Thorne Magnesium BisglycinatevsNOW Foods L-Theanine Double Strength 200 mg

Magnesium acts as a cofactor in hundreds of enzymatic reactions and helps regulate neurotransmitter systems, including blunting excitatory NMDA-receptor activity and supporting inhibitory GABA tone. The bisglycinate (chelated) form binds magnesium to the amino acid glycine, which improves absorption and reduces the laxative effect seen with oxide or citrate, while glycine itself has mild calming properties.

L-theanine is an amino acid found almost exclusively in tea leaves. It readily crosses the blood-brain barrier and increases alpha-wave activity, the brain pattern associated with relaxed wakefulness, while modulating the neurotransmitters GABA, serotonin, and dopamine. The result is a relaxed but clear-headed state that can lower the physiological and mental arousal that blocks sleep onset, which is why it is studied for both stress and sleep quality rather than as a sedative.

Evidence is real but moderate. A 2025 randomized, placebo-controlled trial of magnesium bisglycinate in adults with poor sleep found a statistically significant reduction in Insomnia Severity Index at four weeks, though with a small effect size (Cohen's d around 0.2). An earlier double-blind trial in older adults reported improved sleep time and efficiency at 500 mg daily, and a 2021 meta-analysis found about a 17-minute reduction in sleep onset latency while noting the overall literature quality is limited.

A 2019 randomized, placebo-controlled crossover trial found that 200 mg/day of L-theanine for four weeks reduced anxiety and depression scores and improved Pittsburgh Sleep Quality Index subscales for sleep latency, sleep disturbance, and use of sleep medication in healthy adults. A 2025 systematic review of supplementation trials concluded L-theanine can improve some subjective sleep outcomes, and combination studies (for example with a milk-protein hydrolysate) have shown reduced sleep disturbance. Overall the effect is modest and primarily mediated through reduced stress and arousal rather than direct sedation.

The most common issue is loose stools or mild GI upset, which is less likely with the bisglycinate form than with oxide. Excess magnesium is normally cleared by the kidneys, so people with reduced kidney function risk accumulation and should avoid supplementing without medical supervision. This is educational information, not medical advice; individual results vary.

L-theanine is among the best-tolerated supplements in this category, with side effects being uncommon and mild, such as occasional headache or stomach upset. Because it promotes relaxation, combining it with alcohol or sedative medications could be additive, so use judgment. This is educational information, not medical advice; individual results vary.

Expect roughly $40-$44 for a 60-serving jar as of 2026, which is mid-range for a certified chelate. Generic magnesium oxide or citrate costs a fraction as much but is less absorbable and harsher on the gut. Subscribe-and-save on Thorne.com trims about 10%, and the product is frequently HSA/FSA eligible.

Roughly $18-$24 for 120 capsules as of 2026, frequently discounted under $20, with a larger 180-count value size available. At one capsule daily that is months of supply for the price of a few coffees, and the product is often HSA/FSA eligible. Note the formula includes 100 mg of inositol, so it is not a single-ingredient product.

Adults seeking general relaxation and sleep support. Not appropriate without medical guidance for people with significant kidney impairment, heart block, or those on certain medications (such as some antibiotics or bisphosphonates) where magnesium can affect absorption. Pregnant or nursing people should consult a clinician.

Adults whose sleeplessness is tied to stress, anxiety, or an overactive mind, or who want daytime calm without sedation. People who are pregnant or nursing, who take sedatives or blood-pressure medication, or who have a diagnosed anxiety or sleep disorder should consult a clinician. It is not a substitute for treatment of clinical insomnia.