The facts on soy!

So what are the facts on soy

Over the years I have been asked what is my thoughts on soy. I have gone though many journals and come across this study to dismiss many misinformation on soy and the effect on IGF-1.
Breast cancer rates are remarkably different even among developed countries. Japanese women living in Japan have about one quarter the rate of breast cancer as that of women in other industrialized nations (1), and the differences are particularly evident after menopause, when breast cancer rates continue to rise with age elsewhere but plateau in Japan. The rate of breast cancer almost doubles in the first 10 years after Japanese women immigrate to the United States or to Australia, and this difference is thought to be related to environmental and lifestyle factors, especially diet (2,3).

An important biomarker of breast cancer risk is serum insulin-like growth factor (IGF-1). A meta-analysis of 17 studies of breast cancer and serum IGF-1 concentrations reported that high serum concentrations of IGF-1 were associated with increased postmenopausal breast cancer risk (4). Laboratory data support a role for the IGF-1 signaling pathway in carcinogenesis, with increased DNA synthesis and decreased cell cycle regulation leading to inhibition of apoptosis (5). Blocking this pathway has been shown to benefit cancer patients (6).

Serum IGF-1 concentrations can be modified by diet, including dairy products and Animal-derived foods (7,8). In vivo trials with green tea and resveratrol also decreased serum concentrations (9,10). Clinical studies conducted in the United States, a non-soy-consuming culture, have reported increased IGF-1 with soy supplementation (11,12).

Seaweed has not been studied for its effects on IGF-1, although it shows antitumor activity in both in vitro and in vivo breast cancer studies (13–16). In further support for a role in breast cancer prevention, a case-control study of women in Korea reported that women with the highest seaweed and soy intake had about half the rate of breast cancer as women who infrequently or never consumed seaweed or soy (17). The best-studied mechanism for its antitumor activity is the high antioxidant effects observed in both laboratory and clinical settings (18–20). The antioxidants characteristic of seaweed include bioactive compounds not found in land plants, including fucoidan, fucoxanthin, and phlorotannins (21).

In this clinical trial conducted with American women, we investigated the importance of dietary seaweed and soy and their impact on several known biomarkers of breast cancer risk, including serum concentrations of IGF-1 and its main binding protein, IGFBP-3.

Insulin-like growth factor 1 (IGF-1) is an anabolic hormone important for growth and development. However, high-circulating serum concentrations in adults are associated with increased risk of postmenopausal breast cancer. Nutritional status and specific foods influence serum IGF-1 concentrations. Breast cancer incidence is typically low in Asian countries where soy is commonly consumed. Paradoxically, soy supplement trials in American women have reported significant increases in IGF-1. Seaweed also is consumed regularly in Asian countries where breast cancer risk is low. We investigated the possibility that seaweed could modify soy-associated increases in IGF-1 in American women. Thirty healthy postmenopausal women (mean age 58 yr) participated in this 14-wk double-blinded, randomized, placebo-controlled crossover clinical trial. Participants consumed 5 g/day placebo or seaweed (Alaria esculenta) in capsules for 7 wk. During the 7th wk, a high-soy protein isolate powder was added (2 mg/kg body weight aglycone equivalent isoflavones). Overnight fasting blood samples were collected after each intervention period. Soy significantly increased serum IGF-1 concentrations compared to the placebo (21.2 nmol/L for soy vs. 16.9 nmol/L for placebo; P = 0.0001). Once the  combination of seaweed and soy  was added it significantly reduced this decrease by about 40% (21.2 nmol/L for soy alone vs. 19.4 nmol/L; P = 0.01). Concurrent seaweed and soy consumption may be important in modifying the effect of soy on IGF-1 serum concentrations. Therefore there still no sound evidence that soy will increase IGF-1. But we have found with the added intake of seaweed and soy IGF-1 has decreased I must add that this was not though a isolated means but rather though whole foods.


To learn more book today and don't get the raw deal on soy pardon the the pun.


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Data sourced from University of South Carolina, USA.