Links Between Your Diet and Breast Cancer

When I was 17, my mother was diagnosed with breast cancer. Thanks to her illness, I'm sitting here writing this column. And I'm not just referring to today's topic - she's the reason I'm so fascinated by nutrition, period.

When I was growing up, we ate mainstream 70's and 80's fare. We breakfasted on those horrible sugary "cereals", ate white bread sandwiches for lunch, and only had vegetables - frozen peas, carrots, or corn - at dinner. Everything changed when my mom discovered she had cancer. When she got the diagnosis, she opted for surgery but refused chemo - she decided to fight the cancer with food, instead. This might not be the right choice for everyone, but it sure worked for her, and benefited the whole family.

Overnight, my mother became a voracious health researcher. She told me about flax seeds almost twenty years ago, long before the health media got on the bandwagon. When she learned of the link between breast cancer and daily alcohol, she eliminated the nightly sherry she'd shared for years with my father. She dramatically increased her intake of fruits and vegetables (two different salads every day!), and can list all their key cancer-fighting nutrients. She eats lots of whole grains, makes brown instead of white rice, eats very little meat, won't touch anything cured with nitrates, and chooses organic food whenever possible.

Whenever I stay at their house, it's like a refresher course in everything I tell people they should be eating. She doesn't have a university education, but she's one smart, and inspiring, cookie. She's a few thousand kilometers away right now, so unfortunately I've had to rely on what I've learned from her in the past, and my own research, to write this.

So what do we know? Meat-heavy and high-fat diets increase breast cancer risk. The risk from eating a high-fat diet is even higher if those fats are mostly saturated, or come from meats. Being overweight, period, is also a risk factor. One study, involving nearly 2500 postmenopausal women who'd been treated with surgery for early-stage breast cancer, found that a low-fat diet lowered the risk of cancer recurrence by 42% in those with estrogen-negative tumors. Other researchers have hypothesized that fat may affect breast cancer through its role in estrogen production; however, the fact estrogen-negative tumors benefited the most in the above study suggests there may well be another mechanism at work.

Another study asked breast cancer patients and healthy women to recall the diet they ate as teenagers (a research method with obvious drawbacks). The results found that butter intake increased breast cancer risk, while eating eggs seemed protective. The egg effect, if real, may be due to their high levels of folate and vitamin D. Folate, also found in leafy greens, is particularly beneficial to women who drink daily alcohol, as shown by a study that linked blood folate levels to the risk of developing breast cancer.

In my various nutrition columns that I write, I'm fond of pointing out the fact that high-glycemic carbohydrates have been linked to inflammation, aging and chronic disease. This time I found a study that links high carbohydrate intake to breast cancer. A case-control study of almost 2,000 Mexican women found that those who took in more than 57% of their energy intake as carbohydrates had more than double the risk of breast cancer than those who ate more balanced diets. Sucrose (white sugar) and fructose (the sugar in fruit, which is also a component of the sucrose molecule) demonstrated the strongest association with breast cancer in the study.

Does this mean fruit itself is a risk factor? I don't think so. I live in Mexico part-time, and I see what they eat. Mangos, papayas, bananas and sugary fruit drinks predominate; all of these have high glycemic indexes. I've tried, and failed, to find one juice product on the shelf that doesn't have added sugar.
I mention the glycemic index because researchers believe that the link between carbohydrates and breast cancer may be a result of elevated levels of insulin and insulin-like growth factor (IGF). These stimulate cell proliferation (multiplication), and may also cause higher circulating levels of estrogens. Apparently, up to 90% of breast cancers are insulin-receptor positive and over-express IGF. This may also be the link between breast cancer and high-fat diets; women living in countries that favour high-fat foods have been shown to produce more IGF.

As for those magical flax seeds, a 2001 study out of the University of Toronto gave two tablespoons of ground flax a day to newly diagnosed breast cancer patients, for 30 days. Those taking the supplemental flax slowed their rate of cancer cell growth by 33% compared to those who didn't eat flax, accompanied by a 60% drop in the spread of the most aggressive cells. My mom sure knows her stuff. I have a big bag of uneaten flax seeds in my refrigerator as I write this - I'll go grind some up right now, while I still remember! Thanks, Mom.

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