Wednesday, October 31, 2012

Lactose and Dairy Products


Dairy Products and Lactose Intolerance

Lactose is a disaccharide, a carbohydrate made up of two simple sugars, in this case glucose and galactose.  While not exclusive to milk products, lactose is most commonly associated with milk.  The sugar itself makes up approximately 5% of the total weight of milk. 

Lactose is broken down into its two simple sugars in the small intestine by the enzyme lactase.  When the small intestine is damaged, as is may be for many individuals with IBD and in particular those with Crohn’s disease, lactase isn’t produced in sufficient quantities to allow for lactose digestion.  Individuals who have had a bowel resection of the small intestine or active inflammation therein may be the most impacted.

Lactose intolerance is not exclusive to those suffering from IBD.  Infants have the ability to produce lactase, to allow for their consumption of milk during breastfeeding (40% of the calories in breast milk are from lactose).   Most individuals with an ancestry that is not northern or western European lose the ability to digest lactose in adulthood.

The inability to digest lactose is called lactose intolerance and is not to be confused with a milk allergy, which is an adverse reaction to casein, or milk protein.  When lactose isn’t digested properly, it causes symptoms including:
·         Abdominal pain
·         Gas
·         Bloating
·         Nausea
·         Diarrhea

Symptoms of lactose intolerance generally appear between 30 and 120 minutes after consuming a product containing lactose.  The amount of lactose that needs to be consumed to trigger symptoms varies.  Many individuals are able to tolerate up to a cup of milk a day before showing symptoms.  Additionally, even in those with Crohn’s disease, dairy is frequently well tolerated and should not be avoided unnecessarily unless adverse symptoms occur. 

Lactose appears in many products as both a milk product and as a stabilizer.  Products that include lactose vary widely, and include:

  •  Prescription and over-the-counter medications
  • Baked goods
  • Processed meats (e.g. hot dogs)
  • Salad dressings
  • Protein bars
  • Candy
  • Butter substitutes

Recognizing the inclusion of lactose can sometimes be difficult.  It can be listed on the ingredient list as lactose, milk, whey, milk solids, or milk products. 

The amount of lactose in varies foods is often misunderstood.  Cow milk tends to have the highest lactose content, but milk-based products vary greatly in their lactose content.  Sheep milk and goat milk contain a commensurate amount of lactose.  Skim milk and low fat milk actually contain slightly more lactose by volume than whole milk or cream – lactose is not fat soluble and the removal of the fat reduces the volume while not removing any lactose.

One way to estimate the lactose content is to review the ingredients list and look for the number of grams of sugar present.  If no other sugars are listed in the ingredients, the listed amount is the amount of lactose in the product.  If other sugars are present, the amount listed is the upper bound of the amount of lactose.  If less than .5 grams of sugar are present, the product can be legally labeled as “sugar free”.  The reference amounts of sugar in a particular product can be found at http://ndb.nal.usda.gov/.  A sample of the lactose amounts in particular products is shown below.

Product
Serving Size
Amount of Lactose (in mg)
Milk
8 oz
8290
Yogurt
1 container (8 oz)
6580
Vanilla Ice Cream
1 scoop
4390
Mozzarella
1 cup, shredded
1150
Cream Cheese
2 Tbsp
940
Ricotta Cheese
1 cup
660
Cheddar Cheese
1 cup, shredded
590
Sour Cream
1 cup
390
Cream, Heavy Whipped
1 cup, whipped
130
Parmesan Cheese
2 Tbsp, grated
80
Half-and-Half
2 Tbsp
40
Butter
2 pats
7

In cheese making, milk is separated into curds and whey.  The whey generally contains the bulk of the lactose, but may be added back in certain cheeses (e.g. processed cheeses like American cheese, cream cheese, and fresh mozzarella).  Additionally, lactose breaks down naturally over time in aged cheeses due to the presence of the lactobacillus bacteria, which use it as a food source.   As a general rule, the amount lactose goes down for harder and older cheese.  This means that a few spoonfuls of aged parmesan on top of your spaghetti are likely okay, but the nachos at the bar are a stay-away food if you experience lactose intolerance.

Similar to cheese, butter is made from milk fats and contains marginal amounts of lactose.  Because of this, butter can be used in cooking and well tolerated by individuals with lactose intolerance, though the fat absorption may cause problems for those with IBD.  Margarine does not contain lactose by itself, but specific butter substitutes may add in lactose for stabilization.

