Multivitamins: When you should – and shouldn’t – take them

Around half of British adults take a regular supplement

Around half of British adults take a regular supplement, hoping to cover our nutritional bases. But do we need to?

Many experts say that they have their place. Others say they’re expensive and unnecessary. It’s certainly true that supplement brands are raking in profits. This year, revenue generated by the industry reached a staggering £610 million in the UK, and the market is projected to grow by 6.53 per cent annually over the next five years.

The benefits promised by these brands cover everything from improved immunity and general wellbeing, to addressing specific concerns such as gut issues or brain health. It’s easy to see why they’re so popular – who wouldn’t want to pop a pill to fix our ailments? But could taking unnecessary supplements actually do more harm than good? Let’s find out.

Jump to:

• What’s in a standard multivitamin?
• Is it worth taking a multivitamin?
• If you take too much of a certain nutrient, will it do any harm?
• If not a multivitamin, is it worth supplementing individual nutrients?
• Should I take a supplement if I’m vegetarian?
• Should I take a supplement if I’m vegan?
• Should I take a supplement during pregnancy?
• Do women have different nutrient requirements to men?
• What about probiotic supplements?
• When should supplements be avoided?
• Is there any science behind supplements?

What’s in a standard multivitamin?

An all-rounder will usually include vitamins A, C, D, E and the B-vitamins, as well as minerals such as iron, calcium, magnesium and zinc. The difference is that vitamins are made by animals or plants, whereas minerals come from the soil and environment. Plants absorb minerals, which are then eaten by animals and humans.

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Is it worth taking a multivitamin?

As much as we would love a yes or no answer to this, the truth is more complicated. “If you’re generally well, and have a healthy diet, you don’t need a multivitamin,” says Dr Emily Leeming, a registered dietitian, nutrition scientist at King’s College London, and the author of Genius Gut: The Life-Changing Science of Eating for Your Second Brain. “Meta analyses of randomised controlled trials find that you won’t live any longer by taking multivitamins, and there’s no benefit in terms of cardiovascular disease. But there are some groups of people for whom supplements can be useful.”

“Changes in farming and soil practices have significantly reduced the mineral content in our food over the past decades,” says Aidan Goggins, a pharmacist, nutritionist and independent adviser to the supplement industry. “Judicious use of a high-quality multivitamin can be beneficial given the challenges modern diets face,” he argues.

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If you take too much of a certain nutrient, will it do any harm?

Fat-soluble vitamins, such as A and E, can accumulate in your liver, and could become toxic because your body isn’t able to clear them. “Too much vitamin A can cause headaches, liver damage and impact your bone strength,” explains Dr Leeming. “Water-soluble vitamins, such as C and the B vitamins, will pass through in your urine, but could still be a problem in excess doses over the long-term.”

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If not a multivitamin, is it worth supplementing individual nutrients?

Everyone agrees on vitamin D, which is absorbed through our skin from the sun. In the UK, we don’t get enough sunlight in the winter months, so supplementation is advised for everyone, but particularly children and the elderly. Vitamin C is the second most popular individual nutrient supplement in the UK, although it’s actually pretty easy to get from food, so unnecessary as long as you eat enough fruit and veg. Good sources are citrus fruits, berries, peppers, broccoli, kale, parsley and even the humble potato.

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Should I take a supplement if I’m vegetarian?

Yes: an algae omega-3 supplement. “Plant sources of omega-3, such as ALA, have poor utilisation in the body,” says Goggins. “We need the superior DHA, which can only be obtained from microalgae if we don’t eat fish.” He adds that plant sources of iron can be less well absorbed because of other components in plants, such as lectins and tannins, so that’s another one to consider.

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Should I take a supplement if I’m vegan?

“Vegans should definitely supplement with B12,” advises Dr Leeming. “It’s found in meat and animal products, and it’s important for neurological processes, including mood.” The vegetarian who’s eating dairy and eggs wouldn’t necessarily need a B12 supplement. But, if they’re not having it that often, it might be worth getting their levels checked.

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Should I take a supplement during pregnancy?

The advice here is clear: yes, and ideally start before conception. It will contain folic acid, which is important for helping the neural tubes stay healthy, as well as iron and iodine. Be sure to choose a pregnancy-specific supplement, as it won’t contain vitamin A, high levels of which have been shown to contribute to birth defects.

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Do women have different nutrient requirements to men?

