Vitamins and Supplements: Six Popular Products You Should Think Twice About Taking

Vitamins and supplements are often presented as an easy way to improve health, boost energy or fill nutritional gaps. They are widely available in supermarkets, pharmacies and online, and social media has made it increasingly common to see people sharing their daily supplement routines.

But a supplement being available without a prescription does not automatically mean it is suitable for everyone.

A GP has warned that taking certain vitamins, minerals and herbal products without understanding their appropriate dose or potential interactions can sometimes lead to unwanted health effects. Some supplements can cause problems when taken in excessive amounts, while others can interfere with medicines or even affect the accuracy of medical tests.

The important point is not that everyone should stop taking supplements. People with diagnosed deficiencies and certain medical or nutritional needs may genuinely benefit from them. Instead, experts advise checking exactly what you are taking and whether you actually need it.

Vitamin B6 and the risk of nerve problems

Vitamin B6 is commonly included in multivitamins, B-complex supplements and products marketed towards energy and general wellbeing.

However, taking too much supplemental vitamin B6 over time can cause peripheral neuropathy. This can lead to symptoms such as tingling, numbness, burning sensations or reduced feeling, particularly in the hands and feet.

The NHS advises adults not to take more than 10mg of vitamin B6 a day from supplements unless advised to do so by a doctor.

One potential problem is that people may unknowingly take B6 from several different products. A multivitamin, energy supplement and separate B6 tablet could all contain the vitamin, causing the total intake to become considerably higher than intended.

Anyone experiencing persistent tingling, burning or numbness should discuss the symptoms with a healthcare professional.

Iron is not simply an energy booster

Iron supplements can be extremely useful when someone has an iron deficiency. However, feeling tired does not necessarily mean that iron is the answer.

Taking too much iron can cause side effects including constipation, nausea, vomiting and stomach pain. Large amounts can be particularly dangerous for children, which is why iron-containing products should always be stored safely.

A suspected deficiency may need investigation rather than self-treatment. Blood tests can help establish whether iron levels are low, while doctors may also need to investigate why a deficiency has occurred.

People who have been prescribed iron should follow their healthcare professional's instructions rather than changing the dose themselves.

Vitamin A can build up in the body

Vitamin A is another nutrient where more is not necessarily better.

Retinol, a form of vitamin A, can be found in some multivitamins and fish liver oil products. Unlike some water-soluble vitamins, vitamin A can accumulate in the body, meaning excessive long-term intake can potentially cause problems.

The NHS advises against consuming more than an average of 1.5mg of vitamin A per day from food and supplements combined over many years, because higher intake may increase the risk of bone fractures later in life.

There is an additional concern during pregnancy. Pregnant women should avoid vitamin A supplements containing retinol unless specifically advised by a healthcare professional. Liver and liver products should also be avoided during pregnancy because they can contain high levels of vitamin A.

Vitamin D still needs to be taken at the right dose

Vitamin D plays an important role in maintaining healthy bones and muscles. In the UK, adults and children aged four and over are generally advised to consider taking a daily 10 microgram supplement during the autumn and winter months, while some people may be advised to take it throughout the year.

The problem comes when people assume that a higher dose must provide greater benefits.

Long-term excessive vitamin D intake can increase calcium levels in the body. This can potentially damage the kidneys and affect the heart and bones.

The NHS advises that adults should not take more than 100 micrograms, or 4,000 IU, of vitamin D per day unless recommended by a healthcare professional.

It is particularly important to check the strength of a product. Some medically prescribed vitamin D treatments use much higher doses at specific intervals, such as weekly dosing. Taking a high-dose product every day instead of following the prescribed schedule could be dangerous.

St John's wort can interact with medicines

Herbal supplements can sometimes create a false impression that they are automatically safer because they are described as natural.

St John's wort is commonly used by people seeking support for low mood, but it can interact with a wide range of medicines.

It can reduce the effectiveness of some hormonal contraceptives and can also interact with medicines including certain antidepressants, blood thinners and treatments used for epilepsy, heart conditions and cancer.

Anyone taking regular medication should therefore speak to a pharmacist or doctor before starting St John's wort.

Biotin could affect blood-test results

Biotin, sometimes marketed as vitamin B7, is frequently found in supplements promoted for hair, skin and nails.

One lesser-known concern is that high doses of biotin can interfere with certain laboratory tests. This includes some thyroid tests and tests involving troponin, a protein that doctors may measure when investigating possible heart problems.

Depending on the test, excessive biotin can produce misleading results. In some circumstances, that could complicate diagnosis or lead to inappropriate treatment.

If you take a hair, skin or nail supplement, tell the healthcare professional conducting your blood test. Include the name of the product, its dose and, if possible, when you last took it.

If you are receiving emergency medical care, you should never delay treatment simply to allow a supplement to leave your system.

Check your entire supplement routine

Perhaps the biggest lesson is that supplements should be considered as part of your overall healthcare rather than as harmless additions to your diet.

Taking several products can make it difficult to work out exactly how much of a particular vitamin or mineral you are consuming. The same ingredient might appear in a multivitamin, a specialist wellness product and a separate single-nutrient supplement.

Before starting something new, check the label and consider whether there is a genuine reason for taking it. A pharmacist can also help identify potential interactions with medicines and other supplements.

People should not suddenly stop prescribed medicines or supplements without speaking to the appropriate healthcare professional. Supplements may be necessary for people with diagnosed deficiencies or particular nutritional requirements.

The safest approach is therefore not to assume that all supplements are dangerous, nor to assume that they are all harmless. Understanding the dose, purpose and potential interactions is the key.

Sources

UK NHS, including its advice on vitamin B6, iron, vitamin A, vitamin D and St John's wort, alongside the medical comments supplied in the original article from GP Dr Asiya Maula.

Disclaimer: This article is for general information only and is not medical advice. Individual nutritional requirements vary, and some people may need supplements because of a diagnosed deficiency, pregnancy, dietary requirements or another medical reason. Speak to a GP, pharmacist or other qualified healthcare professional before starting, stopping or changing a supplement, particularly if you take prescription medicines or have an underlying medical condition.