Nobody’s digestion is perfect. And finding the foods that won’t frustrate your gastrointestinal tract is often a game of trial and error. Dealing with digestive concerns like gas, bloating, abdominal pain, diarrhea, or constipation aren’t fun. These problems may be caused by the FODMAP foods you’re eating.

FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols. (Saccharide is just another term for sugar.) These types of sugar can be minimized in the low-FODMAP diet some people adopt to support good digestive health.

Traditional health recommendations tell you to eat a large variety of fruits, vegetables, and whole grains. Research even shows a highly varied diet helps support a healthy gut and healthy microbiome. But no two people are exactly alike. Your diet may contain some normally healthy foods that your personal digestive system doesn’t work well with.

So, if you have digestive concerns, it might be worth limiting some of that variety in your diet. Low-FODMAP diets aim to eliminate or reduce the foods that most commonly feed into occasional indigestion and stomach discomfort.

What are FODMAPs?

To understand why you might be feeling the effects of FODMAPs in your diet, you first need a basic understanding of digestion in the gut. (Find a full recap of your digestive system here.)

After being broken down in your mouth and stomach, most of the food and liquid you eat is absorbed in your small intestine. Fiber and other waste products pass through the small intestine and into your large intestine.

The molecules that make it all the way into your large intestine become food for your microbiome. The sugars and carbohydrates that pass into the large intestine are fermented by bacteria. This fermentation process can create gas—and the accompanying feelings of bloating, cramping, and abdominal discomfort.

Due to individual digestive differences, you may have trouble breaking down and absorbing certain types of sugars and carbohydrates that others can absorb. This means more of the sugars pass into the large intestine, more fermentation takes place, and you’ll potentially feel more digestive discomfort.

The foods targeted by low-FODMAP diets are ones most frequently associated with poor digestion. They don’t need to be avoided by everyone, but some people do benefit from limiting or eliminating certain high-FODMAP foods.

The Chemistry of FODMAPs

As you learned above, FODMAP is an acronym for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. If you know the basic chemistry of carbohydrates, then you might be worried this is a far-reaching diet with a goal of eliminating all carbohydrates in your diet. But that’s not the case. A low-FODMAP diet only limits the intake of specific types of sugars within these carbohydrate categories.

For example, sucrose, lactose, and maltose are all disaccharides commonly found in the diet. Only fructose is limited in a low-FODMAP diet. So, you don’t need to worry about reducing all disaccharides in your diet.

These are the specific molecules targeted within each category of a low-FODMAP diet:

• Fermentable oligosaccharides (polysaccharides): fructans and galactooligosaccharides
• Disaccharides: lactose
• Monosaccharides: fructose
• Polyols: sorbitol, mannitol, and maltitol

You’ll discover your individual needs vary. For example, some fermentable oligosaccharides may need to be eliminated for a successful low-FODMAP diet, while the disaccharides and polyols foods can still be eaten, just in small amounts.

Unlike the other molecules targeted by a low-FODMAP diet, fructose isn’t limited to a threshold amount. Instead, it is limited in relationship to the amount of glucose you eat. That’s because glucose, when eaten together with fructose, helps increase the absorption of fructose in the small intestine.

When fructose is eaten alone or too much is eaten in relationship to glucose, then it will pass into the large intestine. Once in the large intestine, then fructose can cause some of the same problems as the other FODMAP molecules.

High and Low FODMAP Foods

A simple online search for “FODMAP foods” will help you find lots of lists and charts of foods to avoid or include in your diet. Below you will find a short sample list of some high-FODMAP foods (to avoid or limit), and others that are low (less likely to cause problems) in FODMAPs.

