No milk today

Although I am not a gastroenterologist, I feel that I am well qualified to write on this topic. My “gut rot” really started around seven years ago, in my mid-30s. I had been diagnosed as having irritable bowel syndrome as a student, but this was something more. The symptoms became quite distressing and, after a negative colonoscopy, a simple test revealed that I was lactose intolerant.

In other mammals, milk would be present in the diet only while they were breast fed

The milk sugar lactose is a disaccharide found naturally only in milk products. In non-sufferers it is split in the small intestine by lactase into glucose and galactose, which are readily absorbed. In the absence of endogenous lactase enzyme, the sugar passes into the large bowel, where it is broken down by lactobacilli, part of the normal flora. The products of this digestion include hydrogen, some of which is absorbed and excreted via the lungs, the remainder leaving by an alternative route. The raised level of hydrogen in exhaled breath forms the basis of the lactose tolerance test. In addition, unabsorbed lactose has an osmotic effect not unlike that of lactulose, a synthetic laxative, increasing the amount of fluid retained in the bowel. It does not take too much imagination to see the effect that this fluid and gas might have on the colon, with the diarrhoea, colic, and flatulence being similar to the symptoms of irritable bowel.

In other mammals, milk would be present in the diet only while they were breast fed. After weaning lactase would no longer be required. In Western society, milk products constitute a major part of a normal diet and the gene coding for lactase usually remains active. However, adult consumption of milk is a relatively recent phenomenon, compared with around 5 million years of human evolution and in excess of 50 million years since early mammals evolved. Small wonder, then, that this gene can switch off in adult life. In fact, although it is thought to be relatively uncommon in the United Kingdom, in parts of Asia and Africa lactose intolerance affects up to 90% of the population.

Since diagnosis I have tried to avoid lactose, substituting olive oil and soya products (many of which are actually quite palatable). However, this is not as simple as it might seem and, even more than a year on, hidden lactose still catches me out. Cutting out the obvious—milk, butter, cream, yoghurt, and cheese—is not enough. Many breads contain skimmed milk, even though it is perfectly possible to produce excellent bread without the stuff. Furthermore, lactose is added to many prepared foods (listed on the label as “sugar”) and is a major constituent of prescribed and over the counter medicines, including many brands of aspirin and paracetamol. In fact, I find that the concentrated lactose in these tablets affects me more than the odd piece of cheese. In practice, lactose is surprisingly difficult to avoid and, in my experience, taking enzyme supplements really doesn't help.

Searching the internet yields numerous sites devoted to lactose intolerance in the United States and Australia, but I can find only a few in the United Kingdom. I am told that in Finland (my sister in law is Finnish) the disorder is well recognised and most food shops have a lactose-free section.

How many general practitioners in Britain have patients diagnosed as having irritable bowel? Of these, how many have been seen by a gastroenterologist before being labelled, and how many have had lactose intolerance excluded? Why is it that the simple and non-invasive test for lactose intolerance should be considered only after invasive and expensive investigations, such as colonoscopy, have proved negative? I am not even sure how widely the importance of this condition is appreciated, even in non-white patients. Moreover, many older people have symptoms of diarrhoea and flatulence. As lactase levels naturally decline with age, how many are actually suffering the effects of undiagnosed lactose intolerance?

I do not believe I am such a rarity in this country. I have Spanish and Portuguese ancestors on my father's side, but otherwise only western European blood, as far as I am aware. Not too many years ago coeliac disease presenting in adulthood was considered rare and yet, as a histopathologist, I see many positive small intestine biopsies from a previously undiagnosed older population. Lactose intolerance in Britain may be even more common and currently under-diagnosed as a source of morbidity.

I may be wrong, but I have a hunch I represent the tip of the iceberg. The consequences of uncovering a large scale problem may be difficult to deal with, having major implications for the food, dairy, and pharmaceutical industries. There are also dietary implications such as the need to ensure adequate calcium intake. Certainly, with the current prevalence of lactose in food and medicines, the solution may prove difficult.

However, unless you look you won't find it.