Some people love it and swear by its muscle-enhancing powers. Some say it’s a useless waste of money. Some just say the weird dreams you have while taking it will blow your mind.

ZMA, short for Zinc and Magnesium Aspartate, is a supplement often cited as capable of raising testosterone levels and improving athletic performance. A coach recommended I try it in college, but after reading about some of its weird side effects (like the aforementioned crazy dreams) and its seemingly hit or miss nature, I decided to pass. Ever since, I have been curious. Could I have performed better with the help of ZMA?

I talked to Dr. Mike T. Nelson, a member of the American College of Sports Medicine and operator of miketnelson.com, and nutrition researcher Kamal Patel, director of Examine.com, to shed some light on this curious and mysterious supplement.

So What Exactly is ZMA?

ZMA is basically just a blend of zinc, magnesium and vitamin B6. It contains a specific form of magnesium and zinc, magnesium aspartate and zinc monozyline. A serving size of original formula ZMA includes 450mg of magnesium, 30mg of zinc and 10.5mg of vitamin B6.

The creation of ZMA is credited to Victor Conte, the founder of BALCO Labs, a sports nutrition center made notorious in the mid-2000s when it was revealed that they had supplied Barry Bonds, Bill Romanowski and Marion Jones with a steroid that was virtually undetectable by drug tests.

ZMA was released before the controversy, and Nelson recalls the hype around the supplement. “I was in college when it first came out, and people were going crazy for it. But I wanted to see if it hung around for a while and remained popular after the initial big splash.” After the BALCO scandal, sales took a big hit. But in recent years, ZMA has regained popularity.

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Why Might ZMA Work?

“Zinc and magnesium are two common micronutrients that many athletes are deficient in,” Nelson says. “Athletes sweat so much that they can lose those micronutrients at a high rate. ZMA can help to get their zinc and magnesium levels back to where they should be.”

Zinc is crucial for supporting optimal testosterone levels and increasing immune health, and magnesium supports muscle and nerve function and is critical for energy production.

The typical ZMA supplement contains 200 percent of your daily value of zinc, 113 percent of your daily value of magnesium and 525 percent of your daily value of vitamin b6. So it definitely supplies more than adequate amounts of zinc and magnesium, but what’s up with all the vitamin B6? Vitamin B6 has a ton of benefits, including helping in the formation of red blood cells, which deliver oxygen to muscles and promote endurance. A high red blood cell count is desirable for athletes.

Why is ZMA Taken Before Bed? And What’s with the Crazy Dreams?

The right time to take a supplement is usually either pre-workout or post-workout, but ZMA should be taken 30 to 60 minutes before bedtime. Nelson says, “the reason ZMA is supposed to be taken before bed is the magnesium content. Magnesium can make people groggy and is often prescribed to those with sleeping problems.”

Simple enough, but why do so many people who take ZMA say it gives them weird, vivid dreams?

Nelson isn’t quite sure, but it might have something to do with the high dose of vitamin B6. He says, “Vitamin B6 could have an effect on someone’s ability to recall their dreams the next day, but there just hasn’t been enough research yet to draw a conclusion.” The only scientific research on the subject seems to be a 2002 study at the City College of New York, which suggested that subjects given a 250mg dose of vitamin B6 were able to recall dreams better the next day than those given a placebo.

Many ZMA users have also reported stomach pain, which Patel says is caused by the magnesium content. He says, “Most forms of magnesium have some risk of causing an upset stomach, especially if you take a lot at once rather than divided doses.”

Does ZMA Work?

The most controversial question about ZMA is also the most important: does ZMA work?

Only two studies have been conducted on the effects of ZMA. The most famous study, conducted by Dr. Lorrie Brilla on Western Washington University football players, was a double-blind study in which 12 participants took either ZMA or a placebo on a nightly basis for eight weeks. The participants who took ZMA displayed an 11.6 percent gain in muscle strength, more than twice the 4.6 percent gain in muscle strength displayed by the placebo group. The ZMA group also displayed a 30 percent increase in testosterone levels compared to only a 10 percent increase in the placebo group. So basically, the study showed that ZMA works.

But a more recent study, conducted at Baylor University’s Exercise and Sports Nutrition Lab, showed different results. The researchers looked at 42 healthy male participants whose average age was 27, each of whom had engaged in resistance training for at least a year. The study was double-blind, with participants taking either ZMA or a placebo every night for eight weeks. Their strength was tested at zero, four and eight weeks. After eight weeks, there was no significant difference in strength gain between the two groups.

So what gives?

Nelson says, “My guess is that in the first study, the majority of those guys were deficient in zinc and magnesium coming in. So the ZMA was getting those micronutrients back to an optimal level, which really helped them. In the second study, the majority of the participants were likely at optimal or near-optimal zinc and magnesium levels when they came in, so the ZMA didn’t do much of anything.”

Initial zinc levels also probably made a difference in testosterone gains between the two studies. As Patel says, “Zinc deficiency leads to low testosterone. But you can’t raise your testosterone level with zinc if you have sufficient zinc already.” The participants in the second study likely had sufficient zinc entering the study.

Who Should Take ZMA?

If you eat a well-balanced diet and your levels of magnesium and zinc are where they need to be, ZMA won’t do much of anything in terms of increasing performance.

Nelson says, “Athletes should look at their nutrition. You don’t need to solve everything with a supplement. If you are eating enough good food that has those nutrients in them, ZMA won’t do anything. The idea of the more zinc or magnesium the better simply isn’t true once you reach a certain level.”

But if you are deficient in magnesium or zinc, taking ZMA can give you an uptick in performance, because it gets those important nutrients back where they need to be and helps your body operate more efficiently.

Both Nelson and Patel agree that many young athletes could be low in zinc and magnesium without knowing it, due to an unbalanced diet and because they sweat more than non-athletes.

Before trying ZMA, make an effort to include more zinc and magnesium in your diet. Foods such as oysters, beef and cashews are high in zinc; foods such as raw spinach, brown rice and soy beans are high in magnesium. Choosing the right foods can help you achieve the results you want without causing weird dreams or upsetting your stomach.

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