Glycine vs Vitamin D3 (+ K2)
Both are used for live longer. Here's how they compare on human evidence, mechanism, safety and availability — in plain English.
| Glycine | Vitamin D3 (+ K2) | |
|---|---|---|
| Human evidence | ★★★☆☆ | ★★★★★ |
| Legal status | OTC Supplement | OTC Supplement, Prescription |
| How it works | Smallest amino acid; inhibitory neurotransmitter at spinal/brainstem glycine receptors (GLRA1), lowers core body temperature (a sleep-onset trigger) via peripheral vasodilation, and supplies one-third of collagen's amino acids. Mimics some… | Cholecalciferol → 25(OH)D (liver) → 1,25(OH)₂D (kidney), which binds the VDR (vitamin D receptor), a nuclear transcription factor regulating 200+ genes including those for calcium transport, immune peptides, and testosterone synthesis. K2… |
| In plain English | An amino acid that gently cools you down and quiets the nervous system for sleep, and is the main brick in collagen. Dirt cheap, very safe. | A hormone your skin makes from sunlight that switches on hundreds of genes. Indoor life (very common in Singapore) leaves most people deficient, which quietly lowers testosterone, immunity, and mood. |
| Bottom line | One of the most undervalued supplements — sleep + connective tissue + longevity. | Highest-value fix if you work indoors. Almost everyone benefits. |
| Availability | Available over the counter | Available over the counter |
Which is better for live longer?
We do not publish an indication-specific evidence grade for Glycine or Vitamin D3 (+ K2) for live longer, so we are not going to name a winner. The star ratings shown below are whole-compound summaries across everything each has been studied for — they are not a grade for this use, and comparing them here would be misleading. What actually differs is mechanism, side-effect profile, interactions, availability and cost. Those are compared in full below.
Full breakdowns: Glycine · Vitamin D3 (+ K2).
Common questions
Is Glycine or Vitamin D3 (+ K2) better for live longer?
We do not publish an indication-specific evidence grade for Glycine or Vitamin D3 (+ K2) for live longer, so we are not going to name a winner. The star ratings shown below are whole-compound summaries across everything each has been studied for — they are not a grade for this use, and comparing them here would be misleading. What actually differs is mechanism, side-effect profile, interactions, availability and cost. Those are compared in full below.
What's the difference between Glycine and Vitamin D3 (+ K2)?
Glycine: One of the most undervalued supplements — sleep + connective tissue + longevity. — Vitamin D3 (+ K2): Highest-value fix if you work indoors. Almost everyone benefits.