Introduction
It is well recognised that there is a lower incidence of certain cancers, such as breast and prostate cancer, in populations consuming soy as a regular part of the diet
1 ,
2 . The risk of developing breast cancer in Japanese women is four to five times lower than in Western women1, and the incidence of prostate cancer is four to tenfold lower in men from certain Asian countries compared to Western men
3 .
Population studies in Asia have found that the consumption of soy foods is correlated with a decreased incidence of various cancers including breast
4 ,
5 , prostate
6 ,
7 , lung
8 , stomach
9 ,
10 , endometrium
11 and colorectal cancer
12 ,
13 . In one American study, consuming soy drinks on two or more occasions per day was linked with up to a 70% reduction in prostate cancer risk among Seventh-day Adventist males
14 .
Traditional diets in many Asian countries contain much higher amounts of soy compared to typical Western diets. It has been estimated that older adults in Japan and China (Shanghai), typically consume between 25 mg and 50 mg of isoflavones per day
14 whereas people in the US and Europe, on average, consume less than 3 mg isoflavones daily
15 ,
16 ,
17 . In addition, soy foods are introduced early in life in Asian countries and the diets of some vegetarians, rather than being included only in adulthood.
Key Findings
- Epidemiological evidence and animal studies overall suggest that soy consumption is correlated with a lower incidence of breast, prostate, colon, lung, stomach and endometrial cancer.
- Soy isoflavones, as well as phytic acid, trypsin inhibitors and saponins are components of soy foods that have been correlated with anti-cancer effects.
- Soy isoflavones, which have been mostly studied, appear to behave like the anti-oestrogen breast cancer treatment drugs, Tamoxifen and Raloxifene, but may also protect against cancer in other non-hormone-like ways.
|
