Casein-free/gluten-free (GFCF) Diets
last updated 8.25.05
GFCF Theory and Digestive Enzymes
Some people believe that dairy and grain products may cause adverse effects in some people (in particular, autism and other neurological conditions) due to poor digestion of these foods. One diet that eliminates dairy and grains focuses on removing these foods to prevent insufficiently digested proteins (called peptides) from entering the body. Casein is one of the many proteins from milk and gluten is one of the proteins found in small grains (wheat, barley, oats, and rye). There are multiple issues surrounding these foods.
One theory proposed these peptides caused a reaction in the brain similar to opiates - the 'opiate peptide theory' - which resulted in behaviors similar to someone on morphine. However, more investigation and newer information have brought that under intense review. Some of these types of compounds are regularly produced in the body anyway for good and beneficial purposes. Some such compounds are produced internally so it is virtually impossible to rid the body of every molecule especially if one is only relying on food removals. Another hurdle is that other foods and factors besides just dairy and grains may produce such similar shaped peptides (like corn, soy, rice, internal blood decomposition, yeast overgrowth, etc). It was once thought that you may need to get every single molecule of peptides too. However, this is not consistent with what many people experience or with science. Many people have been encouraged to get certain tests to measure the levels of peptides as a guide, but this has proved to be a inaccurate as well. Because the tests can pick up sources and compounds besides just casein and gluten by-products, the test results cannot clearly tell if it is casein and gluten that is the problem. An example is that a high peptide result may very well indicate a yeast problem instead.
Further, if you want to say something is a reaction due to certain opiate receptors, you need to work with what is known about how this mechanism works...a well-studied area.
Opiate Receptor Mechanics - click here to read about known science
Another theory is that gluten and casein (and probably other foods) need to be eliminated because they are insufficiently digested and thus provoke an immune system reaction, or an IgG-mediated reaction. Perhaps because of an injured gut, or poor overall digestion.
Fortunately the development of special enzyme products have provided the necessary enzymes to sufficiently break these foods down so that such an elimination is not necessary for many people, should that be their choice. In fact, many people find their health is better with enzymes and dairy and grains in their diet than even being on a casein-free, gluten-free diet plus enzymes (that is, adding the dairy and grains produced improvement). The dairy and grains are adding something nutritional that was missing on the restrictive diet. Further research is needed to determine why some people benefit more from this alternative. Some people may still need to follow certain food eliminations, or they may choose to eliminate foods as their preference. Enzymes can still be very beneficial to reaching these dietary goals as well.
Actual experiences with enzymes instead of a GFCF diet
It is logical that enzymes would be able to replace a GFCF diet because that theory is based solely on the premise that two specific types of peptides may cause adverse reactions simply because they are not sufficiently broken down. If enzymes can sufficiently break them down, then the same thing is accomplished and the diet is replaced. Often the enzymes may be able to break down other proteins that are not suspected of potentially causing problems or peptides that are produced within the body, or come from an unknown source whereas food eliminations may not. Enzymes (particularly those with DPP IV proteases) can assist with fighting yeast and bacteria, pro-actively heal an injured gut, and aid in detoxification.
It has been proposed in the past that sometimes if a person has been eliminating casein and gluten from their diet, and then resumed eating these foods without enzymes, there may be a sudden and severe regression in behavior and health as much as two to three months later (particularly in someone with pervasive developmental condition/autism). However, since May 2001 when the enzymes group was started and results tracked, no one has reported such an event when taking these enzymes. This adverse reaction which only happens to some, appears to be a situation either created or provoked only by following a strict GFCF diet and then leaving it without enzymes. Further research is needed to find out why such a diet may cause this. One discussion is given below.
Why no sudden regression with enzymes
In addition, some people with autism follow the Specific Carbohydrate Diet which includes dairy products and casein. Since a number of people with autism conditions improve greatly on this diet, this further shows that not everyone with a neurological problem benefits from being dairy-free. Some do far better with dairy in the diet. Be sure to thoroughly research the options when selecting a nutritional program. There are many available. What works well for someone else may not be optimal for your situation.
