Scientists have known for decades that drastically reducing calories -- but not nutrients -- can prolong the lives of everything from yeast to mice and monkeys, but they didn't know why, until now.
In a study released Thursday, US researchers suggest that the link between food restriction and longevity may be a molecular response to the stress from cutting back calories.
That reaction preserves critical cellular functions, helping the body to fight off age-related diseases.
In laboratory experiments on human cells, investigators found that cutting calories, while preserving the nutrients they need, starts a chain reaction in the mitochondria -- or power houses of the cell -- that results in the build-up of a coenzyme called NAD (Nicotinamide adenine dinucleotide).
This in turn amps up the activity of enzymes created by two genes called SIRT3 and SIRT4. The effect of all this is to strengthen the mitochondria, increase energy output and slow down the cell's aging process.
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