Reducing the risk of breast cancer through diet
Nutrition and breast cancer
Breast cancer is the most common cancer in UK women. Overall, 1 in 9 women can expect to develop breast cancer over the course of their lifetime, with the incidence rising from approximately 20 per 100,000 women under the age of 39 to 360 per 100,000 at the age of 70 years. Whilst deaths related to breast cancer are falling, the incidence of breast cancer appears to be rising rapidly.
Whilst age and sex are the most important risk factors for breast cancer, with 99% of cases found in women and the majority diagnosed between the ages 50 and 64 years, age and sex are not the only factors. Recent research has placed a great deal of attention on aspects of behaviour, including how many children a woman has, whether she breast feeds and the age she has her first child and, therefore, broadly the number of menstruations she has, or the amount of oestrogens to which she is exposed. Genetic factors are only thought to account for 10% of all breast cancers.
Epidemiological research shows women in Japan and China to have an incidence of breast cancer around a 6th of that found in the UK. That is until they move to another country, as it seems women adopt their host country’s risk of developing breast cancer within as little as 5 years. One cause of this rapidly transferable environmental risk is thought to be diet.
Most cases of breast cancer are adeno-carcinomas or cancers of the gland and, as with other cancers of this nature, it is thought the primary trigger for the development of cancer is exposure to hormones, in the case of breast cancer oestrogens.
Oestrogens are primarily synthesised by the ovaries, and are produced in comparatively large amounts throughout a woman’s menstrual years. Whilst the amounts of oestogens produced vary with the monthly cycle, breaks from oestrogens production only occur during pregnancy and whilst breastfeeding.
The more children a women has, the earlier her menopause and the later menarche the lower her risk of developing breast cancer. It seems, however, that some women produce more oestrogens than others, are more sensitive to the effects of oestrogens or are slower at eliminating oestrogens than others.
Weight and alcohol
Fat (lipid) cells are oestrogenic, or produce oestrogens, so it is not surprising to find that overweight women have an increased risk of developing breast cancer. What is surprising is that this only applies to post-menopausal women, with obesity (BMI >30) doubling the risk of breast cancer in post menopausal women when compared to women of a normal weight (BMI 20-25).
A number of studies have shown that consuming alcohol increases levels of oestrogens and it’s still bioactive metabolites, and it is thought this is the likely cause of the 32% increased risk of breast cancer with drinkers of alcohol, in comparison with those who drink no alcohol. It has also been noted, however, that drinkers of alcohol have lower levels of folic acid and that supplementing the diet with 400iu of folic acid negates this risk.
Fibre is required for the sequestration of the bioactive metabolites of oestrogens from the liver in order for elimination via the bowel. A diet rich in grain fibre is associated with a decreased risk of breast cancer, and this is a marked effect in younger (pre-menopausal) women.
A large intake of fruit and vegetables has also been shown to correlate well with a reduced risk of breast cancer, and whilst this might relate to the fibre content of fruit and vegetables, there are many other compounds found in fruit and vegetables which are believed to have anti-cancer properties.
There is little doubt that oestrogens are important to the development of breast cancer and it seems anything which can alter the exposure of breast cells to oestrogens could be helpful. It was thought the high consumption of soya produce, rich in phytoestrogens, in Japan was a cause of the relatively low incidence of the disease in that country, although research has failed to confirm this.
Phytoestrogens are oestrogen-like substances which occur naturally in some plant foods and which are concentrated in soya produce. Some evidence suggests these relatively weak oestrogen-like substances, when consumed, block oestrogens receptor sites, preventing the stronger oestrogens synthesised by our bodies exerting their effect.
The use of soya phytoestrogens (primarily the isoflavones diadzein and genistein) has gained considerable popularity, not as a protective against breast cancer but as an alternative to hormone replacement therapy by menopausal women. More recent research, however, has indicated that even weak phytoestrogens might hasten the development of a breast tumour. So, whilst phytoestrogens might protect against breast cancer the consumption of these substances could exacerbate an existing tumour.
Not all oestrogens our cells are exposed to are produced within our bodies. Some comparatively rich sources of oestrogens are found in our water, as a by-product of the breakdown of synthetic contraceptives and hormone replacement therapy.
