ZMA is a well-known sports performance supplement touted by weight lifters and bodybuilders for its ability to raise testosterone and other anabolic hormones and some say it improves muscle strength too. Others take this vitamin and mineral supplement to improve the quality of their sleep and aid with muscle recovery after intense exercise. All well good and testimonials aside, does ZMA really work? And if it does, are there any side effects or contraindications? Fortunately, there is clinical research on this sports supplement.
What Is ZMA
ZMA is a proprietary blend of vitamin B6, magnesium, and zinc. Three capsules of contain the following nutrients:
|Men's Formula||Women's Formula|
|Vitamin B6||105 mg (618% DV)||7 mg (412% DV)|
|Magnesium (aspartate & Oxide)||450 mg (107% DV)||300 mg (71% DV)|
|Zinc (Mono-L-Methionine, Aspartate & Oxide)||30 mg (273% DV)||20 mg (182% DV)|
There is both a men's and women's formula however clinical research involving the woman's ZMA supplement could be located.
How Do You Take ZMA?
The company recommends men take 3 capsules a day, 30-60 minutes before bedtime on an empty stomach. Women, take two capsules on an empty stomach, 30-60 minutes before going to bed. For best results avoid taking alongside foods or supplements containing calcium.
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ZMA Clinical Research
The first study of this popular supplement involved 27 college football players who were instructed to take ZMA supplements or a placebo each day for 8 weeks. 3-day diet analysis revealed the football players were not deficient in zinc, magnesium, and vitamin B6 and actually exceeded the RDA for these nutrients. Here, it was found that ZMA vitamin and mineral supplements significantly raised the anabolic hormone profile of the athletes including total testosterone, free testosterone, and IGF-1. To see the before and after levels, watch the video. In contrast, these hormone levels actually declined in placebo-takers.
An additional finding was that ZMA supplements also improved muscle power in the quadriceps and hamstrings (thigh muscles) too. In theory,
this might improve football game performance.
One possible criticism however was that the study was funded by SNAC, the company which makes ZMA supplements. Victor Conte, one of the researchers in the investigation, is the founder of SNAC. The acronym SNAC stands for Scientific Nutrition for Advanced Conditioning.
In an attempt to shed light on the original findings, other researchers recruited 42 men and gave them ZMA supplements or a placebo, and instructed them to take the capsules before going to bed each night for 8 weeks. During that time, the men also performed a progressive strength training program. These investigators reported that the vitamin and mineral supplement did not raise total or free testosterone or IGF-1 levels. Likewise, there were no significant improvements in muscle strength either.
A major drawback to this study however was that it did not use the original ZMA formula. Instead, a different dietary supplement called Z-Mass was used. While the Z-Mass supplement did contain similar amounts of vitamin B6, zinc, and magnesium, it also contained other ingredients such as L-Dopa, potassium, and Mucuna pruriens (velvet bean) which, in theory, may have interfered with the results.
In another clinical investigation, 14 healthy, weight-trained men with normal to high blood levels of zinc were given ZMA supplements or a placebo for 56 days and instructed to follow their usual strength training program. While the supplement did raise zinc levels, it proved ineffective at boosting free or total testosterone levels.
What Does This Mean?
So far, 3 clinical trials have reported results. Of those, one study involved a supplement that contained additional ingredients which may have contributed to its negative findings. This leaves one clinical trial showing ZMA boosts strength and anabolic hormone levels, and another study, where the results show just the opposite effect. No studies were located that specifically tested whether this supplement improves the quality of sleep (REM sleep, delta wave, etc) or aided with muscle recovery following intense exercise. So far no investigators have tested whether the supplement works better when cycled. In other words, if people periodically stop taking it for a few weeks.
What About ZMA-5?
The ZMA-5 supplement, touted as “the next generation,” gets its name from 5-HTP, a metabolite of the amino acid tryptophan. ZMA-5 contains similar amounts of magnesium, zinc, and vitamin B6 as the original formula but in addition, also has 50 mg of 5 HTP and 100 mcg of folic acid. Bioperine ( black pepper extract) is also added to enhance nutrient absorption. Some studies show 5-HTP may help with sleep, weight loss, and depression.
How They Compare To Each Other
|ZMA-5||Original (men's formula)|
|Vitamin B6||10.5 mg||10.5 mg|
|Folic acid||100 mcg||–|
|Magnesium||450 mg||450 mg|
|Zinc||30 mg||30 mg|
|Bioperine (black pepper extract)||5 mg||–|
No studies could be located comparing the effects of ZMA-5 to the original formula.
ZMA Side Effects and Cautions
The supplement has been around many years and is likely safe in healthy people for at least 2 months of use, which was the duration in time of the studies summarized above. General guidelines to reduce the chances of adverse side effects include:
- Start with less than recommended
- Avoid if you are pregnant/breastfeeding
- Stop at least 2 weeks before having surgery
- Speak to your doctor/pharmacist if you take any medications
- Magnesium can cause diarrhea at doses above 350 mg
While not confirmed by research, some testimonials report the following:
- Improved sleep
- Enhanced libido
- In one of the ZMA clinical studies, the urine of people became more alkaline and their urine output almost doubled
- Vitamin B6 may be found in other sports supplements you take. Taking more than 1000 mg of vitamin B6 can irritate nerves, causing feelings of pins and needles (called paresthesia). Vitamin B6 can reduce folic acid levels too.
- Some research finds people taking 50 mg/day of zinc had higher bad LDL cholesterol levels.
Does ZMA Work?
I don't think there is enough evidence, either way, to say for certain if ZMA supplements raise free or total testosterone or improve muscle strength. So far, there's just one study finding it works and another investigation finding it didn't work. No studies involving women could be discovered. Magnesium is probably responsible for why the supplement improves sleep.
April James says
there was no mention on whether they test the zinc and magnesium levels in the first study were they tested pre/post study? since low levels of zinc and magnesium decrease testosterone in the body I would think that would be an important thing to test for. The second study they said the levels were tested and normal; so it makes sense that taking more of something that you are not deficient in would not have much of an impact
Joe Cannon says
April, good call. I re-read the first study (the original ZMA study) and the football players’ intake of zinc, magnesium, and vitamin B6 was higher than the RDA so they were not deficient. I have corrected this and added it to the review.