Food Intolerance: A Result of Enzyme Insufficiency or Deficiency

By: Dr. Mamadou 

Food intolerance can be defined as the body’s inability to accept a particular food or some of its molecules. This inability to accept the food is expressed by adverse physio-biochemical reactions. Some of the reactions include vomiting, diarrhea, flatulence, bloating, intestinal imbalance, dysbiosis, and inflammatory conditions.

These conditions in turn will lead to mal- absorption, loss of nutrients, weakness, fatigue, and increased susceptibility to diseases. However, in most cases, when there is intolerance to a specific food, the usual tendency is to avoid that food. A better alternative is to take supplements that correct the intolerance and ensure the bioavailability of the nutrients of that food.

The focus of this paper is to bring attention to the fact that food intolerance results from an impaired digestion of the food molecules. The key molecular agents to perform the digestive function are the enzymes produced in the digestive system. However, for various reasons, some of the enzymes are missing, insufficient, and/or ineffective. As a result, some foods, based on their chemical composition, create various types of discomfort and other digestive disorders.


I often heard people say “I am allergic to that food” when in fact, in a biochemical and medical terms, they are not allergic to that food: they are intolerant to that food. So what is the difference between food intolerance and food allergy?

While food allergy is an immune condition, food intolerance is usually not. Although some of the symptoms may overlap, food allergy and food intolerance are very distinct biochemically and physiologically. To further complicate the issue, let’s say that both conditions are caused by the inability of the digestive system to break down the molecules in the target food.

This impairment in the digestive function is mostly the result of inadequate enzyme activity (function): this could be due (1) to the inability of the pancreas and the intestinal cells and other organs to make the necessary enzymes and/or (2) the malfunction or absence of key messengers that regulate the enzyme producing organs.

So, irrespective of the cause of digestive impairment, the end-result is a lack of adequate enzymes to break the food macromolecules (big molecules) into smaller molecules. Unless and until the big molecules in a food are broken into smaller molecules, that food could be a health liability to the body. That liability is either food allergy or food intolerance.

The path of the undigested or un-broken molecules to food intolerance or food allergy is determined by the nature of the molecules that are not broken and the physio-biochemical reactions that will take place when those molecules react with the cells or other molecules in the gut. Most human foods contain one or more of the following macromolecules: proteins, lipids (fats), and carbohydrates. They are called macromolecules because they are made of many smaller molecules bound (linked) together. In order for these major molecules to benefit the body, they must be broken down into smaller molecules that could be absorbed into the blood circulation and transported to the various cells.

However, when these big molecules are not fully broken down, i.e., digested, there would be in various sizes within the gut. These molecular pieces that could not be taken up by the intestinal cells could still interact with cells and other molecules in the gut environment.

As they remain in the gut, some of these partially broken molecules interact with the cells in the digestive tract and create various biochemical reactions. The effects of these reactions on the physiology of the body are diverse. This diversity of reactions determines whether there is food intolerance or food allergy.

As mentioned above, both food intolerance and food allergy refer to reactions of the body when certain foods are ingested. Furthermore the reactions are simply because the food is not digested properly.

Although many people use the terms food intolerance and food allergy interchangeably, the two conditions are different.

An allergy is always the result of an immune response to a molecule, and that molecule is invariably a protein or a protein combined with some fat (lipoprotein) or some carbohydrate (glycoprotein). If a protein is not fully digested, broken down, it has the ability, when introduced in a foreign body, to trigger an immune reaction. That immune reaction is expressed in the form of rashes, inflammations, and even death, as in anaphylactic reaction (Please refer to the paper “Enzymes as Allergy Modulators”). It should also be mentioned that partially digested proteins could also trigger other biochemical reactions that are not immune in nature, but could rather affect the functioning of the nervous system (see paper on “Autism and Supplemental Enzymes”).

Food intolerance is mostly caused by either carbohydrates or fats, but proteins could also be culprits. The types of reactions caused as a result of food intolerance are different from immune reactions and are often expressed as colics or abdominal pain, diarrhea, oily stools (Steatorrhea), imbalances in the ecological balances of the probiotics, yeast infections, excess production of toxigenic amines, and excess gas.

Besides fats and carbohydrates, there could be other molecules that could trigger some form of reaction similar to the ones associated with food intolerance. Usually, those are relatively small molecules that could interact with the gut cells and trigger an adverse reaction like vomiting, nausea, toxicity, or increased peristaltic movement resulting in diarrhea.

However, there are conditions when the same food could provoke both food allergy as well as food intolerance. That is the case of milk or some dairy products.

A good example of food intolerance is lactose intolerance. Lactose intolerance is not a food allergy! Lactose is a sugar, not a protein. Lactose intolerance does not mean that one is allergic to milk or dairy products. However, there are cases when someone may have lactose intolerance and also suffer from allergy caused by the proteins in the milk.

Let’s look at the physio-biochemical reactions taking place in lactose intolerance. Lactose is the main milk sugar and is made up of glucose and galactose linked together. In order for this milk sugar, lactose, to be absorbed in the gut, it needs to be broken down: that means the bond linking the glucose and the galactose molecules must be broken, i.e., digested. The enzyme responsible for breaking down that bond is called lactase.