One reason that eliminating just casein or gluten foods may only be of temporary help is because a more fundamental issue is involved - the person has an injured gut, or leaky gut. This leads to a problem with whatever foods a person eats...and usually the most problematic foods are the ones the person eats the most of. Since many in North America and in Europe eat mainly foods with dairy and grains, it is no wonder that these foods would be the most problematic right off. But if the gut is not healed, then whatever food the person substitutes in the diet for the casein and gluten foods will next become a problem. It is often the experience of families that start off eliminating all casein and gluten, then shortly afterwards they see a problem with soy, or then corn, or then sugar, or then fruits...because the gut is still injured. So the basic problem is not casein and gluten but an injured gut. Until the gut is healed anything you eat may become a problem.
see below GF (gluten-free) and Leaky Gut: An Important Distinction in Development
Enzymes are excellent in this area because they proactively heal an injured gut by several mechanisms, whereas food eliminations only slow down the damage or postpone it a little longer. Any type of insufficiently digested food can lead to intolerance reactions. Note: If you have a 'true' allergy or IgE-mediated immune system reaction, enzymes may not relieve this because mechanisms other than food digestion may be at work. It it advised to avoid dairy or gluten in the case of true allergies. No enzymes are currently available that help with celiac and gluten, which is a different issue than just food breakdown.
see Leaky gut
see Specific Carbohydrate Diet
more information on GFCF diet
There are many components to dairy, many are very nutritious. However, this also leads to many possible reasons that dairy may be problematic. See the links below for the possibilities. If you remove diary, take care to compensate for the many healthful properties you will be losing. One factor in particular are the anti-bacterial components and minerals (not limited to calcium). Proper balance of microbes in the gut is essential for good gut function.
see Dairy - the Multi-faceted Substance
see Milk Types
There are many components to grains, with many being very nutritious. Whole grains have been found to be very good for proper health. A thorough evaluation needs to be done before removing any entire food group, and ideally with the supervision of a proper nutritionist or medical professional.
Grains are a prime source for magnesium, molybdenum, natural B vitamins, and several other nutrients. They contain carbohydrates and protein. Some people may find that reducing grains in their diet is helpful because they have trouble digesting starches, and/or they have trouble digesting proteins. If you substitute with other starches or proteins, you might have the same problems as with grains. Supplementing with enzymes for breaking down starch and/or proteins may help with not only grains but with all starches or proteins.
If you are having difficulty with grains or typical commercial bread, you may want to consider what else is in the product that might be a problem. It may be a preservative, artifical flavors or colors, barley malt, the corn syrup, sulfites, or something else. Many commercial bakeries spray the bread pans with a non-stick spray which may contain one of several artificial preservatives. A preservative may also be added to the packaging to, well...preserve the final baked product. These compounds are often phenolic and people who are sensitive to phenols or salicylates may not tolerate it. They may be reacting poorly to the phenolic preservative and not the grains.
So if you are thinking there is a problem with some breads, try making some homemade bread and coat the pan with parchment paper or just plain oil (this way you don't have to worry if the spray you use at home contains one of these same preservatives - some do). If you try baking at home, use unbleached flour as well (some people are sensitive to the bleaching agents). Some of the families say they notice a distinct difference in flours. This may be more noticeable with people who are sensitive to phenolic/salicylate/benzoate compounds. The bleaching process strips out some of the good nutrients and leaves some residues behind.
see Flour types
see Feingold Program
Another source of this artificial preservative is in the partially hydrogenated oil or shortenings that are commercially used, and is often in store-bought bread. Interestingly, plain old Crisco (not the butter flavored) does not contain this. If the homemade bread is tolerated but not commercial bread, the answer may be the preservative and not the food grain.
So if someone is intolerant of bread, it might be gluten or carbohydrates, but then again it might be the bleaching process, or the other additives in bread.
Another often over-looked additive is barley malt which is in quite a few flours. Some people don't tolerate that ingredient. And if you have Candida yeast, some of the yeast diets advise strictly avoiding barley malt.
A couple of good flour brands are King Arthur's or Hodgson's Mill flours. Both are commonly available in grocery and nutrition stores.
Research on Flour Additives
1. Determination of benzoyl peroxide and benzoic acid levels by HPLC during wheat flour bleaching process. Saiz AI, Manrique GD, Fritz R.
J Agric Food Chem. 2001 Jan;49(1):98-102.
