Levelling up with lactose

Lactose and its effects on the human body are often in the media and lactose-free milks are part of the offerings for most large dairies, but do we really need them to be, or is it just a marketing gambit? And, do plant-based drinks providers have a point?

These were two of the many questions that Dairy UK sought to answer with its webinar on Lactose and the Evolution of Dairy Consumption on World Milk Day. Erica Hocking, senior nutrition scientist at Dairy UK, introduced the proceedings, with registered Juliette Kellow, chairing the event. Kellow introduced the event by saying she “is really passionate about dairy products and the nutritional benefits they bring to the diet, but I am also near the misunderstandings about it. Lactose is the source of so much confusion among consumers. Doesn’t everyone have lactose intolerance? In short, we have so many misunderstandings and myths around lactose.”

Ten thousand years

First up was Professor Mark Thomas, from the University College in London, and an expert in genetic and cultural variation in human populations. He examined how dairy made it onto our plates. “About 10,000 years ago, the first milkable animals were domesticated – cows, sheep and goats, among others. There is plenty of archaeology to show a history of cheese making, with the presence of bog butter (bogs being nature’s first refrigerators), people herding cattle and dairying in places such as Iraq 4,500 years ago,” he noted. In China, there was evidence of kefir cheese being worn as a necklace – the first to-go products. “The best way to demonstrate that people were using milk and processing, is to analyse dairy fats on pottery shards,” Thomas states. “Researchers extract fats absorbed into surface of pottery and then use gas chromatography and mass spectrometry, assess the amount of carbon-13 in the fatty acids, differentiate fats of plant and milk origin. The biochemical processes that generate fats in milk are different to plants.

“Using this method, we have been able to identify origin of use, 9,000 years in Anatoli. It is quite clear that dairying followed hot on the heels of animal domestication. In fact, dairying was a very early feature of keeping domestic animals. As farming spread throughout Europe, dairying spread with it. From southeast to northwest. In Britain, dairying is there at the beginning, along with farming.”

In humans, lactase is produced in small intestine to break down lactose into glucose and galactose, he says. Lactase production is there in infants, but drops to very low levels sometime after weaning. However, in the last 10,000 years, lactase persistence developed into adulthood, and one-third of adults globally are lactase persistent. One of the key points about lactase persistence is highly structured global distribution – Ireland, British isles and southern Scandinavia, India’s northwest, and among, pastoralist populations in Africa. It is rare in Asia.

“Lactose in two-thirds of the population goes into large intestine, is fermented by bacteria, causes loose stools, and we can measure it via the hydrogen coming out in breath. It’s high about 90 minutes after eating a lot of lactose,” he explains. However, people who are lactase

non-persistent don’t always suffer intolerance. The lactase persistence is caused by at least five different gene variants, which have mutated multiple times over the last 10,000 years. Despite the fact that lactase persistence is common today, the variants were rare or absent more than 5,000 years ago. This is due to strong natural selection and convergent evolution. 

“Many studies that gene selection favouring lactose persistence was huge and when scanning the genome for variants, lactase persistence is the Everest for natural selection,” he notes. The demand for lactase persistence in humans is so strong that five per cent more people survive to reproductive age in every generation with it. “Being able to digest the sugar in milk was probably the biggest benefit in human populations over the last 10,000 years,” Thomas states.  

The question is why. He admits, “We don’t know. It could be extra calories, as milk is effectively a superfood, and the only food that we consume that specifically evolved to be nutritious. Some food evolves to be tasty (and thus eaten), but milk’s evolved is only to be nutritious.”  

Thomas cited a study examining a large amount of data in the UK’s Biobank. “What difference does this make to health outcomes? It makes very little difference to milk drinking habits, as there only slightly higher frequency than with lactase non-persistent. This makes it harder to explain its evolution, and helps to explain countries like China, where its milk imports have skyrocketed over the last 10 years.” 

Querying further, he asked, “What drove the strong natural selection favouring lactase persistence? Does milk usage change through time explain LP evolution (better than constant selection)?” The answer was no, it didn’t explain the evolution.  

Reality versus belief 

Dr Professor Dennis Savaiano, Virginia C Meredith Professor of Nutrition Science at Purdue University in Indiana in the US, examined the underlying dogma surrounding lactose maldigesters. He noted that with milk avoidance, perception is reality. “Lactose malabsorption can be uncomfortable, and many maldigesters don’t know they are maldigesters, while some dairy avoiders may be digesters,” he states. “The word intolerance is clearly a problem. Lactose maldigestion implies a GI disorder, and a lactase deficiency implies a disease state.”  

However, milk avoidance and bone health are clearly related, inversely, he adds. “For companies, profit margins are quite large for digestive aids to improve lactose digestion and lactose free milks. The real question is, do you need to?” 

For humans, lower calcium intake is related to bone density and in later life, it increases the fracture rate. A study for females aged 10 to 13 showed that 47 of them saw themselves as dairy intolerant, but only 20 were. “Their calcium intake was related to their perceived ideas of milk intolerance, and the spine density was related to their perceived milk intolerance. The perception is more important than reality,” he notes.  

“We have a large population that think they are milk intolerant, but aren’t and that has implications for the dairy industry. Food sources vary in lactose. For example, hard cheese has no lactose and ice cream lactose is not digested in the same way. It is also dose dependent and yogurts are well tolerated regardless of their lactose content,” he explains. For example, many Moroccans consume fermented dairy foods despite being lactose maldigesters, as yogurt takes its own lactase enzyme with it into the body. It is an excellent alternative for people, and there are rarely symptoms from yogurt. 

Another interesting area is colon adaptation, which seems to adapt after a week of being fed large amounts of lactose. There are no symptoms of intolerance after a week. Another issue is A2 milk, suggesting that it’s not the lactose causing digestive issues. “The response to milk may not just be lactose, it may be other parts of the milk.” He recommended eating a meal with one’s dairy intake to reduce digestive issues.  

Further, on the plant-based drinks side, there is the belief that milk is a food appropriate for cows and not for humans. “Beliefs are reality and a lot of what’s happening in marketing today. It is not biology that influences the behaviour, it’s the belief that influences it. It acts as a tool to create a disease.” 

Fermented foods 

Dr Catherine Stanton, principal researcher at Teagasc at Moorepark in Ireland, examined fermented dairy, health and the gut microbiome for her talk. “Fermentation is one of the oldest forms of food preservation,” she reminded the audience. “The methods have involved from spontaneous fermentations to in-depth characterisation of fermenting microbes. 

Fermented dairy products are a good source of bioactive microbial metabolites, vitamins, and antimicrobials, produced during dairy fermentation. Benefits also include the bioactive compounds produced, which offer antioxidant and anti-atherosclerotic properties. 

Dairy products may also contain prebiotics (whey protein, etc) to reach the intestinal microbiome, and play a role in immune modulation. “Increasing diet diversity including dairy, fruit and vegetables, enhances microbial diversity, while a poor diet leads to enhanced inflammation and frailty,” she observes. “Fermented foods have led to enhanced beneficial bacteria in the gut microbiome, and there is a reduction of potential pathogens. This leads to decreased BMI and cholesterol, decreased inflammatory markers and an improvement in insulin resistance. “ 

For children, yogurt consumption appears to improve health (aged 4 to 24 months), reduce symptoms of diarrhoea and respiratory infections, and offer improved oral health and plaque indexes. Yogurt and cheese are also associated with significantly reduced cardiovascular disease, as well as bladder, colorectal and oesophageal cancers. “The benefits are far beyond doubt,” she ends.  


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