Yes, pregnancy is not the only time when women might need to supplement. A lot of premenopausal women have iron deficiency, especially if they have heavy periods, which can cause debilitating fatigue. You can increase your iron through diet, but often women need that boost from a supplement, particularly if they don’t eat meat.

What about postmenopausal women?

After menopause, iron levels might go back to the same as men, but there are different considerations. “Some women are advised to take calcium supplements because of the concern around osteoporosis,” says Dr Leeming. Many of us can get all the calcium we need from food but, if you don’t eat dairy, then it’s worth considering a supplement.

Similarly, B12, the brain nutrient, can be low after menopause. “But, to be honest, we don’t really know because there hasn’t been enough research into it,” sighs Dr Leeming. “It’s frightening how little research we have because it’s always been so male-focused. Around 50 per cent of the population will go through menopause, and yet we are severely lacking in information and options to improve their quality of life.”

Do men’s nutritional needs change over time, too?

Not as much as women’s, but we all need more protein later in life to maintain muscle mass. And we’re less able to absorb nutrients as efficiently as we get older, so we should pay more attention to getting everything we need.

Overall, which is better: a multivitamin or individual nutrient supplement?

“A multivitamin is a trade-off designed to cover as many bases as possible, but with some compromises,” explains Goggins. “For instance, water-soluble vitamins are best absorbed on an empty stomach, while fat-soluble vitamins and minerals are better absorbed with food. Nutrients often compete with each other: copper is inhibited by zinc, while vitamin E inhibits vitamin D absorption. And minerals like magnesium, iron and zinc compete to cross the gut wall into the bloodstream.”

While multivitamins are quick and convenient to take, the nutrients in whole foods are designed to work together, not against each other - which is impossible to replicate in a pill. If you’re going to supplement then, ideally, you will take a specific nutrient after identifying a deficiency. “If you’re having symptoms, your GP can arrange blood tests to check iron and B12 levels, but there are many nutrients we can’t test through blood,” says Dr Leeming. “For most people, really focusing on their diet is going to be so much more impactful for their health.”

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What about probiotic supplements?

“Again, if you’re generally healthy, don’t bother,” says Dr Leeming. “Most of the ones on the market don’t contain enough live microbes to have any health effect.” And fermented foods are high in good bacteria that will keep your gut happy. She mentions kefir, in particular, as having robust research around its benefit on brain health. If you’re not a fan of kefir (or its fermented friends: sauerkraut, kimchi and kombucha) the good news is that more foods are fermented than you might have thought, including cheese, olives, sourdough bread and natural yogurt. The other thing that will keep your gut microbiome happy is fibre, otherwise known as plant roughage. It’s in all plants, so fill up on fruits, vegetables, nuts, seeds, beans, legumes and whole grains.

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How regulated is the supplement industry?

“Supplements in the UK are covered under Safe Food Law, which is not the most stringent as long as they do not cause outright harm,” says Goggins. “Studies of fish oils, for example, show that many do not meet industry guidelines and are rancid.”

Dr Leeming heartily agrees. “It’s a Wild West,” she laughs. “And just because something’s got fancy packaging, it’s not superior. There is no need to spend up to £80 on a jar of pills when a supermarket’s bog-standard own-brand contains everything you need.”

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When should supplements be avoided?

Goggins says there are additives in some supplements that could be cumulatively harmful, despite being within the safe limits set for daily intakes. “Concerns exist about synthetic dyes that are often added, including to children’s gummies,” he says. “They potentially cause neurodevelopmental problems. Avoid them entirely – their inclusion is unnecessary and merely a cheap manufacturing solution.” Some brands add sugar, tantamount to having sweets with your breakfast, but Goggins says sugar substitutes can be just as bad: “Sorbitol can cause gut issues and should be avoided when possible.”

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Is there any science behind supplements?

It’s mixed, to say the least. One study from January this year showed that a multivitamin slowed cognitive ageing by two years. But a study of more than 20,000 adults in 2020 found no difference in diseases or health conditions between those that took multivitamin supplements and those that didn’t. Having said that, the same study found those who took supplements reported feeling 30 per cent better. Could this be a placebo effect? The jury’s out. “If someone’s looking for a failsafe, it won’t be a green powder or a multivitamin,” says Dr Leeming. “You’re better off spending that money on subscribing to a fruit and veg box, making it easier to eat a variety of seasonal plant foods. It’s going to be much more impactful for your health, and more enjoyable too.”

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