Freshly milled wheat flour has a pale yellow color due to its carotenoids content. Benzoyl peroxide is a bleaching agent typically used to give such flour a better appearance. This free-radical initiator promotes carotenoids oxidation, thereby producing less colored compounds, and benzoic acid is a main final product. Samples of wheat flour were treated with 150 ppm of benzoyl peroxide to begin a bleaching process, and then subjected to ethyl ether extraction at different intervals of time. Benzoyl peroxide and benzoic acid levels in these extracts were monitored by means of HPLC in individual experiences. The resulting concentration of benzoyl peroxide after 9 days of contact with the bleaching agent was 11 ppm, dropping afterward to nondetectable levels. A maximum value for benzoic acid of 16 ppm was found after 12 h of bleaching. Subsequently this level decreased continuously until reaching a residual value of 6 ppm after 3 months.
PMID: 11305258 [PubMed - indexed for MEDLINE]
2. Controlled trial of cumulative behavioural effects of a common bread preservative. Dengate S, Ruben A. J Paediatr Child Health. 2002 Aug;38(4):373-6.
OBJECTIVE: Many anecdotes and one scientific report describe cumulative behavioural effects of bread preservative on children.
METHODOLOGY: Twenty-seven children, whose behaviour improved significantly on the Royal Prince Alfred Hospital diet, which excludes food additives, natural salicylates, amines and glutamates, were challenged with calcium propionate (preservative code 282) or placebo through daily bread in a double-blind placebo-controlled crossover trial.
RESULTS: Due to four placebo responders, there was no significant difference by ANOVA of weighted placebo and challenge Rowe Behaviour Rating Inventory means, but a statistically significant difference existed in the proportion of children whose behaviours 'worsened' with challenge (52%), compared to the proportion whose behaviour 'improved' with challenge (19%), relative to placebo (95% confidence intervals 14-60%).
CONCLUSIONS: Irritability, restlessness, inattention and sleep disturbance in some children may be caused by a preservative in healthy foods consumed daily. Minimizing the concentrations added to processed foods would reduce adverse reactions. Testing for behavioural toxicity should be included in food additive safety evaluation.
Clinical Trial; Randomized Controlled Trial
PMID: 12173999 [PubMed - indexed for MEDLINE]
People with celiac disease need to follow a strict gluten-free diet. There are scattered reports where someone with celiac was able to resume eating gluten by using amylase or papain (or perhaps both of these enzymes). However, at this time there are no known enzyme products that will consistently and reliably allow a person with celiac to resume eating gluten, although there continues to be research and development in this area.
Some people with celiac can tolerate oats, while others cannot. Recently oats have been declared 'okay' for the celiac gluten-free diet, if you can tolerate them and want to consume them. Oats do not have the same type of gluten as other small grains.
see Celiac and Enzymes
Much information on celiac:
GF (gluten-free) and Leaky Gut: An Important Distinction in Development
Celiac is an autoimmune condition where an element in gluten causes damage to the intestines. The absorptive tissue called villi are damaged, flatten, and nor longer function. This results in malabsorption and can lead to leaky gut. Once a gluten-free diet is started, the villi can heal and function properly again. The gut can heal. If the celiac person resumes eating gluten, the process repeats and the leaky gut returns.
This is different than what can happen with food intolerances (including such as in autism or related problems). In this case, the gut can become injured from a variety of reasons. Whenever the gut becomes damaged, and leaky gut develops, digestion can be impaired. This means that no matter what you eat, any food can be insufficiently digested, cross into the bloodstream when it should be kept out, and cause some unwanted reaction. If you remove gluten from the diet, the gut is still leaky (because gluten was not the cause itself), and whatever food you are eating now can still be poorly digested and cause an unwanted reaction.
.......so you take those foods out..but the gut is still damaged, and this leads you down that very slipperly slope as you head toward the Food- free diet.
In this case, removing the gluten does not necessarily heal the gut. So you need to pro-actively heal the gut, the villi will heal and digestion returns to proper functioning. Eating gluten or not eating gluten will not cause the leaky gut to return, not will it necessarily cause it to heal. It is the other way around from celiac.
The point is that eliminating foods doesn't fix the core problem with leaky gut. You have to fix the hole in the boat. Enzymes can pro-active heal tissue as well as breakdown any food you eat so it is not in an inappropriate state even if it does cross the gut barrier.
Most people, particularly children, happen to eat a lot of dairy and grain containing foods in North America and Europe.
