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Muscle Growth and Estrogen

7208-anabolicEstrogen is often called a “female hormone,” which is a misnomer, as this steroid hormone is also produced in the male body. It’s also true that women produce far greater amounts of estrogen than men, just as men produce about 10 times more testosterone than women.

Men’s greater testosterone levels are often cited as the reason that they are able to build more muscle than women. Recent studies, however, show that despite the negligible amounts of testosterone they produce while weight training, women are able to make similar muscle gains to men’s. That relates more to the fact that anabolic hormones produced during exercise don’t have as great an effect on muscle growth as was previously realized. Think about that the next time you read an article about the best ways to boost anabolic hormones during training.

If men’s bodies produce estrogen, what is the purpose? After all, nature is not known to be profligate in its actions; everything it does, it does for a reason. Although the precise functions of estrogen in men aren’t entirely clear, it appears to play a role in the maturation and development of sperm, which means that estrogen may effect male fertility.

Estrogen is vital to bone development in women, and a lack of it in older women often results in osteoporosis, a bone-thinning disease. Some scientists suggest that estrogen may play a similar role in men. Men deficient in testosterone are also subject to osteoporosis, although it’s not as common in men as in women, and when it does occur, it usually strikes in the spine.

Men are often advised not to take supplements or drugs that lower estrogen for extended times because of possible adverse affects on the cardiovascular system. That’s based on the established cardiovascular protection offered by estrogen to women. Younger women rarely suffer from heart attacks or strokes, and the reason is attributed to their higher estrogen levels. Estrogen offers cardiovascular protection in several ways. For one thing, it aides the synthesis and release of nitric oxide.

NO maintains vascular flexibility, which is important because stiff blood vessels are linked to atherosclerosis and high blood pressure. Estrogen also acts as a potent antioxidant, preventing the oxidation of low-density-lipoprotein cholesterol, which is the cornerstone of cardiovascular disease. At the same time, estrogen boosts levels of protective high-density-lipoprotein cholesterol. It is no coincidence that cardiovascular disease is higher in older women, who produce less estrogen.

On the other hand, according to a preliminary study released at the annual meeting of the Heart Rhythm Society in May 2013, having elevated blood estrogen is related to sudden cardiac death in both men and women. Sudden cardiac death occurs when the heart suddenly stops beating, known as cardiac arrest. Each year, more than 350,000 people in the United States die this way.

The study looked at people in Portland, Oregon, who either had died from sudden cardiac death or had suffered coronary artery disease. Tests done of the subject’s blood plasma at the time of death showed a similar proportion of the usual cardiovascular risk factors, such as high blood pressure, elevated cholesterol, obesity and diabetes, but the men had lowered testosterone along with elevated estrogen. In women, both testosterone and estrogen were elevated.

Those who died from sudden cardiac death showed higher estrogen levels than those who didn’t die but had coronary artery disease. Both the man and women who died showed elevated estrogen. Although this research doesn’t prove a cause-and-effect association between sudden cardiac death and elevated estrogen, it does suggest that estrogen, when elevated, produces a paradoxical reverse effect—a negative effect on heart function.

Estrogen is a dirty word to bodybuilders. The hormone is associated with greater amounts of muscle-definition-obscuring subcutaneous bodyfat and water retention. Male bodybuilders who use certain anabolic steroids that convert into estrogen can acquire a female-type breast development called gynecomastia. To prevent that and other estrogen-related effects, they often resort to using drugs that either interfere with estrogen, locking onto cellular receptors, like Nolvadex, or drugs that inhibit the enzymes that convert androgens into estrogen, known as aromatase blockers. Some bodybuilders are so fearful of estrogen that they stay on these anti-estrogen drugs year-round, believing that they are benign.

Many bodybuilders aren’t aware of the important role that estrogen plays in training and muscle growth. Women show less muscle damage when they exercise, an effect attributed to estrogen, which acts as an anti-inflammatory during exercise. Women also burn greater amounts of fat when they exercise than men, although it isn’t as apparent simply because most women have higher bodyfat levels than men. The reason is that women secrete greater amounts of growth hormone, which mobilizes fat. On the other hand, women also don’t respond to techniques such as carbohydrate loading, also thought to be due to their higher estrogen.