While yogurt contains a large amount of lactose per serving, many individuals with IBD can consume yogurt asymptomatically.  Because yogurt is cultured with lactobacillus, the initial lactose is slowly converted to lactic acid, which does not cause symptoms.  After approximately two weeks of storage, the lactose content in yogurt is approximately half of the initial amount.  Additionally, yogurt has been shown to be easier to digest than similar quantities of milk products due to the production of lactase from the yogurt during digestion. (1)  While lactobacillus in yogurt breaks down lactose and is naturally present amongst the bacteria in the intestines, lactobacillus supplements have shown no effect on lactose intolerance. (2)

Substitutes for milk for those with IBD include almond milk, coconut milk, rice milk, and soy milk.  Depending on taste preferences, any of them can be used as a general substitute, but may not have the right characteristics for cooking or baking.  Specifically, the above products, with the exception of soy milk, tend to be thinner than milk and may not be sufficient to add the proper texture of creaminess to a dish.  When buttermilk is called for in a recipe, the addition of a tablespoon of vinegar to a cup of any of the above products can be used as a replacement.  Because milk and dairy products are a primary source of calcium in many diets, alternative sources of calcium must be found if these substitutes are used.  Additionally, dairy products are a good source of riboflavin, Vitamin D, and protein and care must be taken to include these in a dairy-free diet as well.

In addition to substitutes, the lactose can be removed from milk or neutralized by several methods.  Lactose-free milk is produced one of two ways – by adding lactase or by removal of the lactose through crystallization.  Adding lactase to milk, either through drops at home or during the production process, doesn’t remove the lactose it just converts it to glucose and galactose, resulting in slightly sweeter tasting milk.  Removal by crystallization uses a chemical process to separately remove the two variants of lactose present in milk.  Commercially available pills provide lactase that works in your digestive track to break down the lactose and are taken concurrent with food.  Milk treated with lactase is nutritionally equivalent to regular milk, and can be used as a cooking substitute without alteration anywhere milk is called for.

The relationship between dairy products, lactose, and IBD is complex.  If you believe you are lactose intolerant, several tests can be done to confirm this.  A blood glucose test measures the amount of blood sugar following the consumption of a high-lactose beverage.  The now preferred test, a hydrogen breath test, involves breathing out following the consumption a similar beverage to the glucose test.  The amount of hydrogen exhaled increases with the inability to break down the lactose.  Your GI doctor can point you toward these tests if you are having trouble digesting dairy products, and can similarly rule out a milk allergy.

Because dairy products are complex, even those without lactose tolerance issues may have trouble with some due to their sugar content, fat content, or added ingredients.  As with most IBD cases, keeping a food diary can help determine trends in responses to specific food items.  

Bottom Line:  

  • Many people that believe they are lactose intolerant are found not to be when presented with challenge tests.
  • For those with lactose intolerance, not all dairy products are created equal.  Many contain minimal amounts of lactose that are unlikely to trigger a response, even in intolerant individuals.
  • IBD sufferers should not automatically avoid all dairy products, at least not for the sake of the disease.

Introduction

This is a new pseudo-weekly blog related to inflammatory bowel disease, primarily Crohn's Disease and Ulcerative Colitis.  Like the excellent http://www.sciencebasedmedicine.org/, I will cover IBD topics from an evidence-based perspective.

Like many other conditions, IBD patients are inundated with information, both from medical practitioners and others, most well-meaning, about how best to treat their condition.  Much of the information is overly speculative (new treatment holds promise for the cure of UC after 5 person study), or sensational (cure Crohns in 10 days!), or just plain wacko (there is a conspiracy between the government and the dairy industry to keep the cause of IBD a secret).  This blog will look at various topics related to IBD, including nutrition, treatments, causes, and living with the disease.

What differentiates this blog is that I don't claim to have any answers.  None.  I have a background in biomedical research and am a published author, but I am not a registered nutritionist, doctor, or other medical practitioner.  As such, I will strive to present the latest evidence on various topics, along with pointers to solid research, related to IBD.  I will not provide a forum for anecdotal stories or idiosyncratic responses.  Science-based medicine is about well formed, double blind studies that evaluate a treatment or approach as an isolated variable.  There is a place for self reporting, and there is value to large scale epidemiological studies, but these tend toward correlative results.  It is all too easy to find correlations that support pre-conceived biases rather in less-than-perfect studies.

I don't work for a pharmaceutical company (in full disclosure I did IT work for a pharma company years ago), nor do I work for any manufacturer or peddler of alleged IBD cures.  I don't have any built-in bias against any particular treatment, from herbal remedies to diets to the latest biological drugs.  My only bias is to what has been adequately tested and shows results in a well controlled study that is large enough to have statistical significance.

I hope my blog will be helpful to sufferers of IBD everywhere!