If you find that the longer you are on restrictive diets, the more and more foods your child 'reacts' to, and thus need to be eliminated...this is what to think about.
Or if you do a food allergy/sensitivity test and it comes back showing you are sensitive to 48 or 97 different foods. This is more leaky gut or poor digestion than all those foods being forever forbidden.
In addition, with every food taken out, you are loosing a source of nutrition...particularly when you take out entire food groups.
What are major causes of leaky gut to begin with?
- yeast is a big one
- bacteria a big one too
- poor diet, highly refined, highly processed foods; excess sugar
- low zinc and EFAs
- asperin, some medications
- artificial ingredients and additives; and whatever compound your body might see as a something that needs to be detoxed
- surgury or illness
What are major helps in healing a leaky gut?
- ***digestive enzymes***
- probiotic in yogurt, fermented food or supplements (live cultures)
- treat yeast or bacteria, if a problem
- whole-food balanced diet
- add zinc, essential fatty acids, perhaps vitamin A is deficient
- detox with epsom salts, antioxidants
- reduce artificial additives and toxins as much as possible
- reduce sugar and highly refined, processed foods
see Leaky Gut
What About...? Q and A
Q.Why take enzymes for casein and gluten foods if you are on a GFCF diet?
If you take digestive enzymes, particularly one that works on gluten or casein, as well as staying gluten free or casein-free or GFCF..... what do the enzymes break down then? If someone does well on the diet, would he or she do even better on enzymes? What would enzymes have left to break down (except maybe for hidden gluten or casein) ?
A. The enzymes still break down the food that is eaten. The DPP-IV component in the some enzyme formulations does break down specific amino acid links in the gluten and casein molecules that then stop the morphine-like chemicals from forming (note: these are not morphine or opiate chemicals themselves, just cousin forms with a related shape). If you are not interested in stopping the GFCF diet, the general broad-spectrum enzyme formulaes (such as Digest Gold, Omega-zyme, Elite-zyme Ultra, etc) still have proteases in them for general protein digestion, as well as lipases for fat and whatever they are called -ases for carbohydrates. It is a good idea for all people who eat cooked and/or processed.
General broad-spectrum enzymes help digest most foods. If you spend any time on diet lists, you will find that in addition to gluten and casein, most autistic kids have a laundry list of other foods they cannot tolerate. This is because those other foods were not broken down properly and eventually the body started reacting to those as well. Taking enzymes will usually prevent more food sensitivities since this cycle will be broken. Not only that, they will help break down complex carbs which when improperly digested become food to yeast and bacteria. As a result, taking enzymes can help with kids that have yeast overgrowth which can aide in the permanent healing of the gut.
Food eliminations help with foods you know cause problems on the macro level (the big obvious things). But enzymes help on the macro and micro levels. Micro or small things would be trace amounts,contamination, hidden ingredients, etc. Enzymes also help with other foods you don't realize are contributing to the problem.
For example, a lot of people also have problems with soy proteins because the breakdown elements may act in the same way gluten and casein particles do. Enzymes take care of all the foods at the same time - they just act on the particles no matter where those particles
There might be other sources of protein peptides as well. Enzymes will work on these internally even if researchers haven't identified them yet.
Some peptides can be produced internally as well - breakdown of blood, yeast or bacteria production. Enzymes tackle these as well. And these sources can't be reached by food eliminations.
Is it good to note that just about everyone on a GFCF diet has seen further improvement when adding enzymes to the diet.
One reason may be that protease enzymes do more than just breakdown food proteins. They proactively help in healing the gut, killing off pathogens, supporting and strengthening the immune system, and some other things. Food eliminations...eliminate foods.
In addition, most people can put foods back into the diet with enzymes instead of having to progressively take more and more foods out which often happens with just diets.
These are things that happen over and above what is accomplished by the diet. You don't have to leave a diet to get these benefits if you don't want to. The reason that people use elimination diets is because they aren't digesting the foods, right? So tackling the issue
closer to the root cause, the point of digestion, goes farther. Hopefully, healing the gut will improve one's own digestive function so you eventually wouldn't need many enzymes, supplements, or food eliminations.