• Fructans and galactooligosaccharides
  • High: wheat, rye, barley, onion, garlic, artichoke, asparagus, Brussels sprouts, cauliflower, legumes
  • Low: corn, rice, quinoa, potatoes, bell pepper, cucumber, green beans,
• Lactose
  • High: milk, yogurt, sour cream, ice cream
  • Low: lactose-free milk, almond milk, hard cheeses
• Fructose
  • High: pears, apples, watermelon, honeydew, papaya, star fruit, fruit juices, agave nectar
  • Low: blueberries, strawberries, oranges, pineapple, cantaloupe, kiwi
• Polyols
  • High: apples, apricots, avocados, foods sweetened with honey, sorbitol, mannitol, or maltitol
  • Low: dark chocolate, table sugar, maple syrup, brown sugar

Implementing a FODMAP Diet

Not everyone will benefit from avoiding FODMAP foods. But if you decide to try a low-FODMAP diet, it’s best to work through the list of foods systematically. It’s unlikely that all high-FODMAP foods are causing you problems.

Where possible, keep as many foods and as much variety as you can in your diet. The three-step approach below will help you find out which foods may be causing problems for you. Then you know which foods you can continue to enjoy.

1. Elimination and Restriction

The best way to start is by restricting or eliminating as many high-FODMAP foods as possible. After sticking to this strict diet for a few weeks, hopefully your digestive system will feel better.

If symptoms still haven’t improved, you should work with your doctor or dietician to develop a personal plan for you and look at foods outside the FODMAP list.

2. Reintroducing Foods

If the FODMAP foods elimination has helped, it’s time to start reintroducing some options you eliminated from your diet. Reintroduce foods one at a time, and only in small amounts.

By testing out foods one at a time, you will learn which ones are safe for you to eat, and which ones need to be either eliminated or only eaten in very small amounts. After testing out a food, wait one or two days to feel how you tolerate it.

Take your time with the reintroduction phase. You’re going to be tired of eating a restricted diet and anxious for some freedom in your food choices. If you try too many FODMAP foods at once or don’t wait enough time between testing new foods, then you won’t know which choices are responsible when problems arise again (and they probably will).

There may be times when you need to go back to step one and spend a couple of weeks with a more restricted diet, just to let your GI system settle down again. Then you can start testing new foods again.

3. A Personalized Diet

Just like the FODMAP foods lists and charts you’ll find online, it’s probably worth making your own list. It will help you clearly define which foods to avoid, limit, and can be safely eaten.

By following this process of elimination and reintroduction, you may even find foods that aren’t on traditional low-FODMAP lists. This will also help create a very personalized diet.

A low-FODMAP diet requires patience to figure out, and it isn’t a magic solution that will solve all your digestive-health concerns. But it is a tool that can help you on a path to better digestion, while still includes a beneficial variety of healthy foods in your diet.

Your body is full of bacteria, viruses, and fungi. Trillions of these tiny microbes—collectively called your microbiome—exist mainly inside your intestines, in your mouth, and on your skin. They are with you from birth. And, surprisingly, that’s a good thing.

While some bacteria and microbes are potentially harmful, others are extremely important for supporting your health. Maintaining nutritional status, immunity, and the behavior of the brain are related to a healthy balance of these microbes.

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Refresh your knowledge on the microbiome with these helpful stories:

Defining Microbiome: Meet Your Bacterial Buddies

The Gut-Brain Axis: Connecting Your Brain and Microbiome

Your Gut Microbiome’s Reaction to Dietary Fiber

How Your Complex Oral Microbiome Impacts Health

Why Your Skin Microbiome is Important—And 5 Ways to Protect It

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Diversity is Key and Prebiotics and Probiotics Can Help

One established characteristic of a healthy gut environment is the variety or diversity of the microbes. The more diverse your microbial community is, the more resilient it is likely to be.

When your gut is loaded with a variety of friendly bacteria, there’s less empty space for the bad kind to take up permanent residence.

Environment, genetics, and other factors have some influence on your microbiome. But your diet determines what grows best and what microorganisms win the battle for space and resources.

