Digestive enzymes, the natural ones in our gastrointestinal tracts and the supplemental ones that come in capsules, are proteins that have the catalytic ability to disassemble large food molecules. Digestive enzyme supplements come from plant or animal sources (classified legally as "foods") and they can help us to digest food when they are taken with a meal. The different types of digestive enzymes include: proteases for breaking proteins down into peptides and peptidases for breaking peptides down to individual, free-form amino acids or short-chain peptides. Short-chain peptides are dipeptides (two amino acids linked together) and perhaps some tripeptides (three amino acids linked together). Lipases split dietary fat molecules into smaller pieces (glycerol and fatty acids). Amylases break dietary starch down into simpler carbohydrates like disaccharides or monosaccharide sugars. Disaccharidases break complex sugars down into simple sugars. We often need disaccharidase help in autism: lactase (for processing milk sugar into glucose and galactose ), and maltase and isomaltase for processing some complex sugars into simple ones like glucose or fructose. Sometimes additional enzymes are present that break down the cellular structure of plants -cellulases, hemicellulase and xylanases. When nutritional supplements are needed, digestive enzyme supplements are usually needed also, because they improve the body's ability to extract needed nutrients from food.

A natural peptidase enzyme of particular interest in autism is dipeptidylpeptidase IV (DPP4 ).I DPP4's job is to break apart peptides that have the amino acid proline at every other position in the peptide molecule. Such peptides, "exorphins" have morphine-like action on neuronal cells. Beta-casomorphin 7, from casein, is such a peptide:

T yrosin e-protin e-pheny lal anine-pro tin e-gl y cin e-pro tin e- iso leucine

So is gliadorphin (gliadinomorphin), from gliadin from gluten:

T yrosin e-pro tin e-gl utamin e- pro tin e- gl utamin e-pro lin e- p hen y 1 alanin e

DPP4 cleaves peptides such as these at the second bond (a proline-amino acid bond) from the N- terminal end (the left end as written and where H2N- is understood to be attached). Thus, DPP4 acting successively on beta-casomorphin 7 causes -

Tyr-Pro I Phe-Pro-Gly-Pro-De

Tyr-Pro I Phe-Pro I Gly-Pro-De

Tyr-Pro I Phe-Pro I Gly-Pro I lIe

In the human digestive tract, only DPP4 can do this. But, DPP4, like many enzymes, is subject to inactivation or poisoning by external substances. During the 1980s and 1990s, Reichelt, Cade and others found undigested exorphin peptides in the urine of autistics.2,3,4,5 These findings are

consistent with impaired and deficient activity ofDPP4. In 1982, Puschel et al. examined DPP4 from human placenta and found that it is inactivated by mercury (mercuric chloride), organophosphates (pesticide sprays), zinc and cadmium chlorides, and lead acetate.6

The exorphin peptiduria presented by autistics is consistent with deficiency of DPP4 digestive activity .There also are biochemical connections between the DPP4 protein as a digestive enzyme and adenosine deaminase binding protein and cluster differentiation factor CD26, which is a binding and signaling site on l~phocytes. All these are the same protein. So, a plant-source protein with DPP4 digestive activity, a "DPP4 analog", should be among the peptidases in a digestive enzyme supplement for autistics. The analog form of the protein is used because we don't have the exact human form available and because we don't yet have the know-how or justification for genetic engineering to produce human DPP4 for this purpose.

You will find in the literature that there can be immune response to DPP4 in autism.7 This is related to the fact that certain exogenous (from outside the body) molecules or substances bind to cellular DPP4 (CD26). Some casein peptides ( casomorphins ) do this~ they'd have to for DPP4 to digest them. But mercury in Thimerosal form also binds to DPP4, as does the toxin from strep germs, streptokinase. This does not mean that plant-source DPP4 analog causes immune response or dysregulation. That's what's going on with the human CD26 in the autistic's body after it gets loaded up with foreign (toxic) materials, including peptides. The supplemental, digestive DPP4 analog is supposed to digest these peptides. If they are not digested and if they get into the bloodstream, then they can bind to cellular CD26 and cause trouble.

Now, let's switch to carbohydrate digestion which has been found faulty in autistics by Horvath and others and by Kushak and Buie.8,9,10 Lactase, which digests the milk sugar, lactose, is the disaccharidase enzyme that is most often weak in autistics. Lactose, a disaccharide sugar, is glucose attached to galactose. Lactase in the small intestine separates lactose into glucose and galactose. Lactase is most active at a pH of 5.4 to 6.0 (slightly acidic), and the pancreas has to put adequate bicarbonate into the much more acidic food matter coming from the stomach for lactase to work. For whatever reason, though, lactase deficiency is present in at least 60% of tested autistics.9,10 So, lactase must also be in digestive enzyme formulations for use in autism.

