Could your daily vitamin pills take years off your life? They're taken by thousands to boost their health but recent studies have found some supplements could do more harm than good

• Fish oil capsules have been linked to high levels of prostate cancer
• In another study, high dosages of vitamin C led to kidney stones
• Vitamin E supplement takers developed heart failure
• Better off getting vitamins by eating healthy diet 

Are supplements a quick health fix or can vitamins actually be bad for you?

Vitamin pills are big business - from chewable ones for children and tablets especially tailored for women going through the menopause to essential oils for dodgy joints and high-dose vitamin C to pep up your immune system, there’s a supplement for everyone.

But can vitamins actually be bad for your health?

It seems that your daily pill can do more harm than good. Indeed, last week saw the revelation that fish oil capsules have been linked to high levels of prostate cancer - a shock for the millions who take fish oils or omega-3 fatty acids every day in the quest to ease joint pain, improve heart health and fight mental decline.

A study of more than 2,000 men found that those with the highest levels of omega-3 in their blood were 71 per cent more likely to develop the most lethal form of prostate cancer, and 44 per cent more likely to develop low-grade prostate cancer.

And it’s not just omega-3 that is under scrutiny. According to Dr Alan Kristal, who led the study at the Fred Hutchinson Cancer Research Centre in Seattle, there is surprisingly little evidence that any vitamin or mineral pills prevent disease - unless people are suffering from a nutrient deficiency.

‘As we do more and more of these studies, we find high doses of supplements have no effect or increase the risk of the disease you are trying to prevent,’ he says. Yet millions of busy Britons take vitamins to compensate for a poor diet.

One in three of us takes a supplement, and we spend about £209 million a year on vitamin pills. The message last week from experts was not to panic.

For most people, taking multivitamin and mineral supplements at the recommended dose is safe.

So amid all this confusing and sometimes contradictory advice, which supplements work and, more importantly, which ones are safe?

MULTIVITAMINS

Big business: One in three of us takes a supplement - but is it worth it?

While they might be the most wide-ranging supplement in the UK - providing 100 per cent of our daily allowance of everything from vitamin B to copper - there is little evidence that they do any good.

In 2010, French researchers followed 8,000 volunteers who had taken either a multivitamin or a dummy placebo pill for six years.

They found that those who popped the vitamin pill were just as likely to suffer heart disease or cancer as those taking the placebo.

That work followed a 2008 major review of 67 studies - involving 230,000 people - which found no evidence that multivitamins prolonged life.

Some studies have even suggested that high doses could do more harm than good.

In 2011, the Iowa Women’s Health Study looked at the health of more than 38,000 older women and found that women who regularly took multivitamins were 2.4  per cent more likely to die over the 19 years of the study.

Their research also showed that use of vitamin B6 increased the risk of death during the study by 4.1 per cent, folic acid by 5.9 per cent, iron by 3.9 per cent, magnesium by 3.6 per cent, zinc by 3 per cent and copper by 18 per cent.

However, the study didn’t take into account the fact that many people start taking heavy doses of vitamins only when they develop serious diseases such as cancer.

But Dr Kristal says: ‘Dozens of studies of multivitamins show that they do absolutely nothing at the recommended doses.’

So if your diet contains plenty of fresh food and your five-a-day, it’s unlikely a multivitamin pill is essential.

VITAMIN C

Doctors have known since the 1750s, when British sailors were first issued with limes, that vitamin C is essential for health. It helps to heal wounds, strengthens the body’s connective tissues and keeps cells healthy.

But despite the many health claims made about vitamin C, there is little evidence that it does much good as a supplement.

While it does appear to shorten the duration of colds, there is little real proof that it staves off illness, Dr Kristal says.

And the high doses recommended by some supporters of alternative medicine may do more harm than good.

In February, an 11-year study of more than 23,000 men found that those who took high doses of the supplement - typically 1,000 mg - were twice as likely to develop kidney stones compared to men who took no pills.

A 2002 study showed that 1g doses of vitamin  C and vitamin E almost trebled the risk of premature death among postmenopausal women in any year.

The Department of Health says adults need 40 mg a day but doses up to 1,000 mg a day are unlikely to cause harm. Anyone worried about their intake should decide whether they are exceeding their safe daily dose.

'For example, the effervescent vitamin drink Berocca contains 476 mg. Two doses would take you close the recommended limit.'

VITAMIN E

Found in nuts, germs, wheat and oils, vitamin E is vital for healthy cells. According to the Department of Health, most adults need between 3 mg and 4 mg a day.

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Studies have shown that foods rich in vitamin E may protect against heart disease. But there is little evidence that vitamin E pills do the same - and some that say they may do harm.

In 2011, U.S. researchers at Cleveland Clinic found that men who took a ‘high strength’ 268 mg vitamin E pill each day during the seven year study were 17 per cent more likely to develop prostate cancer than men who did not take the supplement.

And, in 2005, a seven-year study of 4,000 people found it increased the risk of heart failure by 13 per cent.

While the Department of Health says taking 540 mg or less a day is unlikely to do harm, the prostate cancer study published by Dr Kristal also looked at the effect of daily 400 mg vitamin E doses.

Dr Kristal says: ‘It increased the risk of prostate cancer by 17 per cent. We don’t know why. But one thing to remember is that, unlike vitamin C, it is soluble in fat and so levels build up in the body over time.’

Experts say that one egg or 28 g of almonds a day should provide all the vitamin E you need - making it unlikely that any of us need a supplement.

Enough: A glass of milk and a yoghurt meets our daily calcium limit

CALCIUM

Calcium is often taken by middle-aged and older people to protect their bones. There is also evidence that it can prevent the recurrence of bowel polyps - growths that may develop into cancer.

However, calcium supplements could increase the risk of heart disease in men, according to a study in February from the U.S. National Cancer Institute.

A study of 388,000 people found that men who took more than 1,000 mg, or 1 g, a day in supplements were at greater risk of heart problems - and had a 20 per cent higher risk of death.

Women were not at greater risk, the Journal of the American Medical Association found. Scientists believe that high calcium levels harden the arteries, increasing the risk of cardiovascular disease.

The Food Standards Agency recommends adults have 700 mg of calcium a day. One yoghurt and a 300 ml glass of milk would meet your daily calcium limit, so it’s unlikely you would need a supplement.

SELENIUM

Selenium is a trace mineral found in seafood, meat and grains. It is essential in small doses and selenium deficiency is linked to mental decline, impaired immune systems and premature death.

But although it is commonly recommended to help prevent heart disease, too much can be harmful. The Department of Health says men need 0.075 mg a day, and women 0.06mg, in their diet. But after looking at data from 20,000 adults, Warwick Medical School researchers found that it did little to lower the incidence of heart disease in people with a good diet.

High doses were linked to type 2 diabetes, the authors reported in the Cochrane Library journal.

BETA CAROTENE

Beta carotene is a pigment that gives yellow and orange plants colour. The body converts beta carotene to vitamin A, which we need for good vision, healthy skin and a strong immune system.

Beta carotene is a natural antioxidant and is usually taken to prevent cancer. But there is no evidence it works, and plenty to show that high doses can be harmful.

In 1994, researchers found that smokers who regularly took a large 20 mg dose of beta carotene a day were 8 per cent more likely to die from lung cancer than people who did not take the supplement.

As well as all this, beta carotene can also give white skin an orange tint, and can trigger upset stomachs, joint pain and dizziness.