What moves biomarkers — and does it matter?

Improves instrument-measured skin elasticity and hydration

This is collagen's best-supported claim: randomised placebo-controlled trials, summarised by a 2021 systematic review and meta-analysis, consistently report improvements in cutometer-measured skin elasticity and hydration after 8–12 weeks. The honest framing: these are instrument readings of skin properties, replicated but modest, not a health outcome.

Raises NAD+ levels in blood

Human trials have measured increases in blood NAD+ concentration following oral NMN. This is the best-supported claim about NMN — and it is a claim about a laboratory measurement, not about health.

Improves cardiometabolic risk factors in healthy non-obese adults

CALERIE randomised 218 healthy non-obese adults to around 25% intended calorie restriction or usual diet for two years. Achieved restriction averaged about 12%, and multiple cardiometabolic risk factors improved.

Produces substantial weight loss in adults with obesity

STEP 1 randomised 1,961 adults with obesity to weekly semaglutide or placebo alongside lifestyle support: roughly 15% average body-weight loss versus 2.4% on placebo at 68 weeks. The wider STEP programme repeated the pattern. Body weight is recorded here as a surrogate — the health value of drug-induced weight loss depends on what happens to composition, and to the weight after discontinuation.

Improves biomarkers of mitochondrial health

The first-in-human randomised study found urolithin A safe and reported a molecular signature of improved mitochondrial and cellular health in muscle tissue. This is the claim the product is actually built on — a biomarker change, upstream of any demonstrated benefit.

Intravenous NAD+ increases NAD+ availability in the body

An 11-person pilot study infused NAD+ over six hours and tracked the plasma and urine metabolome, showing the molecule is taken up and metabolised — with most of the change appearing only after two hours. That is a pharmacokinetic observation, several steps removed from any benefit.

Improves blood glucose and lipid markers in people with metabolic dysfunction

A 2025 systematic review and meta-analysis of randomised trials found berberine reduced triglycerides, fasting glucose, waist circumference and LDL cholesterol versus control, echoing the small pilot trials in type 2 diabetes that started the field. Real, modest, marker-level effects — in metabolically unwell populations, not healthy optimisers.

Lowers C-reactive protein

A meta-analysis of randomised trials using bioavailability-enhanced curcuminoid preparations found reduced circulating C-reactive protein. A marker moved is a marker moved: no outcome trial has tested whether curcumin's CRP effect translates into less disease.

Activates brown fat and increases cold-induced thermogenesis

Young men who winter-swim routinely showed different brown-fat thermoregulation and higher cold-induced heat production than matched controls. Solid physiology from a small comparative study — a measured bodily response, not a demonstrated health benefit.

Improves immune function in older adults at low doses

A 2014 trial found low-dose mTOR inhibition improved influenza vaccine response in older adults, and a 2018 follow-up reported fewer infections. But the subsequent phase 3 programme failed to confirm clinical benefit, and development was halted.

Regenerates ageing skin

The support here is mechanistic: GHK-Cu resets expression of genes involved in tissue remodelling in laboratory models, which is why it earned its place in cosmetic formulations. Controlled human trials demonstrating visible or measured skin outcomes are lacking — the claim currently lives on biology, not on people.

Lengthens telomeres

In human cell lines, recent work reports telomere lengthening via telomerase upregulation. That is a laboratory observation twice removed from a health benefit: no human trial has measured telomeres after epithalon, and telomere length itself is a contested marker of ageing.

Improves blood pressure

A meta-analysis has examined NMN's effect on blood pressure across the available randomised trials.

Matches GLP-1 drugs for weight loss

No trial supports the comparison. Berberine's measured effects on weight-adjacent markers are centimetres of waist circumference and fractions of a BMI point; semaglutide's flagship trial produced roughly 15% body-weight loss. The nickname is the entire evidence base.

Improves glucose control and insulin sensitivity in people without diabetes

A meta-analysis of eleven randomised trials found no significant effect of resveratrol on glucose or insulin measures in non-diabetic participants. A signal exists in type 2 diabetes — but the supplement is overwhelmingly sold to healthy people, for whom the pooled answer is no.