It was actually my boyfriend who first asked me about peptides. He has a knee injury that hasn't really healed, and he'd heard there are peptides that can help with joint health. He'd also heard that heaps of people in the fitness industry are taking them for muscle mass and physique. My first thought was, mm, sounds a bit dodgy. But I wanted to look into it properly.
What are peptides, really?
As a nutritionist, I always known peptides as little chains of amino acids. When you eat protein, your body breaks it down into amino acids, then rejuggles them into the peptides and proteins it actually needs. Those go on to do a whole heap of jobs: repairing and rebuilding muscle, making hormones, building immunity, repairing hair, skin & nails, balancing blood sugar, supporting digestion, and much more.
So my first thought was, surely you can just eat protein? For most people, that's still the answer.
Peptides worth knowing about: Collagen
One type I do get is collagen peptides. Marketing says they're great for skin, hair and nails, and they might be, but the research tends to be strongest for joint health. That makes them a reasonable option for someone recovering from a joint injury or surgery.
Here's how I'd use them:
- Pair them with vitamin C. Your body needs vitamin C alongside collagen to build connective tissue for recovery.
- Choose a powder over capsules. You can easily gauge how much you're having. Around 10 to 15 grams a day is a good dose.
- Buy from a pharmacy like Chemist Warehouse, and look for products that are third-party tested.
So my advice to my boyfriend was simple: collagen peptides plus vitamin C, and look after the basics.
The black market and injectable peptides
This is where I get nervous. Many of the injectable peptides marketed for physique and recovery are bought online or off the 'black market', and people often don't know where they come from or what's actually in them.
My main concerns:
- They're not approved. Ideally, we want products approved by a medicines regulator, like Medsafe in New Zealand (or the FDA in the US), so we know they've been assessed for safety in the short and long term.
- The research is very limited. There's little evidence on how well many of them work, or what they do over time.
- You don't know what's in them. Unregulated products may contain extras that react with your body or carry risks nobody has studied.
Some peptides are tested and fine, and some aren't. It's really important to tell the difference.
And what about GLP-1s?
GLP-1s are peptides too, but they sit in a completely different category. GLP-1 stands for glucagon-like peptide-1. It's a natural gut hormone that helps regulate blood sugar and appetite.
GLP-1 medications (receptor agonists) mimic and amplify that hormone. They:
- Help your body release insulin
- Slow digestion
- Lower glucagon, to prevent excess sugar release into the blood
- Act on receptors in the brain to reduce hunger signals and food cravings
That's why they're so useful for blood sugar control in people with diabetes, and for weight management. They're prescription injectables, and you may know them by brand name:
- Semaglutide: Ozempic and Wegovy
- Tirzepatide: Mounjaro and Zepbound (this one targets both GLP-1 and GIP receptors)
- Liraglutide: Victoza and Saxenda
- Dulaglutide: Trulicity
So what should you actually do?
There are real benefits to some peptides: collagen for joints, and GLP-1 medications for diabetes and weight management. But whether any of it is right for you comes down to a few things:
- What you can financially support
- What's suitable for you
- Whether you can deal with the side effects
- Whether you're working with a nutritionist or your healthcare team
And this is the really important part: are you optimising what you can control? Simple lifestyle basics (nutrition, exercise, sleep and stress management) are the core of good health. They also protect your bank account, so you're not spending a heap of money on random peptides that may not even work, may be dangerous, or may have long-term effects.
The takeaway
Just eat enough protein. Nourish your body, because your body knows what it needs. If you're considering peptides, talk to your GP or healthcare team first, buy from reputable sources, and for the love of all us nutritionists... Don't. Forget. The. Basics.