For years bodybuilders have been told that you need a certain amount of estrogen to maintain androgen cell receptors, which interact with testosterone to produce anabolic effects in muscle. Recent studies, however, show that estrogens may play an even more direct role in muscle hypertrophy, or growth. A 2012 study with rats explains why.1

There are two types of estrogen cell receptors (some suggest there are three), estrogen receptor-A and estrogen receptor-B. ER-A is predominant in reproductive organs, such as the uterus and breasts, but is also found in the heart, liver and kidneys, as well as the prostate gland. ER-B is found in the vascular lining, where it boosts NO, and gastrointestinal tract. Both receptors exist in the skeletal muscle of both sexes, but they have differing effects. For example, stimulation of ER-A by estrogen promotes changes in the prostate gland that are linked to prostate cancer (ironically, it is more potent than testosterone in that effect), but activation of ER-B in the prostate blocks the negative effects of ER-A, thereby helping prevent prostate cancer. Natural substances that activate ER-B, but not ER-A, such as genistein from soy, can offer some protection against it as well.

In the recent study, rats whose ovaries had been removed (so no estrogen is produced) were paired with other rats that were selectively bred not to have either ER-B or ER-A estrogen receptors. All the rats were then purposely injured with a substance that attacks muscle. Some of the rats without ovaries were also given genistein from soy and synthetic chemicals that selectively interact with either ER-B or ER-A receptors. Other of the rats without ovaries didn’t get those substances but did receive the muscle toxin. As expected, the latter rats showed greater amounts of substances linked to muscle injury, but those given the estrogen-stimulating compounds got some protection, including lesser amounts of muscle damage enzymes and reduced levels of inflammatory chemicals linked to muscle injury.

One such particular chemical, called tissue necrosis-factor-A is associated with catabolic effects in muscle and rises with age in humans. Some suggest that TNF-A is the primary arbiter of muscle loss with age, known as sarcopenia. Treatments with estrogen itself and the substance that specifically interacts with ER-B led to increases in myogenic substances aid the activity of satellite cells, the muscle stem cells that are involved in muscle repair and growth. As such, activating ER-B selectively appears to encourage muscle growth.

The researchers also tested the effects of estrogen on muscle growth in male rats. Once again, specific stimulation of ER-B, but not ER-A, triggered muscle growth in the males. It was traced to a strong induction of intramuscular IGF-1, long known to promote satellite cell activity in muscle and considered the primary anabolic hormone produced during exercise that stimulates muscle growth. The authors noted that this estrogen-related effect worked in tandem with testosterone, acting as an additive to testosterone in stimulating muscle growth. That confirms previous findings that estrogen is involved in promoting the activity of intramuscular IGF-1, and it may explain why women show less damage after exercise to men.

This animal-based study shows that selective activation of ER-B is involved in muscle growth—promoting less inflammation while boosting anti-inflammatory mechanisms that speed muscle recuperation after injury, including the injury associated with intense exercise. Activation of ER-B also boosts satellite cell activation and increases the effect of testosterone in that area as well. The question is how to use this information in your workouts and diet.

First, understand that this is an animal study, so it may not be completely replicable in humans. Even so, all the aspects studied do also occur in human muscle, so it is likely that the effects do apply to human physiology. Second, the fact that estrogen appears to be vital for muscle repair and regeneration calls into question overenthusiastic efforts to lower perceived high estrogen levels in men. Taking estrogen too low—as would occur with estrogen-lowering drugs or chronic use of supplements touted to lower estrogen—would be working against yourself in terms of muscle gains.

The best natural way to control elevated estrogen is to keep your bodyfat low. Higher bodyfat means greater activity of aromatase, the enzyme that converts androgens into estrogen. Another way to control estrogen safely is to eat generous amounts of cruciferous vegetables, such as broccoli, brussels sprouts, cabbage and kale, among others. Eating those foods converts the dangerous form of estrogen to a form that is benign, but you still get the benefits of estrogen for health and muscle growth. Consuming soy is a bit of a slippery slope, since it involves a U-shaped curve. Too much can interfere with testosterone and produce an estrogenic effect in men, but small-to-moderate amounts do no harm, and as noted, genistein, an isoflavone found in soy, is a specific activator of the ER-B receptors associated with promoting muscle growth and repair. About 25 grams a day of soy protein would be sufficient.

Editor’s note: Jerry Brainum has been an exercise and nutrition researcher and journalist for more than 25 years. He’s worked with pro bodybuilders as well as many Olympic and professional athletes. To get his new e-book, Natural Anabolics—Nutrients, Compounds and Supplements That Can Accelerate Muscle Growth Without Drugs, visit   IM


1 Velders, M., et al. (2012). Selective estrogen receptor-B activation stimulates skeletal muscle growth and regeneration. FASEB J. 26;1909-1920.

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