Thirty-one melatonin supplements were bought off the shelf and tested. The melatonin inside ranged from 83% less than the label said to 478% more. Two batches of the same product differed by as much as 465%. Eight of the bottles also contained serotonin, a different chemical altogether.
That's the aisle you're standing in. Ashwagandha, rhodiola, valerian: hundreds of bottles and zero guidance on what works, what's marketing, and what might clash with your medicines. One label claims "clinically proven stress relief". The next promises "ancient wisdom for modern stress". A third guarantees "fast-acting calm without drowsiness". So you grab the fanciest label or the one with the most reviews, and months of daily capsules later you feel no different.
Why most of them fail
Nobody checks before they're sold. In the United States, the regulator has no authority to approve a supplement for safety or effectiveness, or to approve its label, before it goes on sale. The maker is trusted to get it right.
The reason is a 1994 American law that treats supplements as food. It followed an industry campaign against tighter labelling rules, which told the public that supplements were about to be banned. One advert showed Mel Gibson being raided and arrested by federal agents for taking vitamin C.
When someone checks afterwards, the results look like the melatonin. Of 32 fish oils on sale in New Zealand, only 3 held as much omega-3 as the label claimed, and most had oxidised past the recommended limits, which is the chemistry of going rancid. Price and best-before date predicted nothing. When 30 immune-support supplements were bought on Amazon and analysed, 17 had labels that were wrong: 13 listed ingredients that were missing from the bottle, and 9 held substances the label never mentioned. None of the 30 carried an independent seal.
It's an old trade. Clark Stanley, the "Rattlesnake King", made his name selling Snake Oil Liniment. The US government tested it in 1916. It held mineral oil, about 1% fatty oil thought to be beef fat, chilli pepper, turpentine and camphor. No snake.
The pinch of everything. A capsule can list every fashionable ingredient and hold a fraction of the amount that was ever tested. The industry's slang for it is "pixie dusting", or angel dusting: adding a tiny amount of a popular ingredient just to print its name on the label. You're paying for expensive placebo pills. "Placebo" is Latin for "I will please", and it usually does.
Eighty adults with irritable bowel syndrome were given pills and told plainly that they were placebos, "like sugar pills", or were given nothing. After three weeks the pill group had improved more. So a friend's glowing report can be honest and still prove little.
The words "proprietary blend" hide the individual amounts behind a fancy name. When you see thirty ingredients in one capsule, you're getting pixie dust of most of them.
They're aimed at the wrong person. The more deficient you are, the more dramatic your response. That's why one person swears by a supplement and the next dismisses it as useless. The evidence agrees. When the tests of B vitamins were pooled, the benefit looked strongest in people whose nutrition or mood was poor to begin with. Every test of magnesium for anxiety recruited people who were already prone to it. And when 18,353 adults aged 50 and over took vitamin D or a dummy pill for five years, whatever their starting level, their mood scores ended up the same.
Stress does make withdrawals. Reviewers who gathered the findings on psychological stress, lost sleep and hard exercise found that all three tend to run down certain nutrients, with magnesium, zinc, calcium, iron and one of the B vitamins on the list. Think of your phone charging overnight, except that stress keeps draining the battery faster than you can recharge it. So the useful question is which nutrient you are short of. A calming capsule sold to everyone skips that question.
Who is most likely to be short
Some people have better odds than others of being the one a supplement helps. Vitamin B12 is low in about 6% of people under 60 and about 20% of those over it. Metformin, the common diabetes tablet, counts B12 deficiency among its common side effects, and long-term acid-reducing tablets can pull B12 down as well. Magnesium runs low with heavy drinking, with water tablets and with those same acid tablets.
If you're on that list, a blood test for B12 tells you more than any symptom checklist. Magnesium is harder to catch: about 1% of it is in the blood, so a normal result can hide a shortage.
Subtract before you add
The cheapest stress supplement is one coffee fewer. Ninety-six adults went five days without caffeine and were then given it through the day: their cortisol, the main stress hormone, climbed and stayed up. After five days of daily caffeine, the morning caffeine no longer moved it. The afternoon caffeine still did, into the early evening. A calming capsule on top of that is money spent undoing your own cup.
