The phrase “this product destroys the intestines” sounds impressive, but it does not describe the real physiology well. One serving of chips, sausage or dessert does not destroy the intestinal microbiota. The overall structure of the diet is important: what a person eats regularly, how much fiber they get, how diverse the plant-based food is, and what part of the menu is occupied by ultra-processed foods.
Points of attention
- Ultra-processed foods, processed meats, sugary drinks, and low-fiber foods can negatively impact the gut through changes in the microbiota.
- It is important to balance your diet with a variety of plant-based foods to maintain gut health and gut microbiota.
- A healthy diet, with an emphasis on whole grains, vegetables, fruits, and legumes, promotes gut health.
Of greatest concern is a diet high in industrial snacks, processed meats, sugary drinks, alcohol, and refined foods, but low in vegetables, fruits, legumes, and whole grains.
Current research links high consumption of ultra-processed foods to changes in gut microbiota, reduced diversity, and potential disruption of the gut barrier. However, many mechanisms are still being studied, and the effects of a particular food depend on the amount, frequency, and overall diet.
What does "healthy gut" mean?
Gut health is much more than the absence of pain or constipation.
A normally functioning digestive system should efficiently digest food, absorb nutrients, maintain regular bowel movements, and protect the body from potentially dangerous microorganisms.
An important role is played by the intestinal microbiota — a vast community of bacteria and other microorganisms that live mainly in the large intestine.
Some bacteria ferment dietary fiber and produce short-chain fatty acids, including butyrate, acetate, and propionate. These substances are involved in maintaining the intestinal barrier, regulating the immune response, and metabolic processes.
Therefore, one of the most important ways to support your gut is to regularly give bacteria a substrate to work with: fiber from vegetables, fruits, legumes, whole grains, nuts, and seeds.
1. Ultra-processed finished products
Ultra-processed foods may include industrially prepared meals, snacks, some sweet breakfasts, desserts, bars, and products with a significant amount of industrial ingredients.
The problem is not the fact of factory production itself.
Frozen vegetables, plain yogurt, canned beans, or whole grain bread also undergo some processing, but can still be a nutritious part of the diet.
Ultra-processed foods often have a different combination of properties:
little natural fiber;
high energy density;
a lot of salt or free sugars;
refined starches;
various technological additives;
very high taste appeal, which makes it easy to overeat.
Gut microbiota studies are increasingly linking high levels of ultra-processed foods in the diet to changes in microbial community composition. However, the researchers emphasize that the causal mechanisms in humans are not yet fully established.
The practical guideline is simple: it is better to form the basis of the menu from minimally processed products, and leave ready-made snacks and desserts as an addition.
2. Sausages, hot dogs, bacon and other processed meats
Processed meats are products that have been salted, smoked, fermented, cured, or otherwise treated to alter flavor or extend shelf life.
These include:
sausages;
sausages;
bacon;
salami;
part of the tavern;
smoked and cured meats.
The problem goes beyond the microbiota. There is strong evidence linking regular consumption of processed meat to an increased risk of colorectal cancer. The World Cancer Research Fund recommends consuming as little as possible.
Microbiome studies also show that high levels of processed red meat consumption may be associated with reduced microbial diversity and changes in bacterial functional activity. A large 2025 study of nearly 9,700 people found significantly more associations with the microbiota specifically for processed red meat than for unprocessed red meat.
Substitutes can include fish, legumes, eggs, poultry, and unprocessed meat in moderation.
3. Chips and industrial salty snacks
Chips, cheese snacks, flavored crackers, and similar foods combine several unfavorable characteristics.
They are typically low in fiber, high in salt, and high in energy density. They often crowd out nuts, fruits, dairy products, and other more nutritious snacks.
The problem for the intestines arises primarily when such snacks become a daily part of the menu.
The body does not need to completely avoid potatoes or salt. The question is the form of the product and the frequency of consumption.
A baked potato with vegetables and protein and a big bag of chips in front of the TV have completely different nutritional values.
4. Sugary carbonated drinks
Carbonation itself does not “destroy” the intestines. The main problem with regular sweet carbonated drinks is the large amount of free sugars.
They are quickly consumed, provide little to no satiety, and can significantly increase overall sugar intake.
The World Health Organization recommends limiting free sugars to less than 10% of daily energy, and reducing to around 5% may have additional benefits.
Another problem for the microbiota is that a sugary drink usually does not contain fiber.
For example, an orange provides water, natural sugars, fiber, and plant compounds. Sweet soda is mostly water, sugar, and flavorings.
Water remains the best everyday replacement. Unsweetened tea or sugar-free sparkling water are also suitable if well tolerated.
5. A large number of sweets and industrial pastries
Cookies, waffles, cakes, donuts, and other desserts do not become toxic to the gut after one bite.
The problem arises when they systematically take up a significant portion of the menu.
Such products often combine:
refined flour;
a lot of sugar;
a significant amount of fat;
low in fiber;
high calorie content.
If cookies regularly replace fruit, and sweet pastries are a normal breakfast, the intestinal microbiota receives less dietary fiber.
