The concept of lactose intolerance has become embedded in Western medicine and developing economy medi- cine. It is based on evidence that intestinal lactase activity persists into later childhood and throughout life in only a minority of the world’s population, notably northern European–derived populations. These people have the T single nucleotide polymorphism (SNP) of the rs49882359 allele (C/T), also known as C/T-13910, the MCM6 gene which positively influences the lactase LCT gene. Other lactase persistent (LP) populations are found in Af- rica and the Middle East with different genetic variants. These SNPs represent co-evolution with dairying since the agricultural revolution and nutrient-dependent ecological adaptation. That said, gastrointestinal symptoms considered due to small intestinal lactose malabsorption are poorly correlated with lactase non-persistence (LNP), the situation for most people. With LNP, colonic microbiome lactase enables lactose fermentation to occur so that none is found in faeces. Whether the short chain fatty acids (SCFAs) and gases (hydrogen, carbon dioxide and methane) produced cause symptoms is dose-dependent. Up to 25 g of lactose at any one time can usually be con- sumed by a LNP person, but its food and meal pattern context, the microbiomic characteristics, age and other fac- tors may alter tolerance. Thus, the notion that lactose intolerance is a disorder or disease of LNP people is mis- placed and has been one of cultural perspective. What actually matters is whether a particular dairy product as normally consumed give rise to symptoms. It is, therefore, proposed that lactose tolerance tests be replaced with dairy food tolerance tests.
Lactose is the main carbohydrate in infant feeding, but its impact decreases as the child gets older and consumes less milk and dairy products. Congenital lactose intolerance is a very rare condition. However, lactase activity may be low and need to mature during the first weeks of life in many infants. However, the evidence that unab- sorbed lactose is causing infantile crying and colic is contradictory. Unabsorbed lactose has a bifidogenic effect and improves calcium absorption. Lactose malabsorption may occur secondary and thus temporally to other eti- ologies such as infectious gastroenteritis, cow’s milk allergy and celiac disease. One the cause is treated, lactase activity will gradually return to normal. The vast majority of Asian children will develop late onset congenital lactase deficiency. However, this entity only exceptionally causes symptoms before the age of 4-5 years. Symp- toms are abdominal cramps, flatulence and watery, acid stools, and decrease the quality of life but lactose intoler- ance is not associated with “true disease”. The diagnosis is made on clinical grounds and confirmed with a lac- tose breath test, if needed. These patients need to have a lifetime long reduced lactose intake to improve their quality of life.
The health relevance of dairy products has mostly been judged by their abundant nutrients (protein, calcium and riboflavin) and recommendations for these derived in lactase-persistent Caucasian populations. Extrapolation to Asians who are generally lactase non-persisters may not be biologically, culturally or environmentally sound. A number of studies, especially among north-east Asians as in Taiwan, provide guidance for their optimal dairy in- takes. In Taiwan, the NAHSIT (Nutrition and Health Surveys in Taiwan) linked to the National Health Insurance and Death Registry data bases provide most of the evidence. Cultural and socio-economic barriers create popula- tion resistance to increase dairy consumption beyond one serving per day as reflected in food balance sheet and repeat survey trend analyses. For the morbidity and mortality patterns principally seen in Asia, some, but not too much, dairy is to be preferred. This applies to all-cause and cardiovascular, especially stroke, mortality, to the risk of overfatness (by BMI and abdominal circumference) and diabetes and very likely to fracture and its sequelae. In Taiwan, there is no apparent association with total cancer mortality, but among Europeans, there may be protec- tion. Historically, while fermented mammalian milks have been consumed in south Asia and various Asian sub- groups and regions, most of the uptake of dairy in Asia after World War 2 has been from imported powdered milk or fresh liquid milk, encouraged further by the use of yogurts and popularization of milk teas and coffee. Asian dietary guidelines and clinical nutrition protocols need to encourage a modest, asymptomatic dairy intake.
Lactose handling by the human gut by most people, beyond being breast-fed, has been considered a disorder ra- ther than physiological. A non-human mammalian milk source is novel for the majority. During the first 6 months of life, when neonates and infants are best breast-fed, lactose along with other macronutrients, provides energy, but may have other functions as well. At birth, babies are endowed with their mother’s vaginal microbiome, but not if they are born by Caesarean section. How much maternal milk lactose survives the infant’s small intestine and is processed by this unique gut microbiome and to what end is still uncertain, but no lactose or galactose ap- pears in the faeces. Once intestinal lactase activity declines in most infants, lactose may enhance innate immunity through the cathelicidin antimicrobial peptide (CAMP), which is best achieved by lactose synergy with other co- lonic fermentation metabolites such as butyrate. It is of interest whether this lactose function or a variant of it per- sists. It might not be evident when lactase is persistent, as it is in most people of northern European ancestry. Population genomics indicate that lactase persistence became prevalent only about 3000-1000 BC, the Bronze Age of Eurasia. Gastrointestinal symptoms (GIS) in lactase nonpersisters who consume dairy foods are partly dose dependent and not usually evident with single lactose intakes ≤25 g per day. Spreading intake across the day reduces the risk as can various dietary patterns. Nevertheless, individual differences in GIS lactose sensitivity may merit public health and clinical consideration.
Indonesia is the largest archipelago blessed with one of the richest mega-biodiversities and also home to one of the most diverse cuisines and traditional fermented foods. There are 3 types of traditional dairy foods, namely the butter-like product minyak samin; yogurt-like product dadih; and cheese-like products dali or bagot in horbo, dangke, litsusu, and cologanti, which reflect the culture of dairy product consumption in Indonesia.
“Lactose intolerance (LI)” is considered a common problem in Asians, and in many parts of the world. Its preva- lence and age of manifestation varies between by Asian country, for possible genetic or cultural reasons. Studies in Indonesian children 3-15 years old (y) are available within the past two decades, using a pure lactose tolerance test. The prevalences of lactose malabsorption (LM) in pre-elementary (3-5 y), elementary (6-11 y), and junior high (12-14 y) school-children were 21.3%, 57.8%, and 73%, respectively. An increasing trend for LM preva- lence was seen within the pre-elementary group, from 9.1% at 3 y to 28.6% at 5 y. The most frequent symptoms of LI in junior high school (JHS) group were abdominal pain (64.1%), abdominal distention (22.6%), nausea (15.1%), flatulence (5.7%), and diarrhea (1.9%), mostly within one hour of lactose ingestion. In children with regular and irregular milk drinking, LM occurred in 81.2% and 69.6%; LI was found in 56.2% and 52.1%, re- spectively. Most JHS children with dairy-associated recurrent abdominal pain (RAP) symptoms proved to be malabsorbers. Dairy products most related to RAP were milk and yogurt. LI was found in 81% of RAP children with abdominal pain most frequently, followed by nausea, bloating, diarrhea, borborygmi, and flatulence. Symp- tom onset occurred 30 minutes after lactose ingestion, especially nausea, bloating, and abdominal pain. In RAP children LI symptoms mostly found in breath hydrogen concentration >20 ppm. More LI symptoms were found in lactose malabsorbers, but symptoms were mild and generally disappeared in 7 hours, and in most by 15 hours.