NOW Magnesium Glycinate review: can magnesium help testosterone and sleep?

Many men don't get enough magnesium from food, especially if they eat few nuts, seeds, beans and leafy greens. Magnesium matters for muscles, nerves and sleep, and small studies have linked it to testosterone. This review looks at what the research shows and whether NOW Foods' magnesium glycinate is a sensible choice.

What is in this product

According to the Amazon listing, a serving of two tablets gives 200 mg of elemental magnesium from 2,000 mg of magnesium bisglycinate (Albion). Each tablet holds 100 mg. The bottle contains 180 tablets, and the listing marks it as halal, vegan and vegetarian.

In magnesium glycinate, the magnesium is bound to the amino acid glycine. It's absorbed well and usually causes fewer stomach problems than magnesium oxide or citrate.

What the studies found

In a 2011 study by Cinar and colleagues, men who took magnesium for four weeks had higher testosterone, and the rise was bigger in the men who also trained. The study was small, and the men were young and active.

In a 2011 study of older Italian men, Maggio and colleagues found that men with higher magnesium in their blood also tended to have higher testosterone. That study shows a link only, not that magnesium causes the rise.

For sleep, a small 2012 trial in older adults with insomnia found that magnesium may help with sleep quality and falling asleep. Better sleep matters here, because short sleep is known to lower testosterone.

Overall, magnesium may help men who are low in it, train hard, or sleep badly. It's unlikely to do much for men who already get enough.

Who it may suit

• Men who eat few nuts, seeds, beans, whole grains or greens
• Men who train hard and sweat a lot
• Men who want a gentle magnesium in the evening as part of a sleep routine

Who should be careful

The NIH lists 350 mg a day from supplements as the upper limit for adults. Too much can cause diarrhoea and stomach upset. People with kidney disease should avoid magnesium supplements unless a doctor approves. Magnesium can also interfere with some antibiotics and with osteoporosis medicines. Check with a doctor or pharmacist if you take any regular medicine.

Bottom line

NOW Magnesium Glycinate is a well-priced, gentle, halal-listed magnesium that's easy to find on Amazon. Treat it as support for sleep and recovery if you may be low in magnesium, not as a testosterone booster.