Tori Hudson, N.D.Professor, National College of Naturopathic Medicine and Bastyr University; Medical Director, A Woman's Time; Director of Research and Development, Vitanica.
Thyroid Function and Soy
Concerns about the possible goitrogenic effects of soybean isoflavones abound. These concerns are based primarily on in vitro research,1 animal studies,2 and older reports of goiter occurring in infants who were fed soy formulas that did not contain added iodine. This problem was addressed by adding iodine to formulas and there have been no cases reported since then.3 In a 2003 randomized, double-blind, placebo-controlled study, researchers investigated the effect of a daily soy supplement on thyroid function in 38 postmenopausal women who were not on hormone replacement therapy. One group of women took a soy product containing 90 mg/day of isoflavones and the other group took a placebo.Customary thyroid tests, thyroid stimulating hormone, thyroxine, and tri-iodothyronine were measured at baseline and after 3 and 6 months. All three measures, in both groups, were statistically almost identical at 6 months, and levels were similar between the isoflavone-treated group and the placebo groups for each of the measurements. The conclusion was that, in healthy individuals, who do not have iodine deficiency, soy isoflavones do not affect thyroid function adversely.
Commentary
The potential adverse effects of soy have been aggressively publicized by a number of people who are vehemently against soy use. I do not know or understand the source of this opposition, but I believe it has created unnecessary confusion among consumers and patients who use natural medicine. I prefer a studious, academic approach to evaluating and understanding the benefits and risks of soy, based on reliable research, rather than perspectives dominated by personal opinions and heated emotions.In vitro studies have shown that genistein and daidzein, the two main isoflavones in soy, interfere with thyroid enzymatic reactions that are critical to the production of thyroid hormone. Animal studies have demonstrated that soy isoflavones, in a dose-dependent manner, have an inhibitory effect on thyroid peroxidase, and goiter development is more common in rats fed a soy diet, especially if they are deficient in iodine. Other aspects of thyroid function including thyroid-hormone levels and thyroid gland weight were not affected adversely in the animal studies.
Concerns regarding soy and thyroid function in humans began when there were some case reports of goiter development in infants who were exclusively fed soy formulas. Since iodine was added to the formulas, no cases of goiter have been reported. A study on women with elevated cholesterol levels revived concerns about thyroid hormone suppression.4 These women were fed 40g of soy daily with either 90mg or 56mg of soy isoflavones per day for 6 months. Cholesterol figures, steroid hormone levels, and thyroid hormones were measured at 90 and 180 days. Small effects on thyroid hormone were measured but there were no clinical changes detected.
The dose of soy isoflavones (90 mg/day) in the 2003 study represents a higher daily dose of isoflavones than is consumed in the typical Asian diet. This study is significant in light of concerns about the effect of soy isoflavones on thyroid function in adult women. The potential antithyroid effects of soy appear to be directly related to iodine. If there is an iodine deficiency, then soy may be able to interfere with optimal thyroid function. However, iodine deficiency can be addressed easily with simple dietary changes or supplementation. It is my opinion, from reading the research on soy and thyroid hormone, whether in men or women, that women should feel reassured that there is no clinically significant effect of soy on thyroid function or hormones as long as these patients have normal iodine levels.
Green Tea Enhances Survival of Ovarian Cancer Patients
Binns C, et al. Green tea consumption enhances survival of epithelial ovarian cancer patients. Asia Pac J Clin Nutr 2004;12(Suppl):S116A cohort of Chinese patients with confirmed epithelial ovarian cancer were recruited and followed for a minimum of three years. Subjects or their close relatives were traced and interviewed using a questionnaire. The number of deaths was obtained and hazard ratios calculated. Increasing frequency and quantity of tea consumption were associated with a longer survival in women with epithelial cell cancer. 109 out of 137 tea drinkers survived to the time of interview, compared with only 77 women still alive among the 157 non-tea drinkers. Compared with non tea-drinkers, the adjusted hazard ratios were 0.6 (95% CI 0.4 – 0.9) for tea drinkers, 0.3 (95% CI 0.2-0.8) for consumption of at least one cup of green tea per day, 0.4 (95% CI 0.2-0.8) for brewing at least one batch of green tea per day and 0.3 (95% CI 0.2-0.8) for consumption of 500 gms or more dried tea leaf per year.
