# Supplements: what is actually evidence-based?

> Save your money, keep your health

Category: Nutrition · 3 min read · Written by the Splash team · Sources checked October 2026
URL: https://splash.care/learn/nutrition/supplements

## Quick answer

- Most people get what they need from a varied diet.
- Vitamin D in autumn and winter, and folic acid if you could conceive, are well supported.
- PMS supplements have limited evidence, and high doses of B6, zinc and vitamin D can harm.
- Check with a pharmacist, especially if you take medicines.

The supplement aisle is full of pretty bottles promising [hormone](https://splash.care/learn/cycle-basics/hormones-explained) balance. The NHS and the BDA agree that most people can get what they need from a varied diet, and that most people do not need supplements. There are a few important exceptions.

## Well supported

- **Vitamin D:** the NHS says everyone should consider 10 micrograms a day in autumn and winter, when UK sunlight is not strong enough. If you are rarely outdoors, cover most of your skin outside, or have dark skin (for example African, African-Caribbean or south Asian backgrounds), consider taking it all year.
- **Folic acid:** 400 micrograms a day if you could get [pregnant](https://splash.care/learn/fertility-ttc/early-pregnancy-signs) or are trying, taken before conception and until 12 weeks of pregnancy. Some people are advised a higher dose, so speak to a [doctor](https://splash.care/learn/conditions/talk-to-your-doctor).
- **Iron:** only if a blood test shows you need it, as advised by a doctor.

## Some evidence, not a sure thing

- **Calcium, vitamin B6 and zinc** show some benefit for [PMS](https://splash.care/learn/glossary/pms) in small trials, but the NHS says there is not much evidence that [PMS](https://splash.care/learn/conditions/pms) supplements work. Our PMS supplements read goes through the details and the safe limits.
- **Magnesium** may help some people, but the evidence is limited.

> More is not always better. The NHS says not to take more than 10mg of vitamin B6 a day in supplements unless a doctor advises, because very high doses (200mg a day or more) can cause nerve damage, and the effect of doses in between is unclear. Too much vitamin D (over 100 micrograms a day) can also be harmful.

**Myth:** "Hormone balancing" blends are proven to fix PMS.

**Fact:** No good trials back them. In the UK, supplements are regulated as food, not medicines, and some herbal products can interact with medicines, including contraception. Always check with a pharmacist.

> **Splash says:** before buying, ask a pharmacist "Is this evidence-based for me, and does it clash with anything I take?" They are free to ask, friendly and know their stuff.

**Quick quiz:** Which supplement does the NHS advise for anyone who could get pregnant?

1. Vitamin B6
2. Folic acid
3. Evening primrose oil

Answer: Folic acid. Folic acid (400 micrograms a day) helps prevent neural tube defects like spina bifida in early pregnancy.

### When to see a doctor

Talk to a GP or pharmacist before starting supplements if you are pregnant, breastfeeding, have a health condition or take any medicines, including the pill.

## Sources

1. [NHS: Vitamins and minerals](https://www.nhs.uk/conditions/vitamins-and-minerals/)
2. [NHS: Vitamin D](https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/)
3. [NHS: B vitamins and folic acid](https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-b/)
4. [NHS: Calcium](https://www.nhs.uk/conditions/vitamins-and-minerals/calcium/)
5. [BDA: Supplements food fact sheet](https://www.bda.uk.com/resource/supplements.html)
6. [NHS: PMS (premenstrual syndrome)](https://www.nhs.uk/conditions/pre-menstrual-syndrome/)

This is general information, not medical advice. Splash can’t diagnose. If you’re worried, talk to a GP, pharmacist or sexual health clinic. In an emergency call 999 (UK) or 911 (US).