Supplements for stress: what actually has evidence?

Can supplements for stress really work?

Yes – a handful have reasonable evidence, but most of the ones being marketed do not. Stress is not just a feeling but a physiological reaction: cortisol rises, sleep is disrupted and the body burns through more nutrients.

That explains why two approaches can help. On one hand, adaptogens like ashwagandha, where studies have shown an effect on perceived stress. On the other, nutrients like magnesium and B vitamins, where deficiency worsens tiredness and where an adequate intake supports the normal functioning of the nervous system.

Here we go through what the research actually shows – substance by substance.

Ashwagandha – the adaptogen with the most research

Ashwagandha is the herb that appears most often in stress research, and with some justification. In a randomised study from 2012, 64 people with chronic stress took 600 mg of KSM-66 extract per day for 60 days. The ashwagandha group lowered their score on a stress scale by 44 percent, compared with 5.5 percent for placebo. Blood cortisol dropped by 28 percent.

In a 2019 study, researchers saw similar results with 240 mg per day: lower perceived stress and lower morning cortisol than placebo after 60 days.

The doses in the studies range from 240–600 mg of extract per day, and the effect is usually evaluated after one to two months. We've written more about how the herb affects cortisol in our article on ashwagandha and stress, and in our comparison of ashwagandha supplements you can see what sets different extracts apart.

Magnesium – the mineral your nervous system needs

Magnesium contributes to normal functioning of the nervous system, normal psychological function and a reduction of tiredness and fatigue. These are EFSA-authorised claims – statements the authorities have judged to have a scientific basis.

The research on magnesium for perceived stress and anxiety is more mixed. In a systematic review from 2017, researchers went through 18 studies and saw signs of an effect on mild anxiety, but judged the quality of the studies to be uneven.

The reference intake is around 300 mg per day for women and 350 mg for men. Many people don't get there through food alone, and stressful periods don't help. A supplement of 250–350 mg in the evening is a simple foundation – more on evening timing in our article on magnesium and sleep.

B vitamins – for energy and psychological function

B vitamins work in the body's energy metabolism, and several of them – B6, B12 and folate – contribute to normal psychological function. B2, B3, B5, B6, B12 and folate also contribute to a reduction of tiredness and fatigue.

Studies where healthy adults took a B complex during stressful periods have shown mixed but partly positive results on perceived stress. The benefit is clearest when intake is low to begin with, for example with a one-sided diet or a vegetarian diet without B12 sources.

A B complex around the reference intakes is plenty. High doses add nothing extra – water-soluble vitamins the body doesn't need are simply excreted in the urine.

L-theanine, rhodiola and omega-3 – thinner but interesting evidence

Three substances often come up in the discussion, with weaker but not non-existent support:

• L-theanine – an amino acid from green tea. Smaller studies with 200 mg have seen a calmer response to acute stress, without drowsiness.
• Rhodiola – an adaptogen where a few studies have seen less tiredness under stress, but the studies are small and uneven.
• Omega-3 – DHA contributes to the maintenance of normal brain function. As a stress supplement, however, the evidence is preliminary.

What you can skip

"Anti-stress" blends with fifteen ingredients in token doses rarely deliver anything – the dose of each individual substance is too low to match the studies. Megadoses of vitamin C have no evidence for stress, and homeopathic remedies show no effect beyond placebo. Energy drinks and caffeine tablets are, if anything, counterproductive: they mask the tiredness for a while but disrupt your sleep, which is the thing you need most.

Also be careful with combinations if you take medication. Ashwagandha can, for example, interact with thyroid medication and sedatives – check with your doctor or pharmacist first. Pregnant women should avoid ashwagandha altogether.

Supplements are not the whole solution

The boring answer comes last: what lowers stress most is free. Seven to nine hours of sleep, regular physical activity and genuine breaks beat any capsule. Supplements work best as support on top of those habits, not instead of them.

Food matters too. Regular meals keep blood sugar steady, which many find takes the edge off irritability on pressured days. Aim for whole grains, legumes, nuts and fish – that way you also get magnesium, B vitamins and omega-3 the natural way. And go easy on caffeine after lunch if your sleep is already fragile.

Starting at the sleep end is a good idea – our guide on sleeping better covers both evening routines and supplements. Our range for calm and recovery is gathered in the stress collection.

And importantly: if you have been stressed for a long time, sleep badly week after week or suspect burnout – contact your doctor. No supplement will fix that.

Frequently asked questions

Which supplement is best for stress?

Ashwagandha has the most research support. In randomised studies with 240–600 mg of extract per day, perceived stress and cortisol were lower after 60 days. Magnesium is a good second choice, especially if you sleep badly or eat little whole grain, nuts and legumes. Combining the two covers both the herbal and the nutritional angle.

How quickly does ashwagandha take effect?

Expect weeks rather than days. In the studies, the effect was evaluated after 30–60 days, and that's when the difference from placebo became clear. Some people notice better sleep sooner, but give the herb at least a month at a studied dose before judging whether it does anything for you.

Can I combine ashwagandha and magnesium?

Yes, that's fine – they work in different ways and there is no known interaction between them. A common approach is taking both in the evening, since many find they support winding down. Stick to normal doses: 300–600 mg of ashwagandha extract and 250–350 mg of magnesium per day is enough.

Do stress supplements have side effects?

At normal doses the risks are small. Ashwagandha can cause stomach upset or drowsiness in some people, should be avoided during pregnancy, and should be checked with a doctor if you take thyroid medication or sedatives. High doses of magnesium can cause loose stools. B vitamins at sensible doses are well tolerated since any excess is excreted.

When are supplements not enough?

If the stress has gone on for months, if your sleep is disrupted night after night, or if you notice signs of burnout – such as memory problems, cynicism and complete lack of energy – you need more than capsules. Contact your doctor. Stress management, talking therapy and sometimes time off work are measures with far greater effect than any supplement.

Sources

1. Chandrasekhar et al. 2012 – A prospective, randomized double-blind, placebo-controlled study of ashwagandha root extract in reducing stress and anxiety
2. Lopresti et al. 2019 – An investigation into the stress-relieving and pharmacological actions of an ashwagandha extract
3. Boyle et al. 2017 – The effects of magnesium supplementation on subjective anxiety and stress – a systematic review
4. 1177 (Swedish health service) – Stress
5. Swedish Food Agency (Livsmedelsverket) – Magnesium
6. EU Register of authorised health claims (EFSA)