While cow's milk has long been prized in many parts of the world as an excellent source of protein, calcium and several other useful nutrients, a sizeable minority are unable to reap the benefits either because they have problems digesting milk and other forms of dairy produce.
These people have a condition called lactose intolerance. Their bodies are unable to metabolise lactose _ the naturally occurring sugar found in dairy produce _ and as a result they commonly suffer abdominal discomfort, bloating and/or diarrhoea after drinking milk or consuming milk products such as cheese and cream.
In order for our bodies to break down the lactose in cow's milk, we must first produce an enzyme called lactase, explained Assoc Prof Visith Chavasit. However, some people are born without the natural ability to produce lactase _ or to synthesise it in sufficient quantities _ and so they invariably have difficulty digesting milk products, he said.
Lactose intolerance is quite prevalent among people of Asian or African origin, Visith continued, adding that a study carried out by Mahidol University's Institute of Nutrition, of which he is currently the director, found that in excess of 90% of Thai adults have problems with lactase production.
"Also, as we grow older, our bodies tend to naturally produce less of this enzyme, lactase. And so lactose intolerance often worsens with age."
Individuals who are lactose intolerant are often surprised that they have absolutely no problems consuming yoghurt. Visith explained that this is because the lactose in the milk used to make yoghurt is mostly digested by the bacteria which is intentionally cultured during the production process. A possible way to cope with lactose intolerance, Visith suggested, is only to drink small amounts of cow's milk at any one time, rather than downing a large glass in one go.
"Try drinking a small amount immediately after a meal. Doing this helps reduce digestive problems. But if you're lactose intolerant it's always best to avoid drinking milk on an empty stomach," he advised.
This strategy does not work for some people, however, who ultimately decide to avoid dairy produce altogether. Commonly used substitutes _ including soya, rice and almond milk _ are often healthier than cow's milk since they are lower in cholesterol and/or saturated fat but, unless they have been fortified, these dairy-free liquids lack the vitamins and dietary minerals present in regular milk (such as vitamin B12 and calcium).
But a recent development means that lactose-intolerant individuals may no longer have to cut dairy out of their diets. For Mahidol's Institute of Nutrition was recently successful in producing a lactose-free form of cow's milk, the first of its kind in the country. Responsibility for its production and sale has now been handed over to a local manufacturer of dairy products. "This lactose-free milk can be an alternative for people with lactose intolerance," Visith reasoned. "It can be a good option for the elderly for whom milk is a convenient source of protein, calcium and vitamin D."
To create lactose-free milk, Visith explained, lactase is added to ordinary cow's milk and the mixture is then processed, allowing the lactase time to split the lactose into two simpler forms of sugar called glucose and galactose.
"Since the lactose in the cow's milk has already been completely broken down, the intestinal tract is able to absorb the simple sugars more easily. So people with lactose intolerance who drink lactose-free milk should not experience any unpleasant digestive problems," Visith said, noting that the process does not interfere in any way with nutritional content.
"Lactose-free milk delivers the same nutritional value as regular cow's milk," he stressed.
"And the use of the enzyme lactase in the production process makes lactose-free milk taste naturally sweeter than regular milk. So no extra sweetener is necessary." he said.
In addition to the lactose intolerant and elderly people with a diminished ability to digest lactose, sporty types may also find the new product beneficial. A recent study conducted on Thai athletes by the Institute of Nutrition demonstrated that lactose-free milk has a high potential for use as a "recovery" drink after workouts.
The naturally occurring carbohydrate and protein in lactose-free milk was found to be good for water-retention and for replenishing tired muscles after a strenuous exercise session.
One group of people who will not be helped by lactose-free milk are individuals who suffer from an allergy to cow's milk as opposed to being simply lactose intolerant. Dr Pipop Jirapinyo, a paediatrician based at Samitivej Children's Hospital Srinakarin, explained that the two conditions are very different.
People who are allergic to dairy produce are in fact allergic to a protein found in milk, he pointed out. After they consume milk or milk products, their bodies produce antibodies to fight this protein and this triggers an allergic reaction, the symptoms of which can include chronic runny nose and nasal congestion, nausea, abdominal discomfort, diarrhoea as well as chronic dermatological reactions including itchy skin, hives and eczema. Infants who are allergic to cow's milk often develop physically at a slower rate than normal babies, the paediatrician said.
"Lactose intolerance and cow's milk allergy sometimes have overlapping symptoms. So, people often confuse the two terms," said Dr Pipop. "But people who have lactose intolerance do not experience skin allergies when they consume [regular] milk."
Cow's milk allergy, he continued, commonly shows itself in the first year of life, while lactose intolerance is more likely to occur from late childhood onwards, although a handful of adults do develop an allergy to dairy produce later in life.
"Simply put, a milk allergy is to do with an immune [system] reaction, while lactose intolerance is a metabolic issue," the doctor said.
"So, if you're allergic to the protein in milk, you may not derive any benefit from drinking lactose-free milk."
A locally developed lactose-free pasteurised cow’s milk.