Three other disaccharide sugars are also known to be poorly digested by autistics: Maltose: glucose + glucose with a I-+ 4 glycosidic bond

Isomaltose: glucose + glucose with a 1-+ 6 glycosidic bond Palatinose: glucose + fructose with a I-+ 6 glycosidic bond

The difference between maltose and isomaltose is how the two sugars are linked together~ two different digestive enzymes, maltase and isomaltase, are needed, one for each. Palatinose uses the isomaltase enzyme for digestion. Because many autistics have maltase and isomaltase/palatinase deficiencies too, these also need to be provided as supplemental digestive enzymes. Maldigestion of carbohydrates, especially sugars, can provide a food supply for dysbiotic flora. Dysbiosis has been identified as a problem for autistics, 11,12 and intestinal dysbiosis contributes to inflammation and discomfort. Besides dysbiosis and inflammation increased permeability of the gut mucosa is documented,13 and this provides a means of entry to

the bloodstream for intestinal toxics and peptides. Intestinal inflammation in autism has been identified by Wakefield et al.14 and confirmed by BuielS and Krigsman.16

Lipase is the digestive enzyme that breaks complicated dietary fats into two types of molecules that can be absorbed more easily- fatty acids and glycerol. For years, we saw elevated fats in the stools of autistics when a stool or digestive stool analysis was done. At the Atlanta DAN! Conference in May 2001, JeffBradstreet MD (Melbourne, FL) spoke about this. Over 50% ofhis autistic patients showed some degree of excessive stool fat per the Great Smokies Diagnostic Lab (now Genova Diagnostics) CDSA test. (Other labs now offer this test too.) When this problem gets bad enough, fatty acid, vitamin D and calciwn deficiencies can occur, and dietary uptake of vitamins A and E may be reduced as well. A temporary , and sometimes long-term, remedy is to provide lipase orally with meals. The amino acids glycine and taurine, if subnormal, can be supplemented to help biliary function. This contributes to uptake of these lipid nutrients.

The general rule is to follow the manufacturer's or provider's instructions for use. Most of the enzymes offered for autism are plant-based. Some come from highly refined aspergillus strains, and the refining has removed the allergenic substances that used to be a problem with supplements from this source. Nevertheless, do a careful trial with just one capsule before a meal to check for tolerance.

Enzyme formulations for autistics contain protein analogs of the human enzyme forms. These analogs can be quite stable and typically remain active over wide pH ranges (acid-base conditions). Most are designed to work at pH 1.5 to above 7 and begin digestion (or do all their digestive work) in the stomach. This includes the peptidases such as DPP4 analogs. So, the usual procedure is to give digestive enzymes that are formulated for autism just before or at the beginning of each meal -not afterward Alternatively, gelatin-encapsulated enzymes can be opened and the enzyme powder can be sprinkled on the food. The amount to be given depends upon the size of the meal, not the size of the person. The specifics of how much depend on enzyme potencies -follow the label or provided instructions.

Based on many parent responses, it isn't uncommon to have a period of "worse before better" with digestive enzyme use in autism. Many parents have contacted me directly, describing a worsening of autistic traits, sometimes (increased) hyperactivity and irritability. Almost always, this is a temporary phase.

When digestive enzymes with DPP4 are used, the exposure to dietary opiate peptides is further decreased as more casein and gluten are digested by the enzymes. This usually brings about a period of opiate-like withdrawal, which may last 5 to 10 days or longer in some cases. During this period, the individual may become irritable or tantrum, develop hyperactivity, experience an increase in stimming or may present increased levels of inappropriate behavior or regression. Cravings for discontinued foods can occur which may potentiate these withdrawal symptoms. Not all children experience withdrawal or adverse symptoms when starting the enzymes; prior elimination of casein foods from the diet can significantly lessen or eliminate withdrawal symptoms. This is the reason for starting these enzymes several weeks after starting the CF diet trial. (The first week of the CF diet trial may also produce some withdrawal symptoms.)

Decreased amounts of undigested food in the lower gastrointestinal tract can lower or eliminate a food supply that may have fostered the growth of dysbiotic, possibly pathogenic flora. Remember that autistics often have increased permeability of the gut wall,13 which allows for an increased toxic burden. A temporary result of using digestive enzymes can be die-off of dysbiotic flora with consequent release of even more toxins. The die-off period usually does not last more than a week, but may continue longer with persistent, adaptable dysbiotic strains.

