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Myth 2: Antioxidants are good and free radicals are bad
In December 1945, chemist Denham Harman's wife suggested that he read an article in Ladies' Home Journal entitled 'Tomorrow You May Be Younger'. It sparked his interest in ageing, and years later, as a research associate at the University of California, Berkeley, Harman had a thought “out of the blue”, as he later recalled. Ageing, he proposed, is caused by free radicals, reactive molecules that build up in the body as by-products of metabolism and lead to cellular damage.
Scientists rallied around the free-radical theory of ageing, including the corollary that antioxidants, molecules that neutralize free radicals, are good for human health. By the 1990s, many people were taking antioxidant supplements, such as vitamin C and β-carotene. It is “one of the few scientific theories to have reached the public: gravity, relativity and that free radicals cause ageing, so one needs to have antioxidants”, says Siegfried Hekimi, a biologist at McGill University in Montreal, Canada.
Yet in the early 2000s, scientists trying to build on the theory encountered bewildering results: mice genetically engineered to overproduce free radicals lived just as long as normal mice4, and those engineered to overproduce antioxidants didn't live any longer than normal5. It was the first of an onslaught of negative data, which initially proved difficult to publish. The free-radical theory “was like some sort of creature we were trying to kill. We kept firing bullets into it, and it just wouldn't die,” says David Gems at University College London, who started to publish his own negative results in 2003 (ref. 6). Then, one study in humans7 showed that antioxidant supplements prevent the health-promoting effects of exercise, and another associated them with higher mortality8.
Nutrition: Vitamins on trial
None of those results has slowed the global antioxidant market, which ranges from food and beverages to livestock feed additives. It is projected to grow from US$2.1 billion in 2013 to $3.1 billion in 2020. “It's a massive racket,” says Gems. “The reason the notion of oxidation and ageing hangs around is because it is perpetuated by people making money out of it.”
Today, most researchers working on ageing agree that free radicals can cause cellular damage, but that this seems to be a normal part of the body's reaction to stress. Still, the field has wasted time and resources as a result. And the idea still holds back publications on possible benefits of free radicals, says Michael Ristow, a metabolism researcher at the Swiss Federal Institute of Technology in Zurich, Switzerland. “There is a significant body of evidence sitting in drawers and hard drives that supports this concept, but people aren't putting it out,” he says. “It's still a major problem.”
Some researchers also question the broader assumption that molecular damage of any kind causes ageing. “There's a question mark about whether really the whole thing should be chucked out,” says Gems. The trouble, he says, is that “people don't know where to go now”.
In December 1945, chemist Denham Harman's wife suggested that he read an article in Ladies' Home Journal entitled 'Tomorrow You May Be Younger'. It sparked his interest in ageing, and years later, as a research associate at the University of California, Berkeley, Harman had a thought “out of the blue”, as he later recalled. Ageing, he proposed, is caused by free radicals, reactive molecules that build up in the body as by-products of metabolism and lead to cellular damage.
Scientists rallied around the free-radical theory of ageing, including the corollary that antioxidants, molecules that neutralize free radicals, are good for human health. By the 1990s, many people were taking antioxidant supplements, such as vitamin C and β-carotene. It is “one of the few scientific theories to have reached the public: gravity, relativity and that free radicals cause ageing, so one needs to have antioxidants”, says Siegfried Hekimi, a biologist at McGill University in Montreal, Canada.
Yet in the early 2000s, scientists trying to build on the theory encountered bewildering results: mice genetically engineered to overproduce free radicals lived just as long as normal mice4, and those engineered to overproduce antioxidants didn't live any longer than normal5. It was the first of an onslaught of negative data, which initially proved difficult to publish. The free-radical theory “was like some sort of creature we were trying to kill. We kept firing bullets into it, and it just wouldn't die,” says David Gems at University College London, who started to publish his own negative results in 2003 (ref. 6). Then, one study in humans7 showed that antioxidant supplements prevent the health-promoting effects of exercise, and another associated them with higher mortality8.
Nutrition: Vitamins on trial
None of those results has slowed the global antioxidant market, which ranges from food and beverages to livestock feed additives. It is projected to grow from US$2.1 billion in 2013 to $3.1 billion in 2020. “It's a massive racket,” says Gems. “The reason the notion of oxidation and ageing hangs around is because it is perpetuated by people making money out of it.”
Today, most researchers working on ageing agree that free radicals can cause cellular damage, but that this seems to be a normal part of the body's reaction to stress. Still, the field has wasted time and resources as a result. And the idea still holds back publications on possible benefits of free radicals, says Michael Ristow, a metabolism researcher at the Swiss Federal Institute of Technology in Zurich, Switzerland. “There is a significant body of evidence sitting in drawers and hard drives that supports this concept, but people aren't putting it out,” he says. “It's still a major problem.”
Some researchers also question the broader assumption that molecular damage of any kind causes ageing. “There's a question mark about whether really the whole thing should be chucked out,” says Gems. The trouble, he says, is that “people don't know where to go now”.
יש שם עוד כמה מעניינים:
The science myths that will not die