The nine with something behind them
1. Magnesium
This is the one with the most reasons behind it. Running short is common: almost half of Americans (48%) got less magnesium from food than they require. Reviewers call stress and magnesium a vicious circle: stress may increase the loss of magnesium, and a shortage may make the body react more strongly to stress. Eighteen tests have looked at magnesium for anxiety. About half found a benefit, all of them in people who were already vulnerable: mildly anxious, premenstrual, or with high blood pressure. The reviewers rated the quality of those tests as poor.
Magnesium has a long history as a remedy. In 1618 a farmer at Epsom in England found his cows refusing to drink from a bitter well. The salt left when the water was boiled away became famous as Epsom salts. It is magnesium sulfate.
The bath is the weak part of that story. Reviewers who went through the evidence called the claims for magnesium through the skin, from flakes, sprays and salt baths, "scientifically unsupported". Enjoy the bath, and take the magnesium by mouth.
In a larger test, 264 stressed adults with low magnesium saw their stress scores fall by more than 40% in eight weeks. Nobody got a dummy pill, so expectation takes some of the credit.
Form matters. Magnesium oxide, the cheap one, was absorbed at about 4%. Other forms did far better, and magnesium glycinate has a name for being easy on the stomach. carries NSF's contents certification, which means an outside lab checked the bottle against the label.
Too much of any form gives you diarrhoea. Kidney disease makes it a different matter: failing kidneys struggle to clear magnesium, and a build-up in the blood is dangerous. Have it checked before you take any.
Verdict. The first to try if you're stressed and your diet is short on it.
2. B vitamins
The word "vitamin" was coined in 1912 from "vital amine", by a biochemist who believed they were all amines. Not all of them are, and the name stuck with its last letter dropped.
Sixteen tests with 2,015 people found a small benefit for stress, none for anxiety, and no clear one for low mood. The gain looked largest in people who were running low or already struggling. A high-pressure week can leave you feeling like your brain is wrapped in cotton, and a plain B-complex with breakfast is a cheap thing to rule out.
Would a multivitamin do? Across eight tests of at least four weeks in healthy adults, a multivitamin and mineral lowered perceived stress, anxiety and fatigue against a dummy pill, and did nothing clear for low mood. The products rich in B vitamins looked best.
One caution belongs here. Large amounts of vitamin B6 taken for months can cause a loss of feeling in the arms and legs, and B6 turns up in magnesium blends and "stress formulas" as well as in B-complex. Add up what's in everything you take.
There is a second one. Biotin, a B vitamin found in B-complex products, can distort thyroid blood tests. Mention it before any blood test.
Verdict. Worth a month if your diet has been thin. Megadoses buy nothing.
3. L-theanine
An amino acid from tea leaves. In nine tests it eased stress and anxiety in people put under pressure. In one of them, 30 adults who took it for four weeks scored lower for anxiety and low mood and slept better.
It seems to work fast, too. Twelve people took it before a mental-arithmetic stress task, and their heart rate rose less than on a dummy. Its selling point is calm without drowsiness. has the same NSF certification.
Verdict. The one to try for a keyed-up mind that still has to work.
4. Omega-3
Across 19 tests and 2,240 people, omega-3 lowered anxiety, and it did more for people with a diagnosed condition. One test followed 68 medical students through their exams: those on omega-3 had 20% fewer anxiety symptoms and lower markers of inflammation.
The capsules are where it goes wrong, as the New Zealand fish oils showed. If your fish oil smells sharp or rancid, it has oxidised. Bin it. A tin of has no such problem.
Verdict. Eat oily fish twice a week first. If you buy capsules, buy tested ones.
5. Vitamin C
Your adrenal glands, the pair that make your stress hormones, hold a store of it, and they let it go under stress. When 26 people were given the hormone that sets off the stress response, their adrenal glands released vitamin C within minutes, ahead of the cortisol.
