This is a warning : avoid soy-based food.
One link and one excerpt.
The link (here) leads to a page on www.thyroid-info.com by Mary Shomon, that warns about the dangers of soy, especially for infants. The information doesn't circulate too much, given the huge financial interests at stake (dear food industry).
Let us just quote the conclusion: 'According to the Soy Online Service, for infants, any soy is too much. For adults, just 30 mg of soy isoflavones per day is the amount found to have a negative impact on thyroid function. This amount of soy isoflavones is found in just 5-8 ounces of soy milk, or 1.5 ounces of miso.'
The excerpt is from the best-seller The 4-Hour Body by Tim Ferris. It is found in the Appendices and Extras — but should really be expanded in a fullfledged chapter, IMO.
'A high percentage of vegans use soy as their primary source of protein. This is a bad idea.
Based on all the literature I've reviewed, the phytoestrogens in soy are dangerous for adults and, to a greater extent, children, even when used in moderation. Studies have demonstrated that just 30 grams of soy per day (about two tablespoons) for 90 days can disrupt thyroid function, and that's in Japanese subjects. The Swiss Federal Health Service equated 100 milligrams of isoflavones (phytoestrogens) to a single birth control pill in terms of oestrogenic impact. How many birth control pills are you inadvertently eating each day?
FOOD : TOTAL ISOFLAVONES (MG IN 100 G SERVING)
Instant soy beverage : 109.51
Raw soybeans (Japanese) : 118.51 (in less than half a cup)
Fried tofu : 48.35 (7-8 small pieces)
Tempeh : 43.52 (in less than two-thirds of a cup)
Common infant soy formula : 25
Estrogen overdosing isn't good for either gender, unless you're aiming for sterility.' (p.523)
How does this apply to us?
While experimenting with menus, two of the main ingredients were soy-based: tofu and natto. I wasn't ingesting half-assed rations and quickly found myself in an altered state (without knowing the cause then) which main trait was absolute lack of lust and sexual drive. Very, very eery. Only when I did a bit of research and reading did the dots connect. I quit eating natto and tofu, and everything went back to normal.
A side note. If you are in Japan, be careful with local soy bean-based dish — which are everywhere, really. If you think local is cool you might want to reassess your priorities.