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Multivitamins: what you need to know

Find out what multivitamins are, what they do, any benefits from taking them and whether you might need them

Written by Rosalind Ryan on December 11, 2018 Reviewed by Dr Sarah Schenker on December 18, 2018


What are multivitamins and what do they do?

Multivitamins are supplements that contain a wide range of different vitamins and minerals. Some will also contain other nutrients such as friendly bacteria or ginseng. They are the most popular vitamin supplement sold in the UK.1 We should be able to get all the vitamins and minerals we need from a healthy balanced diet but for some people in certain circumstances, it may be tricky to get enough. A multivitamin can plug any small but critical nutritional gaps in your diet, helping to prevent low intakes.2 Taking separate supplements on top of a multivitamin can be dangerous, as some vitamins can build up in the body.

Benefits of multivitamins

What do multivitamins do in the body?

We need 13 vitamins to maintain our health and wellbeing: A, C, D, E, K and the eight B vitamins. Apart from vitamin D and B3 (niacin), our bodies cannot create these nutrients, so we need to get them from our food.3 The way we process certain vitamins also means we need to replenish them every day. The B vitamins and vitamin C are water-soluble – what we don’t need, we flush out in our urine – so we need to consume adequate amounts of them each day.4

Eating a wide range of fresh fruit and vegetables, nuts and seeds, wholegrain foods and healthy sources of protein should provide us with a good balance of nutrients, but not many of us eat this well all the time.

Research found only 25% of adults in England ate five or more portions of fruit and veg a day in 2015, while nearly 50% of adults ate less than three portions a day.5 If we don’t get enough nutrients from our food, or can’t absorb nutrients properly, we could end up with health problems related to low nutritional intakes.

Who should take a multivitamin?

Certain groups of people can benefit from taking a multivitamin,6 such as:
  • those with allergies or intolerances – they may not be able to absorb certain nutrients or may not be eating enough varied food groups
  • vegetarians and vegans – they could be missing certain nutrients that are mainly found in animal products, like vitamin B12 and iron7
  • pregnant and breast-feeding women – pregnancy increases your body’s need for certain nutrients, such as iron and folate, and can help protect your unborn baby from developmental problems8
  • older people – our bodies find it harder to absorb some essential nutrients as we age, including vitamin B129
  • children aged six months to five years – the government recommends young children take supplements containing vitamins A, C and D every day10 

A multivitamin may also be helpful if you’ve recently been ill or have a medical condition that means you need a top-up. If you’re stressed, going through times of upheaval, or training hard for a sporting event such as a marathon, you might also benefit from taking a multivitamin.

Even if you’re not in one of the groups above, it may be useful to take a multivitamin. An ongoing study found that nutrient levels in fruit and vegetables have declined significantly over the past 70 years, thanks to declining mineral levels in our soil.11


Are there any side-effects from taking multivitamins?

A quality multivitamin will contain all the vitamins and minerals you need in safe doses. However, it can be dangerous to take some individual vitamins on top of a multivitamin supplement.

Vitamins A, D, E, and K are fat-soluble, which means they can be stored in the body as reserves until we need them.12 But this also means that consuming too much can lead to harmful levels building up in the body. For example, too much vitamin A can affect your bone strength, and could harm your unborn baby if you’re pregnant.13 Taking too much vitamin C every day can lead to nausea, diarrhoea and stomach pains,14 while an excess of selenium can trigger a condition called selenosis – essentially selenium poisoning.15 If you’re taking a range of supplements, such as a multivitamin and cod liver oil, check you are not exceeding the safe limits for each vitamin. Talk to your GP or a qualified nutritionist or dietitian if you’re unsure. Shop Multivitamins Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies.


1. NHS. Supplements – who needs them? 2. Ward E. Addressing nutritional gaps with multivitamin and mineral supplements

3. As Source 1

4. Christian Nordqvist. Medical News Today. Vitamins: What are they and what do they do? 5. NHS. Statistics on obesity, physical activity and diet, England 2017 6. NHS. Do I need vitamin supplements? 7. National Institutes of Health. Vitamin B12 8. Sullivan K, et al. Multivitamin use in pregnant and nonpregnant women 9. British Nutrition Foundation. Older adults 10. NHS Choices. Vitamins for children 11. McCance RA, Widdowson EM. The Mineral Depletion Of Foods Available To Us As a Nation (1940–2002) – A Review of the 6th Edition of McCance and Widdowson

12. As Source 4

13. NHS. Vitamin A 14. Katherine Zeratsky. Mayo Clinic. Is it possible to take too much vitamin C? 15. European Food Safety Authority. Scientific Committee on Food. Tolerable upper intake limit for vitamins and minerals