answer:I can’t answer all of your questions, but I can answer some of them, based on nutrution and human physiology classes I’ve taken. LI can be linked to genetics, (for example full-blood Native Americans are almost always completely lactose intolerant), but it can also be linked to aging. How this works is, “Normally, your body produces large amounts of lactase (the enzyme that digests lactose) at birth and during early childhood, when milk is the primary source of nutrition. Usually your lactase production decreases as your diet becomes more varied and less reliant on milk. This gradual decline may cause symptoms of lactose intolerance.” (from
http://www.mayoclinic.com) Before 1492, the Native American diet did not include any form of dairy products, (such as cows, sheep, goats as these were not present in the North America at the time), after infancy, they did not inject lactose at all, so their bodies stopped producing lactase. After generations of this, Native Americans are just more prone to LI. So, not everyone gets LI as they get older, but if you have it, it can get worse as you get older. Different dairy products have differing amounts of lactose, and they are consumed in varying amounts. For example, of the list you mention, I think butter has very little actual lactose, since lactose is milk sugar, and butter is only a part of milkfat. Also you wouldn’t eat 8 oz of butter or sour cream in one sitting, like you would milk. Also, “hard cheeses such as Swiss or cheddar have small amounts of lactose and generally cause no symptoms.” Apparently yogurt is usually cool too, because yogurt, because “the bacteria used in the culturing process naturally produce the enzyme that breaks down lactose”. Yes, it is still LI if it does not happen all the time. So the enzyme lactase is essential to digesting lactose. If your body does not make enough, that’s when you have a problem. So let’s say your body makes enough to digest one glass of milk, but not two, or enough for one glass of milk, but not that AND mac. and cheese. When you only eat the mac&cheese, you’re fine, but when you drink the milk too, then you have symptoms. I guess I did answer all your questions. The Mayo Clinic website was pretty straightforward, if you still are unclear, don’t hesistate to ask me, or you could look there. Also, you didn’t ask this, but I read about something called “lactase enzyme tablets”. It sounded like you could get them at a pharmacy without a prescription. Basically you take the tablet right before eating, and it replaces the lactase your body was lacking.