| Q: Is Soy Dangerous? | | | | answers where soy and breast cancer are |
| Q: I've been reading quite a bit about | | | | concerned. However, the evidence is |
| the dangers of consuming too much soy, | | | | sufficient to say that soy consumption |
| but to date I have not figured out what | | | | does not increase risk of breast cancer |
| those dangers are other than too much | | | | and may reduce risk in some people, |
| estrogen production with its | | | | especially if soy is consumed from an |
| consequences for higher cancer risk. A | | | | early age. For those who have |
| friend told me that a woman with a | | | | estrogen-positive breast cancer, it also |
| Vegetarian Nutrition course to her | | | | appears safe to use soy in moderation. |
| credit told her that she would recommend | | | | Soy and Thyroid |
| rice beverage over soy. Why? Would you | | | | Claim : Soy contains natural chemicals |
| kindly clarify this matter for me. | | | | known as goitrogens that interfere with |
| Thanks, | | | | thyroid function. These can cause an |
| Joyce Ward, Winnipeg | | | | enlargement of the thyroid gland (a |
| A: Dear Joyce, | | | | “goiter”) and symptoms of |
| Thank you for the opportunity to provide | | | | hypothyroidism, such as lethargy, |
| some clarity about this issue. As you | | | | dullness, coldness, and depression. |
| may be aware, soy has enjoyed | | | | It is true that soy contains goitrogens, |
| considerable favourable press over the | | | | as do many other foods such as |
| past decade. We have seen reports of soy | | | | cruciferous vegetables (cabbage, |
| reducing risk of heart disease, cancer, | | | | cauliflower, broccoli, and brussel |
| osteoporosis, and reducing symptoms of | | | | sprouts), sweet potatoes, lima beans, |
| menopause. Just when soy seemed to be on | | | | and millet. However, these foods have |
| top of the world, articles and websites | | | | been found only to cause problems when |
| began to appear claiming that this | | | | iodine intake is low , because |
| new-found health hero was really a | | | | goitrogens do their damage by |
| villain in disguise. Soy bashers said | | | | interfering with the thyroid gland's |
| all the hype about soy was really just | | | | ability to utilize iodine. Between 1951 |
| propaganda, and that in truth, soy was | | | | and 1961, several cases of goiter were |
| not a health food, but rather a | | | | diagnosed in infants who had been fed |
| dangerous substance that should be | | | | infant formula made from soy flour. |
| carefully avoided by humans. In fact, | | | | These cases are frequently cited by the |
| anti-soy advocates claim that eating soy | | | | anti-soy lobbyists to prove soy damages |
| raises risk of cancer, osteoporosis, | | | | thyroid function (especially in |
| thyroid problems, birth defects, | | | | infants). But not a single case of |
| reproductive problems, nutritional | | | | goiter in infants has been caused by soy |
| deficiencies and Alzheimer's disease. | | | | formula since the 1960s. At that time |
| This has left consumer wondering if soy | | | | the soy formula base was changed from |
| is really a saint or a sinner. | | | | soy flour to soy protein isolates, which |
| First, it is important to understand | | | | are low in goitrogens, and manufacturers |
| that soy is not something new. The | | | | began fortifying soy formula with |
| soybean has been used for food for | | | | iodine. |
| centuries, particularly in the Orient. | | | | Soy does not cause thyroid problems in |
| Traditional forms of soy foods included | | | | healthy, well-nourished people who are |
| fresh or frozen beans from the soy pod | | | | not deficient in iodine. However, people |
| (called edamame ), soy milk, tofu, and | | | | who do not have a reliable source of |
| fermented foods, such as tempeh, miso | | | | iodine could increase their risk of |
| and soy sauce. More recently soy has | | | | thyroid problems if they eat a lot of |
| become a huge hit in North America, with | | | | soy and/or other foods rich in |
| all of the traditional forms of soy | | | | goitrogens. Iodized salt, dairy |
| widely available in addition to numerous | | | | products, and fish are the main dietary |