Does taking more help? In one test, 120 young adults took vitamin C or a dummy pill for two weeks and were then made to speak in public and do mental arithmetic in front of an audience. The vitamin C group's blood pressure rose less, they felt less stressed, and their cortisol settled faster. The amount used was large, well above the level at which stomach pain and diarrhoea begin. The fashion for huge amounts owes much to one chemist, Linus Pauling, who took vitamin C daily against colds and published Vitamin C and the Common Cold in 1970.
Verdict. One promising result. Food covers ordinary needs.
6. Vitamin D
Vitamin D behaves more like a hormone than a vitamin, and low levels go with low mood. Topping up people whose levels are normal does nothing, as the 18,353 showed. Your skin makes it from sunlight, which in northern countries works from spring to early autumn, and you need no sunburn for it: short spells with shade and a hat to hand are enough. Oily fish, red meat, egg yolks and liver supply some as well. People who are rarely outdoors, who cover most of their skin, or who have dark skin may not make enough. Too much from a bottle, over a long time, builds up calcium and can damage the kidneys and heart.
If you do take it, take it with food. When 50 older adults took vitamin D with breakfast, 32% more reached the blood with a meal containing fat than with a fat-free one. A keto or carnivore plate has that covered.
Verdict. Worth it in a dark winter, if you're in one of those groups, or if a test shows you're low. Otherwise skip it.
7. Glycine
A small amino acid with a sweet taste: its name comes from the Greek glykys, "sweet". People who slept badly took it before bed and fell asleep faster, rated their sleep better and felt less sleepy the next day. It was a small test.
Verdict. Thin evidence, low stakes. One for sleep that stress has broken.
8. Melatonin
Pooled from 19 tests and 1,683 people, melatonin got people to sleep 7 minutes sooner and kept them asleep 8 minutes longer. It works as a signal to your body clock more than as a sedative, so it suits jet lag and shift work better than a racing mind. Start with the lowest amount that works, and remember what the labels are worth.
Verdict. For a shifted clock. It does little for stress.
9. Phosphatidylserine
A fat found in cell membranes. Eighty adults took one of three amounts or a dummy pill for three weeks and then faced the same public-speaking ordeal. The lowest amount blunted both cortisol and distress. The two larger amounts did nothing. A result that vanishes as the amount goes up deserves suspicion.
Verdict. Interesting and unproven. Last on the list.
Three to leave on the shelf
GABA. It's the brain's own calming chemical, and there is doubt about how much of a swallowed capsule reaches the brain. Reviewers who went through 14 tests found "limited evidence for stress and very limited evidence for sleep".
Taurine. Sound human tests of it are missing altogether. It occurs naturally in meat and fish.
Tryptophan and 5-HTP. Sold as serotonin in a capsule. Of 108 tests for low mood, two were sound enough to count, with 64 people between them, and both can clash with antidepressants.
More you'll be offered
Ashwagandha. It's the bottle you picked up first, so here is the short version. Across 12 tests and 1,002 people, it lowered stress and anxiety more than a dummy pill, though the reviewers rated the certainty as low. It has also been linked to rare cases of liver injury.
Rhodiola. Of five tests for mental fatigue, three found a benefit, and every one had flaws that make the result hard to trust.
Valerian. For anxiety there is a single small comparison, and valerian did no better in it than a dummy pill.
Herbs are a subject of their own, and they need more care than vitamins.
Probiotics. Sold on the same shelf with the same promise. Across seven tests and 1,146 healthy volunteers, probiotics lowered how stressed people said they felt, and left their cortisol where it was. A modest result, from tests that used different strains.
The plate that covers most of the list
Look at where this list comes from. Vitamin B12 comes from meat, fish and eggs. Omega-3 and vitamin D come from oily fish. Glycine makes up about a third of collagen, so it's in skin, slow-cooked cuts and broth. Even taurine, from the shelf of three, comes from meat and fish, and a vegan diet supplies little or none. A plate built on meat, fish and eggs delivers most of this list before you open a bottle.
Keto and carnivore eaters report the calm, too. In two surveys, of 147 and 276 adults, those eating a ketogenic diet reported feeling calmer and more content, with less stress, anxiety and low mood, than people on no particular diet. Among 2,029 adults who had eaten carnivore for six months or more, 95% reported better overall health and most reported better well-being.
