Think and Eat Positive
It's not all gloom and doom though, there are many things you can do to protect yourself against breast cancer and other diseases. For example: stopping smoking, losing weight, exercising more and cutting down on alcohol. Changing the way you eat is vital and in your control.
Fruit and vegetables
Fruit and vegetables can protect against breast cancer through a variety of mechanisms involving their antioxidant, fibre and other nutritional content (Michels et al., 2007). Indeed the evidence linking fruit and vegetable consumption to a reduced risk of breast cancer is accumulating.
A large-scale US survey published in the Journal of the National Cancer Institute called the Nurses' Health Study, reported a negative association between premenopausal breast cancer and women consuming five or more vegetables per day compared with those consuming less than two vegetables per day (Zhang et al., 1999). In other words, premenopausal women who ate the most vegetables had a lower risk of developing breast cancer than those who ate the least. The authors concluded that the consumption of fruits and vegetables high in specific carotenoids (nutrients found in brightly coloured vegetables and fruits such as carrots, sweet potatoes, spinach, kale, spring greens and tomatoes) may reduce breast cancer risk among premenopausal women. This, they noted, applied particularly to those who were at a higher risk because of a family history of breast cancer or consumption of alcohol.
Another study looking at the role of diet and breast cancer risk in 8,984 Italian women over nineand-a-half years follow-up (the length of time that passes between the start of the study when information is collected and the end of the study when the participant's health status is assessed) recorded 207 cases of breast cancer (Sieri et al. 2004). This study identified four dietary patterns among the participants: salad vegetables (mainly consisting of raw vegetables and olive oil); Western (mainly consisting of potatoes, red meat, eggs and butter); canteen (pasta and tomato sauce); and prudent (cooked vegetables, pulses and fish, with little or no wines and spirits). Results showed that only the salad vegetables dietary pattern was associated with significantly lower (34 to 35 per cent) breast cancer incidence. Women with body mass index of less than 25 had an even greater risk reduction (50 per cent). Whereas for women with body mass index above 25, the salad vegetable dietary pattern had no protective effect. The authors suggest this latter finding may reflect how leaner women might be more health conscious and how overweight women may be dieting and so consuming more vegetables than they would normally. These findings provide compelling evidence that a healthy diet, containing plenty of salad vegetables, can protect against breast cancer.
Three years later, a further 31 breast cancer cases had occurred among this cohort and new analysis revealed that that the salad vegetables dietary pattern offered a significant amount of protection (75 per cent lower), against a specific subtype (HER-2-positive) of breast cancer (Sant et al., 2007). HER-2positive breast cancers have higher than normal levels of a protein known as HER-2 on the surface of the cancer cells. This protein encourages the cancer cells to grow which is why HER-2-positive cancers tend to grow faster than those that are HER-2 negative. Approximately 20 to 25 per cent of breast cancer patients are described as having HER-2-positive breast cancer (Breast Cancer Care, 2007a).
Taken together, this research suggests that fruit and vegetables play an important role in protecting against breast cancer. This is certainly an area that warrants further investigation.
Folic acid (folate) is an important B vitamin necessary for the production of red blood cells and the synthesis of deoxyribonucleic acid (DNA - the blueprint for life). It is also required for the normal methylation of DNA. This refers to the 'flagging' of genes with a methyl group (a group of carbon and hydrogen atoms) that is used to mark out specific genes for expression (activation). This process is essential for normal growth, development and function. If the methylation process is disrupted, unregulated gene expression may lead to uncontrolled cell division or cancer.
The deficiency of certain vitamins has been said to mimic the effects of radiation damage to DNA. Indeed a low intake of folic acid could increase the risk of several cancers, including breast cancer, whereas a sufficient intake of folic acid and related B vitamins may protect against this disease (Wang et al., 2006).
Several studies show how dietary folic acid might protect against breast cancer, particularly among women who are at an increased risk as a result of high alcohol consumption. A prospective study of 17,447 Anglo-Australian women (among whom there were 537 cases of invasive breast cancer) investigated the effects of dietary folic acid on the relation between alcohol consumption and breast cancer risk (Baglietto et al., 2005). Results showed that women who had a high alcohol consumption coupled to a low intake of folic acid had an increased risk of breast cancer, but those with a high alcohol consumption and a moderate to high intake of folic acid had no increased risk. It was concluded that an adequate dietary intake of folic acid might protect against the increased risk of breast cancer associated with high alcohol consumption.
Folic acid is found in many foods including broccoli, Brussels sprouts, asparagus, peas, chick peas and brown rice. Other useful sources include fortified breakfast cereals, wholegrain bread and certain fruits (oranges and bananas).
Fibre has been hypothesised to reduce breast cancer risk through a number of mechanisms including the inhibition of oestrogen reabsorption back into the bloodstream, the inhibition of human oestrogen synthetase (an enzyme that we use to make oestrogen) leading to a reduction in oestrogen production and finally, a reduction in the levels of steroid hormones called androgens which influence levels of oestrogens and proliferation of breast tissue or by some mechanism involving insulin and IGFs (Cade et al., 2007). As stated above, IGF-1 is associated with an increased breast cancer risk and IGF-1 levels are influenced by diet.
Fibre intake and breast cancer incidence was investigated among a large group of women called the UK Women's Cohort, which included high number of vegetarians to allow for meaningful comparisons with fish and meat-eaters (Cade et al., 2007). This study showed that in premenopausal, but not postmenopausal women, those who ate 30 grams of fibre per day had half the risk of those who ate less than 20 grams. These findings suggest that in premenopausal women, total fibre is protective against breast cancer; in particular, fibre from cereals and possibly fruit. Dietary fibre has been shown to regulate oestrogen levels in the body. The researchers believe that this may explain why the effects of increased fibre intake were only seen in premenopausal women and not in postmenopausal women.
