# Questions, Answered at the Price the Evidence Supports

> Questions, answered at the price the evidence supports — Common questions on Research Peptide Fundamentals — semaglutide, NAD+ and GHK-Cu — answered from the cited literature, with each answer marked by how strong the underlying evidence actually is.

**FREQUENTLY ASKED**

Short answers drawn from the cited literature. Where the evidence is thin, the answer says so rather than filling the gap with confidence.

## What is semaglutide?

Semaglutide (Ozempic, Wegovy, Rybelsus) is a laboratory-modified copy of glucagon-like peptide-1, a hormone the gut releases after eating. It is a 31-amino-acid acylated analogue sharing roughly 94% of its sequence with the natural hormone. Two backbone substitutions and a fatty di-acid side chain that binds albumin let it survive about a week in circulation instead of the natural hormone's couple of minutes, which is why it is administered once weekly. It is an approved prescription medicine, available as a subcutaneous injection and as an oral tablet.

## What is semaglutide used for?

It is approved for type 2 diabetes, for chronic weight management, for reducing major adverse cardiovascular events in adults with established cardiovascular disease and overweight or obesity, and, since 2025, for metabolic dysfunction-associated steatohepatitis. Those indications were granted on the strength of large randomised trials — the cardiovascular indication rests on a study of 17,604 adults reporting a hazard ratio of 0.80 for the primary cardiovascular composite against placebo [3]. This site describes what those trials found; it does not recommend the compound to anyone or advise on its use.

## How does semaglutide work?

It activates the GLP-1 receptor across several tissues. In the pancreas it amplifies insulin release when blood glucose is high and suppresses inappropriate glucagon release. In the stomach it slows emptying, which blunts post-meal glucose spikes and also produces most of the digestive side effects associated with it. GLP-1 receptors in cardiovascular and kidney tissue are the working explanation for the protective effects observed in the outcome trials, including the reduction in major kidney-disease events reported in 3,533 people with type 2 diabetes and chronic kidney disease [2].

## How does semaglutide work for weight loss?

The weight effect is mostly a brain effect rather than a digestive one. Semaglutide reaches appetite circuits in the hypothalamic arcuate nucleus and the brainstem area postrema, activating appetite-suppressing POMC and CART neurons and inhibiting appetite-driving NPY and AgRP neurons. Food intake falls and food preferences shift, without a reduction in energy expenditure. In a randomised trial in adults with overweight or obesity and without diabetes, mean body weight changed by -14.9% at week 68 against -2.4% on placebo [4]. Weight regain after stopping is documented, which frames it as an ongoing rather than curative intervention.

## What is NAD supplement used for?

NAD+ supplements — usually the precursors nicotinamide riboside or nicotinamide mononucleotide rather than NAD+ itself — are marketed for age-related decline, energy metabolism and general healthspan. What the controlled human evidence actually establishes is narrower: the precursors raise blood NAD+ dependably and dose-dependently [7][10]. A 2025 review of the human evidence concluded that trials have shown limited efficacy and that tissue-level data remain sparse [6]. The honest summary is that a measurable biological change has been demonstrated and a health benefit has not.

## What is the downside of taking NAD+?

Several, and they are mostly not about toxicity. Oral NAD+ itself is poorly absorbed intact, so plain NAD+ capsules may deliver little. Supplement-grade products vary widely in purity and actual content, and third-party testing is not guaranteed. Compounded injectable NAD+ has been subject to an FDA Class I recall for elevated bacterial endotoxin. Intravenous infusion can cause chest or abdominal discomfort, flushing and nausea if run too fast. A theoretical concern exists that raising NAD+ could support the metabolism of an existing cancer, so caution is advised in cancer populations. And the largest downside is an evidential one: the clinical benefit remains unproven in humans [6].

## Is it safe to take NAD daily?

That is a question for a clinician about a specific person, and nothing here answers it. What the trials reported is this: nicotinamide riboside at 100 to 1000 mg per day for eight weeks in healthy overweight adults showed no significant difference in adverse events from placebo at any dose, no flushing, and no disruption of LDL cholesterol or one-carbon metabolism [10]; and oral NMN at 300 to 900 mg per day for 60 days reported no safety issues at any dose [7]. Those are short trials in specific populations, and short-term tolerability in a trial is not the same claim as long-term safety for an individual.

