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UK study casts doubt on widespread lactose intolerance diagnoses

Despite our ancestors drinking milk for thousands of years, intolerance among Britons is rising, but is it as widespread as it seems? A recent study published in Nature found that on closer examination, many lactose intolerances are self-diagnosed, often through dubious methods.

Seven years ago, reports The Telegraph, Sam Curtis (32) began to experience sudden flares of bloating and stomach cramps. She felt these attacks were particularly acute after consuming dairy products, ranging from ice cream to cheese, and even hot chocolate.

“My symptoms seemed to vary with the quantity of milk,” she says. “Ice cream would keep me locked in the bathroom, while if a sauce contained dairy and I wasn’t aware, I would bloat and have unusual bowel movements for a day or two.”

After a bad episode of cramps, Curtis decided to diagnose herself with a test she ordered online based on a “holistic therapy” called bio-resonance testing.

On receiving their report, which listed proposed sensitivities to different dairy products, she switched to vegan alternatives for butter, milk and cheese.

It is hard to drink coffee with friends these days without hearing about their lactose intolerances – a condition linked to a deficiency in the lactase enzyme – and a look at the science suggests it is on the rise. According to the British Nutrition Foundation, five percent of the UK is lactose intolerant. Private healthcare specialist Bupa places it closer to one in 10. Soy, oat and almond milks are deemed to be healthier, and the UK’s plant milk market is thought to be worth in the region of £263m.

Yet the study published in Nature casts doubt on this malaise. Using genetic analysis, scientists from University College London and the University of Bristol have found that our ancestors consumed milk for thousands of years, despite lacking the ability to produce lactase as adults. Humans only evolved this capability in the past 3 000 years and, even now, genetic surveillance shows it is present in only a third of the world’s population.

But just as humans tolerated milk for millennia without lactase, it seems most of us are still capable of doing so. China is now the world’s second largest consumer of dairy products, even though 92% of its adults don’t produce lactase.

When Mark Thomas, professor of evolutionary genetics at UCL and a co-author of the Nature study, examined data from the UK Biobank, he found little relationship between the ability to produce lactase and milk-drinking habits. “People who don’t produce lactase actually generally don’t suffer symptoms at all, without drinking very large quantities of milk, over a litre of milk or something like that,” he says.

On closer examination, many lactose intolerances are self-diagnosed, often through dubious methods. The bioresonance-based testing method used by Curtis is scientifically unproven.

Then there’s Anne Larchy (50) who maintained she had never “liked” milk since childhood, and after consuming dairy products like cottage cheese, yogurt or cheesecake often left her with rashes or an upset stomach. She received a diagnosis of lactose intolerance through a form of alternative medicine called muscle kinesiology testing, in which a practitioner applies force to a muscle group and asks the body about its nutritional status. While Curtis and Larchy have reported improved health since excluding all forms of dairy from their diet, both bioresonance testing and muscle kinesiology have been described as forms of pseudoscience.

Scientists suspect that many such cases of lactose intolerance are often confused with cow’s milk allergy, which is a severe and in some cases dangerous condition, where the body overreacts to the protein casein found in many dairy products.

“One good way of telling if somebody has milk allergy rather than lactose intolerance is if they say that they get symptoms when they eat cheese,” says Thomas. “Hard cheese has got virtually no lactose in it at all, butter has virtually none. Yogurt has about a third of the lactose of milk, and soft cheese has got some but not a massive amount.”

Rather than self-testing, Tom Sanders, an emeritus professor of nutrition and dietetics at King’s College London, recommends a hydrogen breath test. “It’s not something GPs do as they regard it as such a minor thing, but it’s quite an easy test,” he says. “You give someone a standard dose of lactose, wait half an hour, and then get them to breathe, a bit like with an alcohol breath test. If hydrogen is present, it shows that the lactose hasn’t been digested fully.”

But at the same time, paediatricians are alarmed at the rise in alternative milk products for infants and toddlers. Cow’s milk allergy is thought to only affect around 1% of under-twos.

