While the consumption of fermentable carbohydrates from vegetables, fruits and other plant-based whole foods is associated with growth of beneficial bacteria in the colon and increased production of short-chain fatty acids, there are examples of people who seem to maintain excellent health even on a diet with little to no plants. We know that healthy gut flora is one of the cornerstones of a well-functioning body and that fermentable carbohydrates found in plant-based foods are the primary fuel for beneficial gut bacteria, so how is it then that diets with little to no prebiotics in some cases cause no adverse effects?
In part 1 of the series of post on prebiotics we established that a lot of fermentable substrates work as prebiotics since the seem to stimulate the growth and/or activity of bacteria in the digestive system in ways claimed to be beneficial to health. In part 2 the focus was on health disorders that lead to poor breakdown of fermentable substrates. In this segment I’ll investigate how it’s possible for some people to maintain very good health even with little to no plants and fermentable substrates in their diet.
Some traditional cultures eat little to no plant-based foods, but still maintain good health
The traditional diet of the Inuit contained almost no plant-based foods while living a traditional lifestyle. They ate mostly seafood, land mammals, and birds, and around 75% of their energy intake came from fat. Their carbohydrate intake was very low, so the remaining 25% came primarily from protein. Despite their limited consumption of fermentable substrates, the Inuit were virtually free from chronic non-communicable disease. (1)
Other traditional people such as the Masai have also thrived on a high-fat, moderate protein and low-carbohydrate diet (2).
I believe there are four primary reasons why these people maintain such good health even when eating diets with little to no fermentable substrates:
- “Meat contains complex polysaccharides, e.g. glycosaminoglycans, such as chondroitin sulfate and heparan sulfate proteoglycans, which are bacterial fodder equivalent to soluble fiber.” (3)
- The Inuit breast-fed their children for about three years, and similar practices are often seen in other traditional hunter-gatherer societies. Mother’s milk is a rich source of both prebiotics and probiotics. Breastfeeding and vaginal birth both help colonize the gut of the newborn with healthy gut flora.
- Hunter-gatherer tribes usually have an extremely healthy lifestyle with nutrient-rich diets, no antibiotics, plenty of time outdoors etc.
- Most hunter-gatherers are continuously exposed to germs from food, dirt, and drinking water. Some tribes even eat the stomach and intestines (bacteria!!) of the animals they capture. (4) All of this exposure to microorganisms certainly increases the risk of coming in contact with pathogens, but it’s also important for developing a competent immune system and establishing a diverse human microbiome.
Plant-based foods contain no essential nutrients we can’t get from animal products
Vitamins and minerals
Although fruits, vegetables and nuts are considered important sources of several vitamins and minerals, the fact is that animal foods contain all of the micronutrients humans need. This is especially true if the diet is rich in a wide spectrum of animal source foods such as milk, eggs, bones (e.g., bone broth), and organs. Even vitamin C is found in the liver, brain and heart of many animals.
Gut flora also synthesize a lot of vitamins and minerals, and this partially explains why humans can survive on limited diets for a long period of time. While the general belief is that gut bacteria primarily synthesize vitamin B and K, it’s likely that we have only scratched the surface in regards to gut flora and vitamin synthesis and that gut bacteria are able to synthesise a lot of the nutritional chemicals humans need.
Plant-based foods are an important source of antioxidants that help decrease the incidence of oxidative stress induced damage in the body. While the latest scientific reviews show that consumption of antioxidant-rich foods is advantageous (5,6), there are several factors that could confound or impact the results in most of the studies:
– “There is no evidence to date that isolated antioxidants as food supplements improve health outcomes or survival” (7). In other words, it could be that some other component of the antioxidant-rich foods used in most trials is partially responsible for the favourable changes in health.
– Antioxidants are substances which can scavenge free radicals, and lifestyle factors such as smoking, diet and exercise impact the levels of free radicals in the body (8). I find it likely that the beneficial effects from antioxidant consumption is far greater for someone with a typical western lifestyle (e.g., western diets, antibiotics, little exercise), compared to hunter-gatherers eating nutrient-rich diets and living most of their lives outdoors. In other words, it’s possible that antioxidants are effective in reducing the damage that’s already been done, but a healthy lifestyle could limit the need for antioxidants in the diet.
Phytochemicals such as antioxidants warrant for a longer discussion, but this is outside the scope of this post.
Carbohydrates and fermentable substrates
Grains, fruits, vegetables and other plant-based foods are the primary sources of carbohydrate in the human diet, since animal source foods contain mostly fat and protein. Polysaccharides are complex carbohydrates that are broken down by bacteria in the gut (with the exception of starch), and this food for gut bacteria is almost exclusively found in plant-based foods.
Probably not optimal with no plant-based foods in the diet
While plant-based foods such as fruits, vegetables and nuts contain no essential nutrients that can’t be found in animal source foods, they do contain antioxidants and fermentable carbohydrates that have been linked to beneficial changes in in health.
Hunter-gatherer tribes who eat high-fat diets, low in fermentable substrates, probably maintain very good health because they eat nutrient-rich diets and spend plenty of time outdoors. These traditional people are also exposed to plenty of microorganisms (e.g., soil microbes) and also get prebiotics from mother’s milk and meat fibers.
In general it seems that the majority of people will benefit from including at the very least some vegetables in their diet.