Vitamins, Vegetables and Breast Cancer

Eating plenty of fruits and vegetables can help protect women from a lot of common women's health problems, but is breast cancer one of them? Judging from some newspaper headlines of the past few years, the answer is anything but obvious. Although thousands of studies have been done on how diet affects breast health, the incomplete reports that reach the mainstream media raise more questions than they answer. In the confusion, many women may be missing out on the benefits of recent discoveries.

Not long ago, most research indicated a diet rich in fruits and vegetables would protect the breasts, along with the rest of the body, from cancer. Scientists had even identified which nutrients helped most.

Then came several studies that, a first glance, seemed to contradict years of research and even common sense. In 2001, scientists at Harvard's School of Public Health analyzed eight studies involving 351,825 European and North American women. Surprisingly, they found no significant association between eating fruit and vegetables and lowered breast cancer risk. Latching on to this provocative announcement, a number of newspapers reported that researchers had discovered a vegetable-rich diet doesn't affect breast cancer risk.

Nutritionists still found reason to believe, though, because the study found women who ate four and a half to 10 servings of fruit and vegetables a day had a 7% lower risk than women who ate only one to three servings a day. This number wasn't considered statistically significant, but it still shows fruit and vegetables do play a role in preventing breast cancer.

A second blow to long-held beliefs came from the University Medical Centre in Utrecht, Netherlands in 2005. After analyzing data on 285,526 European women ages 25 to 70, researchers again found no significant difference in breast cancer risk between those who ate vegetables often and those who didn't.

So, what's going on? Were the earlier, more focused dietary studies wrong or are the larger studies missing something?

The missing ingredients

The seeming contradictions between research results often come from factors that don't make the papers. Age is one of these. Most breast cancer prevention studies have involved adult women, usually no older than 25. Unfortunately, even this young age may be too late for the effects of a good diet to help ward off breast cancer. For breast health in later life, girls and young women need good nutrition while the breasts are developing. Even in adulthood, stage of life still matters. What works for premenopausal women may not work as well for women after menopause. On the other hand, while a vegetable-rich diet may not prevent breast cancer in older women, it can increase the odds of survival for those already diagnosed. Another factor is the type of breast cancer studied-genetic or environmental. Strange as it may sound, some studies have shown certain nutrients do better at preventing one kind than the other.

And then there's the way the studies are conducted. The research showing vegetables have minimal effect combined data from multiple studies. The way food or vitamin supplement intake was measured varied from study to study, leaving a lot of room for error when all these data are combined. Another open door for inaccuracy is that researchers looked at the overall amount of vegetables and fruits in the diet, rather than examining the effects of each food individually. If a particular type of vegetable, such as berries or cruciferous vegetables, decreases cancer risk, the effects may have been ignored as "not statistically significant."

Despite the contradictory reports, the US National Cancer Institute continues to advocate a diet rich in beta-carotene, folate, and vitamins A and C. They have good reason. No amount of vegetables can guarantee immunity to breast cancer, but the effects of diet aren't negligible.

Eat your greens and reds

Two groups of vegetables are especially powerful allies in the fight against breast cancer. Cruciferous vegetables, like broccoli, cauliflower and cabbage, and red and orange vegetables like carrots, butternut squash, red peppers, and sweet potatoes, both contain natural compounds that reduce breast cancer risk.

In 2003, a team at the University of Illinois at Urbana-Champaign discovered that sulphurophane, a compound in broccoli, disrupts the growth of later-stage breast cancer cells. Research by scientists from the Roswell Park Cancer Institute, the University of New York, and the Lombardi Cancer Center found that eating cruciferous vegetables, particularly broccoli, reduces premenopausal women's breast cancer risk in a small, but significant way. Unfortunately, though, it had little effect on postmenopausal women.

More recently, in 2006, researchers at the University of Leicester discovered that the compound indole-3-carbinol (I3C), found in Brussels sprouts and cabbages, slows down the growth of breast cancer cells. This nutrient may work especially well against breast cancer caused by environmental factors.

Carotinoids, which give red and orange fruits and vegetables their color, also support breast health. In 2001, researchers at New York University collected data on the levels of a variety of carotenoids in several hundred women. Up to 11 years later, the scientists compared the levels of 270 women who had developed breast cancer to the levels of 270 who were cancer-free. Their findings showed women with the highest levels of carotenoids had half the breast cancer risk of women with the lowest carotenoids levels. A number of other studies on caretenoids support these findings.

Are supplements enough?

Part of the confusion about the effects of diet on breast cancer comes from uncertainly over whether a specific vitamin can lower the risk or whether it's some more elusive quality of whole food products. While researchers aren't clear on exactly how vegetables do what they do, it does seem just popping pills isn't enough. One study, conducted at the State University of New York at Buffalo, found vitamin C, alpha-tocopheral (a form of vitamin E), folic acid, cartenoids, and dietary fiber from vegetables and fruits all reduce breast cancer risk. Because vitamins C and E and folic acid taken as supplements didn't offer any protection, however, researchers suggested the combination of nutrients in a variety of vegetables may have a "synergistic effect on breast cancer risk."

Another study, at Hanyang University in Seoul, Korea also found that vitamin A and C from food reduced the risk of breast cancer, but taking extra supplements didn't.

In the well known Nurses' Health Study, which tracked 83,234 women over 14 years, vitamin E in the diet appeared to protect premenopausal women from genetic breast cancer better than from environmentally-caused breast cancer. Vitamin E supplements (alpha tocopherol acetate) alone, though, didn't offer any protection. This suggests other forms of vitamin E, such as gamma tocopherol and tocotrienols, found in food may be doing the trick.

It's never too late

Many studies have found eating more fruits and vegetables doesn't lower breast cancer risk for postmenopausal women. This may make it seem like a later life diet makeover will do nothing for breast health, but fortunately there's evidence to the contrary. In 2006, Nutrition and Cancer published the results of a study lead by Archana Jaiswal McEligot that found less dietary fat, and more fiber and nutrient-rich vegetables improve survival rate for postmenopausal women with breast cancer. According to researchers, the benefits come from a "plant-based, high-fiber diet."

Despite what some newspaper headlines claim, eating lots of fruits and vegetables can protect women from breast cancer. Just starting a vitamin regime in your mid-forties won't do it, though. The teen years, when the breasts are forming, are a critical stage for establishing life-long breast health. While improving your diet after menopause may not help reduce the risk of developing breast cancer, it can improve the chances of survival for those who've already been diagnosed. Whatever a woman's age, nutrients should come from a diet rich in a variety of vegetables, rather than from supplements.

Considering the number of serious health concerns a balanced diet can prevent, making the effort to fit in those recommended five to ten servings of fruits and vegetables a day is well worth it. When it comes to reducing breast cancer risk through diet, it's vital to investigate the research reports behind the headlines before making any dietary changes.