This is why your beauty supplement could mean doctors miss a key sign of a heart attack

Think you can't overdose on face cream? Or the more vitamins and minerals you take the better?

Think again. As our beauty routines get more complicated, we need to be wary of inadvertently overdosing on ingredients, or mixing and matching products with potentially dangerous results.

'We're loading ourselves up with too many topical products and insane amounts of supplements,' says aesthetic expert Dr Mervyn Patterson at Woodford Medical. 

He warns this can cause skin damage, interfere with medical tests, and possibly lead to serious health problems. 

Read on to find out more...

  Be biotin aware 

Biotin, or B7, is a very popular vitamin widely used in supplements for hair, skin and nails. It's water-soluble, which means it doesn't build up in the body and you don't need huge amounts. 'Biotin is only useful as a supplement if you have a deficiency,' says nutritionist Emma Bardwell, who warns excess use can come with dangers, including interfering with both thyroid and heart tests.

Last year, the British Generic Manufacturers Association wrote to healthcare professionals warning that biotin can affect thyroid function results, and patients should be asked about biotin or skin, nail and hair supplement use before testing.

Shockingly, biotin can also interfere with heart test results. In 2019, the FDA reminded that high doses of biotin can significantly interfere with tests used to measure troponin, a protein in heart muscle that's released into the bloodstream during a heart attack, with concerns about both false high or low results depending on the test. 

'If you go to hospital with chest pain your troponin levels will be measured,' says Dr Oliver Guttmann, consultant cardiologist at the Wellington Hospital, part of HCA Healthcare UK. 'Biotin might be used to check these levels, so a biotin supplement can affect the measurement. The concern is falsely low/negative levels of troponin as heart attacks can be missed.'

Similarly, biotin is used to check the thyroid, so wrong measurements can occur. Dr Guttman says that falsely high and low measurements have been detected, depending on which tests have been used. 

The NHS says that less than 0.9mg daily is unlikely to cause harm. But in the wild west of the supplement world, it's easy to buy tablets containing as much as 12mg. While packaging recommends consulting a doctor or pharmacist should you be on medication or have medical conditions, we're so conditioned to view supplements as safe, how many actually do so? Make sure you follow their advice.

Keep an eye on vitamin A

Hailed as a skincare wonder ingredient, retinol increases collagen production. But this April, the EU warned of overexposure and is implementing new legislation to limit retinol levels in products. 

Experts warn overuse of retinol (applied as creams and serums) can irritate and thin skin

'The contribution of vitamin A from cosmetic products to the overall consumer exposure, although low, may be of concern for consumers with the highest exposure to vitamin A (5 per cent of the total population) from food and food supplements,' said the Scientific Committee For Consumer Safety.

'If you have too high a concentration in your system it can damage the liver and cause bone thinning. I wouldn't be worried about skin irritation so much as the systemic effect,' says Dr Patterson, although he warns overuse of retinol alone can irritate and thin skin.

The UK RDA for women is 600mcg (men is 700mcg), while the NHS website advises not to exceed 1500mcg via food and supplements. The Mayo Clinic warns more than 3,000mcg daily on a long-term basis can cause the problems already highlighted, as well as joint and bone pain, headaches, nausea and diarrhoea.

Vitamin A is often marketed as a beauty supplement which can be bought cheaply and easily in very high doses. In fact, it's feasible to take one, along with a general multivitamin (providing more than 100 per cent of your daily needs), eat a portion of spinach and carrots, then use a topical cream containing retinol - all adding up to almost 10,000mcg.

... and on too much Vitamin C 

'The RDA for adults is 40mg daily, but this is the lowest level, to prevent things like scurvy,' says Bardwell. 'There's a trend for taking very high dose vitamin C for skin health and immunity. The upper limit is 2,000mg a day and even 1,000mg can cause stomach problems - nausea, vomiting and gastrointestinal discomfort'.

It's easy to consume these levels, especially in powder form. 'High doses are unlikely to cause harm, but it could certainly cause discomfort when taken orally, and is likely to be very expensive as an IV.'

Don't mix and match

If you're a fan of the TikTok trend for layering on skincare products, beware, as cross-mixing ingredients can be harmful. 

'The skin can only absorb so much and mixing products can be problematic,' says Dr Patterson. Retinol (or other forms of vitamin A) and vitamin C cream applied at the same time might cause irritation, as might vitamin C and AHAs, or retinol and salicylic acid, which can over-dry the skin. 

Dr Patterson advises against using two products with the same actives and 'stick to five basics from the same range'.

Something's fishy... 

Ideally, we ought to be eating our omega-3 in, for example, oily fish. On top of this, supplements, which are said to help combat dry and irritated skin and boost hair and nail health, should be used with caution by those on blood thinners, due to fears of increased risk of bleeding. 

Omega-3 supplements should be used with caution by those on blood thinners

'Too high a dose of omega-3 can change the way in which it's used by the body, potentially making the warfarin [blood thinner] more potent,' says Dr Guttman.

The British Heart Foundation recommends that if you take omega-3 supplements you should aim for roughly 450 mg per day (and choose ones containing DHA and EPA omega-3s). It's known fish oil can thin blood; a study of 56 healthy adults taking 640mg a day for a month had decreased clotting.

Dr Guttman says: 'People react differently, but stay within recommended limits and inform your doctor about supplements.'

Other, less-known side effects from very high doses of fish oil may include heartburn and diarrhoea.