whereas the ratios of the fish oil supplements we use at the Block Center are specifically formulated for cancer.
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.

Back in the 80’s and 90’s there was controversy as to whether an estrogen-sensitive breast cancer patient might worsen their disease by consuming soy products. In fact, there were a few leading breast cancer specialists that railed against the consumption of soy, raising worries of its safety. However, the bottom line is that 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, tempeh and soy milk, soy cheese or soy yogurt. 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.

A 2002 study found that breast cancer patients with the highest quartile of insulin levels, which are correlated with high body mass index, had markedly elevated risks of breast cancer mortality and recurrence. Several studies since then have implicated elevated insulin, and elevated blood glucose and related variables to a worse outcome for patients with breast cancer. To reduce elevated insulin and blood glucose, we suggest consuming low-glycemic index foods, which have been found to only minimally raise blood glucose levels. Avoiding refined flours, refined sugar and related products (white and brown sugar, molasses, honey, cane juice and others) as well as sugar-sweetened beverages, and eating nuts such as almonds or walnuts can help. In one study, almonds reduced C-peptide, a marker for insulin production, more effectively than whole-wheat muffins. Alternatives to refined sugars include sweeteners such as monk fruit, stevia and limited quantities of other natural sweeteners such as agave or brown rice syrup. And, a sweet piece of nutritious fruit can make a delicious dessert!
Our general dietary recommendations
At the Block Center, we recommend a diet low in saturated fats and high in fiber, plant-based sources of protein, cold water fish rich in omega-3 fatty acids, complex carbohydrates, fruits and berries rich in antioxidants, and nuts, seeds and cruciferous vegetables, foods containing other cancer fighting substances such as allium compounds, dithiolthiones, flavonoids, glucosinolates, indoles, isothiocyanates, phenols, and d-limonene. This nutritional strategy is intended to do several things, including:
Help curtail inflammation, which is essential for combating recurrence and progression. In fact, elevated inflammatory markers increase risk and mortality of breast cancer by 2 to 3-fold, whereas countering this can be the difference in preventing proliferation and dissemination of breast cancer cells, and even never seeing the cancer again!

Reduce free-radical damage
Minimize platelet activation and deaggregate platelets, essential elements in preventing migration, dissemination and metastases. (This can also lead to dangerous blood clotting).
Manage and contain blood sugar and insulin surges.
Reduce serum levels of insulin-like growth factor 1, or IGF-1 (which stimulates malignant cell multiplication and inhibits cell death).
Evidence shows that reducing glycemia, insulinemia, inflammation and oxidation makes a huge difference in every challenge a breast cancer patient faces, including improving the biological integrity needed to counter growth while reducing the risk of recurrence.
One last thing: remember that while diet and nutrition are fundamental when it comes to overcoming any malignancy, it is only one aspect of our comprehensive, innovative and integrative approach to effectively combatting – and ultimately defeating – cancer.

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