Billions of dollars are spent by people who pop antioxidant supplements in an effort to stave off cancer, keep the heart healthy, and protect against a multitude of diseases.
But Nobel laureate James Watson - one of the scientists who discovered the structure of the DNA, said such supplements do not contain the "solution to health", despite what many commercial companies claim.
"If I have any message, it is that you won't be healthy by taking antioxidants," said the 87-year-old, who is chancellor emeritus at Cold Spring Harbor Laboratory in Long Island, New York.
The American molecular biologist and geneticist was in Singapore recently to deliver a public lecture, in conjunction with a symposium and exhibition to celebrate fellow Nobel laureate Sydney Brenner's life in science.
Antioxidants slow down oxidation, a process that is part of normal bodily functions but which also damages cells. So, it would appear that antioxidants such as vitamin C, vitamin E, and others found in various foods, are a healthy choice.
But some studies have shown that, when taken in high-dose supplement form, the opposite has happened: Antioxidants actually increased the risk of certain diseases.
This could be because people are taking the wrong doses, or that different antioxidants have different effects on people.
Dr Watson said antioxidants, found in fruit and vegetables and produced naturally in cells, exist in a fine balance with oxidants - which are also produced, in small quantities, in normal cells.
He said: "The public has the perception that because oxidants kill cells, you would be better off with antioxidants."
But he said conflicting research has shown that oxidants are not all bad. For instance, exercise, which is known to reduce one's cancer risk, produces oxidants, which have been largely portrayed as the villains that cause cancer.
Studies have also shown that antioxidant supplements may do more harm than good.
In a 2013 paper, for instance, Dr Watson, who has spent decades studying cancer, wrote that anti- cancer therapies such as chemotherapy and radiation depend on oxidants to kill cancer cells.
So, consuming too many antioxidants could very well work against cancer patients, he said.
So eat blueberries "because they taste good, not because their consumption will lead to less cancer".
Antioxidants are found naturally in foods such as berries and prunes but companies also market them as supplements in pill form, or in other products such as drinks, sports bars, cereals and cosmetics.
And they are growing in popularity. According to a report by market research firm Transparency Market Research, the global antioxidant market is expected to grow from US$2.1 billion (S$3 billion) in 2013 to about US$3.1 billion in 2020.
Yet, despite the miraculous claims on some bottles, the medical benefits of many are unproven, and - unlike drugs - they do not have to go through stringent trials to ensure they are safe or actually work.
So, when it comes to staying healthy and living longer, Dr Watson has only one piece of advice - and that is to exercise.
"Now, at my age, the chief disease I worry about is dementia. And we know that exercise somewhat prevents, or helps prevent, dementia. So, my advice is, if you want to live longer, you have to exercise," he said.
He still keeps fit by playing tennis with a tennis pro every week.
"I play tennis with a racquet given to me on my 80th birthday, which (tennis star) Roger Federer once played with, so it's got Federer's signature on it," said Dr Watson.
This article was first published on October 9, 2015.
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