Research Review: "Natural" supplements wreak hormonal havoc | Precision Nutrition

Research Review: “Natural” supplements wreak hormonal havoc

By Jennifer Koslo, Ph.D.


In the quest to build muscle, get lean and perform better, many active people turn to herbal supplements because they’re “natural”. Among the most popular supplements are those containing plant-derived hormones, such as Tribulus terrestris, which claim to increase testosterone levels. However, new research has shown that instead of increasing testosterone, many of these herbs are actually increasing estrogen levels.


Everyone wants an edge when it comes to performance, health, and even just life in general. You want to read faster, have better concentration, run farther, and build bigger muscles.

And boy, do supplement manufacturers know it.

The global supplement market is a multi-billion dollar business (1).  Sports nutrition products occupy a large segment of this market; studies estimate that up to 88% of athletes use supplements (2).

Active folks are particularly vulnerable to misinformation and misleading claims when it comes to supplements. I mean, who wouldn’t want to “reset your metabolism” and shave off pounds while you sleep? Or better yet, build muscles while eating nothing but cookie dough ice cream?

A brief history of supplements

Doping, or using a substance to enhance performance, is as old as athletic competition itself.

Ancient Greek athletes swore by garlic and wine as pre-competition superfoods, while early European athletes indulged in heavy cream and plenty of meat. More recently, athletes at the 1904 Olympics slammed down a mix of heroin and cocaine. (Not sure if it helped them win, but maybe with all that stuff swirling in their veins, at least they didn’t care so much if they lost…)

It wasn’t until 1968 that anti-doping rules were created with the original intent of preventing the death of athletes, but now those rules also protect the integrity of the games (3). With the London Olympics taking place, supplements are on the radar of the International Olympic Committee (IOC), the World Anti-Doping Agency (WADA), and the United States Anti-Doping Agency (USADA).

Here’s another eye opener for most people: in the US, manufacturers are not required to test a product for safety, or prove that the supplement does what it claims to do before it is put on the market. And while regulations vary, this is pretty much the case around the world.

Before 1994, supplements were classified as drugs and were regulated by the FDA. However, in 1994 the DSHEA (Dietary Supplement Health and Education Act) was passed, which changed how supplements are regulated, putting the burden of proof on the manufacturer.

Supplements became classified as foods, not drugs. This opened up the market to thousands of products.

Do you know your supplements?

The U.S. Food and Drug Administration (FDA) recently made it illegal to sell HCG (human chorionic gonadotropin), and ordered manufacturers to cease distribution of DMAA (1, 3-dimethylamlyamine, aka Jack3D, Hemo Rage Black, Napalm), two potentially dangerous supplements. The European Union is a step ahead of the US and has made the sale of DMAA illegal.

You’ve probably heard of those supplements, and may have considered — or even tried — one of them. But how much do you really know about the supplements you are taking?

For example, if you’re taking supplements to enhance performance, do you know how they work?

Many products aimed at the bodybuilding community claim to alter hormones. Are they altering the right ones? Hmmm…

Plant-derived hormones

Supplements that contain plant-derived hormones sound safe, don’t they? I mean, using a natural, legal substance that mimics a pharmaceutical isn’t considered doping.

So why not go the au naturel route to improving performance? Well, as generations of unlucky mushroom foragers have already discovered: natural doesn’t mean safe.

But first, let’s sort out what a plant-derived hormone is and what it is intended to do.

Plant-derived hormones can work in several ways.

  • They can enhance the action of existing hormones by increasing concentrations in the body.
  • They can block the conversion of one hormone, diminishing the effects of another (eg., block the conversion of testosterone to estrogen which diminishes the effects of estrogen in the body).
  • They can mimic actions of hormones (for example, they can build muscle or enhance recovery).
  • They can be anabolic (a substance that enhances the body’s ability to build tissue) and/or androgenic (stimulate development of male characteristics).
  • They may have generalized health benefits, as is the case with phytoestrogens.

Some of the most popular plant-derived supplements contain ecdysteroids (a steroid hormone of arthropods with reported anabolic properties), phytoestrogens, and phytosterols (thought to have beneficial effects on blood lipids).

One that is popular in the body building community is Tribulus terrestris (TT). Manufacturers claim that TT works by increasing testosterone through the activation of endogenous testosterone production. This claim is currently unproven, and side effects are unknown.

Here’s the problem though — and guys, you may want to have a seat for this one: Many of these supplements are actually increasing estrogen levels, not testosterone levels. Wow – just what you wanted to hear.

Most supplements simply haven’t been studied. (There’s no incentive to do so – in the US you can’t patent a plant.) So most users aren’t aware of the possible side effects of “natural” supplements on their endocrine and reproductive systems.

Research question

This week’s research review looked at how much physically active people know about their supplements, and how these supplements affect their health.

Borrione, P., et al. Consumption and biochemical impact of commercially available plant-derived nutritional supplements: An observational pilot-study on recreational athletes. J Int Soc Sports Nutr. 2012, 9:28 (19 June 2012).


This study was an observational study (there was no actual intervention), in which researchers collected data on habitual supplement use using an anonymous questionnaire.


740 subjects participated over 6 months. Everyone in this group had been training regularly for over a year for at least 1-2 hours per day, 3-6 days a week. In other words, they were a very fit group of individuals.

Out of this total:

  • 420 were body builders;
  • 70 were cyclists; and
  • 250 were fitness athletes.

Researchers also put together a control group of 30 people who didn’t use any nutritional supplements, and were matched for age, gender, sports discipline, body mass index (BMI), and training volume.

