How are B12 and skin aging related?

The relationship between vitamin B12 and skin aging is not directly addressed in the provided context. Generally, B12 is involved in homocysteine metabolism; elevated homocysteine may promote collagen cross-linking and contribute to skin aging. However, evidence for a direct, clinically relevant anti-aging effect of B12 supplementation is weak and largely mechanistic. The context discusses DNA tests for skin glycation and collagen, noting that current tests lack strong scientific backing. Therefore, caution is warranted: while B12 deficiency has health consequences, supplementing beyond normal levels for skin aging is not supported by robust evidence. The evidence level is best described as 'mechanistic' or 'unclear'.