Microsoft word - what about soy

What about Soy?
The idea that soy foods (i.e. tofu, soy milk or textured vegetable protein, miso) may protect against breast cancer is a popular health claim. We at The Genesis Breast Cancer Prevention Appeal believe that the jury is still out on soy - surprisingly there is little evidence that eating soy as an adult reduces our risk, equally there is insufficient evidence of its harms, and on balance it is safe to include soy as part of a healthy balanced diet. The case for soy on paper is certainly compelling and came originally from the striking observation of much higher soy consumption of Asian women who have much lower rates of breast cancer than Western women. Soy foods are the major source of amazing oestrogen like substances called isoflavones. The 2 main isoflavones in soy are dazdein and genestein which are structurally very similar to oestrogen. Isoflavones need to be processed by bacteria in the bowel to their active forms, only one out three can achieve this process. Oestrogen effects the growth and development of a number of tissues in the body including breast cells, by fitting into an oestrogen shaped lock on the cells, which triggers the cells to grow and develop. Isoflavones can fit in the lock, and block oestrogen from binding to the cell, preventing oestrogen driven cell growth. Isoflavones have other potential anti cancer effects acting as an antioxidant, inhibiting tumour growth and progression. Isoflavones can lower a woman’s natural levels of oestrogen and also promote oestrogen to be metabolised to the less harmful (2 –hydroxysterone) form rather then the cancer causing (16–hydroxysterone) form (see hormones). If soy is consumed before or at the time of puberty it is thought to encourage breast cells to undergo similar changes which occur during pregnancy, which if you recall makes the cells more resistant to damage and cancer development later in life.{Lamartiniere 2002 119 /id} Many studies have shown eating soy during adolescence protects against the JOIN OUR FIGHT TO MAKE 1 IN 10, NONE IN 10
later development of breast cancer. For example a study of 1459 breast cancer cases and 1556 age-matched healthy women in the Shanghai Breast Cancer study women who consumed at least 11g of soy protein / day (i.e. at least half a pint of soy milk) during adolescence were half as likely to develop breast cancer in later life. {Shu, Jin, et al. 2001 116 /id}. So far so good but there are also some worrying aspects of soy – which may in some situations, help to promote breast cancer. The Committee on Toxicity of Chemicals in Food and Consumer Products and the Environment recently highlighted concerns that as well as blocking oestrogen, soy foods can also have oestrogen like effects on the breast {The Committee on Toxicity of chemicals in food / consumer products and the environment Phytoestrogens and Health 2003 118 /id}. This is supported by two studies including work within our own institution by Professor Bundred and a further study by scientists at the University of California who found high soy diets (typically 1- 1 pints of soy milk or 100g of tofu/ TVP) actually stimulated breast cells to multiply {Hargreaves, Potten, et al. 1999 113 /id}{Petrakis, Barnes, et al. 1996 115 /id} which may increase their cancer potential. So what is the balance of these good and bad effects? Earlier reports from small studies showed soy to be protective. Seven of the nine more recent larger population studies in Western and Japanese women failed to link soy intake with risk. One UK based study found rates of breast cancer were 20-40% higher amongst women with the highest blood levels of soy isoflavones and their metabolites {Grace, Taylor, et al. 2004 120 /id}. Soy during childhood or adolescence may be beneficial, but current evidence does not recommend increasing soy intake as an adult to minimise your breast cancer risk. Moderate amounts of soy foods can safely be included as part of a healthy diet. Although high soy intakes may be an issue in women with low levels of oestrogen i.e. post menopausal women, or in breast cancer patients taking tamoxifen or Arimidex. (See breast cancer patients). If soy JOIN OUR FIGHT TO MAKE 1 IN 10, NONE IN 10
foods were really so harmful you would not expect to see the low rates of breast cancer amongst the Japanese and Chinese where women typically have 10 times the amount of soy foods we do in the UK, typically ½ pint – 2/3 of a pint of soy milk, or 3-4 oz of tofu day. This suggests it is safe to include soy in the diet provided that the other essential components of their lifestyle is met i.e. if it is part of an energy restricted, healthy lifestyle. Current evidence suggests soy foods have a neutral effect on risk if you enjoy soy products, it seems reasonable to continue to use them. They should not for example be chosen in preference to foods which are known to be protective i.e. don’t chose soy milk in preference to low fat dairy milk. Alternatively a soy meat substitute is a much better choice than a high animal fat meat which may increase risk. Soy foods are good low fat sources of protein which are well known to reduce cholesterol levels. Much of the soy in Western diets is eaten in manufactured foods such as breads, baked products and noodles. It is fine to include 1-2 portions of soy foods a As well as soy foods there is growing interest of the effects of isolated phytoestrogen in a tablet form. The effect of these supplements on breast cancer and health is not known. A recent study looked at the effect of red clover supplements on the density of breasts which is a measure of gland tissue and risk. One year of supplement did not affect density and is presumed not to affect risk {Atkinson, Warren, et al. 2004 117 /id}. These supplements are not currently recommended, they are not especially helpful for controlling hot flushes interestingly they are not as effective as soy foods in lowering cholesterol. These tablets are not recommended especially for breast cancer patients receiving certain breast cancer treatments (aromatase inhibitors, i.e arimidex, letrozole or exemestane . JOIN OUR FIGHT TO MAKE 1 IN 10, NONE IN 10

Source: http://www.genesisuk.org/downloads/pdf/76928689676256c870b6914b338ac21e.pdf