PT on the Net Research

Herbs - Inherent Risks and Apparent Benefits

Editor’s Note: The following is an expanded response from a recent member question in the Research Corner. The rapid growth of herb use across the entire health and fitness industry made us think this would be a useful article to members around the world.


A friend just started taking (1) Tribulus Terrestris (for improved weight training performance) as well as (2) Ginkgo Biloba (for memory). I have looked on the Internet, but all the information is found on biased web sites (selling the stuff) or the research is old. I am concerned about such things as drug/vitamin/nutritional interaction. How I do get the facts, and how can I explain to clients about the dangers of products that may affect our hearts, hormones, liver functions, etc? My doctor does not know anything.


Ah…herbs. So much confusion and mystery surrounds the use of herbal supplements. There is no doubt that many herbs affect the physiology of the human body. In fact, there are many herbs that have drug like effects. When a herb is shown or known to elicit a specific effect on a condition or function of the human body, scientists try to identify the unique compound(s) of that herb. These compounds are referred to as active markers. Active markers are the unique substances that exist in one herb versus another, possibly similar botanical, and are credited (not always accurately) with that herb’s influence on human physiology. Pharmaceutical manufacturers and scientists have been busy for decades trying to reliably identify active markers for scores of herbs that have a long history of use in Chinese, European and herbal medicine. I’m sure there is hope of using these substances as drugs or to model synthetic derivatives that could treat a myriad of problems and bring in additional revenue.

The widespread access and use of herbal supplements, often referred to as botanicals, troubles many due to the inconsistencies in product potency and possible interactions with health problems, other botanicals and medications (over-the-counter and prescription).

There are potentially thousands of factors that can affect the potency and content of active markers in an herbal supplement. They include:

These are just a few of the possible variables. Scary, huh?

Added to this confusion is the fact that manufacturers are not required to test raw materials and/or finished products for purity, and the use of herbal supplements can become a rather scary endeavor.

When researching the possible uses, benefits and risks of a particular substance my first trip is usually to PubMed. PubMed is a database of pretty much any study ever done, on a truly bewildering array of subjects. In the case of Ginkgo, I would enter the herb name and do a general search. This gives me a good idea of what affects of ginko supplementation have been investigated. From there, the abstracts of the studies can be viewed. If possible I resort to the Apex Fitness Library to find the journal cited, and review the entire study. The complete study can also be ordered online through PubMed or may be accessed for free at the journal’s web site. Other great resources for unbiased, scientific data on botanicals include the PDR for Herbal Medicines and the Natural Medicines Comprehensive Database. Dr. Andrew Weil also supplies helpful information on herbs at his web site and in his newsletter. The book An Evaluation of Popular Fitness-Enhancing Compounds can also be a useful tool when investigating compounds used by fitness enthusiasts.

The decision to use herbal supplements should be done only after careful study and evaluation of particular compounds and how they fit into one’s lifestyle, training program, diet and other supplement use. It is not safe to assume that just because botanicals are natural, they must be safe. Conversely, is also not fair to assume that all herbal supplements are useless or dangerous.

Herbs have been used in Chinese and Ayurvedic medicine for thousands of years. In Europe, herbal medications are often used in place of common synthetic drugs, due to their lower cost and lower incidence of side effects

Due to the possibility of side effects and drug/nutrient interactions, only a physician well studied in the use of dietary supplements or a Doctor of Herbal Medicine should make recommendations on the use of dietary supplements and herbs to treat medical and health problems. The personal trainer should advise their clients considering the use of botanicals to seek physician approval if they have a known medical or health condition or are taking prescription or over-the-counter drugs.

If it were my physician, I would not accept “I don’t know” as an answer to my herb questions. Physicians have access to sources of information as good, if not better, than you or me. Laziness or lack of desire to expand their knowledge may be to blame. If that were the case, I would shop for a more helpful, knowledgeable physician.

Now let's take a look at the two specific herbs you enquired about.


Ginkgo leaf extract (Ginkgo biloba or EGb761 as it is known clinically) comes from the Ginkgo tree, the oldest living tree species on the planet, with individual trees living to be over a thousand years old. Ginkgo’s use to treat asthma and bronchitis was listed in the first pharmacopoeia in 2600 B.C. In Germany and France; it is the most commonly prescribed herbal medicine and the preferred choice for the treatment of dementia.

Ginkgo’s most common use in the US is to help improve memory and prevent age related memory loss (dementia), especially in those with Alzheimer’s. Several studies have confirmed that Ginkgo is effective in treating the symptoms of dementia and cerebral vascular insufficiency (reduced blood flow to the brain). These include improvements in cognitive function, social functioning, dizziness, vertigo, sleep patterns, depression, headaches and tinnitus (ringing in the ears). As mentioned earlier, in herbal medicine Ginkgo is used to treat asthma and other respiratory problems. Due to the variety of flavonoids and other natural chemical constituents, Ginkgo has gained interest in anti-aging medicine as a potent antioxidant. Finally, Ginkgo may positively affect vision, specifically macular degeneration, cataracts and diabetic retinopathy.

