Some time ago, an inquisitive mind inquired of me as to whether being lactose intolerant could affect the sufferer’s tolerance of wine that has undergone malolactic fermentation. Fair question. “Lactose” and “lactic” are obviously related, and thinking about an intolerance to the “lactic” in wine is a sensible leap with everyone and their brother speculating over what causes wine headaches and the like (derivatory of the overarching food intolerance fad, I expect.)
The good and the bad news is that lactose intolerance has no bearing whatsoever on the ability to digest malolactically-fermented wine. Good news, as the lactose-intolerant among us can drink wine without reservation. Bad news, as the lactose-intolerant among us are equally as enlightened as everyone else as far as identifying a cause of the wily wine headache, i.e. still in the dark.
Short answer: lactose intolerance is unrelated to the ability to tolerate wine that has undergone malolactic fermentation.
Longer answer: Most people who react poorly to lactose suffer from an intolerance, not an allergy. Allergies are inappropriate immune responses to specific epitopes, which can be thought of as molecular shapes. An intolerance, on the other hand, isn’t necessarily an immune response. Lactose intolerance is caused by a deficiency in the enzyme responsible for breaking down lactose in the small intestine. Since we can only absorb lactose after it has been broken down into its component parts – glucose and galactose – a lactase deficiency means that undigested lactose builds up in the intestines to cause bloating, diarrhea, gas, and other discomforts. Unlike lactose, lactic acid can be absorbed without first being acted upon by the lactase enzyme.
Incidentally, even if lactic acid absorption was somehow related to lactose absorption, quantity would be a pertinent consideration. Milk contains 2-8% lactose, i.e. relatively a whole lot, while wine contains much less than 1% lactic acid.
In conclusion, then, the lactic acid in wine should be of no concern to most people who need to avoid lactose. A glass of wine makes a far friendlier companion to a good dinner than a glass of milk, don’t you think?