Soy

Scientific studies (review articles) on the relationship between soy/isoflavones and disease prevention:
One swallow does not make a summer. A famous Dutch saying that could not be any more obvious. Just because one single scientific study about a certain topic makes certain claims, it does not necessarily mean it is true. On the other hand, a review article (a collection of scientific studies on a certain topic) of randomized, placebo-controlled double blind clinical trials (RCTs) will answer the following question:
"Do taking dietary supplements make sense?" Yes for a positive conclusion and no for a negative conclusion.

One swallow does not make a summer. A famous Dutch saying that could not be any more obvious. Just because one single scientific study about a certain topic makes certain claims, it does not necessarily mean it is true. On the other hand, a review article (a collection of scientific studies on a certain topic) of (prospective) cohort studies or case-control studies will answer the following question:
"Should I change my diet?".

1. 10 mg/d isoflavone dietary intake reduce breast cancer
2. Daily 61g tofu reduce cancer 
3. <100 mg/day isoflavones reduce IL-6 and TNF-α levels
4. 54 mg/day genistein increase bone mineral density in postmenopausal women
5. Soy supplementation improves insulin resistance for nonalcoholic fatty liver disease
6. Soy protein dietary intake reduces type 2 diabetes
7. Daily 40g soy consumption for <12 weeks increase IGF-1 level
8. Soy consumption causally lowers blood pressure in adults
9. Soy/soy products consumption reduce risk of mortality from cardiovascular diseases
10. ≥75 mg/day isoflavones reduce BMI
11. Dairy products, high purine vegetables, soy foods and coffee decrease gout
12. Daily 54 mg soy isoflavone for 6 weeks to 12 months reduces the frequency and severity of hot flashes
13. 20 mg/d isoflavones dieatary intake reduces risk of colorectal neoplasms in Asians
14. Isoflavone-rich soy products decrease FSH and LH in premenopausal women

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• Soybeans typically contain 35-40 percent protein, 15-20 percent fat, 30 percent carbohydrates, 10 to 13 percent moisture and around 5 percent minerals and ash.
• Plant proteins generally have lower content of some essential amino acids such as lysine and methionine. Therefore, plant proteins have a lower biological value than meat, egg or dairy proteins.
  Soy protein is one of the best plant proteins, but nevertheless, the most limiting amino acid in soybeans is the essential sulphur-containing amino acid methionine.
• Isoflavones are a subclass of flavonoids with a chemical structure similar to 17ß-estradiol, the most potent, naturally occurring estrogen.
• Isoflavones are found in small amounts in a number of legumes, grains and vegetables, but soybeans are by far the most concentrated source of isoflavones in the human diet.
• Traditional Asian foods made from soybeans include tofu, tempeh, miso and natto.
• In soybeans, isoflavones are present as glycosides (bound to a sugar molecule).
• Fermentation or digestion of soybeans or soy products results in the release of the sugar molecule from the isoflavone glycoside, leaving an isoflavone aglycone.
• Soy isoflavone glycosides are called genistin, daidzin, and glycitin, while the aglycones are called genistein, daidzein, and glycitein.
• Soy protein isolate (SPI) is more refined than soy protein and contains lower amounts of isoflavones.
• 25 g of soy proteins contain about 45 mg of isoflavones.
• Scientific studies show that the minimum amount of isoflavones, which is needed in order to achieve positive effects in the body is about 30 to 50 mg per day.
• The safety upper limit of isoflavones is probably 100 mg per day.
• The FDA allows soy foods containing 6-½ grams of soy to carry a heart-healthy label. Evidence suggests that a daily intake of 25 g of soy protein is adequate to noticeably reduce cholesterol. This amount is typically found in about 2-½ cups of soy milk or ½ pound of tofu.