Q. What is DPP IV and which products contain this stuff?
A. DPP IV is a certain enzyme or enzyme activity that occurs in nature. It breaks down a certain bond in proteins.
Here is a list of products that various companies specifically say contain DPP IV enzyme activity (listed in alphabetical order by company name in parenthesis). Other products may have this activity but the manufacturer may not have tested for it, or made that specific claim for the product. Some products are much more effective than others, so check around.
- Digest Gold (Enzymedica)
- GlutenEase (Enzymedica)
- Lacto (Enzymedica)
- Peptizyde (Houston Nutraceuticals)
- EnZym-Complete/DPPIV (Kirkman Lab)
- EnZym-Complete II Isogest Formula (Kirkman Lab)
Spectrum EnZym Complete/DPPIV Fruit Free Isogest® Formula (Kirkman Lab)
- Peptidase Complete (Kirkman Lab)
- DPP-IV Forte (Kirkman Lab)
- Serenaid (Klaire Labs)
- Vital-zymes Complete (Klaire Labs)
- Digest Right (Learner's Edge)
- GlutenZyme is made by Biocare with reports of it being successful with gluten and casein, but it isn't known at this date if it contains DPP IV
- A DPP IV Biocore blend may be included in certain products
Some probiotics may also produce fairly large amounts of DPP IV enzyme activity as well. However, there
are not label or company claims on specific probiotic products on this at the moment.
While DPP IV is one enzyme to consider, it may not be the main or only enzyme an individual may seriously benefit from.
Q. Will enzymes interfere with running a peptide test?
A. Enzymes will not interfere in any meaningful way with the peptide test results. But that is more because the validity of the peptide test isn't very good whether you use enzymes or not. You really might want to save your money on this one. At first years ago parents were told to spend money on this test to see how those alledged peptides were doing and how many might be getting at the brain. But the whole opiate theory still remains just a theory...it still hasn't been proven to be true. Since then it has been very clear to many that the tests really don't tell you much of anything useful. Other things in your body (blood breakdown, yeast by- products) can generate peptides that register on the test. If you get a high peptide reading, it might be because you have a yeast overgrowth and no problem with casein and gluten at all.
Parents constantly report over the years that they would get a high peptide reading so scurry right on the GFCF diet 100% strict for over a year or more. Then they would run the test again after a year and get an even higher peptide reading than before. Other parents would say their tests results came back normal but they took out casein and gluten foods and their child did very well when supposedly he shouldn't have improved per the test results. The take home message is that whatever the test says, it isn't anything you can translate into a meaningful course of action or base a decision on.
I wrote one of the lead fellows who studied the peptide issue and came up with these tests, some time ago and asked him what is the percentage of typical people with healthy guts getting 'high' or elevated peptide readings from this test. He said about 25%. That is 1 in 4 typical people.
If you are interested in trying diet, just try a diet. If you are interested in enzymes or other gut healing measure, just try them. If you want to run a test for giggles and get a piece of paper with random numbers on it, do a peptide test. Other tests might be much more worth your time or money.
Studies: Casien and gluten foods improve removal of toxins and heavy metals?
It is known a certain chunk of people with autism do significantly better with casein and gluten foods (dairy and grains) IN their diets with digestive enzymes than on a GFCF diet with enzymes. So the dairy and grains are very beneficial for some reason. Maybe the child is less stressed and gets to participate> more, and this improves their overall health and immune system.
Maybe some unknown nutrient deficiencies are being fixed.
Another possibility are given in the studies below. These show that components in both dairy and grain foods bind with heavy metals (mercury specifically) and help facilitate their removal. There is a good possibility that if you are wanting to remove heavy metals or otherwise remove toxins, having dairy and grains in the diet would be beneficial.
Interaction of mercury with human and bovine milk proteins.
Mata L, Sanchez L, Calvo M.
Biosci Biotechnol Biochem. 1997 Oct;61(10):1641-5. PMID: 9362112 [PubMed - indexed for MEDLINE]
Food Technology and Biochemistry Department, Faculty of Veterinary Science, University of Zaragoza, Spain.
The interaction of inorganic mercury with human and bovine milk proteins was studied. Gel filtration chromatography of skimmed milk and whey incubated with mercury showed that, in human milk, mercury was mainly bound to caseins, while a low proportion was bound to albumin. In bovine milk, mercury was associated with two protein fractions, caseins and beta-lactoglobulin. Furthermore, it was shown by electrophoresis that mercury induced the formation of dimers of beta-lactoglobulin. Thus, in both human and bovine milk, mercury possessed greater ability to interact with milk proteins than to the low-molecular-weight substances. However, the pattern of mercury distribution was different between the milk of these two species.
