Peptides are short chains of amino acids, the same building blocks that make up proteins. Your body makes many of them, and you eat them in foods like milk, eggs, soy and fish. In Australia, some peptide products are prescription-only medicines.
A peptide is a short chain of amino acids held together by chemical links called peptide bonds. The US National Human Genome Research Institute defines a peptide as a chain of typically 2 to 50 amino acids. Longer chains are called polypeptides, and proteins are built from one or more polypeptides (NHGRI genetics glossary entry on peptides [1]).
Picture amino acids as beads. A few beads on a string make a peptide. Long strings, folded into shape, make a protein.
Your body uses 20 different amino acids. It can make some of them itself. The rest, called essential amino acids, have to come from the food you eat (Healthdirect guide to protein [2]).
Peptides in your body mostly work as messengers and helpers. Some carry signals between cells and organs, and others help tissues such as muscle work normally.
The TGA notes that many peptides occur naturally in the body and take part in signalling for growth, metabolism and tissue repair (TGA overview of peptide products [3]). A large group of hormones are peptides. A university physiology textbook groups hormones into three chemical classes, and peptide hormones are one of them (OpenStax Biology chapter on types of hormones [4]).
Here are some everyday jobs that peptides do:
These are natural processes. They don't mean a peptide product will change how your body works.
Peptides fall into four groups by where they come from. Your body makes some, food and cosmetics contain others, and a few are approved medicines. Australian law regulates each group differently.
Any food with protein either contains peptides or releases them when you digest it. Researchers call peptides with measurable biological activity "bioactive peptides". Milk proteins are the most studied source, and meat, fish and egg proteins are also sources (review of bioactive peptides of animal origin [8]). Soy is a well-studied plant source, and soy protein can be broken down into soy peptides (review of soybean-derived peptides [9]).
Collagen peptides are made by heating collagen into gelatin and then breaking it down with enzymes. The raw material comes from sources such as cattle hides and fish skin (review of hydrolysed collagen sources and uses [10]).
All food sold in Australia must comply with the Australia New Zealand Food Standards Code, which FSANZ develops (FSANZ guide to the Food Standards Code [11]). A lab finding about a food peptide doesn't mean a food or powder will have that effect in your body.
Peptides are common skincare ingredients. A dermatology review groups cosmetic peptides by how they are designed to act, with categories such as signal peptides and carrier peptides. The same review notes that clinical evidence for them is often weak and that absorption through the skin may be poor (dermatology review of topical peptides [12]).
No. Peptides and steroids are different kinds of molecules. A peptide is a chain of amino acids, while a steroid is built from cholesterol and keeps cholesterol's ring-shaped core.
A physiology textbook explains that most lipid-derived hormones come from cholesterol and can pass through cell membranes. Peptide hormones are chains of amino acids and can't pass through cell membranes, so they act on receptors on the outside of cells (OpenStax Biology chapter on types of hormones [4]).
| Feature | Peptide | Steroid |
|---|---|---|
| Building blocks | Amino acids linked in a chain | Cholesterol, with a ring-shaped core |
| Dissolves in | Mostly water | Fat |
| How it reaches the cell | Acts on receptors on the cell surface | Passes through the cell membrane |
| Natural examples | Carnosine, beta-endorphin | Hormones the body makes from cholesterol |
| Found in food | Yes, in protein-rich foods | Not as a dietary source |
How a peptide product is regulated depends on what it contains, how it's promoted and what it's meant to do. Food peptides fall under food law, cosmetic peptides fall under cosmetic and chemical rules, and peptide products with a therapeutic purpose are regulated by the Therapeutic Goods Administration (TGA).
These rules decide how a peptide product is treated in Australia.
"Research peptides" are not a regulated pathway. The TGA says labels like "research use only" or "not for human use" don't change how a peptide product is regulated, and unlawfully imported products may be seized (TGA explanation of how it regulates therapeutic peptide products [17]). The TGA also warns that many peptide products promoted online are unapproved and haven't been assessed for safety, quality or effectiveness (TGA overview of peptide products [3]).
For more, read are peptides legal in Australia and prescription vs grey-market peptides.
Not quite. Peptides and proteins are both made of amino acids, but peptides are shorter. The US National Human Genome Research Institute describes a peptide as typically 2 to 50 amino acids, while proteins are built from one or more longer chains called polypeptides.
Protein-rich foods such as milk, eggs, meat, fish and soy contain peptides or release them during digestion. Milk proteins are the most studied source.
No. Skincare peptides are cosmetic ingredients, and Australia regulates them differently from medicines. Prescription-only peptide medicines are regulated by the TGA and need a doctor's prescription.
Food and cosmetic products containing peptides are sold in ordinary shops. Prescription-only peptide medicines need a doctor's prescription and are dispensed by a pharmacy. The TGA says a "research use only" label doesn't change how a product is regulated.
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