After 5 months, hair growth was significantly increased in 64.5% of human volunteers administered with capsaicin and isoflavone, compared with 11.8% in the placebo group.
A teaspoon of dried chili, cayenne or red pepper per day would probably have more than enough capsaicin. As for soy, the best source of isoflavones are soy beans, which contain about 200 mg isoflavones per 100 grams.