Common modern diets are rich in sugars, saturated fats, and processed food. They also lack fiber. This tends to select for certain bacterial species to dominate. A vegetarian or Mediterranean diet, on the other hand, includes a lot of fiber, healthy fats, and is rich in fruits, vegetables, and whole grains. Different species of bacteria are known predominate in guts of people who regularly consume these diets.

The amount of prebiotic fiber (which feeds the microbiome) and probiotic foods (which provide live bacteria) are part of these dietary calculations, too. A varied diet rich in fiber, and its positive impact on the microbiome, is an important piece of the health puzzle. It’s just one reason health professionals emphasize abundant fruits, vegetables, legumes, and whole grains in your daily diet.

Putting the Focus on Prebiotics

The most effective way to influence your gut microbiome in the right direction is to consistently include a wide variety of fiber in your diet. Probiotics is a more well-known microbiome vocabulary word, and they’re important to health. But certain fibers, known as prebiotics, are just as important.

Prebiotics essentially act as a gut fertilizer. That’s because they are certain non-digestible carbohydrates (fiber) that nourish healthy microorganisms (probiotics). For example, prebiotics like inulin support the balance of healthy bifidobacteria (important gut bacteria in mammals) in the digestive tract. If you’re going to populate your gut with a variety of healthy microbes, you need a variety of fibers and prebiotics in your diet.

Here’s where you can find them. Check out the food sources that provide healthy fiber and prebiotics to your diet:

Chicory root – inulin

Dandelion Greens – fiber

Jerusalem Artichoke – inulin

Garlic – inulin and FOS (fructooligosaccharides)

Onions – inulin and FOS

Leeks – inulin

Asparagus – inulin

Bananas – inulin and resistant starch

Barley – beta-glucans

Oats – beta-glucans and resistant starch

Apples – pectins

Konjac root – glucomannan fiber

Burdock root – inulin and FOS

Flaxseeds – gums, cellulose, and lignans

Jicama – inulin

Wheat Bran – arabinoxylan oligosaccharides (AXOS)

Probiotics Can Help Change Bacteria’s Bad Reputation

Most people are taught to watch out for spoiled food, which is generally caused by an overgrowth of unhealthy bacteria or mold. It’s a legitimate concern. But certain types of bacteria help support your health and are safe in the proper balance. They’re called probiotics—meaning “for life.”

As mentioned above, these healthy bacterial probiotics support the balance and health of the intestinal environment in several different ways. This includes providing competition, supporting immune function, and communicating through chemical signals.

It’s much more complex than that, but that’s the basic idea. If you want to dive deeper, this recent review article will give you a more complete understanding of how probiotics work.

Acquiring probiotics from your diet is a matter of choosing and incorporating certain foods into your meals. You can find them in fermented dairy foods, like yogurt, buttermilk, kefir, and some types of cheese. Fermented soy products like tempeh, miso, and natto are also excellent sources. Even vegetables get into the act with kimchi, pickles, and sauerkraut. Another popular trend is making or drinking kombucha, which is made from fermenting a mixture of tea, yeast, and sugars.

Combining probiotics and prebiotics could multiply potential benefits. Some symbiotic fermented foods do that for you. Yogurt and kefir are two examples of foods that have living bacteria and prebiotic substances to feed them.

Answers to Common Prebiotic and Probiotic Supplement Questions

Under normal circumstances, diet is the most important factor in a healthy gut environment. Everyone should prioritize a healthy, balanced diet as a lifelong practice. But that’s often easier said than done.

Sometimes life and health just doesn’t go as planned, regardless of intent. In these cases, supplemental prebiotics and probiotics can help fill gaps where the diet may come up short. Take a look at some of the common questions about these dietary additives.

Why take a probiotic or prebiotic supplement?

Many realities of life can disrupt the stability of your gut environment. A few include: stress, a nutrient-poor diet, dehydration, unhealthy sleep patterns, certain medications, and exposure to new microbes when traveling.

