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Virtually all living things—including those we cook and eat—contain enzymes. Enzymes, which act as the spark plugs for the vast majority of chemical reactions that make life possible, are a sine qua non for life.

Although most food eaten in the United States has been cooked, which inactivates the enzymes it contains, all the plant and animal foods in our meals are derived from once-living, enzyme-abundant things.

Over 2,500 different kinds of enzymes are found in living things. All enzymes are proteins, very special kinds of proteins that act as catalysts. Enzymes give our body chemistry its vitality, literally giving our metabolism a jump start. Plus, as molecules that enable the breaking down of our food, they also play a critically important role within our digestive system. Enzymes in our saliva allow us to break apart starches. Enzymes in our stomach help us break apart proteins. Enzymes in our intestines help us break apart fats, proteins, and carbohydrates of all kinds.

When we eat fresh, uncooked foods, those foods can still contain active enzymes. When we chew a freshly picked leaf of lettuce, we break the cells in the leaf apart, releasing its nutrients, including enzymes. Enzymes are not automatically destroyed by the acids or temperatures in our digestive tract. Enzymes in the stomach—called gastric enzymes—are specially designed to function in the stomach's extremely acid conditions and are critical to our health. Our bodies can overheat from fever, extreme exercise or summer weather, but not to temperatures that will prevent the enzymes inside us from continuing to function.

Our digestive tract has specialized areas for absorbing large molecules, including enzymes (which are proteins), from food into our bloodstream. These areas house our M cells. M cells are specialized cells designed to selectively deliver large molecules from our intestines into our cells and bloodstream. The passing of enzymes from a mother to her nursing newborn is a good example of this M cell function. A mother's milk contains the milk sugar, lactose. An enzyme called lactase is needed to digest lactose, but an infant's body is not yet capable of manufacturing this enzyme. So, the mother sends lactase along with her milk, and in this way enables the baby to digest and absorb its lactose.

Ordinarily, we cook food at temperatures at least twice that of normal body temperature. For this reason, fresh, raw plant foods are our primary source of food enzymes. (Due to their high potential for bacterial contamination, most animal foods would be too risky for us to eat raw). While there have been no large scale, controlled studies to document the impact of enzyme-containing, fresh, raw plant foods on digestion and health, practitioners in fields of complementary, natural, and functional medicine have used enzyme supplementation successfully to help treat a wide variety of health problems and have long advocated the inclusion of fresh, organic, raw plant foods in the diet.

For serving size for specific foods see the Nutrient Rating Chart.


Enzymes are not difficult to pick out in a science book, because 90% of all enzymes are given scientific names that end in the letters -ase. Following are two types of enzymes contained in foods.

Digestive Enzymes

Plant foods contain many of the same enzymes that humans use to metabolize different kinds of macronutrients. Proteases and peptidases, which help digest protein; lipases, which help digest fat; and cellulases and saccharidases, which help digest starches and sugars are examples of the kind of digestive enzymes that would normally secreted in our digestive tract or in a nearby organs like the pancreas or liver. However, these same digestive enzymes can be found in the plant foods that we eat.

Antioxidant Enzymes

Like humans, plants must protect themselves against oxygen-related damage, and they depend on enzymes to help them do so. A recently germinated sprout, for example, starts to generate many new oxidative enzymes in preparation for its journey up through the soil and into the open air. Superoxide dismutase (SOD) and catalase (CAT) are examples of oxidative enzymes that occur in higher concentrations in young plant sprouts than in the older, mature leaves. Glutathione peroxidase (GPO) is another example of an important oxidative enzyme that is found in the human body and in the plants we eat.

How it Functions

Necessary for Proper Digestion

Digestive enzymes play an integral role in the digestion of proteins, fats and carbohydrates since they catabolize these macronutrients into smaller molecules, which can be absorbed in the intestines. Our optimal physiological functioning depends upon the proper digestion and absorption of these nutrients.

Confers Inflammatory and Oxidative Protection

Certain enzymes, such as bromelain (found in pineapple), have anti-inflammatory properties. Bromelain seems to confer anti-inflammatory protection through a variety of mechanisms. It is thought to inhibit intermediates of the clotting cascade, increase fibrinolysis (the dissolution of clots), and reduce the production of inflammatory molecules such as bradykinin.

Support for the Immune System

Enzymes support the immune system in a few different ways. Since enzymes can work on substrates wherever the substrate is found, some of their targets include molecules other than the macronutrients associated with food. For example, protease enzymes can break apart the proteins that are found in unwanted bacteria and therefore reduce our risk of infection. In addition, the enzyme bromelain has been found to increase the production of a host of different immune system messenger molecules, including cytokines such as tumor necrosis factor-alpha, interleukin-1-beta and interleukin-6.

Promoting General Metabolic Eficiency

Evidence shows that the body conserves it own digestive enzymes by absorbing intact both endogenous (produced in the body) and exogenous (supplemented to the body by food or supplement) enzymes. Exogenous pancreatic enzymes have been found to be absorbed intact from the gut, transported through the bloodstream, taken up by the pancreatic cells, and resecreted into the intenstines by the pancreas, mixed with newly synthesized pancreatic enzymes. It is suggested that oral supplementation of enzymes may have a sparing effect on the body's own digestive enzymes, perhaps aiding organ regeneration, by breaking down substrates, such as foods, for which endogenous enzymes would otherwise be used, thus freeing these enzymes for other beneficial activities.

