In 1994 I was diagnosed with celiac disease, which led me to create Celiac.com in 1995. I created this site for a single purpose: To help as many people as possible with celiac disease get diagnosed so they can begin to live happy, healthy gluten-free lives. Celiac.com was the first site on the Internet dedicated solely to celiac disease. In 1998 I founded The Gluten-Free Mall, Your Special Diet Superstore!, and I am the co-author of the book Cereal Killers, and founder and publisher of Journal of Gluten Sensitivity.
The following is a summary of lactose intolerance which was written by Ellen Eagan firstname.lastname@example.org. Ellen is a blood specialist at UC San Francisco Medical Center. Ellen Eagan on Lactose Intolerance:
The area in the intestines where lactase, the enzyme needed to break down lactose, is produced is called the brush border. It is at the ends of the microvilli. It is only one cell deep. As most people age, their ability to produce lactase decreases. Sometimes it decreases to the point where you are unable to deal with all of the lactose that you ingest. If you have decreased production of lactase and then something else happens to compromise the integrity of the brush border, it cases further reduction of lactase production. If you continue to take in lactose, that causes more irritation and loss of lactase production. It becomes a vicious negative feedback cycle.
When you are suffering from celiac sprue, there is damage to your intestinal villi. This can make one temporarily lactase deficient to the point where lactose becomes a problem also. This happened in my case. Once I started on the gluten-free diet and my intestines had healed, lactose was no longer a problem for me. I can eat any diary product now with no problems.
Not everyone will be so lucky. A lot of people will remain lactase deficient. Yogurt and aged cheeses are more easily tolerated because some of the lactose has been converted to lactic acid. One rule of thumb is that the higher the fat content of the dairy product, the lower the lactose level. People who are still producing some lactase would then be able to eat a very rich ice cream but would be bothered by skim milk or ice milk.
I highly recommend the book No Milk Today: How to Live With Lactose Intolerance (Steve Carper, Simon & Schuster, Inc., 1986 ISBN0-671-60301-0). I found it at my local library. Its an excellent book for explaining the process, describing hidden sources of lactose (like whey), and tips on eating out. In regards to the fat content and lactose level I quote from page 119 of the book: Foods with high milk fat tend to be lower in lactose than other milk products. Heavy cream is lower in lactose than light cream, which in turn is lower than whole milk. Butter is higher in fat than any of these, and in turn is the lowest in lactose. It was mentioned that aged cheeses are lower in lactose than non-aged cheeses because the lactose had been broken down during the aging process.
So, even though lactase deficiency and gluten intolerance can give the same symptoms, they are not caused by the same processes. Lactase is composed of two sugars. The problems arise when you are unable to break it into its two parts and absorb them.
Gluten is a protein. It seems to cause a problem due to an immunological response, and as far as I know, symptoms are the only similarities between the two.