## Does NAD cause weight gain?

The published literature cited here does not report weight gain as an effect of NAD+ precursors. The nearest direct evidence is a ten-week trial of oral NMN at 250 mg per day in prediabetic postmenopausal women, which improved muscle insulin sensitivity but found no change in body composition and no change in HbA1c [8]. That is a single small study measuring something else, so the accurate answer is that body weight has not been a reported outcome in this literature rather than that an effect has been ruled out — an absence of evidence, not evidence of absence.

## What does a GHK-Cu peptide do?

In laboratory and cell work it does a great deal. It stimulates dermal fibroblasts to synthesise collagen, elastin, glycosaminoglycans and decorin, rebalances matrix metalloproteinases against their inhibitors, and carries copper to enzymes including lysyl oxidase, which cross-links collagen and elastin. In humans, the demonstrated effects are narrower and mostly topical and cosmetic: a canonical review reports increased collagen production in 70% of treated women, against 50% for vitamin C and 40% for retinoic acid [16]. Systemic and injectable use has no validated human data at all.

## What is GHK-Cu and how does it work?

GHK-Cu is a three-amino-acid peptide — glycine, histidine, lysine — holding a single copper(II) ion, appearing in cosmetic ingredient lists as Copper Tripeptide-1. The sequence occurs naturally within human type I collagen. It works as both a copper chaperone and a signalling molecule, active at picomolar-to-nanomolar concentrations. Gene-expression analysis reports it shifts expression of approximately 31.2% of human genes at a 50%-or-greater change threshold, 59% up and 41% down [14]. Its practical limit is delivery: free GHK is strongly hydrophilic, with a clogP of -2.24, which makes crossing intact skin difficult [13].

## Is GHK-Cu peptide really anti-aging?

It depends entirely on which claim is being priced. For topical cosmetic effects the evidence is modest but real, including consistently reported collagen-synthesis comparisons and small placebo-controlled dermatology trials [16]. For systemic anti-ageing — longer life, slower biological ageing, whole-body repair — nothing has been demonstrated in humans. There is no validated human pharmacokinetic data for any systemic route, the gene-expression work derives largely from database analyses needing protein-level in vivo validation, and the widely repeated figure of roughly 4,000 genes is an extrapolation from a table reporting on the order of 2,100 [14].

## What is the difference between GHK and GHK-Cu?

GHK is the bare tripeptide. GHK-Cu is the same tripeptide chelated to a copper(II) ion, bound through three coordination points and leaving the lysine side chain free. The difference is functional, not cosmetic: most of the documented tissue-remodelling activity depends on the copper being properly bound, and plain GHK without copper does not reproduce key effects such as MMP-2 stimulation in cell studies. Intact GHK-Cu also holds copper very tightly, which keeps it from acting as a pro-oxidant. Because the two are frequently conflated in the literature, any study that does not specify which form it used has said less than it appears to.

## Why does this site talk about the price of evidence?

Because in peptide research the supply of confident claims is effectively unlimited and the supply of good evidence is not. A claim costs nothing to make and can be repeated indefinitely. A randomised, placebo-controlled, adequately powered trial measuring a clinical outcome costs an enormous amount, which is why so few exist. Treating both as though they carry equal weight is how a reader ends up believing something for which nobody ever paid. The name of this site is a joke in that direction: the cheap thing here is the claim, and the expensive thing is the proof.

## Does a bigger study always mean a better answer?

Not always, but size is not a technicality either. A larger sample narrows the range of plausible effect sizes, and it corrects a specific distortion: in small studies an effect must be larger to reach statistical significance, so the small studies that get published tend to overstate. Design matters at least as much. A randomised placebo comparator is the most expensive component of a trial and does the most work, and the choice of endpoint decides what the whole exercise is worth — a marker that moves is a different purchase from an event that does not happen [3][10].

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An independent literature digest that prices findings rather than products: the only currency weighed on this desk is evidence, nothing here is sold, and no dose is recommended to anyone.