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What are the pros and cons of taking supplements?

Anyone browsing the health aisles at the supermarket, checking out shelves in the health food shop or scrolling through internet outlets in the hope of improving their health, will find a wealth of supplements on offer. Often these are branded 'natural' or 'herbal' - making them sound healthy and harmless.

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Are vitamin supplements worth it?

Although vitamin supplements may have benefits for those with a deficiency or specific health need, popping a new pill or tincture without consulting a professional is not advisable. In some cases, taking a supplement may even prove harmful. Some products may be unsuitable for those with certain conditions, including those who are pregnant or breastfeeding. They may even react with medications you’re already taking, rendering them more potent or less effective.

Taking vitamin supplements with other medication

"If you’re on any sort of medication - even the contraceptive pill - it's important that you get advice from a healthcare practitioner," says Pharmacist Thorrun Govind, Chair of the English Pharmacy Board. "Even items that seem completely harmless - for example, cranberry supplements - may have an impact on blood thinners such as warfarin, making individuals more prone to bruising or bleeding if they combine the two. Vitamin K can also cause problems for those on this blood-thinning drug."

Herbal and vitamin supplements can interact with your medication

One of the potential issues with herbal supplements and vitamin tablets is that they are widely available and can be picked up from supermarket shelves, or popped in an online basket, without a second thought. This all adds to the impression many have that vitamin supplements are harmless whatever your health status. As we've seen above, such an assumption may be dangerous and so it's always best to check with your pharmacist.

Herbal remedies

Other herbal or vitamin supplements may be suggested for certain conditions - for example, some people take St John's wort to try to mitigate the symptoms of depression. This may seem a more holistic approach for some than prescribed medication from a GP. But self-treatment with herbal supplements comes with a potentially higher level of risk.

"People often believe that because something's 'natural' it’s safer, and that's not necessarily the case," explains Govind. "Whereas medicines from your doctor have been rigorously tested for safety and efficacy, some of the natural remedies haven't had clinical trials and tests - you're missing out on the clinical evidence."

Herbal and vitamin supplement risks

If you're simply hoping to supplement your diet with an everyday multivitamin, rather than to target a specific problem, the risks are relatively low (although if you and your diet are healthy, the benefits are often minimal). However, it's still worth a quick word with a professional for advice, to ensure the vitamin has what you need and is safe for you, particularly if you are pregnant or trying to become pregnant.

For example, vegans are advised to take vitamin B12 supplements, normally found in meat and dairy products. It would be easy to assume they need a higher dose than what is available in a multivitamin. However, this is not usually the case.

"Having supplements such as a multivitamin is not necessarily a bad thing," says Govind. "But you've got to be mindful that they're not tailored to you as an individual. In terms of safety, it's important to access advice from your doctor or a pharmacist. Even if you've taken a supplement in the past, your health status might have changed. For example, if you have issues with your liver, the standard vitamins may not be suitable."

Obtaining vitamins naturally

In addition, you're much better off getting the vitamins and minerals from food (which contains added micronutrients, fibre etc) than from supplements. So if you're tempted to pop a multivitamin rather than improving your diet, this can be bad for your health.

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Common supplement interactions

Some supplements are well known, and you may find that friends or family members swear by their benefits. Despite their familiarity, it's important to know the full facts before taking them. Some known interactions of common supplements include:


Often recommended as a treatment for the common cold, this herb is thought to stimulate the immune system. However, it's important to know that it may affect the level of certain medications in your blood, including tizanidine, a muscle relaxant and some Parkinson's drugs. It may also slow your body's ability to process caffeine.

Evening primrose oil

Many take this oil due to claims of its ability to balance hormones and even reduce inflammation in the body. But beware that this supplement is thought to have a thinning effect on the blood. There is also some limited evidence that it might increase the risk of seizures in susceptible patients.

St John's wort

It has been claimed that St John's wort may relieve some symptoms of depression. However, it can be dangerous to take this supplement without advice, as it has interactions with many different medications. These include the contraceptive pill and SSRIs (selective serotonin reuptake inhibitors) often prescribed by doctors for depression. If you're suffering from symptoms of depression, it's important to talk to your GP.


This familiar supplement claims to increase vitality and improved stress resistance. However, the supplement can interfere with many different medications, including diabetes medications such as insulin and the blood thinner warfarin. It's important to speak to a professional before taking this supplement if you are on any medications.

Ginkgo biloba

Ginkgo biloba may be another familiar name you've glanced at on the supplement shelves. This supplement is promoted as helping to manage symptoms of anxiety or circulation problems, although this is unproven. Importantly the product may interfere with the effectiveness of certain drugs, including antivirals and seizure medications.


We are so familiar with garlic in our diet, it would be easy to assume that garlic tablets would be completely harmless. However, interactions have been reported with a high number of medications. Whilst often mild, it's important to check that it doesn't interfere with your current medication, particularly if you are on blood thinners or antiviral drugs.

Including supplements as part of a healthy diet

Working to improve our health, looking for ways to feel better and get the best out of life should only be applauded, and vitamins and supplements may form a part of a healthy regime for some. However, it is important to ensure that these add-ons to our daily diet are not seen as alternatives to prescribed medication and that we seek guidance from professionals before taking anything new. This will help to ensure we get the best out of our supplements and don't take anything that may affect our health negatively.

Article history

The information on this page is peer reviewed by qualified clinicians.

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