You are what you eat, right? Right, but what's even truer is that you are what your gut microbes eat.

And this appears to be one of the reasons giant pandas are struggling to survive. The microbes inside their guts are "optimized to digest meat" -- this despite the fact that pandas have been eating a nearly exclusive diet of bamboo for some 2 million years.

This conclusion comes from researchers' analysis of panda droppings. They collected fecal matter from 45 pandas in the wild -- in spring, summer and fall -- and sequenced the DNA. The findings are published in the microbiology journal mBio.

"The giant panda evolved from omnivorous bears," the study states. "It lives on a bamboo-dominated diet at present, but it still retains a typical carnivorous digestive system and is genetically deficient in cellulose-digesting enzymes."

The paper adds: "The peculiar characteristics of its gut microbiota may put it at high risk of extinction."

The giant panda is arguably the most beloved animal in the world. But despite decades of effort from conservationists (the panda is the symbol of the World Wildlife Fund), the animal remains endangered. Fewer than 2,000 giants pandas live in the wild, and the animals are well known for having trouble reproducing.

There are many reasons for the giant panda's perilous state, but the low diversity of its gut microbes is definitely not helping the situation. It is becoming conventional wisdom that high diversity in gut microbes makes it easier for animals to adapt to changing environments. The giant panda is not adapting.

"Unlike other herbivores that have successfully evolved anatomically specialized digestive systems to efficiently deconstruct fibrous plant matter, the giant panda still retains a gastrointestinal tract typical of carnivores," the researchers write.

In short, pandas' insides have not evolved to meet their dietary preferences. Their microbes would still like to snack on meat. "They did not develop a longer gut to give themselves more time to break down stubborn plant parts, as other herbivores did," the Los Angeles Times points out. "Nor did they adjust their DNA to make different kinds of enzymes that would have helped them digest bamboo."

As a result, their meals over the evolutionary long haul are not making them stronger and better. They're merely keeping them alive -- for now.

-- Douglas Perry