The idea of not consuming fruits with meats, vegetables, or grains at the same meal originates from unfamiliarity with the digestive system. The theory is founded under the belief that these foods require a longer time to digest in the stomach than fruits because of different ratios of macronutrients (carbs, fat and protein).
Fruits are primarily composed of carbohydrates including sugar, whereas vegetables and grains contain mostly complex carbs and protein and meat is primarily protein. The theory is that while these foods continue to be metabolized, the sugars from the fruit are at risk for being fermented in the stomach. The fermentation process produces excess gas leading to bloating and GI discomfort. However, there are several flaws in this conclusion.
The production of gas through fermentation is created by living microbes feeding on carbohydrates. The stomach’s primary role in digestion is to break down proteins in our food but also in microbes that are frequently ingested. This is accomplished by the stomach’s natural production of hydrochloric acid and specialized enzymes called proteases. Because the stomach is very acidic, it makes a hostile environment for living organisms including those involved in fermentation. Carbohydrate digestion, including sugar, begins in the mouth with the enzyme amylase but is inactive in the stomach. Their digestion resumes in the small intestine when the pancreas releases more amylase through the pancreatic duct. The pancreas also releases lipases to break down fat as well as proteases to continue protein digestion.
Fermentation does occur during digestion but not until the large intestine, which provides a more suitable environment for living organisms than the stomach. Here trillions of bacteria live and directly influence overall health.
The digestive process is intricately designed to metabolize all of the macronutrients as well as essential vitamins and minerals simultaneously. Our bodies are designed for survival and it is advantageous to be able to metabolize and extract nutrients from all foods when they are available. Enjoying plant foods and meats in their whole form in many combinations provides the body access to a variety of essential nutrients, unique flavors, and textures.