What do the experts say,
and what does the research show?

Magnesium is an essential mineral involved in over 300 enzymatic reactions in the human body, including energy production, protein synthesis, muscle and nerve function, blood glucose control, and blood pressure regulation. It is one of the most commonly studied minerals for supplementation, with evidence spanning sleep quality, mood, athletic performance, and metabolic health.

L-Theanine is an amino acid found naturally in green and black tea. It is studied for its ability to promote relaxed alertness, reduce anxiety and stress responses, improve sleep quality, and enhance the cognitive effects of caffeine. Unlike sedatives, it does not cause drowsiness at typical doses.

Creatine is a naturally occurring compound synthesized in the body from arginine, glycine, and methionine, and obtained from dietary sources such as red meat and fish. It is stored predominantly in skeletal muscle as phosphocreatine, where it serves as a rapid energy buffer for ATP regeneration during high-intensity activity. Creatine monohydrate is one of the most studied and consistently effective ergogenic supplements, with strong evidence for increases in muscular strength, power, and lean mass, and growing evidence for cognitive and neuroprotective benefits.

Ashwagandha (Withania somnifera) is a root herb used for centuries in Ayurvedic medicine, classified as an adaptogen for its proposed ability to help the body resist stressors. Its primary bioactive compounds — withanolides — are thought to modulate the hypothalamic-pituitary-adrenal (HPA) axis. Clinical trials using standardized extracts have found evidence for reductions in perceived stress, cortisol, and anxiety, as well as improvements in sleep quality. Some trials also suggest modest support for testosterone and strength in men. Evidence quality is moderate, with most trials being small and short-term; cycling use is recommended given limited long-term safety data.

Fish oil is a rich dietary source of the long-chain omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). These fatty acids are incorporated into cell membranes throughout the body and serve as precursors to anti-inflammatory signaling molecules. Fish oil has been extensively studied for cardiovascular health, triglyceride reduction, brain function, and mood — with the strongest and most consistent evidence concentrated in the area of triglyceride lowering, and more mixed findings for cardiovascular event prevention and cognitive outcomes.

Vitamin D is a fat-soluble secosteroid that functions as a hormone throughout the body, regulating calcium and phosphate metabolism, bone mineralization, immune function, and gene expression. It is synthesized in the skin upon UVB sunlight exposure and obtained in smaller amounts from dietary sources and supplements. Deficiency is common worldwide. The evidence is strongest for correcting deficiency — particularly for bone health and, at adequate doses, immune function — while the case for high-dose supplementation in already-replete adults is considerably weaker and continues to be evaluated in large trials.

Glycine is a conditionally essential amino acid with roles spanning multiple physiological systems: it acts as an inhibitory neurotransmitter in the spinal cord and brainstem, serves as a precursor for glutathione (the body's master antioxidant), is the most abundant amino acid in collagen, and is required for creatine synthesis. Research interest has focused primarily on sleep quality (via a unique core body temperature-lowering mechanism), glutathione support (in combination with NAC), and the hypothesis that modern diets — low in collagen-rich animal parts — may undersupply glycine relative to metabolic demand.

Taurine is a sulfur-containing compound abundant in muscle, heart, retina, and brain. Unlike most amino acids, it is not incorporated into proteins but plays broad roles in osmoregulation, membrane stabilization, calcium homeostasis, bile acid conjugation, and antioxidant defense. Research interest has historically focused on cardiovascular health and exercise performance. A landmark 2023 paper in Science (Singh et al.) elevated interest in taurine's potential role in aging biology, finding that taurine declines with age and that supplementation extended lifespan in mice — an exciting finding that awaits human interventional replication.

Inositol is a naturally occurring sugar alcohol that functions as a critical second messenger in cellular signaling, particularly through the IP3 pathway and insulin signal transduction. It is found in a range of foods and is produced endogenously. The most studied form, myo-inositol, has its strongest evidence base in polycystic ovary syndrome (PCOS), where it appears to improve insulin sensitivity and hormonal regulation. High-dose myo-inositol (12-18g/day) has been studied for anxiety and panic disorder with preliminary positive findings. Lower-dose use for sleep (approximately 900mg) is discussed in wellness contexts but has limited direct trial evidence at that specific dose.

Melatonin is an endogenous hormone produced by the pineal gland in response to darkness, serving as the body's primary circadian timing signal. Unlike most supplements, melatonin is a hormone — a distinction with pharmacological and regulatory significance. Its strongest evidence base is in circadian rhythm disorders: jet lag, shift work disorder, and delayed sleep phase syndrome. Its role in improving sleep in otherwise healthy adults without circadian disruption is supported by evidence of modest effect size. A key evidence-informed insight is that commercial doses (5-10mg) are far above the physiological range, and lower doses (0.5mg) appear sufficient for circadian phase shifting with better tolerability. Timing of administration is at least as important as dose.