Mind & Body

From Day to Night, Your Liver Grows and Shrinks Dramatically

The brain and the heart get a lot of attention, but we think the liver deserves way more time in the spotlight. This organ keeps your sugar levels constant, stores and releases vitamins and minerals into your body as needed, detoxifies your blood, and has a remarkable ability to regenerate. But a study uncovered another fascinating feature: It grows by day and shrinks by night. And that's more than just a cool trick.

Does This Make My Liver Look Big?

Scientists have known that animals follow a "body clock" that triggers regular cycles of function in their brains, organs, and even their cells. But while the liver is also beholden to this internal clock, its function may also depend on when you eat and when you exercise. "Many of them are also influenced by the rhythm of food intake and physical activity, and we wanted to understand how the liver adapts to these fluctuations," Ueli Schibler, professor emeritus at the Department of Molecular Biology the Université de Genève, said in a press release.

In May 2017, Schibler and a team of researchers published a study in the journal Cell that confirms that the liver is very in tune with the body's clock. They studied mice and saw that their livers grew by nearly half during waking hours (which, for mice, is night), and shrunk back down to "normal" size at mousey bedtime.

Specifically, the researchers saw hepatocytes — the main kind of liver cell — growing while the mice were active at night. They credit this growth with the number of ribosomes (the organelles that produce the proteins required for various liver functions), which also fluctuates with the size of the cells. The more ribosomes, the better equipped the liver is to process food into protein and rid the body of toxins. As bedtime draws near, the liver cells start tagging and bagging those excess ribosomes, helping the liver shrink down to its resting size again.

It's Past Your Bedtime, Mister

The study found that the livers of mice that were active and feeding during their usual times (nighttime) reached peak efficiency and size. Weirdly, when the researchers forced the poor mice to flip-flop their schedule so they were eating and being active during the day, the fluctuation of their liver sizes stopped, despite the fact that they were eating just as much. That's the bottom line here: The liver seems to be synced up with the body's circadian rhythm.

We have reason to believe the same liver size shifting happens in humans too, not just mice. A 1986 study found that even over a six-hour period, you can detect size changes in the human liver. So, what does this mean for you and your liver? Your sleeping habits — which, no judgment, are probably not perfect — are keeping your liver from functioning the best it can. The longer your liver operates poorly, the more likely it is that you'll experience unpleasant symptoms like fatigue, swelling, a tendency to bruise, and even jaundice. Add this to the list of why regular, full nights of sleep are so very important.

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For a deep-dive into another underrated organ, check out "Gut: The Inside Story of Our Body's Most Underrated Organ" by Giulia Enders. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Joanie Faletto May 26, 2017

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