What are peptides? A guide to how they work and what they do

Whether you're looking up weight loss tips, healthy hair advice, skin care products or workout enhancements, peptides might feel like the word on everybody's lips.

This diverse biomolecule has hit the healthcare zeitgeist, and with it stirred up news feeds and social media feeds alike, but what are peptides? What function do they perform in your body, and are they really the miracle supplement everyone’s claiming they are?

Here, we’ll crack the case on peptides, their different types and different uses, and equip you with the information you need to work out if they might be right for you.

What are peptides?

Peptides are short chains of between 2 and 50 amino acids linked by chemical bonds known as a peptide bond. If the peptide is made up of more than 51 amino acids, it becomes a polypeptide, which can then be put together to form various types of proteins for your body to use in a whole range of different functions [1].

Peptides vs proteins: what's the difference?

Despite often being talked about in quite different ways, peptides and proteins are fundamentally the same thing. Both are central components and building blocks of all living cells, and both are made up of strings of amino acids, but where peptides are generally shorter, proteins are longer and largely regarded as more complex as a result.

Interestingly, though, the terms are sometimes used interchangeably. For instance, many scientists will call the 51 amino acids that make up insulin both a peptide and a protein, so don’t be concerned if you see different sources refer to it one way or the other [2].

How do peptides work in the body?

Peptides and proteins perform really diverse roles depending on their make-up, with some acting as structural components of the body, enzymes, hormones, transporters or even as antibodies. As a result, how they operate in the body really depends on what type they are and what their biological function is [2].

The main types of peptides

While it can sometimes feel like there are infinite numbers of different peptides from an infinite number of sources (food-derived bioactive peptides are different from your plant-derived bioactive peptides after all!), certain peptides are more common than others. These main peptides are generally your big movers too, performing vital functions for human health.

Hormonal peptides (including GLP-1s)

Produced by the endocrine glands, hormonal peptides are a type of hormone that plays a crucial role in regulating a whole range of physiological processes that your body goes through, including the function of your gastrointestinal and cardiovascular systems, your energy metabolism, as well as your growth, stress management and reproductive processes. It does this by interacting with receptors on target cells and initiating intracellular signalling pathways. They also can serve as tumour markers and are used in the diagnosis and monitoring of tumours, making them vital parts of your body [3].

Signal peptides

Made of between just 16 and 30 amino acids, signal peptides are some of the shortest peptide bonds your body makes, and are crucial in protein synthesis, transportation, and, as the name suggests, signalling molecules. They really help your body to communicate with itself and get things where they need to go [4].

Carrier peptides

Another form of transporter peptide, carrier peptides are best known for moving certain elements like copper and manganese to where your body might use them, particularly your skin, making them major players when it comes to skin health. In particular, it uses these essential minerals in wound healing, cell regeneration and collagen production [5].

Antimicrobial peptides

Put simply, antimicrobial peptides are basically your body’s self-defence squad and security team. Made of between 5 and 100 amino acids, they’re fast-acting, responsive and have antibacterial, antifungal, antiparasitic and antiviral properties, making them key parts of your immune system [6].

Neuropeptides

Vital chemical messengers, neuropeptides, run the gamut as the regulators of many physiological functions, including reproduction, cardiovascular function, water balance, energy homeostasis, circadian rhythm, pain management, learning and memory, and have been linked to many complex social behaviours [7].

What are peptides used for?

With so much diversity across both form and function, peptides have been increasingly utilised in therapeutic treatments that range from insulin for diabetes to tissue repair, weight loss and skincare. Understanding how these synthetic peptides can be used, though, is important to understanding the potential benefits that taking peptide supplements can have on the human body.

Weight loss and metabolic health

When it comes to metabolic health and weight loss, the benefits of synthetic peptides like glucagon-like peptide-1 (also known as GLP-1 medication) are increasingly well-documented. These peptides not only help to manage type 2 diabetes, but also promote weight loss and support your broader metabolism by mimicking the gut hormone that regulates insulin and suppresses appetite [8]. There are some natural supplements that suggest they can mimic this therapeutic peptide medication, which we'll unpack a little later.

Skincare and anti-ageing

Some cosmetic peptides are powerful tools when it comes to modern skincare, with signal peptides able to be used to stimulate cells to increase collagen production and improve skin elasticity, neuropeptides relaxing facial muscles and minimising expression wrinkles, carrier peptides delivering essential trace elements like copper to support skin repair, and enzyme inhibitor peptides reducing collagen breakdown and preserving the integrity of the skin [5].