Two things keep that honest. Surveys of volunteers show a link and no more, and reviewers who went looking for strict tests of low-carb eating for anxiety found none of high quality, only encouraging early reports. And the diet has a gap on this list, vitamin C, and a rough patch at the start: the headache, fatigue and dizziness of "keto flu", which peak in the first week and fade within a month.
How to buy one that works
Look for a seal from USP, NSF or ConsumerLab. These are independent bodies that test what's in the bottle. The mark to look for is "USP Verified": the letters "USP" alone mean only that the maker claims to follow the standard. The same goes for "third-party tested", "verified" or "certified" printed by the maker with no seal beside it: the words alone guarantee nothing.
Buy single ingredients over "stress formulas". Take one supplement at a time, because ten at once create interactions and side effects that are impossible to trace. Store brands from big retailers often hold the same ingredients as the famous names for less. Buy three months' worth once you know something suits you, and never a year of something you've never tried.
The red flags are "proprietary blend", "clinical strength" with no source given, an ingredient list as long as your arm, and artificial colours in a product sold for your health.
Keep them cool and dry, away from the bathroom, the kitchen and the car. Ever notice that plastic taste after leaving a water bottle in your car? That same heat is cooking your supplements. Vitamin C that has turned brown has degraded.
What they can clash with
Never assume natural means safe. In the United States, an estimated 23,000 visits to emergency departments a year are put down to supplements, and about 2,150 of them end in a hospital stay.
The worst of the trade sits on other shelves. Between 2007 and 2016 the regulator found 776 supplements containing hidden drugs that were on no label, and nearly all were sold for sex, weight loss or muscle.
Supplements can interact with medicines, and some raise the risk of bleeding around surgery. St John's wort is the best-known offender: it clashes with antidepressants, the blood thinner warfarin and more. If you take any medicine, check each supplement against it before you buy. Zinc, a regular in "stress formulas", has its own catch: high amounts cut the copper your body can absorb, which can lead to anaemia and weaker bones. Many supplements have never been tested in pregnant or breastfeeding women or in children, so the absence of a warning on the label means little.
When life is the stressor
During a job loss, a break-up, an illness or grief, the instinct is to add bottles. Those times call for adult coping: people, sleep, movement, and help when you need it. Supplements support. They never replace. No capsule fixes poor sleep, dehydration or a diet of processed food.
When it's something else
Feeling anxious a lot of the time for six months or more is a recognised condition with treatments of its own, and no supplement on this page is one of them. An overactive thyroid can pass for stress too: nervousness, irritability, poor sleep, feeling the heat. If either sounds like you, get it checked.
Start with one
The industry wants you buying everything. Your body needs what it's short of, and nothing else.
If you are stressed and eating poorly, magnesium comes first, then a plain B-complex. If you are keyed up before something you have to perform at, L-theanine. If your sleep has been knocked off its clock, melatonin. After a dark winter, test your vitamin D.
Pick the one that matches your biggest symptom, from a brand that has been tested, and give it a month. Judge it by your sleep, your energy and how you react to a bad day. Then run the stop test: leave it off for two weeks. If nothing changes, you've found a saving.
Fewer than three in ten of those melatonin bottles came within a tenth of what the label promised. The label is a promise nobody checked. Check one.
Standing in the herb aisle next? Herbs for Stress and Anxiety: What Works and What to Skip — which calming herbs have a result behind them, and which carry a risk.
Wondering which nutrient you're short of? Nutrient Deficiencies: Who's at Risk and Which Test to Get — who runs low on what, and the test that shows it.
Know someone with a cupboard of half-finished bottles? Send them this before they order the next one.
Disclaimer: This article is general information. For advice about your own health, talk to a qualified health professional. If your mood has been low for weeks or you're having thoughts of harming yourself, reach out for help today.
Affiliate Disclosure: This article contains affiliate links. As an Amazon Associate, All For Life earns from qualifying purchases, at no extra cost to you. We only link to products we would recommend without the commission.
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