Although everyone has this enzyme as a baby to help process breast milk, some people lose its production or produce it in very small amounts once they stop breastfeeding and/or become adult. So, when one does not have this lactase produced in the gut by the intestinal cells, lactose could not be processed: the glucose and the galactose molecules stay bound together.

This is a situation when lactose is small but not small enough to be absorbed. So, when one consumes milk or ice cream, there would be more of lactose in the gut. If the enzyme lactase is missing or not active, the lactose remains in the gut.

As the amounts of lactose increase in the gut, it pulls water from the inside of the body into the gut. This is a bio-physical case of osmosis: the sugar content being higher in the gut (because of the high lactose) than in the cells, water moves from the cells into the gut.

So, now there is plenty of water filling up the intestines. As a result, there would be increased peristaltic movement triggered by the excess water. The end result is diarrhea. Diarrhea is one of the main symptoms observed in cases of lactose intolerance.

Other characteristic symptoms of lactose intolerance are excess gas production and flatulence. The reason for the excess gases leading to flatulence is the action of the microorganisms in the large intestine on the undigested lactose.

As lactose is not broken down in the upper small intestine, it moves in the large intestine where it will serve as feedstock for the various bacteria. When bacteria consume sugars, they produce gas: thus the increased gas production. This increased gas production could also lead to abdominal pain and flatulence.

As one can note, this set of symptoms or discomfort caused by the lactose intolerance is due to the body’s inability to process lactose: the enzyme lactase is either missing or inactive and the sugar lactose is not broken down. This condition could be alleviated by taking supplemental lactase to rectify the deficiency in the gut and ensure the digestibility of lactose.

Another common case of food intolerance is the inability to digest fats. Contrary to some diet craze practices, fats are necessary for the body. The key is to consume good and healthy fats and in moderation. Many key molecules in the body are derived from fats including the molecules that constitute the membranes of the cells, fuel the heart’s function, and make the various sex hormones.

Thus, consuming healthy fats in moderation is a good thing. However, when the fats are not digested they “run through” the gut and cause what is called steatorrhea: an oily stool. It floats but it is not healthy! That oily stool robs the body of many nutrients including the fat-soluble vitamins.

Furthermore, with steatorrhea comes malabsorption as many nutrients are flushed out before they get absorbed because of the diarrhea caused by the undigested fats. As go those nutrients and vitamins, so go vitality, youthfulness, healthy skin, and vigor. The inability to digest fats in the diet is caused by the absence or inaction of the enzyme lipase.

The remedial approach to steatorrhea is to supplement with effective lipase that could ensure the breaking of the dietary fats. It is important to note that some of the supplemental lipases could effectively break down lipids (fats) even if bile is not present. Supplementing with the enzyme lipase will not only prevent oily but also the sometimes “hard to control” diarrhea. Furthermore, taking lipase to supplement the body’s action will help the body retain some key vitamins and nutrients.

In some instances, proteins could be the subject of food intolerance as opposed to food allergy. In those cases, the undigested proteins may damage the intestinal walls leading to intestinal permeability (leaky gut) or overwhelming the metabolism of the organisms in the large intestine.

When undigested proteins reach the large intestine and are reacted upon by the microorganisms, there is formation of many molecules with potential harmful effects on the body. Some of these molecules could promote tumor growth, colon diseases, and excess production of gases with very foul odors.

Some of these concerns related to protein intolerance have led the push of avoiding excess proteins, especially animal proteins, in the diet. However, the main culprit is the digestive enzyme insufficiency and/or inefficacy. Supplementing with effective proteolytic enzymes (proteases and peptidases) could help avoid the problems caused by undigested proteins in the gut.

Another cumulative consequence of any type of food intolerance is disturbance in the ecological balance of the probiotics. Whether the non-tolerated food is carbohydrate, fat, or protein, it will reach the microorganisms and disturb the balance.

Within the taxonomy of the organisms in the large intestine, there are organisms that could grow faster when a specific food is more available. These organisms that could benefit from the result of food intolerance may not be beneficial to the body in a short or long term. Within the functioning of the body, probiotics balance is a key to health!

As can be noted, intolerance of any food is the direct result of inefficient digestive function, mostly lack or inaction of digestive enzymes. The corrective option in cases of any food intolerances is to include supplemental enzymes that could complement the function of the digestive system.

A digested food molecule loses its bioactivity (in terms of harming the body)!


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Medow, MS et al., 1990. Beta-galactosidase tablets in the treatment of lactose intolerance in pediatrics.Am J. Diseases of Children 144:1261

Barillas, C., et al., 1987: Effective reduction of lactose maldigestion in preschool children by direct addition of beta-galactosidase (lactase) to milk at mealtime. Pediatrics 79:766.

Lankisch, P.G., 1993. Enzyme treatment of exocrine pancreatic insufficiency in chronic pancreatitis – review-. Digestion 54 Suppl. 2:21


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