An in vitro study of wheat bran binding capacity for Hg, Cd, and Pb.
Ou S, Gao K, Li Y. J Agric Food Chem. 1999 Nov;47(11):4714-7. PMID: 10552878 [PubMed - indexed for MEDLIN]
Research Center of Food Science and Technology, Jinan University, Guangzhou 510632, People's Republic of China.
Water-soluble dietary fiber (WSDF), water-insoluble dietary fiber (WIDF) from wheat bran, and the carboxymethylated product of WIDF (CIDF), all having low contents of protein, ash, and phytic acid, were evaluated for their scavenging capacity for three heavy metals, Hg, Cd, and Pb. The results showed that WIDF had higher BC(max) (maximum amount of bound heavy metal ions) and BC(min) values (minimum concentration of heavy metal ions below which the ions cannot be bound by dietary fibers) than WSDF at two pH conditions (pH 2.0 and 7.0). Carboxymethylation of WIDF improved its binding capacity for heavy metals (increase in BC(max) and decrease in BC (min)). The pH value significantly affected the binding capacity for heavy metals; BC(max) sharply increased and BC(min) sharply decreased for each heavy metal ion for all of the dietary fibers when the pH was raised from 2.0 to 7.0. The binding capacity of dietary fibers for heavy metals was slightly affected by amino acids, calcium, iron, and zinc but significantly affected by copper. Colon fermentation released part of the heavy metal ions from dietary fibers. From the results it can be concluded that dietary fibers from wheat bran can effectively bind all three tested metal ions to prevent the body from being affected by their toxicity.
More on 'What exactly is a peptide? and a protease?
An enzyme is a large protein the does work in biology, and is made of the same amino acids as other proteins. Each enzyme has a specific job which it does, and only that job.
A protease is an enzyme that breaks down proteins. There are thousands of different types of proteins and thousands of different types of proteases. It is more a general class of compounds rather than on specific item (like dairy is a general class with casein, whey, cheese, lactose, ice cream, etc being more specific parts or forms of dairy).
Most enzyme products contain some proteases of some kind - but the exact kind of protease can be very different. And some enzyme products contain specific proteases for specific jobs. I will send you the name of the product I used (I'm not supposed to post it here), but for the bacteria issue, any really good or strong protease product should work okay.
And just to round things out, a peptide is a 'piece of protein' or protein fragment. It is also a general class of compounds and not one specific molecule. There are tens of thousands of types of peptides because the proteins get broken up in many different ways. A peptide is what you call any piece of protein until it finally is broken down into individual amino acids.
Let's say a dry piece of spaghetti is one protein. You break it into three parts. You know have three peptides of different lengths. You break those three parts into smaller parts. Now you have, say, nine different peptides. You are creating peptides of different types until you finally break the piece of spaghetti into it individual amino acids.
The 'peptide issue' in autism is focused on one particular type of peptide - one particular structure and one particular configuration. The other hundreds of peptides aren't an issue. It is just a specific one. That is why it was so hard to come up with enzyme products that could handle the casein and gluten (and soy) problem. Researchers had to find the right blend that would sufficient break that one particular peptide. It really doesn't have to be broken in a certain way...just broken down in some way to mess up the configuration causing problems.
[Note: In a healthy digestive tract, the peptidase that breaks up this casein or gluten peptide is located in the intestinal lining. If you have an injured gut for any reason, the cells in the lining are not there functioning to produce this peptidase.]
If you see 'peptidase' on an enzyme label, that means there is an enzyme that works on some type of protein fragment. You could say that peptidases are types of proteases. You would need to find out more to see if the peptidase in the enzyme product was sufficient to work on the peptides you are interested in breaking down.
The role of proteases in bacteria control are thought to be:
1. helps breakdown the bad bacteria because these are made of proteins (but probiotics are not in the same group so probiotics and proteases are generally find together....I know that sounds a little hazy so here is a link with more on this:
Probiotics and Enzymes
2. Second reason is the protease may help reduce any die-off by breaking down general crud and dead bacteria cells. This helps to detox them, and thus saving the immune system and body from having to do this.
Die-off: what is it and how enzymes affect it