Gorillas are primarily herbivores, though they have been reported to consume some insects in the wild. Their primarily herbivorous diet may be essential for health. Elevated cholesterol concentrations may lead to premature cardiovascular disease, which is reported to be the leading cause of mortality in captive adult gorillas. Mimicking the nutritional composition of the high fiber, low sugar diet of free-ranging gorillas will promote healthier gorillas. Feeding gorillas animal products, including dairy and eggs, is not recommended as they may promote obesity and increase cholesterol concentrations. The only exception to this would be when hand-raising gorilla infants. At those times human infant formulas supplemented with omega fatty acids are recommend for use over cow's milk.
Successful diets fed to captive gorillas may consist of the following components: 7% fruits, 57% leafy green vegetables, 4% root vegetables, 17% other vegetables and 15% high-fiber primate biscuits. The fruit portion of the diet may be reserved for training. Since fruits and primate biscuits are the most calorie dense items, feeding them to animals individually will help control caloric intake, especially for overweight individuals. Some zoos with obese animals may consider completely eliminating fruit from the diet of gorillas. Browse material is not readily available year-round at northern-climate zoos, so the amount of vegetable material used for forage may be provided at comparatively higher levels than zoos in more temperate climates. Although current diets may contain fruit and vegetable produce equaling about 50% of total food offered, it is suggested that the proportion of fruit in diets be reduced, and vegetable produce increased. Vegetables appear to contain a more suitable nutrient composition than fruits for lowland gorillas, and also provide an economic alternative to fruit.