“There is unnecessary concern about lactose intolerance in babies as well as milk allergy,” says Robert Boyle, an expert in paediatric allergies at Imperial College London. “Babies get a lot of symptoms when they drink milk, be it mother’s milk or formula milk, because they’re drinking such large volumes. Babies will drink up to a fifth of their body weight in milk each day, so it’s not surprising they get some tummy ache, runny poos and vomiting with that. But this gets labelled as lactose intolerance or allergies much more than necessary.”

Boyle points out that alternative milks tend to be high in sugars that can put children at risk of tooth decay and contribute to childhood obesity. Some baby formula milks contain up to twice as much sugar as a Fanta fizzy drink. “In general, if you switch to a lactose-free product, you are usually increasing what’s called your child’s free sugar intake,” says Boyle.

In adults, a theory for why someone might appear to be lactose intolerant is not related to the dairy itself, but general diet. Thomas explains that if someone is deficient in lactase and also consuming a diet high in processed foods, this could lead to imbalances in the gut microbiome and longer transit times. This means undigested milk will be staying in the colon for longer, and certain bacterial species will be able to break it down into chemical compounds that are not necessarily desirable, leading to symptoms such as stomach cramps, bloating and flatulence.

Instead, if that person is consuming a diet much higher in fibre, their transit times will be far quicker and the bacterial species in their colon are likely to be more beneficial, meaning that milk will pass through their body without causing noticeable problems, despite the lack of lactase. One possibility for why our ancestors were able to tolerate milk for such a long period of time, despite not producing lactase, is because their diet is likely to have been very high in fibrous foods. Thomas suggests that milk-drinkers who eat lots of fresh vegetables are less likely to suffer the consequences of lactase non-persistence than somebody who’s eating processed food.

He feels that an exaggerated fear of lactose could have a negative health impact, with people veering away from traditional milk and opting for less beneficial alternatives.

“An unfounded fear could have a detrimental impact because while alternative milks may have nutritional value, nothing approaches milk in terms of nutritional make-up,” he says.

“Milk has an almost perfect combination of nutrients. The protein is of the highest quality. It’s also got lots of nice fat soluble vitamins and lots of minerals. It’s the only food we consume that’s specifically evolved to be nutritious.”

Study details

Dairying, diseases and the evolution of lactase persistence in Europe

Richard P. Evershed, George Davey Smith, Mark G. Thomas

Published in Nature on 27 July 2022

Abstract
In European and many African, Middle Eastern and southern Asian populations, lactase persistence (LP) is the most strongly selected monogenic trait to have evolved over the past 10,000 years. Although the selection of LP and the consumption of prehistoric milk must be linked, considerable uncertainty remains concerning their spatiotemporal configuration and specific interactions.
Here we provide detailed distributions of milk exploitation across Europe over the past 9,000 years using around 7,000 pottery fat residues from more than 550 archaeological sites. European milk use was widespread from the Neolithic period onwards but varied spatially and temporally in intensity. Notably, LP selection varying with levels of prehistoric milk exploitation is no better at explaining LP allele frequency trajectories than uniform selection since the Neolithic period. In the UK Biobank cohort of 500,000 contemporary Europeans, LP genotype was only weakly associated with milk consumption and did not show consistent associations with improved fitness or health indicators.
This suggests that other reasons for the beneficial effects of LP should be considered for its rapid frequency increase. We propose that lactase non-persistent individuals consumed milk when it became available but, under conditions of famine and/or increased pathogen exposure, this was disadvantageous, driving LP selection in prehistoric Europe. Comparison of model likelihoods indicates that population fluctuations, settlement density and wild animal exploitation—proxies for these drivers—provide better explanations of LP selection than the extent of milk exploitation. These findings offer new perspectives on prehistoric milk exploitation and LP evolution.

 

The Telegraph article – An exaggerated fear of lactose is damaging our health (Restricted access)

 

Nature article – Dairying, diseases and the evolution of lactase persistence in Europe (Open access)

 

See more from MedicalBrief archives:

 

Cow milk while breastfeeding may reduce the child’s food allergy risk

 

Lactose-free/reduced-carb formula does not help severely malnourished children

 

Baby dies after being fed alternative gluten-free/lactose-free diet

 

Food fad? New illness? Trying to find what is really behind gluten sensitivity

 

 

 

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