Laboratory testing

Out of the 740 subjects, 26 acknowledged that they used plant-derived supplements. The list was pretty long, and included some that you might recognize:

  • Zingiber — aka the ginger genus
  • Commiphora wightii — aka guggul, used in guggulsterone
  • Cordyceps — a genus of medicinal fungi
  • Prunus africanum bark — aka pygeum
  • Saw palmetto

23 people consented to give blood. Along with the 30 controls, these 23 folks had blood labs done.

Researchers asked all lab subjects not to exercise or use caffeine, alcohol or drugs 24 hours before the lab visit. They also asked them to fast overnight. During their lab workups, participants had blood drawn, and were given a complete physical that included a medical exam and a sports participation personal history.


Laboratory analysis

Researchers analyzed blood samples for key hormones, including:

  • testosterone;
  • dehydroepiandrosterone (DHEA);
  • estrogens;
  • progesterone;
  • luteinizing hormone (LH);
  • follicle-stimulating hormone (FSH);
  • several thyroid hormones including TSH, FT3, FT4; and
  • cortisol.

The researchers also analyzed the samples to test for liver and kidney function (these tests can show if there is organ damage or toxicity). They checked:

  • urea;
  • creatinine;
  • aspartate aminotransferase (GOT);
  • alanine aminotransferase (GPT);
  • lactate dehydrogenase (LDH);
  • creatine kinase (CK);
  • gamma glutamyl transpeptidase (GGT);
  • alkaline phosphatise (APH); and
  • total and partial bilirubin.

Gas chromatography/mass spectrometer analysis

Three supplements used by 20 of the 23 subjects were analyzed by a WADA certified laboratory for contamination with real anabolic steroid hormones (this type of contamination is more common than you might think).


Knowledge and use of nutritional supplements

Presented with a list that included ecdysteroids, phytoestrogens, phytosterols and vegetal sterols, 45% (333 people) didn’t know any of them. 24% only recognized phytoestrogens, 26% only recognized vegetal sterols, and 5% only recognized ecdysteroids.

(Could you recognize any of these?)

Health status

Good news here: no signs of organ toxicity or damage were found in any of the subjects and no significant differences were found between subjects and controls for cortisol, thyroid hormones and female reproductive hormones LSH and FSH.

However, out of the 23 subjects who used herbals, a whopping 65% of them (15) had significantly altered sex hormones, i.e. estrogen and progesterone.

Ten male subjects had increased plasma levels of progesterone. 15 had abnormal estrogen levels, including 2 females and 3 males, where this increase was several hundred times higher than the normal range.

There were also 2 males who had high estrogen, high testosterone, and decreased LH and FSH.

Because some of the results were so abnormal, researchers tested those subjects for any diseases that may have caused this. No underlying health conditions were found. Looks like the supplements are holding the smoking gun.

Dietary habits

Researchers discovered that the subjects with abnormal hormone values were taking multiple dietary supplements, including ones considered “traditional” (vitamins, minerals) as well as “natural” or herbal supplements.

Unfortunately the list was not provided in the study but the researchers did state that these subjects also had a high consumption of soy protein (2 g/kg/day). To put this in perspective, a serving of tofu is about 85 grams. For a 165 lb (75 kg) man that would be 150 grams, or less than 2 full servings of tofu, a day.

That doesn’t seem like very much to me and I wonder if it was from food or from a soy protein isolate powder. That would make a huge difference in terms of the sum total of soy plant hormones (phytoestrogens) consumed. If it was all in the form of the isolate, then yes, that is a lot (e.g. 1 serving of isolate is about 28 grams).

Gas chromatography/mass spectrometer analysis

None of the supplements were contaminated with real steroid hormones.


How much do recreational athletes know about their herbal supplements, especially those containing plant hormones?

What supplements do these folks take, and what effects do those supplements have on important endocrine systems, such as sex hormones and liver/kidney functions?

Well, it seems that most folks don’t really know what they’re taking. Bad enough, but worse — the plant supplements had significant and unintended effects on sex hormones. Men were often ending up with whopping doses of so-called “female” hormones, while women were also throwing their normal hormone levels out of balance.

No doubt about it: Taking herbal supplements is risky. Supplement manufacturing isn’t well controlled nor regulated. And research on the mechanisms of action and actual effects of commonly used herbs ranges from sparse to non-existent.

This study was one of the few to investigate the real consumption of herbs with proposed ergogenic effects by athletes.

Though the study itself involved a large group, only 23 people were habitual plant supplement users, which is a bit of a methodological limitation. Small sample size aside, the results to be striking in a good news-bad news sort of way

  • Good news: no organ damage… yet.
  • Bad news: in this very small sample, several subjects had altered hormones that were several hundred units outside of the normal range.
  • Even worse bad news: most of the subjects with altered hormones were men, and it was their estrogen and progesterone levels that were high, not their testosterone levels. I am guessing this was not the effect that these gentlemen intended.

Bottom line

Buyer beware. Be a skeptical and careful consumer. Remember that natural doesn’t mean safe.

If you take (or are considering taking) plant-based supplements, there are a few things you can do.

  • Check the FDA site and see if there have been any warnings or alerts listed for the supplements that you take. You might also check out, which often tests common sports supplement products.
  • If you’ve been using a supplement designed to alter your hormones for 6 months or more, it might be a good idea to visit your doctor and have your hormone levels and kidney and liver function tested.
  • You might also want to do a cost benefit analysis. Is the long-term risk to your health worth reaching your goals faster, or can you be a little patient, work a little harder and achieve similar results without herbs and with more peace of mind?

Caveat emptor!


Click here to view the information sources referenced in this article.

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