Instability in the gut microbiome can even be associated with the normal aging process. A change in nutritional status and lifestyle can negatively influence gut health, especially in older adults.

In these situations—where your gut health can be in flux—a probiotic or prebiotic (or both) can help support the diversity and balance of your gut microbiome. Supporting a healthy diverse microbial environment can help you maintain normal digestion, which you need to utilize and metabolize energy and nutrients. In the same way your body needs essential vitamins, minerals, and other micronutrients on a daily basis, your gut needs the right nourishment every day to operate at its best.

When it comes to dosage or colony forming units (CFU), is higher always better?

Even at billions of colonies, the amounts of bacteria added through probiotics is minuscule in the context of the entire gut environment. In other words, rather than thinking of a product containing 50 billion CFU being four-times more than 12 billion, it’s more accurate to think of it as 50 billion out of trillions, versus 12 billion out of trillions.

The dosage that’s most appropriate for you depends on your health goals and the specific probiotics included in a particular formula. For general balance and maintenance of healthy microflora, products containing five to 20 billion CFU are typical. A product containing 50-billion CFU may be needed for certain probiotic strains or health concerns. Even higher dosages are sometimes used for intensive therapy or to restore flora to an optimal balance after illness.

So total CFU counts do matter, but so do your personal needs. It’s always a good idea to consult with your healthcare practitioner to determine the best CFU number for you.

Do probiotics survive the harsh environment of the stomach?

It’s true that stomach acid destroys much of the bacteria and microbes you ingest. But not all strains are wrecked by the acidic environment of the stomach. Food poisoning wouldn’t be an issue if stomach acid was 100-percent effective.

When searching for a probiotic supplement, look for strains known to survive the acidic environment of the stomach and the body’s bile. You may find this listed on the label or in company literature. A quick search on Google may also indicate whether the strain has been tested to survive the stomach environment.

Are more strains always better than fewer strains?

Because of the diversity of the microbiome, it is easy to assume that a probiotic containing many different strains is the best option. However, existing research suggests that most often the opposite is true.

The majority of compelling research papers revealing health benefits of probiotics involve single strain and two-strain probiotics. Why? Many factors determine whether a probiotic strain will be beneficial or not, including stability, ability to survive digestion, compatibility with your microbial environment, and formulation of the probiotic product itself.

What should I look for on the label of probiotics?

All probiotics should list the genus, species, and specific strain of bacteria. For example, Bifidobacterium animalis BB-12 is listed by genus (Bifidobacterium), species (animalis), and strain (BB-12). Strains are all different and have unique characteristics, and quality probiotic supplements will designate the specific strains that are included.

When and how is it best to take probiotics and prebiotics?

There really isn’t any solid evidence that timing is important in most cases. Probiotics can be taken in the morning, noon, or night—whenever it’s best for you. There’s also debate about whether it’s better to take probiotics with a meal or on an empty stomach. Unless there are specific product instructions to the contrary, you can take them with or without food.

The recommendation is much the same for prebiotics. Consistency is the most important recommendation, so take them whenever it works best for you to take them on a daily basis. They can be taken together with probiotics, and they are often included with probiotic products and foods.  But it isn’t necessary to combine them or take them together if it doesn’t work best for you.

What is the best form for a probiotic product?

The form and delivery system that is best depends on the specific microbes used, the intended purpose, and distribution of the product. Some probiotics require refrigeration to maintain viability, while others do not. Probiotics can come in capsules, powders, liquids, packets, tablets, or even in food products themselves. Stability and viability are important, so be sure to purchase probiotic products from a company or source you trust.

Who should NOT take probiotics?

Although probiotics are generally safe to use, there are reports linking probiotics to side effects in some people. The people most likely to have problems are those with compromised immunity, people who are critically ill, and those who’ve had recent surgery. If there is a question in these cases, it’s always best to consult a health professional.

Can children take probiotics? 

