Slimr: independent and evidence first Every diet reviewed against the research

The honest supplement guide

Supplements: the few that work, the many that are marketing

The UK supplements industry sells billions of pounds of hope a year, and most of it is regulated as food, not medicine. That means products reach the shelf without proving they do anything at all. A small handful genuinely work. A slightly larger handful are useful in specific situations. And some are not just useless but dangerous, which is where the MHRA has had to step in. Here is the whole truth, sorted pile by pile.

Pile one: genuinely evidence-backed

Creatine monohydrateThe rare supplement that deserves its reputation. Hundreds of trials and the International Society of Sports Nutrition position stand agree: 3 to 5 grams a day improves strength, power and muscle gain from resistance training, with a strong long-term safety record in healthy people. Especially useful if you train while losing weight on GLP-1 medication, because protecting muscle is the whole game. Buy plain monohydrate; the fancy versions add cost, not results.
Protein powderNot magic, just convenient food. Hitting your protein target matters enormously while dieting or on GLP-1 treatment, and a shake is an easy way to get there when your appetite is small. Whey, casein, soy and pea all work. It is food in powder form, nothing more mystical than that.
CaffeineGenuinely improves endurance and high-intensity performance, one of the most studied ergogenic aids there is. You probably already take it. A coffee before training is the same science in a nicer format.
Psyllium fibreA boring powder with real evidence: it lowers LDL cholesterol modestly, steadies blood sugar after meals, and keeps you regular, which matters on GLP-1 treatment. Also nearly free. Nobody markets it hard because there is no margin in it.
Vitamin DCovered in our vitamins guide: 10 micrograms a day through the UK winter is official NHS advice for almost everyone.

Pile two: oversold, underdelivered

Omega-3 capsulesA major Cochrane review found fish oil capsules have little or no effect on heart disease or death for most people. Eating oily fish remains a good idea; the capsules are mostly a fish-flavoured disappointment. (Prescription-strength EPA for specific high-risk patients is a different, medical product.)
CollagenYour gut digests collagen into ordinary amino acids, like any other protein. The skin and joint claims rest on small, industry-funded studies. You will get the same raw materials cheaper from food or a basic protein shake.
BCAA powdersIf your total protein intake is decent, branched-chain amino acids add nothing. They are a tax on people who already bought the protein powder.
ProbioticsStrain-specific benefits exist for a few medical situations, but the general "gut health" capsules on the shelf have weak evidence for healthy people. Fermented foods and fibre are the better-supported route.

Pile three: the nonsense, and the ones the MHRA warns about

Detox and cleanse teasYour liver and kidneys detox you continuously, for free. "Detox" products are usually laxatives and diuretics in a pretty box: you lose water, feel lighter, and learn nothing. The British Dietetic Association has said plainly that detox diets and products are a myth.
Fat burnersNo over-the-counter "fat burner" produces meaningful fat loss. Worse, this category keeps attracting criminals: the MHRA has repeatedly warned about illegal slimming products spiked with sibutramine (a prescription drug withdrawn in 2010 over heart risks) and about DNP, an industrial chemical sold for weight loss that has killed people. If a fat burner seems to work suspiciously well, that is a reason to worry, not reorder.
Raspberry ketones, garcinia, CLAThe rotating cast of Dr-famous weight-loss ingredients. Human trial results range from trivial to nonexistent. They persist because marketing is cheaper than evidence.
Testosterone boostersTribulus, "T-boosters" and friends do not meaningfully raise testosterone in healthy men. If you have genuine symptoms of low testosterone, that is a GP conversation and a blood test, not a supplement.
"GLP-1 support" supplements and patchesThe newest wave: pills and patches claiming to mimic or boost GLP-1. No supplement produces anything close to the effect of the real medicines, and the patches are physically impossible. We wrote a whole page on the patch scam.
Illustration for the Slimr guide to supplements that work and those that do not

How the rules actually work (and how companies skirt them)

In the UK, supplements are regulated as foods. They cannot legally claim to treat, prevent or cure disease, and when a company crosses that line, two regulators get involved. The Advertising Standards Authority bans misleading adverts, and it rules against supplement and diet-product claims every month. The MHRA steps in when a "supplement" contains an actual drug or makes medicinal claims, because at that point it is an illegal unlicensed medicine. The loophole is wording: "supports", "boosts" and "contributes to" are legal even when the product does nothing, which is why those words appear on every tub. When you see them, read them as "unproven". And if a supplement gives you an odd reaction, report it through the MHRA Yellow Card scheme, which accepts reports about herbal products and supplements too. More on all of this on our regulators page.

The research behind this page

We link the actual research, not press releases. These are the papers and reviews the numbers on this page come from.

Sources worth reading yourself

Where to go next

GLP-1 patches: the truth

The impossible product flooding social media, explained.

Read the exposé

Vitamins, honestly

The short list worth taking in the UK.

Vitamin guide

Make creatine worth it

It works when you do. The resistance-training guide.

Exercise guide

Share this page