Niacin supplements linked to greater risk of heart attacks and strokes

 People with high levels of niacin, also known as vitamin B3, in their blood may be more likely to have a heart attack or stroke than those with lower levels. Excessive amounts of the vitamin, which is routinely added to fortified food and can be taken as a supplement, may inflame blood vessels.

Heart attacks and stroke are leading causes of death worldwide. While researchers have made significant strides over the past few decades in discovering the risk factors for these conditions, they haven’t identified them all.

“If you treat [high] cholesterol and [high] blood pressure and diabetes and all the existing risk factors, you can still suffer a heart attack," says Stanley Hazen at the Cleveland Clinic in Ohio. "There is something that we are missing."

In an effort to fill these gaps, Hazen and his colleagues collected blood samples from 2331 adults in the US and 832 adults in Europe who had elected to undergo cardiovascular screenings. The team analysed the samples for substances called metabolites, byproducts of metabolic processes such as digestion. The researchers then tracked incidents of cardiac events, such as heart attacks and strokes, among the participants over three years.

They found that people with elevated levels of a metabolite called 4PY were around 60 per cent more likely, on average, to experience such an event than those with lower levels. This compound only arises when the body breaks down excess niacin.

Further experiments revealed that 4PY inflames blood vessels in rodents. We know that inflammation is a major contributor to the development of heart disease, says Hazen.

It isn't uncommon for people to have high niacin levels, he says. This is partially due to certain foods, such as cereals and flours, being routinely fortified with the vitamin in countries that include the UK and the US.

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Niacin supplements are also increasingly popular as evidence suggests they have anti-ageing benefits, says Hazen. Plus, it wasn’t until recently that doctors stopped prescribing high-dose niacin to people at risk of cardiovascular disease, as it was initially thought the vitamin protected people from these conditions by lowering cholesterol.

“I think this study really shows that sometimes, when it comes to vitamins, you can have too much of a good thing," says Jenny Jia at Northwestern University in Chicago, Illinois.

However, this research was mainly conducted in people of European ancestry. It is therefore unclear if similar results would occur in people of different racial or ethnic backgrounds, says Jia.