Could smells affect your lifespan? Female fruit flies deprived of the ability to smell food outlive their peers. The sense of smell may be linked to the cellular ageing process in many other organisms – even people.
A link has recently been found between sensory experiences and lifespan in both worms and flies. For example, Scott Pletcher, a molecular biologist at the University of Michigan, Ann Arbor, found that eliminating fruit flies' ability to smell any odour at all enabled them to live nearly 20 per cent longer than flies with an intact sense of smell.
Why is this so? Pletcher's team reasoned that food smells were the ones most likely to affect ageing, as nutrition and longevity are known to be linked in many organisms. For example, cutting the amount of food consumed lengthens the lifespan of yeast, mice and monkeys, and keeps a variety of diseases at bay in people.
To test the idea that food odours affect lifespan, Pletcher's team eliminated flies' ability to smell carbon dioxide, which is produced by some fly foods, such as live yeast. They left the rest of the olfactory system intact.
This intervention had no effect on male flies, but the females lived 30 per cent longer than normal. Pletcher reckons eliminating the ability to smell CO2 may deprive flies of information about food availability. This could signal to cells that food is scarce, triggering processes that promote survival.
Indeed, his team found that the CO2-insensitive female flies stored extra fat and that both males and females rendered immune to CO2 were more resistant to oxidative stress than normal flies.
Joy Alcedeo, a neuroscientist at Friedrich Miescher Institute for Biomedical Research in Basel, Switzerland, who has found links between lifespan and sensory experience in worms, says tastes are similarly linked to ageing.
Scent and sensitivity
Pletcher isn't sure why the change in his fruit flies only affected the lifespans of the females, but he suggests that females may simply be more sensitive to the odour of CO2.
Meanwhile, he has reason to believe that it's more than a lack of odours that can extend life in flies: specific odours may perform the same trick. His says his team has identified a brain circuit that extends lifespan when activated and which is also linked to the olfactory system. But he has yet to discover what smells might trigger it.
A smell or taste that stretches lifespan in humans could be a potential preventative for age-related disease, he adds. Although in fruit flies it appears to be the smell of CO2 that affects ageing, he says that an analogue in humans might be a smell or taste linked to human food – or a lack of it.
Matt Kaeberlein studies ageing at the University of Washington in Seattle. He cautions that we don't know whether ageing and smell are linked in mammals, but he's optimistic. "We definitely undergo physiological changes in response to smelling food – I'm getting hungry just thinking about it – so I think it's possible."
Journal references: Science 10.1126/science.1136610; PLoS Biology, DOI: 10.1371/journal.pbio.1000356
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