Research suggesting the femalisation of male fish due to the effects of these metabolites of drugs has been largely discredited. Oestrogens are, however, legally injected into non-organic beef as a growth promoter and it is thought exposure to these comparatively high doses of oestrogens can contribute to oestrogens overload.
All fat cells are oestrogenic, in that they are sites for the synthesis of oestrogens, indeed our fat cells are second only to the ovaries as a source of oestrogens. Not surprisingly, being obese doubles the risk of breast cancer, what is surprising is that this only manifests after the menopause.
Research has shown a linear relationship between the amount of alcohol consumed and the risk of breast cancer. More recent research has also shown that a large consumption of alcohol during early adulthood is more risky than consuming alcohol later in life.
It has been long thought that it is the effect alcohol has on blocking the detoxification of oestrogens which is the likely cause of this increased risk. Recent research, however, indicates alcohol consumption is associated with a low intake/absorption of folic acid, and a low level of folic acid is associated with a 32% increased risk of breast cancer when compared to those with normal levels of this nutrient, a risk which is negated by supplementation with folic acid.
Research suggests a large consumption of insoluble fibre is associated with delayed onset of breast cancer. Fibre is required for the elimination of sequestered oestrogens with the stool and it is thought this the most likely cause of this benefit.
Fruit and vegetables
Fruit and vegetables are largely sources of soluble fibre and this is thought a possible contributor to the benefit conferred by eating large amounts of fruit and vegetables in relation to the risk of breast cancer. The consumers of the greatest amount of fruit and vegetables have a 25% reduced incidence of developing breast cancer when compared to the consumers of the least fruit and vegetables, with the greatest effect coming through the consumption of vegetables rather than fruit.
There are, however, many nutrients contained in fruit and vegetables which are thought to play an important role in protecting against cancer, including, the antioxidant lycopene which has been shown to be specifically beneficial in relation to breast cancer.
Meat and fish
An increased consumption of meat is associated with an increased risk of breast cancer, whilst an increased consumption of fish is thought to protect against breast cancer. The same applies to all cancers and what appears most important is how the meat is cooked, with well done and burnt meat consumption most closely associated with cancer.
Fats and oils
Breast cancer risk is proportional to the amount of animal fat consumed, whilst the consumption of fish and olive oil is inversely proportional to the risk of developing breast cancer.
The consumption of animal fat (from meat and dairy produce) remains the best predictor of breast cancer risk, and is thought to be an important factor in the lower incidence of breast cancer in China and Japan where the consumption of animal fat is much lower than in the UK.
Indole 3 carbinols
These compounds found primarily in brassica vegetables, such as broccoli, brussel sprouts, cauliflower, cabbage, kale and mustard and cress are known to expedite the detoxification of oestrogens and, in effect, neutralise this along with other hormones. Whilst much of this research has taken place in the test-tube, the brassica vegetables have long been known for their anticancer properties.
Breast cancer rates are highest in areas with least sunlight and correspondingly least vitamin D, as sunlight is required for the synthesis of vitamin D. Research has also shown vitamin D to inhibit the growth of breast cancer cells.
Unquestionably, diet is important to the risk of developing breast cancer, with great importance placed on those foods which help detoxify oestrogens. For the prevention of breast cancer it is particularly recommended you;
- Avoid becoming overweight
- Minimize your consumption of alcohol or avoid it altogether
- Limit your intake of meat to no more than 3 portions per week
- Switch from cow’s milk produce to soya alternatives
- Avoid eating charred or well done meat
- Eat more fish and olive oil
- Switch to wholegrain varieties of grain foods ie wholemeal bread, wholewheat pasta, unrefined cereals and brown rice
- Eat at least 5 and preferably 9 portions of fruit and vegetables daily
- Include at least a portion of brassica vegetables every day
- Supplement your diet with a good quality multivitamin with minerals containing 400ug folic acid
- Get outside during the lightest part of the day to increase your vitamin D synthesis.
|About The Author
Peter Cox is a fully qualified Nutritional Therapist located in Westminster, London. He typically sees clients from the surrounding areas of Kensington, Camden Town and Paddington.
For more information about protecting yourself against breast cancer contact Peter on 07788 447843 and at firstname.lastname@example.org
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Visit his website www.petercoxnutrition.co.uk