TMG (Betaine) Supplement Guide: Methylation, Longevity & Performance 2026

TMG — trimethylglycine, also known as betaine — is an amino acid derivative found naturally in beets, spinach, quinoa, and shellfish that has emerged as one of the most versatile and multi-beneficial supplements in the longevity space. As a methyl donor, TMG directly supports methylation — one of the most fundamental biochemical processes in the body, responsible for regulating gene expression, synthesizing neurotransmitters, detoxifying homocysteine, and maintaining cardiovascular health. It also has a distinct evidence base as an ergogenic aid for athletic performance, separate from its methylation benefits.

What Is TMG and How Does It Work?

Methylation: The Master Regulator

Methylation is the transfer of a methyl group (CH₃) from one molecule to another — a reaction that occurs over a billion times per second in the human body and regulates critical processes including:

• DNA methylation: Controls gene expression — which genes are "on" or "off" — without changing the DNA sequence. Epigenetic methylation patterns change with age and lifestyle; proper methylation support is central to longevity interventions.
• Homocysteine clearance: Homocysteine is a toxic amino acid byproduct that accumulates when methylation is impaired; elevated homocysteine is a potent cardiovascular and neurotoxic risk factor. TMG directly converts homocysteine to methionine via the enzyme betaine-homocysteine methyltransferase (BHMT), reducing homocysteine levels.
• Neurotransmitter synthesis: Methylation is required for the synthesis of dopamine, serotonin, norepinephrine, and melatonin — explaining why methylation deficiencies often present with mood and cognitive symptoms.
• Creatine synthesis: Approximately 40% of the body's methyl groups are consumed in creatine synthesis; TMG supports this process, making it synergistic with creatine supplementation.

TMG as a Methyl Donor

TMG donates one of its three methyl groups to homocysteine, converting it to methionine (an essential amino acid) while TMG becomes DMG (dimethylglycine). This direct homocysteine-lowering mechanism is one of TMG's most clinically significant effects — multiple studies show 500–3,000 mg/day of betaine reduces homocysteine levels by 10–20%. The remaining two methyl groups in the resulting DMG can continue supporting other methylation-dependent reactions.

Key Benefits of TMG Supplementation

Homocysteine Reduction and Cardiovascular Protection

Elevated homocysteine is an independent risk factor for cardiovascular disease, stroke, and cognitive decline. A Cochrane review confirmed that betaine supplementation at 1.5–6 g/day significantly reduces plasma homocysteine. For individuals with the MTHFR gene variant (which reduces folate-mediated methylation, causing elevated homocysteine in 40–60% of the population), TMG provides an alternative methylation pathway that bypasses the MTHFR enzyme — making it particularly valuable for this large subgroup.

Liver Health and Fat Metabolism

TMG is FDA-approved (as Cystadane) for the treatment of homocystinuria, a metabolic disorder causing severe homocysteine accumulation. Beyond this approved indication, betaine has substantial evidence as a liver protectant — it reduces hepatic fat accumulation, protects against nonalcoholic fatty liver disease (NAFLD), and supports bile acid production. Studies show betaine supplementation reduces liver enzyme markers (ALT, AST) in NAFLD patients and animal models of alcohol-induced liver damage.

Athletic Performance

A separate and distinct body of research has examined betaine as an ergogenic aid for strength and power sports. Multiple randomized trials have found that betaine supplementation (2.5 g/day for 2+ weeks) improves bench press power, squat volume, and sprint performance. The proposed mechanisms include:

• Osmolyte function — betaine acts as an organic osmolyte, helping cells maintain volume under thermal and dehydration stress during exercise
• Creatine synthesis support — by providing methyl groups for endogenous creatine production
• Direct cellular water retention — improving muscular endurance

This performance benefit is well-documented enough that betaine is included in several commercial pre-workout and creatine formulations.

Epigenetic Aging

Because DNA methylation patterns are central to epigenetic aging clocks (the most accurate biological age measurement tools), maintaining optimal methylation capacity is directly relevant to longevity. TMG is increasingly recommended in longevity protocols alongside NMN/NAD+ precursors to ensure methylation capacity is not rate-limiting as NAD+ metabolism increases methyl demand.

TMG and NAD+: A Critical Synergy

This interaction is particularly relevant for longevity-focused supplement users. NAD+ precursors (NMN, NR) boost NAD+ levels, but the conversion of nicotinamide (a NAD+ breakdown product) back to NMN requires methylation via the enzyme NNMT. This creates additional methyl demand — potentially depleting SAM (S-adenosyl methionine, the universal methyl donor) and raising homocysteine. TMG supplementation alongside NMN or NR directly addresses this potential methylation burden, making it a standard cofactor recommendation in NMN protocols.

Dosing

• Methylation support and homocysteine lowering: 500–1,500 mg/day with food
• Athletic performance: 2.5 g/day (typically 1.25 g twice daily with meals)
• NMN/NAD+ cofactor: 500–1,000 mg/day alongside NMN or NR
• Liver support: 1,000–2,000 mg/day

Best TMG Supplements 2026

1. Double Wood Supplements TMG — Best Value

Double Wood Supplements produces a well-regarded TMG product at 500 mg per capsule, allowing flexible dosing across a wide range of therapeutic targets. Double Wood specializes in cognitive and longevity supplements and sources high-purity ingredients with third-party testing. Their TMG is consistently well-reviewed for purity, price, and capsule quality. For daily methylation support alongside NMN or as a standalone homocysteine-lowering strategy, Double Wood provides excellent cost efficiency.

Best for: Daily methylation support, NMN protocol cofactor, or longevity-focused users who want reliable TMG at accessible pricing.

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2. Thorne Betaine HCl — Best for Digestion and Methylation Dual Support

Note that Betaine HCl (hydrochloric acid) is a different form than TMG (Betaine Anhydrous) — it provides both betaine and supplemental stomach acid for digestive support, rather than being purely a methyl donor. Thorne's Betaine HCl is NSF Certified for Sport and provides the best quality certification of any betaine supplement. For users who want both methylation support and improved protein digestion/stomach acid support, Betaine HCl provides dual benefit. For pure methylation and performance applications, seek Betaine Anhydrous (TMG). Thorne also makes a pure TMG product.

Best for: Users who want both methylation support and stomach acid supplementation for improved protein digestion, particularly those with low stomach acid symptoms.

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3. NOW Foods Betaine HCl — Best for Athletes

NOW Foods produces TMG (Betaine Anhydrous) at high potency doses (1,000 mg per serving) — appropriate for the 2.5 g/day performance protocol. GMP-certified with third-party testing. NOW's TMG product is straightforward, clean, and cost-effective for athletes who want the performance benefits documented in the sports science literature. The higher per-capsule dose reduces the daily capsule count compared to lower-potency options.

Best for: Athletes using TMG for its documented strength and power performance benefits at the clinically studied 2.5 g/day dose.

The Bottom Line

TMG is one of the most versatile and evidence-backed supplements in the longevity and performance space — simultaneously reducing homocysteine, supporting liver health, potentiating NAD+ protocols, and improving athletic performance. At 500–2,500 mg/day, it provides genuine, mechanistically sound benefit across multiple health domains. Double Wood provides the best daily value; Thorne offers the highest quality certification; NOW is the best option for athletes targeting the 2.5 g/day performance dose.