Steroids have gotten a bad reputation
Synthesized by the body from cholesterol, the naturally occurring end products of steroid metabolism in the human body include:
- Sex hormones, such as estrogen, testosterone, and progesterone. These hormones make reproduction possible and cause the expression of physical characteristics identifying an individual as male or female.
- Stress hormones, such as cortisol and epinephrine, that help the body protect itself against predators, infections, injury, cold, heat, and blood loss, and
- Growth hormones that interact with testosterone to encourage the growth of bone and increased muscle mass.
Scientists have been able to synthesize many of the steroids and steroid hormones essential to the body since the 1930's. Steroid treatment has become nearly universal for inflammatory disease. But steroids are not only made by the body or available by injection, they also appear in food.
Naturally Occurring Human Steroids
The number of steroids appearing in food that are exactly the same as the steroids made by the human body is very low. Milk and milk products, specifically the dairy fat in butter and cheese, provides a very small amount of progesterone. This is the hormone that predominates in the first half of a woman's menstrual cycle and that supports the growth of the unborn child during pregnancy. It also relaxes the "smooth" muscles, such as those surrounding the bronchial passages, normalizes blood clotting, reduces gallbladder activity, and encourages the immune response.
Eggs, meat, and fish contain small amounts of estrogen and testosterone identical to their human form, eggs providing approximately 10 to 20 per cent as much as meat and fish. Plant foods have not been found to supply actual human estrogen (which is not the same as the phytoestrogens), but some plant foods contain miniscule amounts of testosterone.
Bioidentical hormones in food occur in only trace amounts. In comparison to production by the human body, the steroid hormones found in food is insignificant. Food, however, provides huge quantities of the steroid precursors the human body can use to make its own hormones.
Naturally Occurring Steroid Precursors
The food we eat contains copious amounts of the building blocks of human steroids. These precursor chemicals include pregnenolone, androstenedione, hydroxyprogesterone, dehydroepiandrosterone (DHEA), dihydrotestosterone, androsterone, 17-alpha-estradiol, and estriol. The human body turns these chemicals into a wide variety of sex and growth hormones, giving food an intimate connection with human health.
One of the better-researched relationships between the natural steroids in food and human development is the connection between 17-alpha-estradiol and male sexual characteristics. In both men and women, the chemical 17-alpha-estradiol becomes estrogen, the female sex hormone. This naturally occurring steroid precursor is particularly abundant in the hops used to make beer.
In the Middle Ages, monks gave teenaged boys teas made of hops to encourage chastity. The resulting increase in estrogen levels presumably made the boys softer, less aggressive, and easier to manage. In modern Germany, physicians have identified a condition best translated as "beer drinker's droop." By age 50, years of consumption of beer, made with hops, leads to the accumulation of estrogens in a man's body to levels that result in erectile dysfunction.
In high doses, the steroid androstenedione, which also naturally occurs in food, may enhance the growth of muscle size after exercise. The problem with consuming large amounts of androstenedione is that human body makes this steroid from DHEA and uses it to make either testosterone or estrogen. Testosterone encourages the development of muscle mass. In certain individuals, however, excessive consumption of androstenedione, even if derived from natural sources, may result in the development of outwardly feminine characteristics.
The Phytoestrogens as Natural Steroids in Food
While animal-based foods are the best source of the chemical building blocks of the human male sex hormones, plant-based foods are the best source of the chemical building blocks of the human female sex hormones. Plants such as soy, red clover, and Mexican sweet potato are rich sources of the phytoestrogens, sometimes referred to as dietary estrogens. Because certain female sex hormones interfere with conception in the same manner as the contraceptive Pill, the phytoestrogen content of seeds and leaves and tubers prevents the plant from being overgrazed or overharvested by humans or other mammals.
Phytoestrogens are best known as remedies for the symptoms of menopause. Approximately 2 out of 3 women develop unpleasant symptoms during menopause, but many are hesitant to use estrogen replacement therapy. This can be due to fear of increased risk of endometrial and breast cancer, or due to repugnance at the idea of taking a product derived from horse's urine. Many women turn to nutritional supplements containing phytoestrogens.
The surprising revelation of the most recent research is that the herbs and foods long thought to modify women's symptoms through their content of phytoestrogens actually do not increase the production of estrogen. This does not mean they do not work. They work through a previously unexplained mechanism.
Black cohosh is widely used to treat hot flashes and mood swings. There have been at least 12 clinical trials of black cohosh as a treatment for hot flashes, and 11 showed it to be effective. Its presumed mode of action as a stimulant to estrogen production, however, is not borne out by the latest research. Not only does taking black cohosh have no effect on estrogen levels, new studies find it has no effect on show no effect on serum levels of estradiol, luteinizing hormone (LH), follicle stimulating hormone (FSH), sex hormone binding globulin (SHBG), or prolactin. Just how black cohosh works has not been definitively determined, but it is not effective because of its content of common natural steroids.
Soy is touted as the nutritional equivalent of a wonder drug, and with good reason. Various studies have shown soy and soy extracts to:
- Increase HDL ("good") cholesterol and decrease LDL ("bad") cholesterol 
- Encourage bone mineral density and bone strength after menopause  and
- Help maintain mental acuity during aging, especially verbal fluency, among numerous other beneficial effects.
Scientists now know that even though soy contains chemicals that are structurally similar to estrogen (formononetin, biochanin A, daidzein, and genistein), its mode of action has little or nothing to do with the actual production of estrogen. Instead, when estrogen levels are deficient, these soy chemicals increase the activity of the estrogen otherwise made in the human body. When estrogen levels are excessive, these chemicals make it less active. Soy is a profoundly useful component of the diet, but its effects are not due to phytoestrogens. The natural steroids in soy are not the chemicals that make soy so very beneficial to human health.
The Real Significance of Natural Steroids in Food
Food is a significant source of the building blocks of human steroid hormones, but how the body uses these building blocks still depends on many factors other than the mere consumption of food. Do not rely on foods for hormone replacement, but do not fear foods because of their supposed hormone-inducing effects.