Compare interventions

Use the same six evidence dimensions for both. This prevents a strong animal result for one product being compared with a human clinical result for another.

First intervention

versus

Second intervention

Protein and muscle ageing

Leucine

Useful human evidence

Useful as part of protein strategy in selected older adults; isolated leucine is not a longevity treatment.

Human clinical outcomes Moderate

Human biomarkers Moderate

Animal lifespan None

Mechanistic plausibility Strong

Safety certainty Moderate

Direct longevity relevance Preliminary

Verdict: Leucine is an essential amino acid and a potent signal for muscle protein synthesis. Leucine-enriched protein can help some older or sarcopenic adults, especially alongside resistance training and adequate total protein. Isolated supplementation cannot substitute for training, total protein, energy intake or treatment of underlying illness.

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NAD+ precursor

NMN

Early human evidence

Raises NAD-related biomarkers; broad healthspan benefits have not followed reliably.

Human clinical outcomes Preliminary

Human biomarkers Moderate

Animal lifespan Limited

Mechanistic plausibility Moderate

Safety certainty Limited

Direct longevity relevance Preliminary

Verdict: Nicotinamide mononucleotide can raise NAD-related measures in humans, which confirms biological activity. Trials have reported selected metabolic or functional effects, but results are mixed, studies are generally short, and no human evidence shows slower ageing or longer life.

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