Tuesday, February 16, 2010

Are You Lactase Persistent?

The inability to digest milk's primary carbohydrate, lactose, is often cited as the reason why people choose not to consume dairy products.

In fact, the inability to digest lactose into adulthood is the norm. The ability to digest lactose is the exception - resulting from a mutation on a gene on chromosome 2. The normal, non-mutated condition for human populations is the gradual loss of production of the enzyme, lactase, that splits the milk sugar, lactose, into its absorbable components: glucose and galactose. This loss is about 90% complete by age 4.1

Some populations have retained this mutation, allowing them to consume dairy products without the gas, bloating, cramping, and diarrhea typical of lactose intolerance:
"The frequency of lactose maldigestion varies widely among populations but is high in nearly all but those of European origin."

In North American adults lactose maldigestion is found in approximately:
  • 79% of Native Americans
  • 75% of blacks
  • 51% of Hispanics
  • 21% of Caucasians
In Africa, Asia, and Latin America prevalence rates range from 15-100% depending on the population studied"

- The Acceptability Of Milk And Milk Products In Populations With A High Prevalence Of Lactose Intolerance, American Journal of Clinical Nutrition, 1988
Lactose intolerance worldwide:

Click to enlarge.

I've read that, taken together, about 75% of the world's population, and about 25% of the US population, can't effectively digest milk sugar. Our poll seems to bear this out:

Results of our milk poll:
Do you eat or drink milk (raw, skim, powdered, fermented, cheese, butter, cream, etc.)?

1 Wikipedia: Lactose intolerance


Perovskia said...

Well, this is one reason I'm glad I'm Dutch :D

virginia said...

I am Dutch (part), as well, and lactose intolerant. It took me years to entertain/accept that possibility. I thought the ice cream "factory" was contaminated.

I have a friend who had puzzling symptoms as a teenager, and after exhaustive tests, she was diagnosed as lactose intolerant. She wailed: "I can't be, I'm a tall Dutch girl because of milk."

Autumn Hoverter, MS, RD said...

I think the poll needs a third choice: do you drink milk even though you know it's going to make you sick?

Bix said...

(Autumn, Congratulations on your MS, RD!)

Steve Parker, M.D. said...

Even lactose intolerant people who can't drink milk may enjoy certain diary products that use bacteria to pre-digest the lactose: yogurt, cottage cheese, aged and hard cheeses.

[Bix knew this, but many readers may not.]


Dr. Mel said...

Hey, I just discovered I can see all your posts in Gmail Buzz!

Leonard said...

Not speaking for all Native Americans, but I do have issues with dairy, especially milk. The thing is I love cheese but if I eat it, it's not good. I wonder if this is because, well for one thing dairy was not a part of our traditional diet, secondly when we were put on the reservations we were given Government "rations". We call them commodities, which includes can food, beans, rice and evaporated milk, and something called powdered milk. Now I don't if anybody has had powdered milk, but it is nasty. Nasty, nasty! I refused to drink it as a kid but my mom made me because it was the only milk we had. On the other hand, you could add powdered milk to mashed potatoes, mac and cheese (also a commod item) and it worked in that aspect. To drink it though, yuck. As usual Bix great post and it made me think, where did us Natives get our calcium? Do turnips have calcium? We ate a lot of those. ;) peace

Oh and Dr. Mel you can also follow blogs on Blogger and see them all in your Dashboard. ;)

Bix said...

omg, powdered milk is nasty!

I just looked up turnips. The turnip part, not so much calcium, the turnip greens have a respectable amount though.

Speaking of mashed potatoes and turnip greens, one of my favorite foods is smashed red potatoes (with skins) mixed with a chopped boiled bitter green, like rapini (broccoli rabe). &olive oil/garlic/salt. I could eat that for breakfast.

Bix said...

I'm still getting the knack of this Google Buzz. It sure does slow my system.

Autumn Hoverter, MS, RD said...

(Thanks Bix! Took a while but I finally made it! And your blog is still my favorite :)

Leonard said...

Hmmm...interesting, I'm trying to think of where our calcium intake could have came from. ;) peace