The lack of plant foods may be more important than having a separate dessert.
6. White bread and refined grains — when they replace whole grains
White bread, white rice, or regular pasta are not “poison for the gut.”
The problem lies in the degree of grain purification. During the production of refined products, part of the grain shells are removed, which reduces the amount of fiber.
If almost all grain products on the menu are refined, the total fiber intake may be low.
The WHO recommends that adults and children over 10 years of age get at least 25 g of natural dietary fiber per day and prefer carbohydrates from whole grains, vegetables, fruits, and legumes.
To prevent constipation, the American NIDDK recommends a guideline of approximately 22–34 g of fiber per day, depending on age and gender.
Therefore, instead of banning white bread, it is more practical to gradually increase the proportion of oatmeal, buckwheat, whole grain bread, barley, legumes, and vegetables.
7. Alcohol
Alcohol can affect the digestive tract mucosa, intestinal motility, intestinal barrier permeability, and microbiota composition. The effect depends on the amount, frequency, health status, and overall lifestyle.
At high doses, diarrhea, heartburn, nausea, and abdominal pain may occur after alcohol.
It is also worth remembering that alcohol increases the risk of several cancers, including colorectal cancer. The WHO notes that there is no established level of alcohol consumption that can be considered completely safe in terms of cancer risk.
Therefore, a glass of wine should not be recommended “for the microbiome” because of polyphenols. Plant compounds can be obtained from berries, grapes, vegetables and other ethanol-free foods.
8. Products with high amounts of certain emulsifiers
Emulsifiers are used to keep water and fat mixed and the product has a stable texture.
They are found in separate:
desserts;
ice cream;
sauces;
ready meals;
confectionery products.
Interest in them arose after experimental studies in which some emulsifiers affected the intestinal microbiota and mucosal barrier.
Human data is also emerging, but it is too early to draw conclusions about the entire group of supplements.
In a small controlled study, carboxymethylcellulose altered the composition of the microbiota and metabolome in a subset of healthy participants. However, the study included only 16 people.
In a larger study of five emulsifiers, 2025 observed individual changes in the microbiota and decreased short-chain fatty acid concentrations, but did not find convincing worsening of systemic inflammation or intestinal permeability indices.
That is, the formula “any emulsifiers destroy the intestines” is not confirmed. It is more practical to reduce the total share of ultra-processed food, rather than hunting for each individual food additive.
9. Drinks and foods with a lot of sweeteners
Non-caloric sweeteners are often presented as either a completely safe alternative to sugar or as the main enemy of the microbiome. Both statements are too categorical.
Human studies show that individual sweeteners can alter the composition of the microbiota, and the effects vary between substances and people.
In a randomized trial of 120 healthy adults, saccharin, sucralose, aspartame, and stevia caused different changes in the microbiome; saccharin and sucralose also affected glycemic responses.
This does not prove that one can of sugar-free soda will harm your gut.
The data remains mixed, and results depend on the specific sweetener, the amount, and the individual.
Therefore, it is better to keep water as your main drink, rather than replacing several sweet carbonated drinks every day with the same amount of "zero" ones.
10. A lot of fried food and fast food
Fast food is a very broad category.
A burrito with beans, vegetables, and chicken and a double burger with fries and a large sweet soda may formally be sold in fast food restaurants, but their composition is different.
The most problematic is a regular diet high in fried foods, saturated fats, refined carbohydrates, and salt, while lacking fiber.
The WHO recommends replacing some saturated fats with unsaturated fats and getting more carbohydrates from whole grains, legumes, vegetables, and fruits.
If fast food appears occasionally in a varied diet, this is a completely different situation than a daily diet consisting mainly of ready-made meals.
11. Excess red meat in a diet with little plant food
Red meat provides complete protein, iron, zinc, and vitamin B12. Therefore, calling it a “gut-busting” food is incorrect.
Studies on the effects of unprocessed red meat on the microbiome have yielded mixed results. A systematic review of randomized trials found that changes in bacterial composition depend on the type of meat, overall diet, and many other factors, with no single clear pattern.
A diet that is high in meat and low in vegetables, legumes, and whole grains looks more problematic.
In such a situation, not only protein is important, but also what has disappeared from the plate.
Instead of completely giving up meat, it is more advisable to replace some meat dishes with fish and legumes and add vegetables to main meals.
12. “Healthy” foods that people actually have trouble with
There is a fundamental difference between a product that negatively affects health when consumed in excess on a regular basis and a product that causes symptoms due to a specific intolerance.
For example, milk is a nutritious product. But in lactase deficiency, a significant amount of lactose can cause:
bloating;
gas formation;
cramps;
diarrhea.
Wheat is normally tolerated by most people, but in celiac disease, gluten causes immune damage to the lining of the small intestine.
In irritable bowel syndrome, symptoms may occur after eating onions, garlic, apples, legumes, or other high-FODMAP foods. This does not make these foods “bad for the gut” in general.
That is why universal lists of prohibited foods often create unnecessary restrictions.
Is it necessary to give up gluten for a healthy microbiota?
Without medical indications - no.
