Prebiotics are soluble fibers that stimulate the growth of beneficial bacteria in the digestive tract. Gastrointestinal problems are common the first couple of days on a diet with an increased amount of prebiotics. It takes time for the gut flora to adjust.
- The most common types of prebiotics include oligofructose and inulin. Studies show that these two soluble fibers significantly increase the growth of bifidobacteria (1-5). Inulin and oligofructose are found in foods such as chicory roots, onions and leeks.
Pectin has shown some potential as a prebiotic and can be found in apples, citrus fruits etc.
Healthy gut flora is vital for optimal health, and diverse gut flora is needed for proper digestion. Few microbes cause disease, and there’s several different ways to come in contact with new species.
In earlier times, fermentation was one of the most common ways of preserving foods. Different types of yeast and bacteria help ferment and preserve the food. Common fermented foods include:
- Fermented dairy
Different types of lactic acid bacteria are used in the fermentation of dairy products. Aged cheeses, sour cream, yogurt and fermented milk are all examples of fermented dairy products. Get unpasteurized, grass-fed and whole-fat dairy if you can.
Make your own or be sure to get properly fermented sauerkraut, not the dead stuff you’ll find in the average supermarket. Sauerkraut contains several different species of lactic acid bacteria and other types of bacteria that might be of benefit (6).
Make your own kefir or be sure to get quality kefir made from kefir grains, not starter culture. Kefir contains a wide variety of microorganisms (7,8).
- Fermented dairy
Probiotic organisms are live microorganisms thought to be beneficial to the host organism. Supplements provide some microbial strains that might be of benefit. What to look for when choosing a probiotic supplement
In the modern civilization we use harsh chemicals to clean everything around us. This might help us stay clear of harmful pathogens, but it will also make it harder to come in contact with new types of microorganisms that might be of benefit. Washing your hands and body with harsh soaps and antibacterials will have the same effect.
Pasteurization and heating also removes the naturally occurring bacteria in foods and drinks.
In primitive cultures we can assume that they came in contact with microorganisms from hands, dirt etc. This incorporated new strains of bacteria in the gut.
Minimally washed and unprocessed vegetables, spices/herbs, mushrooms, berries etc. are contaminated with microorganisms. Foods from your own garden would be great, but organic also works. Healthy soil contains beneficial bacteria like Clostridium spp. and Bacillus spp..
Every time your breath you release a mist of bacteria, and staying in contact with healthy individuals is a potential source of new bacterial strains.
Humans have eaten animal products since the dawn of time, and one study estimates that our ancestors got around 50% of their energy from animal food sources (9). The exact amount depended on geographical differences. Humans living closer to equator have usually gotten more of their energy from plants, fruits and vegetables than people living closer to the poles.
Meat, fish and fowl contain few gut-irritating substances and are usually easily digested.
Some components in animal products are also digested by enzymes of the gut flora, and this makes it possible for people to live almost exclusively on animal products and still have a functioning gut flora.
Eggs are a good source of protein, fats, minerals and vitamins. Eggs are one of the most concentrated sources of dietary cholesterol, but it has been shown that dietary cholesterol has minimal effects upon blood cholesterol in most people (10,11). It has even been shown that regular egg consumption reduce harmful cholesterol levels (12,13). The evolutionary strategy eggs have taken to protect themselves from microbial invaders is to select toxic substances in the egg white; mainly in the form of antimicrobial proteins. These egg white proteins have some of the same functions as lectins found in grains and legumes.
From an evolutionary standpoint it’s safe to assume that eggs have been part of the human diet for a long time. In nature, bird eggs only appear seasonally, and a point can be made for a moderate egg consumption.
Vegetables are the most important source of soluble fiber that feeds the gut flora.
In general, all types of vegetables can be included in the diet. However, nightshades contain certain gut-irritating substances and should be limited in sensitive people.
Great sources of calories and healthy fats.
Mushrooms are a good source of vitamins and minerals. “Mushroom” describes a variety of gilled fungi that can be problematic for people with candida overgrowth.
