Ice Cream Is Good And Bad For You….Eghosa Imasuen

I remember the anecdotes associated with these words of wisdom, after a period of enjoyment comes a bout of payback. Valentine’s Day was just some weeks ago and I know that some of my readers had ice cream, or at least bought ice cream. How many of those who swallowed the creamy stuff, luxuriating in the coolness, the ease with which it went down the throat, the taste of cow’s milk percolated into fatty cream, and then frozen, ended up in the toilet within hours? If you were one of them, you have Lactose Intolerance.

Lactose intolerance is a condition—completely misnamed, since contrary to what the title suggests, it is actually the normal state for adult mammals—in which the ability to digest the sugar, lactose, is impaired because of a lack of the enzyme lactase. The etymology of the words lactose and lactase are self-explanatory. Lactose is the predominant sugar found in milk. And in adults, the frequency of absence of the enzyme lactase in populations ranges from 5% in Northern Europe, and some pastoral communities in Africa, to 71% in Sicily and up to 90% in Africa and Asia.

What happens is this: lactose is a disaccharide, a sugar made of two smaller units. Disaccharides cannot be absorbed directly through the intestine’s walls. So when a lactase-deficient individual ingests milk, the sugar remains in the lumen of the gut where it is immediately acted upon by bacteria. This fermentation produces by-products, gas: hydrogen, carbon dioxide and methane. These in turn produce the intestinal symptoms some of you remember from the 15th of February: cramps, bloating, heartburn, and flatulence, and of course, diarrhoea. Although to be pedantic, the way Lactose Intolerance produces diarrhoea is through the direct action of the undigested sugar itself, not through the action of bacteria. The sugar draws water into the lumen of the gut leading to the watery stools.

But what is the real-world relevance of Lactose Intolerance, you ask. You see, in the northern-hemisphere-dominated world we live in, assumptions can lead to, and have led to, death. During the Nigerian Civil War, Caritas, the Catholic aid agency, and others pushed large shipments of aid to help the protein-energy-malnourished children in the Biafran enclave. They came with egg yolk, with dried fish, with milk. And doctors, including the pair who would go on to found Médecins san Frontières, noticed that older children were dying from consuming milk. From consuming milk? Yes. The Red Cross initially ascribed these deaths to spoilage, to contamination, to even outright poisoning by the opposing forces. They said Biafrans were preparing the milk wrongly. But it was Lactose Intolerance. Even the brilliant can be slow to latch onto the obvious.

Lactase is an enzyme that every child is born with, an important trait because the infant’s entire diet consists of mother’s milk. The mammalian production of lactase drops off as infants approach the weaning period but some populations—because of a mutation in the genes that code for this trait—have retained the ability to process lactose into adulthood. Unsurprisingly this recent agriculturally associated trait confers an advantage in pastoral communities, so lactose intolerance is rare in societies where dairy products have a long, almost prehistoric, history of being consumed, i.e., the Fulani, the Tutsis, and Northern Europeans. However, most other humans lose this ability. And it is not modifiable, although new research seems to suggest that retaining Lactase activity into adulthood is on the rise worldwide, a sign, some say, of evolution in action.

So those who stole to mommy’s kitchen cupboard to binge on powered milk; those who add coffee to their milk instead of vice versa; those who quaffed Valentine’s Day ice cream as if there was no tomorrow, now you know why you ended up in the loo hours later.