Avoiding gluten is necessary for celiac disease. Some people may have other forms of sensitivity that require individual evaluation.
For the rest of the population, whole wheat can be a valuable source of fiber.
The gluten-free label alone does not make the product healthier. Gluten-free cookies with refined starch and sugar remain a dessert.
Do I need to give up dairy products?
Also no.
Natural yogurt and kefir can be good sources of protein, calcium, and fermented foods.
In a controlled study, a diet with an increased amount of fermented foods was associated with increased microbiota diversity and a decrease in some inflammatory markers, although these results do not mean that everyone should drink kefir every day.
With lactose intolerance, some people tolerate yogurt or lactose-free products well.
What to eat for gut health
Instead of looking for one probiotic yogurt or “detox product,” it’s better to evaluate your entire diet.
The most important component is a variety of plant foods.
A useful base can be:
vegetables of different colors;
fruits and berries;
beans, chickpeas, lentils;
oatmeal, buckwheat and other whole grains;
whole grain bread;
nuts;
seed;
natural yogurt or kefir if well tolerated;
pickled vegetables;
sufficient amount of liquid.
Increasing your fiber intake should be gradual. A sudden change from a nearly fiber-free diet to large portions of legumes, bran, and raw vegetables can cause bloating and gas.
For people with constipation, the NIDDK recommends increasing fiber gradually while maintaining adequate fluid intake.
A simple substitution principle works better than a list of prohibitions
Gut health is often easier to improve not through strict prohibitions, but through specific substitutions.
Instead of a sweet cereal breakfast, have oatmeal with berries.
Instead of sausage every day, have eggs, fish, chicken, or hummus.
Instead of cookies, snack on fruit and a small portion of nuts.
Instead of sweet soda, use regular or sugar-free soda.
Instead of white bread at every meal, eat more whole grain bread.
Instead of a ready-made frozen pizza, have a homemade dinner with vegetables, a protein source, and grains.
Such changes simultaneously reduce the proportion of ultra-processed foods and increase the number of substrates on which intestinal bacteria feed.
When the problem is no longer in nutrition
Abdominal pain, diarrhea, constipation, or bloating do not always mean “bad microflora.”
Similar symptoms may occur with:
irritable bowel syndrome;
celiac disease;
inflammatory bowel diseases;
lactose intolerance;
intestinal infections;
gallbladder diseases;
pancreatic dysfunction;
other conditions of the digestive system.
Blood in the stool, unexplained weight loss, persistent fever, anemia, nocturnal diarrhea, severe or progressive pain, and a sudden significant change in bowel habits require special attention.
In such cases, the search for another “harmful product” can distract from the true cause of the symptoms.
Conclusion
The intestines are not destroyed by one pizza, dessert, or portion of sausage. The main thing is that a person eats regularly.
The most reason to limit your intake is a diet high in ultra-processed foods, processed meats, alcohol, sugary drinks, and low-fiber foods.
To support the gut microbiota, it is important to increase the diversity of plant foods and fiber intake in parallel. This balance is much more important than trying to find one “worst” or “best” product for the gut.
FAQ
What foods are most harmful to the intestines?
Of greatest concern is the regular consumption of large amounts of ultra-processed foods, processed meats, alcohol, sugary drinks, and a low-fiber diet.
What foods are good for the intestinal microbiota?
Vegetables, fruits, berries, legumes, whole grains, nuts, and seeds provide different types of dietary fiber. Fermented foods can also be part of a healthy diet if well-tolerated.
How much fiber should you eat per day?
For people over 10 years of age, the WHO uses a guideline of at least 25 g of natural dietary fiber per day. Depending on age and gender, other recommendations for adults may be around 22–34 g.
Does sugar harm the intestines?
One serving of sweets does not destroy the microbiota. The problem is a regular excess of free sugars in the diet, especially when sugary foods crowd out fiber-rich foods.
Are sweeteners harmful to the microbiota?
Some sweeteners have been shown to alter gut microbiota composition in clinical studies, but the effects vary between substances and individuals. There is not enough evidence to conclude that all sweeteners are equally harmful.
Is it necessary to eliminate gluten for gut health?
No. Strict gluten avoidance is necessary for celiac disease. Without specific indications, whole wheat products can be a useful source of fiber.
Is kefir good for the intestines?
Kefir is a fermented product and can be part of a healthy diet. Its effect on the microbiota depends on the composition of the product and individual characteristics. It is not suitable for everyone with dairy intolerance.
What to eat when constipated?
The diet should usually be gradually enriched with vegetables, fruits, whole grains, legumes, and other sources of fiber while maintaining adequate fluid intake.
Can healthy foods cause bloating?
Yes. Legumes, apples, onions, garlic, and some other nutritious foods can trigger symptoms in people with irritable bowel syndrome or other digestive issues. That doesn't make them bad for everyone.
Can the microbiota be restored with probiotics alone?
There is no universal probiotic supplement that “restores the microbiota” for every person. The composition of intestinal bacteria is individual. For everyday health, the overall diet, variety of plant foods, fiber, physical activity, and a healthy lifestyle are much more important.
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