Everything you learned about getting nutrition from plants is wrong
People have always eaten plants. For a long time, everyone thought we couldn't break down a major plant constituent, cellulose. Cellulose is in plant walls and could give us calories, but it seemed we couldn't use it for energy. Even though we knew eating plants with cellulose was good for us, we thought cellulose had little to no nutritional value. Cows and horses, on the other hand, can digest plants to get energy.
In fact, I did a quick online search for “Can humans digest cellulose?” and came across links to a half-dozen Indian tutorial sites (yes, the wildly popular ones like BYJU’s and Unacademy) that proclaim confidently that we cannot digest this plant component because we lack the enzymes that break it down. The truth is a bit more complex.
A new study in the journal Science by scientists from Israel challenges this thinking. They find that microbes in our gut help to use cellulose for energy after all. This is the topic of my science column this week in Hindustan Times.
We didn’t always appreciate how important gut bacteria are. Back in the 1980s, researchers gave people a type of cellulose marked with a radioactive tag and tracked it. They expected all of it to pass through, but some of it didn’t.
So, where did the rest end up? Back then, scientists thought the cellulose in the study was impure, but now we know that some of it may have been digested by gut bacteria that can break down cellulose.
So here’s the bottom line. Research over the years has shown that some bacteria in our gut actually do break down cellulose, even if our own digestive cells can’t. This means we can get more from plant foods than we used to think.
In the new paper, researchers find bacteria that belong to the Ruminococcus family can break down cellulose into nutrients we can absorb. These bacteria seem to have come from animals our ancestors domesticated. They adapted to live in our guts by picking up genes from other bacteria and are now quite at home.
But here’s the really interesting bit. There seems to be more cellulose-digesting bacteria in people who eat lots of plants and less in those with “industrialized diets” aka city dwellers. In other words, we need to feed these gut microbes for them to stick around.
This is big news for a few reasons. It proves we can digest cellulose with the help of bacteria. It shows plant fiber is not just filler food that provides bulk, it’s a source of nutrients. And it suggests modern diets low in plant fiber might be missing out on their benefits.
This study could lead to new ways to improve our diet by boosting these bacteria in our gut.
But we probably don’t need fancy products sold as prebiotics to start benefiting. Michael Pollan’s sage advice works too: “Eat food. Not too much. Mostly plants.”
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