A member identified as Tanya O responded: "The food myths that bug me the most are: 'All carbs are bad,' and 'It is difficult for vegetarians to get enough protein' - gorillas are vegan and they don't have a problem :)'"
I remembered reading a post by Dr. Barry Groves on his website, Second Opinions, that specifically mentioned gorillas, so I went back to refresh my memory before posting a reply to Tanya with a link to his article.
Dr. Groves says, "No mammal - not even the herbivores - has developed an enzyme that will digest vegetable fibre. This is why we tend to discount it when calculating our calorie intakes, however, while mammals have not developed an enzyme that will digest fibre, there are lots of micro-organisms and bacteria that can do the job for them. The herbivores employ billions of these bacteria...." He goes on to discuss the digestive systems of various mammals, including gorillas and humans.
Herbivores derive nutrients from fiber in two ways. Some, like cattle, sheep, and deer, are foregut digesters. They have multiple stomachs that serve as fermentation tanks where fiber is broken down by bacteria. The dead bacteria then provide short-chain fats that nourish the animal. I took this picture showing the digestive system of a bison in a museum in Montana this past summer. The four stomachs are numbered.
Animals like rabbits, pigs, horses, and gorillas are hindgut digesters. They absorb some nutrients through the stomach and small intestine in the same way carnivores do, but the fiber in their diet is fermented to produce short-chain fatty acids (saturated fats) in the cecum and the colon. These fats are then used as fuel.
All herbivores use one of these two methods to get energy from what appears to be energy-deficient food sources. Obviously, all of them are adapted and designed to live on a high-fat, low carbohydrate diet, with a moderate amount of protein. The illustration below, from Dr. Groves, shows the difference between the digestive tract of a carnivore and a hindgut-digester, such as a gorilla. The gorilla's cecum, the long, spiral-shaped organ in the picture on the right, is analogous to the small human appendix. It is used to breed enormous quantities of bacteria that convert fiber into fat. The gorilla's diet of leaves ultimately breaks down to provide 24.3% of calories from protein; 15.8 % from carbs, and 59.8% from fat.
I encourage you to read all of the 3-part article by Dr. Groves (www.second-opinions,co.uk/should-all-animals-eat-a-high-fat-low-carb-diet.html) so you will be prepared with an answer should you encounter someone like Tanya or Alicia Siverstone, the actress-turned-activist, who says she became a vegan because she loved her dog. When asked what she feeds her dog, she said she gives him the "same healthful, vegan food" that she eats. Poor doggie. She should get a rabbit.
(C) 2011, Judy Barnes Baker, Carb Wars; Sugar is the New Fat