There are various reasons a child may benefit from probiotics. Most pediatricians are familiar with probiotics so it’s best to discuss the appropriate use and dosage in children with your health professional.

You aren’t what you eat. But you are what your body absorbs. That’s because all of your food isn’t used by your body. And if you don’t absorb the nutrients in your food, they do no good for your cells, muscles, brain, and more.

But how are nutrients absorbed by the body? The simple version of this process has five components:

1. Chewing and the introduction of enzymes in your mouth
2. Churning and mixing with acid (gastric juice) in your stomach
3. Contact and absorption in your small intestine—your nutrient absorption center
4. Entrance into the bloodstream
5. Carrier proteins bringing nutrients into your cells

But the journey is much more interesting and complex. A lot goes on behind the scenes to get the good stuff in your meal to enter the bloodstream.

So, follow along as the vitamins, minerals, carbohydrates, proteins, and fats in your food make their way into your cells. And learn how you can help your body continue healthy nutrient absorption.

Your Digestive Systems Prepares Food for the Small Intestine

To sustain your body, your food needs to be broken down into usable pieces. Carbs, proteins, and fats become glucose, amino acids, and fatty acids, respectively. The vitamins and minerals in food need to be extracted, too.

That’s what your digestive system does. And digestion starts right after the first bite. Teeth tear up food into manageable chunks. The enzymes in your saliva (called salivary amylase) break down the food’s chemical structure.

Digestion continues in the stomach, where powerful acid disassembles food even further. With the help of peristaltic motion (rhythmic digestive movement) the food you consume is stirred and mixed as it prepares to enter the small intestine.

If you’re interested in a deeper dive into digestion, take a trip through your digestive tract.

Small Intestine: Headquarters of Nutrient Absorption

The workings of the small intestine can be complex. But its role can be simply summed up in two words: nutrient absorption. That’s because your small intestine is in charge of pulling glucose, amino acids, fatty acids, vitamins, and minerals out of food to be used by the cells.

This is accomplished by tiny projections called villi. The microscopic, brush-like lining of the small intestine acts like a comb that grabs important nutrients out of the digested food that leaves your stomach.

Villi are great at absorbing nutrients because they increase the surface area of the inside of small intestine. With hundreds of thousands of villi lining your gut, that’s a lot of surface area for nutrient absorption.

Each villus (a single protrusion of the villi) is composed of a meshwork of capillaries and lymphatic vessels (called lacteals) underneath an ultra-thin layer of tissue. This special structure makes it possible to pull macro- and micronutrients out of your meals and send them to the bloodstream.

Water is also essential to this process. The small intestine uses a chemical process called diffusion to extract nutrients. Diffusion moves water and water-soluble compounds across barriers, like the villi in the small intestine. These compounds include:

• Glucose (simple sugars)
• Amino acids (parts of proteins)
• Water-soluble vitamins (B vitamins and vitamin C)
• Minerals

Once these nutrients are diffused into the villi, it’s a straight shot to the bloodstream. That’s where these nutrients can work in cells to make proteins and create energy.

Fats and fat-soluble vitamins (A, D, E, and K) require a few extra steps to enter the bloodstream.

First, bile acids from the liver mix with fats in the small intestine. This breaks the fats down into their component fatty acids. Then, the fatty acids and other fat-soluble vitamins are absorbed by the villi into lacteals. These lymphatic vessels transport the fat-soluble compounds to the liver. That’s where they are stored and released in the body as needed.

And there’s a lot of use for fatty acids and fat-soluble vitamins. Cells use the fatty acids to build cell membranes. And vitamins A, D, E, and K are useful in the body to support the health of your eyes, brain, heart, and bones.

Nutrient Distribution into Your Cells

Absorbing nutrients into the bloodstream isn’t the end of the journey. To make energy, move muscles, sense touch, and generally propel your life, the nutrients you eat need to enter your cells.

This is easier said than done.