Extra Virgin Olive Oil, Coconut Oil and Avocado Oil are great sources of calories. Some oils made from nuts can also be a part of your diet if you tolerate them.
Butter and GHEE contain very little lactose, casein, hormones, bio-active peptides and other problematic components found in milk. They can safely be used as dense sources of calories.
- Fermented foods
Fermented dairy is usually well tolerated by most people, and grass-fed, full fat and unpasteurized dairy is the best choice.
Pathogenic bacteria in raw dairy are rarely found, but fermentation will get rid of E.Coli (14) and most other harmful microorganisms! One of the biggest issues with milk is that it contains a wide variety of hormones and growth factors (15), and it’s likely that many of these breach the gut barrier (14,16). Fermentation decreases insulin-like growth factor-I in milk (17), and reductions in other hormones and growth factors seems likely. “Studies have found that the survival of probiotics could be strongly enhanced with dairy products as delivery vehicles” (18, 19). Some may argue that intolerance to dairy products is normal and that it for that reason should be avoided. However, the bacteria usually feeds on lactose so the amount of lactose left in fermented dairy is minimal.
Contain antioxidants and can be be used for seasoning. The consumption of some hot spices has been linked to increased intestinal permeability (20). Eat in moderation if tolerated.
Alcohol abuse has been linked to increased intestinal permeability (21,22). It has also been shown in a study that “leaky gut may be a necessary cofactor for the development of chronic liver injury in heavy drinkers” (23). However, a moderate alcohol consumption is probably fine for most people. Wine and pure spirits are good choices.
Nuts and seeds contain some antinutrients, but most people can eat them in moderation. Especially Phytic Acid is a problem, but it’s possible to decrease the amount of Phytic Acid by soaking, sprouting or roasting (24).
Common nightshade vegetables include potatoes, tomatoes and eggplants. Nightshades contain small amounts of Glycoalkaloids which are a family of “poisons”. They are active as pesticides and fungicides and are produced by the plant as a natural defence against animals, insects and fungi. The levels of Glycoalkaloids found in tomatoes, aubergines and most other nightshades are generally low and therefore not a concern. However, potatoes and other tubers have higher amounts of Glycoalkaloids. The levels of Glycoalkaloids in potatoes have been linked to increased intestinal permeability in animals and humans (25-29). Food processing (cooking, baking, frying) doesn’t significantly alter the Glycoalkaloid content (30). Glycolkoids in potatoes and other nightshades rarely cause acute problems. However, if glycoalkoid-containing foods are a big part of the diet they might contribute to increased intestinal permeability over time.
Potatoes are also a source of dietary lectins, which may cause gut issues. (31, 32) Nightshade vegetables, and especially potatoes, shouldn’t be a big part of a gut-healthy diet. Sweet potatoes contain far less gut-irritating substances and are the preferred choice when looking for a source high in carbohydrates.
Avoid or eat in small quantities
When looking at the gut flora we’re mostly interested in “sugars” ability to change the gut flora and cause other types of gut issues. Studies show that a typical western diet high in sugar and grains promotes an unhealthy gut flora composition (32). Too many sugary foods and processed carbohydrates increase numbers of Candida species, Streptococci, Staphylococci, some Clostridia species, Bacteroids and some aerobic opportunistic bacteria (33). When you eat a meal high in carbohydrates blood glucose levels rise. A diet containing a lot of carbohydrates, especially simple sugars, promotes gut dysbiosis. This is supported by research showing that Candida grow when supported by glucose (34).
“It is evident that vaginal colonization by C. albicans in humans increases with the hormonal changes and increased glycogen secretion that occur during pregnancy. The relevance of the latter change is supported by the observation that uncontrolled diabetics are also prone to develop cutaneous candidiasis. It is the increased concentration of glucose in the body secretions of these diabetics which is thought to play a role in their susceptibility to Candida disease” (35).