Comments:
Green tea is derived from the tea plant (Camellia sinensis). Green tea is very high in polyphenols with potent antioxidant and antitumor properties. The major polyphenols in green tea are flavinoids (catechin, epicatechin, epicatechin gallate, epigallocatechin gallate, and proanthocyanidins). Epigallocatechin gallate (EGCg) is thought to be the most significant active component in green tea. Other components in green tea include a very small amount of caffeine, theanine, lignins, organic acids, protein and chlorophyll.Green tea polyphenols are potent antioxidant compounds that have demonstrated significant antioxidant activity, as well as increasing the activity of antioxidant enzymes. Green tea polyphenols block the formation of cancer-causing compounds such as nitrosamines, suppress the activation of carcinogens, and detoxify and trap toxic immune damaging substances. Green tea consumption has been studied in humans and found to be preventive against some forms of cancer- stomach, small intestine, pancreas, colon, lung and breast.
In 1998 a study on green tea in women with breast cancer determined that in stage I and II breast cancer, increased consumption of green tea was associated with less metastasized lymph nodes in premenopausal women, and increased progesterone and estrogen status in postmenopausal women. (A finding that is associated with less aggressive forms of breast cancer). No benefit was seen in stage III breast cancer patients. In stage I and II patients, there was a 16.7% recurrence rate for those consuming 5 cups or more of green tea (average 8 cups) per day. For those who consumed 4 or less cups per day (average of 2), there was a 24.3% recurrence rate. Disease-free survival was also significantly improved in stage I and stage II breast cancer patients with a greater consumption of green tea.
The current study, although it was not a randomized clinical trial, and was inadequate in providing information about the stage of their ovarian cancers, offers one more encouraging reason to recommend green tea to ovarian cancer patients as part of a management strategy to reduce their risk of recurrence.
Vitamin D advice and cautions
Scientific evidence increasingly suggests that the optimal dietary intake of vitamin D should be higher. New guidelines are recommending 1,000 IU a day for older individuals and other high-risk groups. Some may need as much as 2,000 IU per day. However, vitamin D can be harmful at 2,000 and above, causing problems such as kidney stones and kidney failure. It is extremely difficult to get 1,000 IU per day without taking a supplement. People who live in the northern third of the U.S., Canada, those with dark skin, those who are housebound or institutionalized, and individuals who do not consume foods fortified with vitamin D should also take vitamin D supplementation. Women and men with unexplained bone loss may also need to be tested for vitamin D deficiency.Some people have steered towards cod liver oil as a source of supplemental vitamin D. Cod liver oil is indeed very rich in vitamin D. One tbsp supplies about 1,400 IU. However, what our body manufactures and dietary sources may take some of us over the 2,000 IU per day. Cod liver oil also contains high levels of vitamin A, which can cause increased calcium excretion. Cod liver oil is also a suspect source of contaminants and if utilized, should be from a company that can provide testing and safety information.
| Dietary sources of Vitamin D | ||||
| Salmon, cooked (3.5 oz) | 360 IU | Milk, fortified soy (1 cup) | 100 | |
| Sardines, canned (1.75 oz) | 250 IU | Margarine, fortified (1 tbsp) | 60 | |
| Tuna, canned (3 oz) | 200 IU | Breakfast cereal, fortified (1 serving) | 40 | |
| Milk, cow’s (1 cup) | 100 | Egg (1) | 40 |
References
1. Divi R, et al. Anti-thyroid isoflavones from soybean: Isolation, characterization, and mechanisms of action. Biochem Pharmacol 1997;54:1087-10962. Doerge D, Sheehan D. Goitrogenic and estrogenic activity of soy isoflavones. Environ Health Prespect 2002;110 (Suppl 3): 349-353.
3. Bruce B, et al. Isoflavone supplements do not affect thyroid function in iodine-replete postmenopausal women. J Med Food 2003;6:309-316.
4. Persky V, et al. Effect of soy protein on endogenous hormones in postmenopausal women. Am J Clin Nutr 2002; 75: 145-153. Erratum in : Am J Clin Nutr 2002; 76:695.