Ginkgo contains several active chemical ingredients including flavonoids (colored components of plants with antioxidant and anti-cancer properties), terpenoids (specifically ginkgolides) and organic acids. Although many of the chemicals found in ginkgo exert pharmacological effects individually, it is suspected that they work synergistically to greater effect. The flavonoids are thought to aid in antioxidant and free-radical scavenging activity, protecting tissues from oxidative damage and lipid peroxidation, as well as offering protection from ischemic episodes (lack of oxygen and blood to tissues). Collectively, these functions may help prevent accumulated damage or further decay associated with aging. Ginkgolides have been shown to competitively inhibit platelet activating factor (PAF), a common allergen, by binding to membrane receptors of numerous cells. It is through this action that ginkgo achieves many of its benefits, such as decreased platelet aggregation (preventing clot formation, blood thinner), anti-inflammatory effects, improved venous tone and decreased smooth muscle contraction, increasing blood flow and possibly reducing risk of heart disease. Inhibition of PAF is also attributed to the anti-inflammatory effects of Ginkgo, reducing symptoms associated with respiratory problems such as asthma and bronchitis. Ginkgo is also thought to affect neurotransmitter activity, preventing the age related decline in brain activity. Finally, ginkgo enhances beta cell functioning and lowers blood pressure in response to glucose loading, possibly aiding in the prevention and treatment of Syndrome-X.

Safety and Possible Side Effects

When used orally as directed, Ginkgo leaf extract appears safe. Studies using Ginkgo have looked at its use for several weeks to over a year. Ingestion of the crude plant (non extract) can lead to severe allergic reactions, due to higher concentrations of ginkgolic acid, a toxin. Also, adverse events are associated with the consumption of the ginkgo seed, roasted and especially raw. Typical cited adverse events at normal intake levels include mild GI upset, headaches, dizziness, palpitations, constipation and allergic skin reactions. Larger doses can cause restlessness, diarrhea, nausea and weakness. Due to its inhibition of PAF, excessive, spontaneous bleeding is a potential side effect. Ginkgo use should be stopped at least two weeks prior to elective surgery to minimize the risk of excessive bleeding. There is some anecdotal evidence that links ginkgo and seizures, but no studies have shown this association. Until a definitive answer is discovered, it may be wise for those prone to seizures to avoid ginkgo. Those with bleeding disorders, epilepsy and diabetes should not use gingko, at least not without consulting with their physician.

Drug/nutrient Interactions

Anyone with a health or medical problem or using prescription or over-the-counter drugs should discuss the use of ginkgo or any dietary supplement with their physician or primary care provider prior to beginning use.

Typical Dosage

Most ginkgo extracts are standardized to provide 24 to 25 percent of the flavonoids glycosides and six percent of the terpenoids. Doses showing benefit range from 120-240 mg/day divided into two to three doses. Start with the low dose to gauge tolerance and progress as needed.


I have included an excerpt from the book, An Evaluation of Popular Fitness-Enhancing Compounds by Neal Spruce and Alan Titchenal, Ph.D. to provide this information.

Tribulus terrestris is an herb, also known as the puncture vine, caltrops and Ci Ji Li. The tribulus terrestris plant contains various active compounds, such as glycosides, flavonoids, saponins and alkaloids. The saponins in this herb can be hydrolyzed to yield steroidal sapogenins, such as diosgenin (precursor in the synthesis of pregnenolone, progesterone, etc), gitogenin, chlorogenin, ruscogenin, 25-D-spirosta-3,5-diene and others. The main furostanol saponin is protodiosciN.

One or more of the active compounds (probably the steroid glycosides) in this herb are reported to have a stimulating effect in healthy men and women on luteinizing hormone (LH), follicle stimulating hormone (FSH), estrogen and testosterone. The serum testosterone level in healthy men was increased 30 percent after five days of supplementation. Similar increases in hormones were seen in animal studies. In studies on infertile and impotent men, in addition to the hormones, libido and spermatogenesis were also increased.

Rationale for Terrestris Supplementation

The results of an effective, resistance-training program include (1) creating a stimulus for growth from stress, induced by the workload (muscle damage) and (2) increasing the levels of anabolic/anti-catabolic hormones, such as testosterone in relation to the catabolic ones like cortisol. The increase in testosterone/DHT helps to send an anabolic signal to the body, calling for protein synthesis within the damaged fibers, while combating some of the cortisol’s effect, which is simultaneously released with testosterone. Therefore, higher testosterone levels favorably enhance protein synthesis, compared to lesser levels.

The use of exogenous testosterone or its analogs in doses many times the amount normally produced endogenously has a profound influence on the body’s ability to build muscle. This is easily seen in athletes using large doses of anabolic steroids. These doses of steroids consequently reduce the endogenous production of testosterone by reducing the level of LH.

The rationale of supplementing with precursor hormones or substances like tribulus is to increase the production of testosterone. A large enough increase in the natural production of testosterone in the body should lead to an increase in muscle growth. Whether tribulus supplementation can increase the testosterone level enough to affect protein synthesis needs to be clinically tested.

The use of anabolic steroids often results in a decreased endogenous production of testosterone. Lowered LH and testosterone levels in steroid users illustrate this after drug cessation. An alternative use for tribulus terrestris may be to bring such anabolic steroid-induced hypogonadism back to normal. Human chorionic gonadotropin (HCG), another compound that induces increases in LH and testosterone, has been used with success to reverse this type of hypogonadism.

Typical Dosage

The doses, used in most of the Bulgarian and European studies, range between 750 and 1,500 mg of a standardized tribulus terrestris extract that generally contains 40 percent furostanol saponins with the main saponin as protodioscin.

No side effects were mentioned in the few studies at these doses other than the effects mentioned on libido, spermatogenesis, and hormone levels. The fact that estrogen was increased in healthy males indicates that estrogen-induced side effects may be possible. Those with a propensity towards gynecomastia should use caution if supplementing with tribulus.


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