Surrounding each of your cells—no matter the type—is a cellular membrane made of fatty acids. It protects the cell, and controls what can enter and exit. Some materials, like water, can pass into the cell easily. Others need assistance.

Proteins embedded in the cellular membrane act as ushers. They help carry nutrients from the bloodstream into the cell. Glucose, amino acids, fats, and vitamins use carrier proteins to get inside cells.

Once through the membrane, nutrients play many important roles. Some cells, like muscle fibers, need minerals like calcium to flood the cell in order to move your arms and legs. Others, like nerve cells, need sodium and potassium to be pumped in and out so your brain can pick up sensory information.

Cells use the glucose in your bloodstream to create energy by making ATP, the cellular energy currency. And amino acids are the building blocks for all DNA. When they’re brought into the cell, amino acids help transfer genetic information so cells can replicate.

Nutrients and the Blood Brain Barrier

While the small intestine readily absorbs and distributes nutrients to cells, the brain is more guarded. As a precaution, your brain is selective about the compounds it allows to enter through the bloodstream. This transport of nutrients is managed by a mechanism called the blood-brain barrier (BBB).

The BBB consists of the vessels and capillaries that deliver blood to the brain and surrounding tissue. These vessels are made of tightly packed cells that only allow the smallest molecules to pass through to the brain. Larger molecules can only enter with the help of specialized transport proteins.

Glucose is one of the nutrients that has the easiest time crossing the blood-brain barrier. And with good reason. Glucose is the fuel your brain thrives on, so it’s important that it can freely enter the brain.

Fatty acids also travel across the BBB easily. That’s because your brain’s health relies on them. Omega-3s are especially important for supporting growing brains.

It’s not so easy for amino acids. Carrier molecules attach themselves to amino acids to guide them to the brain. Without the carriers, these protein components wouldn’t be able to do their job in the brain. That includes manufacturing neurotransmitters that help regulate your mood and nervous system.

Other nutrients can enter the brain through the blood-brain barrier. Vitamins B⁶ and B¹² also rely on carrier molecules. But vitamin C can cross the BBB on its own and has been shown to help other helpful compounds make their way to the brain.

3 Tips to Maintain Healthy Nutrient Absorption

Now you understand how nutrients are absorbed by the body. And have a good idea of the importance of this process. But how much of nutrient absorption is within your control?

Quite a bit, actually. Maintaining your digestive health and making smart dietary decisions are two major factors under your control. Here are three simple suggestions to support nutrient absorption. Pick one to work on and see how it makes you feel.

1. Focus on your good bacteria ratio with a probiotic

Your digestive system is helped by the members of your gut microbiome. That’s why probiotics are great for supporting healthy digestion. They help maintain healthy bacterial diversity, which assists your gut in breaking down some types of food so they can be properly absorbed.

2. Make healthy fat choices

Remember those fat-soluble vitamins? They rely on fat to get from the small intestine to the rest of your body. Healthy fats are necessary for storing up vitamins A, D, E, and K. Choose healthy fats (plant sources) over saturated or trans fats to help your body absorb these important nutrients. Just another reason to take your supplements with food.

3. Give your body plenty of nutrients to absorb

This sounds like the most obvious advice, but it’s important to remember. Make a goal to eat a variety of fruits and vegetables to optimize the vitamins you’re getting on a daily basis. Start by eating different colored foods. This can help you meet your nutrient goals. Red and orange foods have lots of vitamin A, while green veggies are packed with B vitamins, vitamin C, calcium, and iron. Colorful foods also contain phytonutrients that support good health. So, try to fill your plate with different colors to meet your daily needs.

About the Author

Sydney Sprouse is a freelance science writer based out of Forest Grove, Oregon. She holds a bachelor of science in human biology from Utah State University, where she worked as an undergraduate researcher and writing fellow. Sydney is a lifelong student of science and makes it her goal to translate current scientific research as effectively as possible. She writes with particular interest in human biology, health, and nutrition.