- Insulin response
Grain consumption leads to a strong insulin response and increased blood glucose. Consumption of grains and especially processed grains increase the numbers of certain members of the opportunistic flora and thereby contribute to gut dysbiosis.(33)
Research shows that grains contain antinutrients such as Alkylresorcinols, Alpha-Amylase Inhibitors, Protease Inhibitors and Lectins. Dr. Loren Cordain has done a lot of research on these antinutrients and the detrimental effect they have on human health (36).
There’s several different types of antinutrients and not all of these are problematic for humans. Especially WGA (Wheat Germ Agglutinin) has been linked to disrupted gut physiology (37-41).
Gluten often cause gastrointestinal problems even in people without celiac disease (42). Gliadin, one of the proteins in gluten, has been linked to increased intestinal permeability in both patients with and without celiac disease (43).
Anti-gliadin IgA is an antibody produced by the gut and end up in the stool if the body sensed that gliadin was a threat. Dr. Kenneth Fine of EnteroLabs developed an assay that detects anti-gliadin IgA in stool. He found that 29% of asymptomatic (healthy) people are positive by the fecal test.
- Insulin response
Legumes pose many of the same problems as grains. They contain many of the same antinutrients as grains and should not be a substantial part of the human diet. If you find that you tolerate legumes well, they can be properly prepared and eaten in moderation.
Dairy is a frequently discussed food item in the paleo community. A case can be made that milk isn’t meant for human consumption and Dr. Loren Cordain, founder of The Paleo Diet, lists 15 important points why milk shouldn’t be a part of a healthy diet (44).
Casein is a milk protein and in people with a damaged gut flora these proteins do not get digested properly (33).
However, including fermented dairy products in the diet is probably fine for most people.
Most vegetable oils are high in omega-6 and should be avoided or eaten in small quantities. These oils potentially contain some of the antinutrients present in the grains they are made from (45).
Why choose organic or wild produce?
You should try to get as much of your food as possible from organic sources. Farming, animal feeding, use of chemicals and so forth varies between countries. There’s also different regulations when it comes to organic farming.
Conventionally raised animals are often given some sort of grain as their staple food. Most animals aren’t designed to eat grains as a big part of their diet, and grains cause some of the same problems as in humans. Some conventionally raised animals are even given animal products and unnatural substances. This puts their health in jeopardy and when an animal is unhealthy, the meat and other products made from it will also be of poor quality.
- “Grain feeding seems to promote the growth and acid resistance of Escherichia coli in fattening beef cattle, and acid-resistant E. coli are more likely to survive the human gastric stomach. When cattle were fed hay for only five days, the number and acid resistance of E. coli decreased dramatically” (46).
- Eggs currently sold in supermarkets are nutritionally inferior to eggs produced by hens raised on pasture (47).
- Cattle raised on grass provide meat that is higher in omega 3, CLA and vitamin E (48).
Crowded living conditions and poor diets make illness more common in industrial farming. Antibiotics are used to treat sick animals and are often given as a preventative dose even to healthy animals. They are also used to make the animals grow faster.
Antibiotics cause the same issues in animals as they do in humans.
We’re also getting bacteria that are resistant to antibiotics and can reach you as a consumer through food, the environment (49) or direct contact with the animals.
“Scientists believe about two-thirds of American cattle raised in for slaughter today are injected with hormones to make them grow faster and America’s dairy cows are given a genetically engineered hormone called rBGH to increase milk production” (48). These hormones don’t only cause problems in the animals, but can reach you through the foods you are eating.
Fruits and vegetables
Pesticides, herbicides, insecticides and chemical fertilizers shouldn’t be consumed by humans (48).
Soil quality is a vital component in the production of quality fruits and vegetables. Different microorganisms in the soil have different functions and poor soil quality leads to inferior products. Soil clinging to edible plants is a good source of bacteria, but should come from a trusted source to avoid chemicals etc.
Generally supplements aren’t needed if you stick to the diet. If you stick to this type of diet, deficiencies are rare and most likely due to an underlying problem. Prebiotics and probiotics are recommended if you have trouble getting them through other sources. Omega-3 supplements are recommended if you eat small amounts of food containing omega-3.
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