| others, such as soy nuts, soy-based meat | | | | sources of iodine, and most multivitamin |
| analogues, soy-based protein beverages, | | | | mineral supplements provide the |
| soy chips, soy ice cream, soy yogurt, | | | | recommended daily allowance. So the |
| and the list goes on. These products | | | | answer is not to avoid soy or |
| have become staples for many vegetarians | | | | cruciferous vegetables, but to get |
| and vegans. So, the question of the | | | | enough iodine. |
| safety of soy is one that certainly | | | | Conclusion : There is no evidence that |
| deserves serious consideration. | | | | eating soy foods regularly causes |
| Let's briefly address a few of the major | | | | thyroid problems in healthy people who |
| claims against soy. For more detailed | | | | include sufficient iodine in the diet. |
| information about each of these issues, | | | | Soy and Cognitive Function |
| the following websites are most helpful: | | | | Claim: Soyfoods, especially tofu, can |
| | | | cause mental deterioration and |
| www.llu.edu//llu/vegetarian/soy2.html | | | | accelerate aging. |
| www.foodrevolution.org | | | | One study done in Hawaii (the Honolulu |
| what_about_soy.htm | | | | Heart Study) found that |
| www.soybean.com/drsuz.htm | | | | Japanese-American men who ate the most |
| Soy and Breast Cancer | | | | tofu in middle age had the greatest |
| Claim : Soy increases risk of breast | | | | mental deterioration and dementia as |
| cancer. | | | | seniors. This study is widely cited as |
| Among the very first health claims made | | | | evidence that tofu may cause a reduction |
| for soy is that it may reduce incidence | | | | in cognitive function. Interestingly, |
| of breast cancer. It seemed so obvious | | | | there have been at least three other |
| when one compared the very low rates of | | | | studies that have suggested that soy |
| breast cancer in Asian countries using | | | | provides significant beneficial effects |
| large amounts of soy with rates in North | | | | on cognitive function. In addition |
| American countries that used | | | | populations with relatively high soy |
| comparatively small amounts of soy. The | | | | intake (about a serving a day), |
| risk reduction was thought to be due to | | | | including people in Asia and Seventh-day |
| the isoflavones (mainly genestein and | | | | Adventists, experience lower rates of |
| daidzen) in soy. Isoflavones are a type | | | | dementia than those populations who eat |
| of phytoestrogen (plant estrogen) that | | | | little if any soy. While this does not |
| has been thought to interfere with the | | | | prove that soy is beneficial, it does |
| ability of the potent human form of | | | | suggest that moderate soy consumption is |
| estrogen to increase cell proliferation | | | | likely not detrimental. |
| and, therefore, cancer risk. However, | | | | Conclusion. The weight of the evidence |
| studies have been mixed. While some do | | | | suggests that soy may offer some |
| indeed show soy acting as an | | | | benefits to cognitive function, although |
| anti-estrogen, others suggest soy may | | | | more research is needed before firm |
| act as a weak estrogen itself, | | | | conclusions can be made on this issue. |
| increasing cancer risk. Interestingly, | | | | What about soy versus rice milk? It all |
| some studies have shown that while small | | | | depends. If you are sensitive to soy or |
| amounts of genestein increase cell | | | | use a lot of soy products, you may wish |
| growth, large amounts inhibit it. | | | | to use fortified rice milk. However, my |
| Finally, there is some evidence that | | | | preference is for soy – especially for |
| women eating soy from an early age | | | | children. Soy is a much richer source of |
| (especially during puberty) do reduce | | | | high quality protein, vitamins and |
| their breast cancer risk, while there | | | | minerals. It also contains isoflavones, |
| seems to be less protection for those | | | | which are protective for heart health |
| who begin to eat soy later in life. | | | | and against osteoporosis. I think it |
| Conclusion: We still do not know all the | | | | tastes better too. |