What are peptides and how do they work in the body?
Peptides are small protein fragments with a wide range of functions in the body, from hormones to defence substances. As a supplement, collagen peptides have the strongest evidence base, particularly for joint pain in active people, but do not expect miracles: the effects are modest and not everyone benefits.
Peptides are short chains of amino acids, the same building blocks that make up proteins. The difference lies in length: peptides are shorter than proteins, which makes it easier for them to pass through cell membranes or bind to receptors on the cell surface. Thousands of naturally occurring peptides have been identified in the tissues and body fluids of humans, animals, plants and bacteria. The majority have been poorly studied, but some perform well-known biological functions: as hormones, as signalling molecules or as defence substances.
A good example of how peptides work is peptide hormones. The body produces them from a larger precursor molecule, which is cleaved into pieces by enzymes. Those pieces are the active peptides. Such a peptide hormone then binds to a receptor on the cell surface via two contact points, triggering a signalling cascade that directs the cell. These receptors play a role in conditions such as type 2 diabetes, obesity and cardiovascular disease.
Another large group is the antimicrobial peptides, more than forty of which are active in the oral cavity. Because they carry a positive charge, they are attracted to the negatively charged outer surface of bacteria. They can attack bacteria via the cell wall, the cell membrane or from within, and a single peptide can deploy multiple mechanisms simultaneously. This makes it harder for bacteria to develop resistance than with classical antibiotics, although resistance cannot be ruled out entirely.
Peptides are also taken as supplements, with collagen peptides having the strongest evidence base. A small study involving eight healthy men showed that 15 g of gelatine (a source of collagen peptides) taken with vitamin C one hour before exercise doubled the blood marker for collagen synthesis. A review of fifteen randomised studies concludes that collagen peptides most reliably reduce joint pain and improve joint function. Effects on muscle strength are more modest and less consistent than those of high-quality protein sources such as whey. In a larger study of active middle-aged adults, 10 g per day helped with joint pain after six months, but only in people who exercise more than three hours per week. A higher dose of 20 g per day improved the physical health score exclusively in women.
This answer draws on several review studies on the biology of peptides, supplemented by two randomised studies and a systematic review on collagen peptides as a supplement. The biological mechanisms (hormones, receptor function, antimicrobial activity) are well described in the literature. The studies on collagen supplements are more limited: small groups, few women, hardly any elite athletes, and the review authors point to small sample sizes as a recurring problem.
How do you use peptides for the best results?
For most peptide supplements that you simply swallow, absorption into the bloodstream is so low that little benefit can be expected. If you want to use peptides for a medical purpose, discuss with your doctor whether injection or a specialised formulation (such as oral semaglutide) is the right option.
What do peptides like BPC-157 do, and are they safe?
BPC-157 shows promising results in animal research for tissue healing, but has barely been studied in humans and its long-term safety is entirely unknown. Do not use it for the time being without medical supervision.
Does quercetin work against ageing and inflammation?
Quercetin shows promising signals in the laboratory and in animals, but in humans there is not yet solid evidence. Taking supplements on the basis of this early-stage research gets too far ahead of the science.
Is rapamycin found in food, or can you get it naturally through your diet?
Rapamycin is not found in food and cannot be obtained through your diet. It is a medicine used only under medical supervision, due to the real risk of immune suppression.
What do we know about rapamycin as an anti-ageing agent in humans?
Rapamycin shows early positive signals in humans for immune function and skin, but long-term safety is unknown and side effects such as infections and unfavourable blood lipids are a real risk. Use outside a clinical trial is premature.
Does spermidine actually do anything against ageing?
Spermidine has a solid biological mechanism and promising signals from animal research, but evidence that supplementation actually works in humans is still lacking; getting more spermidine through your diet (legumes, wholegrain cereals) is a safe and nutritionally sound choice.