Sleep Supplements: Magnesium, Valerian, Glycine and More

First, how supplements are regulated

In the US, dietary supplements do not need FDA approval for safety or effectiveness before sale, and contents can vary from the label. The AASM's 2017 guideline on medications for chronic insomnia suggested against using valerian, melatonin or L-tryptophan for chronic insomnia, because evidence of benefit was weak. Look for third-party verification marks (such as USP Verified or NSF), and tell your doctor and pharmacist about everything you take, because supplements can interact with medicines.

Magnesium

Magnesium is an essential mineral involved in nerve and muscle function. Small studies, mostly in older adults, have suggested possible improvements in sleep, but the overall quality of evidence is low, and benefit may be limited to people who are low in magnesium. Getting magnesium from food (leafy greens, nuts, seeds, beans, whole grains) is a sensible first step.

Safety: the NIH Office of Dietary Supplements sets an upper limit of 350 mg per day from supplements for adults, because higher amounts can cause diarrhea, nausea and cramping. People with kidney disease should not take magnesium supplements without medical advice, and magnesium can interfere with some antibiotics and osteoporosis drugs.

Valerian

Valerian root has been used for centuries. According to the NIH's National Center for Complementary and Integrative Health, studies of valerian for sleep have produced inconsistent results, and it is not clear that it helps. It appears safe for most adults for short-term use. Side effects can include headache, dizziness and stomach upset, and rare cases of liver problems have been reported. Avoid combining it with alcohol or sedatives, and avoid it in pregnancy.

Glycine

Glycine is an amino acid. A few small studies, largely from Japan, suggested that taking it before bed improved subjective sleep quality and next-day fatigue in people with mild sleep complaints. The studies were small and short, and some were connected to manufacturers. It appears well tolerated, but evidence is preliminary.

Other popular options

• L-theanine (from tea): small studies suggest possible relaxation benefits; evidence for sleep is limited.
• Chamomile: widely used as a tea; studies are few and effects modest. Avoid if allergic to ragweed-family plants.
• Tart cherry juice: small studies suggest modest benefits, possibly related to its natural melatonin content; it adds sugar and calories.
• Lavender: some evidence for aromatherapy and oral lavender oil for anxiety, with limited data on sleep.
• Kava: avoid. It has been linked to serious liver injury, and the FDA has issued warnings.

Over-the-counter sleep aids are not supplements

Products like diphenhydramine and doxylamine are antihistamines. They can cause next-day drowsiness, dry mouth, constipation and confusion, and tolerance develops quickly. They are not recommended for chronic insomnia, and older adults are generally advised to avoid them because of risks to memory and balance. Use them only occasionally and ask a pharmacist first.

A better place to start

No supplement has the evidence base of cognitive behavioral therapy for insomnia (CBT-I). Before buying a supplement, try a consistent wake time, morning light, cutting late caffeine and alcohol, and a wind-down routine. If sleep stays poor, a clinician can check for causes such as sleep apnea, restless legs syndrome (sometimes linked to low iron), thyroid problems or medication effects.