This is the first large prospective study to show a relationship between total fibre intake and risk of premenopausal breast cancer. Previous analysis may have missed such a relationship between fibre and breast cancer by combining premenopausal and postmenopausal results together.
The average person in the UK eats 12 grams of fibre per day. To increase your intake you could choose a high-fibre cereal for breakfast or switch from white bread and pasta to wholemeal and ensure you have at least five portions of fruit and vegetables per day.
Eat your greens!
It is well-documented in the scientific literature that cruciferous vegetables (such as spring greens, broccoli, Brussels sprouts and kale) help protect against cancer. Some of this activity has been attributed to a compound in these vegetables called sulphurophane which has attracted much attention since its discovery in 1992. The mechanism underlying this compound's anti-cancer activity has remained unclear until 2004. In a study published in the US Journal of Nutrition scientists proposed just how this compound may offer protection (Jackson and Singletary, 2004). Keith Singletary and colleagues at the University of Illinois exposed malignant human breast cells to sulphurophane in the laboratory and saw that it inhibited cell division and DNA synthesis in the cancer cells. In other words, this compound inhibited the growth of cancer cells, but not normal cells.
Singletary suggests that sulphurophane works by disrupting cellular components called microtubules. These are long slender cylinders of a protein called tubulin that are required for the normal separation of the duplicated chromosomes during cell division. If this process is disrupted then cells cannot divide. These findings may be useful in developing new treatments for breast cancer. In the meantime, including a wide range of vegetables in the diet, including the cruciferous varieties, could offer immediate benefit.
The soya connection
There is strong evidence that soya intake during adolescence may reduce the risk of breast cancer later in life. The Shanghai Breast Cancer Study investigated the role of soya in breast cancer by looking at the dietary history of 1,459 breast cancer cases and 1,556 age-matched controls in China (Shu et al., 2001). This study found that women who consumed the most soya as teenagers had half the risk of breast cancer as adults. This inverse association was observed for each of the soya foods examined (tofu, soya milk and other soya products) and existed for both premenopausal and postmenopausal women. The authors of this study suggest that a substantial difference in breast cancer incidence between Asian and Caucasian women and increasing breast cancer incidence among Asian-Americans may be explained, at least in part, by soya food intake during adolescence. They state that their study emphasises the importance of initiating cancer intervention programs early in life.
A year later, scientists investigating the link between adolescent soya intake and breast cancer asked over 1,000 Asian-American women (including 501 breast cancer patients) how often they ate soya foods such as tofu, soya milk and miso. This study also found that women who consumed soya at least once a week during adolescence had a significantly reduced risk of breast cancer (Wu et al., 2002).
Results showed that those who were high soya consumers as both adolescents and adults had a 47 per cent reduction in risk of breast cancer. Those who ate little soya as adults but had eaten it regularly during adolescence showed a 23 per cent reduction in risk. Women who were low consumers during adolescence and high consumers during adulthood showed little reduction in risk. These studies suggest that high soya intake during adolescence reduces breast cancer risk and the risk continues to fall if people continue to eat soya as an adult.
In an attempt to draw the scientific evidence together, a team lead by Professor Bruce J. Trock from the Johns Hopkins School of Medicine in Baltimore, MD, performed a review of 18 studies on soya exposure and breast cancer risk published between 1978 and 2004 (Trock et al., 2006). Results showed a modest association between a high soya intake and a reduced breast cancer risk. The authors warn that this result should be interpreted with caution and that recommendations for high-dose isoflavone supplementation to prevent breast cancer or prevent its recurrence would be premature. However, they do state that there is no evidence to suggest that consumption of soya foods, in amounts consistent with an Asian diet, is detrimental to breast health, and go on to say that such a diet is likely to confer benefits to other aspects of health. In other words, the research looks promising but more evidence is needed.
The low rate of breast cancer in Japan and the high rate of survival amongst those who are affected is often used to promote soya foods as being beneficial - or at least, not being harmful - for breast cancer patients. Some researchers, however, are cautious and think that even the small oestrogenlike effect of soya foods may be detrimental for women who have gone through the menopause, whose natural oestrogen levels have dropped and who have been diagnosed with oestrogen-receptor positive (hormone sensitive) breast cancer (PCRM, 2002).
Their concern is that the weak oestrogen activity of soya isoflavones may stimulate the growth of tumours which are sensitive to oestrogen. This is not a concern for premenopausal women, who have much higher levels of oestrogens which are many times more potent than phytoestrogens.
These concerns are based largely on the results of a small number of in vitro (test tube) and animal studies but as these have produced mixed results their relevance to human breast cancer patients remains unclear.
To date there have only been two human studies on this subject, the findings of which were also unclear (Petrakis et al., 1996; Hargreaves et al., 1999). The cautious approach would be for postmenopausal women at risk of breast cancer to limit the amount of soya products they eat to three or four a week.
On the whole, the evidence suggests that consuming moderate amounts of soya foods is much more likely to benefit health rather than harm it, both in terms of breast cancer risk and other chronic diseases.
For more information on foods that can help fight cancer see the easy-to-read colourful guide A Fighting Chance. A guide to healthy eating to help prevent and overcome breast cancer available from: http://vivahealth.viva.org.uk/breast-cancer-campaign. This guide summarises the key findings this report and provides vital information on a range of cancer-busting foods. It also includes a seven-day meal plan with inspiring healthy recipes such as our ever-popular Tortilla Wraps with Mango Salsa, Quinoa Superbowl Salad and the fabulous Summer Berry Compote.