Some of these peptides have also been found to help you fight bacteria, heal wounds and build up a stronger skin barrier, which can be very valuable in the treatment of psoriasis, eczema, acne and rosacea.

Muscle growth and recovery

Other peptides, particularly growth hormone-releasing peptides, have also been found to influence the growth hormone axis, which, when paired with regular exercise, may help to promote muscle growth and help you shed body fat. As with synthetic peptides used in skincare, the fact that many types of peptides play a significant role in tissue repair and recovery extends to your muscles after exercise, with compounds like copper peptides helping to increase not just the production of collagen, but elastin too, potentially supporting muscle repair and helping you bounce back faster after workouts [8].

Hair growth

From biotin to keratin to copper, peptides have been linked to hair growth for many years now through improving blood flow to the scalp, stimulating collagen production, and promoting angiogenesis, the process by which your body forms new blood vessels. All of this can help to encourage hair growth, although it’s important to know that there are limitations around this, particularly depending on hair and skin type [9].

Wound healing

The impact of animal-derived peptides on wound healing is well-documented, with many not only helping you to heal faster, but also preventing scar formation and helping with infection control at the wound site itself. These are generally antimicrobial and also help with inflammation, the reduction of oxidative stress and the stimulation of cell proliferation, which are crucial to the skin repair process [10].

Are peptide supplements worth it?

Synthetic peptides make up a really wide range of treatments, with some medically supported, like insulin and GLP-1, and others falling more into the categories of cosmetic treatments like collagen peptides or dietary supplements like dileucine peptide.

When we talk about peptides in the latter context as a dietary supplement, we’re really talking about the peptides you might pick up at your chemist or health food store that are sold to help with your athletic performance, weight loss, muscle building and workout recovery. These are usually available as a pill or as a shake powder, and are generally pretty under-researched and unfortunately under-regulated. In other words, there’s not a lot of evidence out there right now to say that these particular forms of peptide supplements are going to help you to achieve your weight loss goals.

Peptide injections and prescription peptide treatments in the UK

That said, when it comes to other forms of peptide treatments, those prescribed by a doctor or a medical professional are heavily researched, regulated, and their results well-documented.

These peptide injection treatments, such as GLP-1, do offer direct and tangible results when it comes to both type 2 diabetes management and weight loss, but should only be taken as prescribed by your doctor.

Potential side effects and safety considerations

For most healthy people, peptides are safe to take for therapeutic purposes as a medication, a topical cosmetic treatment, and as a dietary supplement; however, your mileage may vary, particularly as in the UK, these different contexts mean different regulations and different levels of oversight. As a result, it’s always worth talking to your doctor about taking peptides in any form before you start taking them.

Some people, though, may find they react badly to peptides or experience side effects that others don’t. Some of these include:

• Allergic reactions such as swelling, difficulty breathing, rashes or hives.
• Skin sensitivity, particularly in the case of topical peptides.
• Stomach problems such as nausea, vomiting and diarrhea
• Headaches, dizziness and fatigue.
• Heart problems such as heart palpitations, a rapid heart rate or high blood pressure.

If you experience any of these symptoms, you should speak to a medical professional immediately.

Are peptides regulated in the UK?

Ultimately, this is a bit of a tricky question to answer, because while the answer is a yes, it’s a yes with a pretty big asterisk.

Peptides officially approved for medical use like insulin or GLP-1 medications are highly regulated by the UK’s Medicines and Healthcare products Regulatory Agency (MHRA), making them very safe, but skincare peptides and dietary peptide supplements such as collagen peptide supplements, while regulated by the UK Cosmetics Regulation and the Food Supplements (England) Regulation 2003 respectively, can also exist in a bit of a legal grey area.

When it comes to food supplements in particular, which is the category many peptide supplements fall under, they don’t require pre-market proof of either efficacy or safety. As a result, they’re not necessarily going to deliver the results you’re looking for or any beneficial effect, so it might be worth speaking to a dietitian or a dermatologist before you buy peptides for weight loss or skincare.

When to speak to a healthcare professional about peptides

If you’re looking to take peptides for any reason, you should speak to your healthcare professional.

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