I’ve mentioned some worthwhile supplements in a previous article. Now I’d like to review another popular supplement: ZMA
ZMA is a combination of zinc magnesium aspartate and vitamin B6. The supplement claims to promote lean muscle mass, testosterone production, and help with sleep.
Why didn’t I include ZMA in my recommended supplements? The best research doesn’t support the hype.* I found a study (double-blind, placebo controlled experiment) comparing men who used ZMA with those who didn’t. Here’s the result:
Results of the present study do not support contentions that ZMA supplementation increases zinc or magnesium status and/or affects training adaptations in experienced resistance trained males with normal zinc status. These findings are in contrast with the notion that ZMA supplementation can increase zinc and magnesium status, anabolic hormone status, and/or strength gains during training.
I’m not ready to completely dismiss ZMA. These minerals are important:
In the USA, magnesium supplementation is dramatically under utilized by conventional physicians and is more important in patient therapy than most physicians realize.
. . . many people do not even get the RDA of 350 mg of magnesium daily. A therapeutic dosage could easily run between 400 mg and 1000 mg daily of elemental magnesium in divided doses. In people with normal kidneys, it is difficult to reach toxic levels of magnesium.
Quoted from: The Importance of Magnesium to Human Nutrition
But here’s the other issue: I’m not convinced the “ZMA formula” minerals are any more beneficial than mineral supplements you could buy at the local drug store.
Yes, there’s the claim that ZMA is better absorbed because it does not contain calcium–calcium is supposed to interfere with the absorption of Zinc. Is this no-calcium formula really better? I’m not sure:
High levels of dietary calcium impair zinc absorption in animals, but it is uncertain whether this occurs in humans. One study showed that increasing the calcium intake of postmenopausal women by 890 mg/day in the form of milk or calcium phosphate (total calcium intake, 1,360 mg/day) reduced zinc absorption and zinc balance in postmenopausal women (11), but increasing the calcium intake of adolescent girls by 1,000 mg/day in the form of calcium citrate malate (total calcium intake, 1,667 mg/day) did not affect zinc absorption or balance (12).
Quoted from Linus Pauling Institute at Oregon State
In one of the new studies, 18 relatively healthy women past menopause increased calcium intake to 1,360 milligrams daily–a little higher than the 1,200 mg now recommended for people over age 50. Their zinc absorption dropped by an average of about 2 mg, as did zinc balance. This happened regardless of whether they got the extra calcium from milk or from a calcium phosphate supplement. The study lasted 36 days.
In a second study, zinc absorption dropped by half when a group of 10 men and women took a calcium supplement with a single test meal. But adding nearly 8 mg of zinc to the calcium supplement offset this effect.
Quoted from The USDA Agricultural Research Service
So there may be something to calcium interfering with zinc absorption, but I’m not sure its something to be too concerned with.
The B-6 in ZMA does seem to help with sleep. But we once again have the same issue–why not just buy a “regular” (inexpensive) B-6 supplement?
There’s really no evidence ZMA will increase your testosterone or lean muscle mass. It isn’t too expensive if you want to try it, but don’t expect much.
Note: I have written an updated ZMA review on my other blog with more references.
*There is an often-quoted study that was done by the one who invented ZMA. I don’t trust that study for obvious reasons–I never trust studies/stats coming from the supplement makers.