Metchnikoff · Lactic bacteria and ageing
Does eating yogurt make you live longer?
That time, that place
Metchnikoff was a Russian-born scientist working at the Pasteur Institute. He was the first to see cells in the body swallow bacteria, and won the Nobel Prize for it in 1908.
But in his last years he held a different question. Why do we age?
Why this question
He believed ageing came from the bacteria in the gut. Bad bacteria there give off poisons, he thought, and the poisons slowly wear the body down.
Then what if you put good bacteria in instead? He heard that villages in Bulgaria had many very old people. They ate sour milk — yogurt — every day.
What was found
The bacteria that sour yogurt — lactic bacteria — push the bad bacteria out of the gut, he argued. And he ate yogurt every day himself.
He never proved it. Whether Bulgarian villagers really lived so long was never certain either. He died at seventy-one: long for the time, but not a hundred.
Yet his question survived. The idea that the bacteria living in your gut affect your whole body became real science a century later.
Gut bacteria are just things living on digestive waste
A rumour of long-lived yogurt-eating villages — a clue rather than evidence
The probiotic drink industry began here. In the 2000s, when gene-reading let scientists count hundreds of gut species at once, some of his guesses turned out right and some wrong