Nutrition and Breast Cancer

Thanks to recent research in nutrition, dietary strategies are helping many more women survive breast cancer and go on to live long, healthy lives. 
Often enough, evidence reveals these strategies may work by influencing inflammation, the immune system, and insulin responsiveness. However, there is no nutritional therapy that is yet “proven” to treat cancer directly or increase survival.
According to large trials of diet and breast cancer such as the Women’s Healthy Eating and Living (WHEL) randomized trial and the Women’s Intervention Nutrition Study (WINS) trial, as well as small intervention studies, a lower calorie diet leading to controlled weight reduced mortality. 
The reason – being overweight or obese appears to increase mortality because of higher risk of metastasis. Crash dieting is not the key, only healthy weight loss and patients should consult a nutritionist for planning meals. 
Patients should note that diets too low in calories can lead to loss of muscle mass, which is already a side effect of chemotherapy, and that generally leads to an increase in fat mass. 
As far as types of foods, red meat should be avoided because it’s associated with increased risk of breast cancer. Saturated fat should be avoided as much as possible since it increases estrogenic stimulation of breast cancer growth. 
A low-fat, high-fiber diet is associated with suppressed estradiol levels. The diet should be based on plenty of plant-based proteins (soy, wheat), eggs, fish and low-fat dairy (whey). 
High-carb diets are also associated with increased mortality, but so are very low-cab diets. The diet should focus on obtaining a moderate amount of complex carbs (mainly from whole grains, fruits, and vegetables) rich in fiber. Blood sugar control is encouraged through eating complex carbs and obtaining regular exercise. 
Patients should seek to obtain higher levels of long-chain omega-3 fatty acids (DHA and EPA) such as from fish oil because low levels are associated with more proinflammatory markers. 
Because high dietary intake of fruits and vegetables are associated with greater breast cancer survival, it’s easy to suggest that taking supplements of phytochemicals may increase survival. However, meta-analyses suggest no single vitamin/phytochemical solely improves outcomes. Instead it’s best to focus on consuming more of whole fruits and vegetables.
Phytoestrogens such as from soy (isoflavones) and flax may, in fact, lower risk of breast cancer and improve survival of breast cancer. Because they mimic estrogen and bind to estrogen receptors, they may inhibit cancer cell growth. However, more research is needed before suggesting as a treatment especially in high-risk women and postmenopausal estrogen-receptive positive breast cancer patients.  Note that it could be that simply replacing meats with soy foods leads to weight management that increases breast cancer survival.
Eating foods rich in iodine such as sea vegetables or using iodized salt may anticarcinogenic effect possibly by optimizing thyroid function. Additionally, maintaining a high vitamin D status may help reduce risk cancer and improve prognosis although more research is needed to understand the relationship.  

Reference 

Kohlstadt I. Food and Nutrients in Disease Management. Boca Raton, FL: CRC Press, 2009.
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