Deficiency Symptoms

There is no research on symptoms of food enzyme deficiency. The clinical experience of many health care practitioners suggests that symptoms related to dyspepsia (indigestion), including heartburn, flatulence, belching and the appearance of undigested food in stool, may suggest enzyme deficiency since these symptoms could be caused by the improper digestion of food, which would occur with a deficiency of digestive enzymes.

Toxicity Symptoms

There is no research on food enzyme toxicity. Enzymes in supplement form may cause allergenic reactions due to the introduction of novel proteins which may increase the risk of antigenic reaction, particularly in immune-compromised individuals. In addition, bromelain may cause allergenic reactions as it has been shown to promote certain types of antibody mediated reactions.

Impact of Cooking, Storage and Processing

Cooking foods at virtually all standard cooking temperatures denatures enzymes, destroying their functioning.

The majority of processing techniques used by food manufacturers destroys the natural enzymes found in foods.

The effects of storage on enzyme integrity varies greatly, depending upon temperature and duration. The higher the temperature and the longer the food is stored, the greater likelihood that any enzymes it contains will be denatured.

Factors that Affect Function

Different enzymes have optimal pH ranges at which the reaction that they catalyze will occur most rapidly.

Temperature can affect enzyme activity level. Increased temperatures increase the rate at which an enzyme will catalyze a reaction, yet only up to a point, since too high a temperature will cause the enzyme to denature, destroying its activity.

Certain heavy metals inhibit the activity of enzymes by interrupting the reactions in which they are involved. These heavy metals include barium, lead and mercury.

Nutrient Interactions

There is limited research on the interaction between enzymes and nutrients, although some minerals serve as cofactors for certain endogenously produced enzymes. Studies have suggested that pancreatin supplementation may reduce folic acid absorption.

Health Conditions

A high dietary intake of enzymes may play a role in the prevention and/or treatment of the following health conditions:
  • Maldigestion and malabsorption
  • Pancreatic insufficiency
  • Steatorrhea (diarrhea due to fat malabsorption)
  • Celiac disease
  • Lactose intolerance
  • Thrombotic disease
  • Acute sinusitis
  • Post-operative recovery
  • Sports injuries
  • Adverse food reactions

Food Sources

Virtually all fresh, organically grown, uncooked plant foods are sources of enzymes. Bromelain is found in pineapples while papain is concentrated in unripe papayas.

Nutrient Rating Chart

Food Source Analysis not Available for this Nutrient

Public Health Recommendations

No public health recommendations for dietary intake of enzymes have been made by any established health agency or organization.


  • Alternative Medicine Review. Monograph:Bromelain. Altern Med Rev. 1998 Aug;3(4):302-5. 1998. PMID:9727080.
  • Barillas C and Solomons NW. Effective reduction of lactose maldigestion by direct addition of beta-galactosidases to milk at mealtime. Pediatr 79:766-772. 1987.
  • Bland J and Berquist B. Nutrient content of germinated seeds. J John Bastyr Coll Naturop Med 1980: 2(1):3-9. 1980.
  • Carroccio, A., Guarino, A., Zuin, G., Verghi, F., Berni Canani, R., Fontana, M. et al. Efficacy of oral pancreatic enzyme therapy for the treatment of fat malabsorption in HIV-infected patients. Aliment Pharmacol Ther. 2001 Oct; 15(10):1619-25. 2001.
  • Gailhofer G, Wilders-Truschnig M, Smolle J, Ludvan M. Asthma caused by bromelain: an occupational allergy. Clin Allergy 1988 Sep;18(5):445-50. 1988. PMID:3233722.
  • Gardner, M. L. Gastrointestinal absorption of intact proteins. Annu Rev Nutr. 1988; 8:329-50. 1988.
  • Gardner, M. L.; Illingworth, K. M.; Kelleher, J., and Wood, D. Intestinal absorption of the intact peptide carnosine in man, and comparison with intestinal permeability to lactulose. J Physiol. 1991 Aug; 439:411-22. 1991.
  • Gaspani L, Limiroli E, Ferrario P et al. In vivo and in vitro effects of bromelain on PGE(2) and SP concentrations in the inflammatory exudate in rats. Pharmacology 2002 May;65(2):83-6. 2002.
  • Gerbert G. Physiologie. Physiologie. Schattauer Publishing Co., Stuttgart, Gemany. 1987.
  • Griffin SM. Acid resistant lipase as replacement therapy in chronic pancreatic exocrine insufficiency: a study in dogs. Gut 1989;30:1012-1015. 1989.
  • Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995. 1995.
  • Kerneis, S. and Pringault, E. Plasticity of the gastrointestinal epithelium: the M cell paradigm and opportunism of pathogenic microorganisms. Semin Immunol. 1999 Jun; 11(3):205-15. 1999.
  • O'Keefe S. The use of lactase enzyme in feeding malnourished lactose intolerant patients. XIII International Congress of Nutrition, Brighton, England 1985: 190. 1985.
  • Pizzorno J, Murray M. The Textbook of Natural Medicine. The Textbook of Natural Medicine. 1998.
  • Russell RM, Dutta SK, Oaks EV, Rosenberg IH, Giovetti AC. Impairment of folic acid absorption by oral pancreatic extracts. Dig Dis Sci 1980 May;25(5):369-73. 1980.
  • Shaw D, Leon C, Kolev S, et al. Traditional remedies and food supplements. A 5-year toxicological study (1991-1995). Drug Saf. 1997;17:342�356. 1997.
  • Trier, JS. Structure and function of intestinal M cells. Gastroenterol Clin North Am. 1991 Sep; 20(3):531-47. 1991.

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