What is ZMA?

In one line

ZMA is a supplement combination that bundles the minerals zinc and magnesium with one vitamin in set amounts, usually taken before bed.

What is ZMA?
The supplement people take before bed
At the gym or the supplement shelf, you hear about ZMA as 'the supplement you take before bed'. This post explains what ZMA is made of, what each ingredient does in the body, and what research has actually found.
In short
Zinc, magnesium and vitamin B6 in one
ZMA is a supplement combination of two minerals, zinc and magnesium, plus vitamin B6. It is not a new substance. It is three nutrients the body already needs, mixed in set amounts.
The name
Z for zinc, M for magnesium, A for aspartate
ZMA stands for 'Zinc Magnesium Aspartate'. It means zinc and magnesium attached to a substance called aspartate (aspartic acid). Vitamin B6 is not in the name, but it is included.
What is aspartic acid?
One of the amino acids that build protein
Protein is a chain of small pieces called 'amino acids'. Aspartic acid is one of those amino acids, and the body makes it on its own. In ZMA, zinc and magnesium come attached to amino acids such as aspartic acid.
Zinc and magnesium
Two minerals that help enzymes
Minerals are elements the body needs, like calcium, iron and zinc. Proteins that help chemical reactions in the body are called 'enzymes', and zinc and magnesium are each needed by more than 300 enzymes. Both are minerals we need to get regularly from food.
Vitamin B6
Needed to use protein and make blood
Vitamin B6 dissolves in water, so the body does not store much of it, and the extra leaves in urine. The body uses B6 to break down the protein we eat, to make hemoglobin, the red blood part that carries oxygen, and to keep nerves working. It is found in tuna, salmon, bananas and beans.
How much is in it
Studies used 30mg zinc and 450mg magnesium
The daily ZMA amount used in studies was 30mg of zinc and 450mg of magnesium, with a small amount of vitamin B6 added. In the studies, people took it before going to bed.
Why it became famous
A first study reported more testosterone and strength
Hormones are substances that travel in the blood and carry signals around the body. ZMA became well known from a 2000 study reporting that a sports team taking ZMA during off-season strength training gained more testosterone (the male hormone) and strength. Since then, ZMA ads have often claimed it raises testosterone.
Studies on sleep
Sleep did not improve
ZMA is sold with claims that it helps deep sleep. But in studies where people took it before bed for two nights, sleep did not improve, and in the largest study total sleep time actually dropped by about 30 minutes. The people in these studies already got enough zinc and magnesium from their usual food.
The magnesium amount
Above the US limit for supplements
The US set an adult upper limit, the amount not to go over, of 350mg a day for magnesium from supplements (not food), set to prevent the diarrhea that large amounts of supplemental magnesium cause. The daily ZMA amount often used in studies contains 450mg of magnesium, which is above this limit.
Common myth
Does ZMA raise testosterone?
No. In people who already got enough zinc from food, taking ZMA did not change testosterone in the blood. In a study where people took it for 8 weeks while doing strength training, testosterone, strength, and the amount of muscle and fat all showed no difference from a fake pill.
Summary
Three nutrients bundled for bedtime
ZMA is a supplement combination of zinc, magnesium and vitamin B6 in set amounts. In people who already got enough zinc from food, it did not raise testosterone. Related terms: zinc, magnesium, minerals.