With more complete digestion of dietary protein comes a more normal amount of free-form essential and protein amino acids. In a few individuals, this can lead to a third effect if there is an underlying problem with transport and metabolism of amino acids. An example of such a problem is malabsorption of the essential amino acid tryptophan which can lead to an increase in indolylacryloylglycine ("lAG"). With this problem, some amount of tryptophan that isn't absorbed in the small intestine travels to the large intestine or meets dysbiotic flora in the small intestine. The flora change tryptophan into a toxic organic acid, indoleacrylic acid. In the liver, this organic acid is detoxified by attaching glycine to it, forming IAG. So, an unusual but possible consequence of digestive enzyme use is temporarily increased lAG.

Thus, an initial period of adverse response to digestive enzymes can occur in some autistics. If this problem period continues beyond two weeks, please consult a knowledgeable health professional, or a "DAN doctor". Clinical "laboratory tests can be informative in cases of prolonged problems -a diagnostic stool analysis, an amino acid analysis (24-hour urine preferred for this situation but fasting plasma is OK), and a food allergy workup. Food allergies can cause inflammation of the intestinal mucosa and worsening of the responses described above.

A capsule of activated charcoal, taken three times per day (away from meds and supplements) may reduce or stop adverse symptoms. Charcoal does this by absorbing toxins from dysbiotic flora before the toxins can cross into the blood stream.

1. Misumi Y and Ikehara Y "Dipeptidyl-peptidase IV" Chapt. 128 in Barrett AJ, Rawlings NO and Woessner JF, eds: Handbook ofProteolvtic Enzvmes Academic Press (1998) 378-382

2. Reichelt KL, Hole K, et al. "Biologically Active Peptide-Containing Fractions in Schizophrenia and Childhood Autism" Neurosecretion and Brain Peotides, Martin m, Reichlin Sand Bick KL eds, Raven Press (1981) 628-643

3. Reichelt KL, Ekrem J and Scott H "Gluten, Milk Proteins and Autism: Dietary Intervention Effects on Behavior and Peptide Secretion" J.Appl. Nutrition ~ no.1 (1990). 1-11

4. Reichelt KL, Knivsberg AM et al. "Nature and Consequences of Hyperpeptiduria and Bovine Casomorphins Found in Autistic Syndromes" Dev. Brain Dysfunct 1 (1994) 71-85

5. Cade R, Privette Met al. " Autism and Schizophrenia: Intestinal Disorders" Nutritional Neuroscience ~ (2000) 57- 72

6. Piischel a, Mentlein Rand Heymann E "Isolation and Characterization ofDipeptjdyl Peptidase IV from Human Placenta" Eur. J. Biochem ll§. (1982) 359-365

7. Vojdani A, Pangbom JB et al. "Infections, toxic chemicals and dietary peptides binding to lymphocyte receptors and tissue enzymes are major instigators of autoimmunity in autism" Int.J.Immunopath and Phannacol.lQ no.3 (2003) 189-199

8. Horvath K. Papdimitriou JC et al. "Gastrointestinal abnormalities in children with autistic disorder" J. Pediatrics ill no.5 (1999) 559-563

9. Horvath K and Pennan JA " Autistic disorder and gastrointestinal disease" CUff. Opinion in Pediatrics 14. (2002) 583-387 ,,~

10. Kushak RI and Buie T "Disaccharidase deficiencies in patients with autistic spectrum diSOrders" lf,; presented at the DAN! New Orleans Think Tank, January 2004.

II. Rosseneu S " Aerobic throat and gut flora in children with regressive autism and gastro-intestinal signs" Syllabus, Fall DAN! 2003 Conference, Portland OR, October 2003, 55-62

12. Rosseneu S, van Saene HFK "Gut flora in autistic spectrum disorder" presented at Fall 2004 DAN! Conference, Los Angeles, CA Oct 2, 2004.

13. D'Eufemia P, Celli Metal. " Abnormal intestinal permeability in children with autism " Acta Paediatr Q2. ( 1996) 1076-1079s

14. Wakefield AJ Murch SH et al. "lleal-Iymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children" Lancet ill Feb 28, 1998637-641

15. Buie T "Examining GI issues in children with autism and the effectiveness of traditional GI medications" Syllabus, Spring 2003 DAN! Conference Philadelphia PA May 2003 163-169

16. Krigsman A "Current concepts in the treatment of autistic spectrum associated enterocolitis" Syllabus, Spring 2004 DAN! Conference Washington DC April 2004253-258