Prevalence of Lactose Maldigestion
Need for the study
Lactose intolerance is the inability to completely digest lactose, the major disaccharide found in milk. Intestinal digestion of lactose involves breakdown of lactose into glucose and galactose by membrane-bound lactase, an enzyme located on the brush border of the small intestine. Lactase activity and transit time of lactose through jejunum mucosa are important for proper absorption. If lactase is absent or deficient (hypolactasia), unabsorbed sugars osmotically attract fluid into bowel lumen. Fluid influx into the bowel is approximately triple the predicted amount based on osmolality of the sugar content alone because the intestine can not maintain a high electrochemical gradient between contents and blood.
In addition to increasing volume and fluidity of gastrointestinal contents, unabsorbed lactose entering the colon is affected by bacteria. Fermentation of lactose by bacteria produces gas, and results in cleavage of lactose into monosaccharides. These monosaccharides cannot be absorbed through the colon mucosa, thus increasing osmotic pressure and draining more fluid into the bowel. In lactase-deficient patients, some of the carbohydrates reaching the colon can be metabolised by bacteria into short-chain fatty acids and absorbed, but the net result of ingestion of lactose is a substantial rise in fluid and gas in the bowel.
All land mammals have a dramatic decrease in lactase levels after weaning. Worldwide, humans lose 90 to 95 percent of birth lactase level by early childhood, and there is a continuous decline in lactase during the course of a lifetime. However, prevalence of hypolactasia varies widely among ethnic backgrounds. Incidence of lactose maldigestion ranges from 11% to 60% in Europe. Also, studies have shown groups among whose lactose malbsorption predominates (60 to 100%) that include:
• Africa: South Nigerian, Hausa, Bantu;
• Asia: Thais, Indonesians, Chinese, Koreans;
• Near East and Mediterranean: Arabs, Greeks, Cypriots, Italians;
• North and South America: Eskimos, and Native Americans (5).
Prevalence of lactose maldigestion in Greek adults is 75%. A study by Ladas, Papanicos and Arapakis on 200 Greek adults showed 75% of this population to be lactose malabsorpers. Therefore, the Greek nation appears to be a group with high prevalence of lactase deficiency.
Dietary calcium is critical for development of the human skeleton and plays an important role in prevention of osteoporosis. Dairy products provide approximately three-fourths of calcium consumed in the diet for people who live in the Mediterranean, and are the most absorbable sources of this essential nutrient. Lactose maldigestion can be an obstacle that interferes with calcium consumption among many ethnic groups because this condition can cause gastrointestinal symptoms such as abdominal pain, bloating, passage of loose, watery stools, and excessive flatus. Real or perceived occurrence of intolerance symptoms after dairy food consumption may cause maldigesters to avoid dairy products. Several investigators have observed a relationship between, lactose maldigestion, dietary calcium, and osteoporosis in different populations.
Although studies have shown prevalence of lactose intolerance in Greek adults, no such study has been conducted on Cypriots. Greek-Cypriots could be another ethnic group with high prevalence of lactose intolerance since they share common characteristics with other ethnic groups that were identified with high prevalence of lactose intolerance: same culture as Greeks, same epidemics as Southern Europeans and people who live in the Mediterranean. Research on the Cypriot population and prevalence of lactose intolerance among them is necessary in order to educate the Cypriot public on how to cope with lactose intolerance and prevent osteoporosis.
Purpose of the study
The purpose of this study was to identify prevalence of lactose malabsorption in a self-selected sample of Greek-Cypriots by using H[sub2] breath test, and identify the frequency of self-reported lactose intolerance and its relation to lactose malabsorption.
1. Using the H[sub2] breath test, what percentage of subjects are lactose malabsorbers by age group?
2. Using the H[sub2] breath test, and the evaluation of symptoms 24 hours after the H[sub2] breath test, what percentage of subjects are lactose intolerant by age group?
3. What is the frequency of self-reported milk intolerance in relation to lactose malabsorption?
Summary of Literature
1. Milk and dairy products are the main dietary sources of lactose, although there are also hidden sources of lactose in other food products.
2. Real or perceived lactose intolerance causes avoidance of milk and dairy product, and it is closely associated with decreased calcium intake.
3. There is high prevalence of lactose intolerance in particular populations.
4. The H[sub2] breath test is the most valuable test in assessing lactose intolerance.
Description of Research Type
The study design was a prospective, non-experimental research design. In this cross-sectional study relationship between lactose intolerance and age, and self reported intolerance among subjects was investigated. The SIUC Human Subjects Committee approved this study.
A self-selected sample from the general population of a small medical centre in Nicosia, Cyprus was studied. Sixty-five subjects (29 males, 36 females, age 7 to 60) were included and underwent H[sub2] breath test after 25 g lactose load. Nicosia’s residents come from different areas of the island. Subjects used in the study represent the population of Greek-Cypriots. Subjects with history of major abdominal operation, diabetes mellitus, overt gastrointestinal disease, recent febrile illness, use of antibiotics or laxatives were excluded.
Data Collection Instruments
H[sub2] hydrogen breath test was performed after an overnight fast of 10 to 12 hours. One g/kg lactose was administered to children weighing less than 25 kg (55 lb) and a standard dose of 25 g was given to all other subjects. The lactose was suspended in 250 to 300 ml (8-10 oz) of water (0.30mol per litre). Hydrogen concentration in each breath sample was measured using Micro H2 meter.
Sixty-five Nicosia residents were included in the study and underwent H[sub2] breath test. Slightly more than half (N=36, 55.4%) were female while 44% (N=29) were male. Specifics of age and weight groups are outlined in Table 1. Subjects were divided into 4 age groups: <24 yrs, 25-34 yrs and 45-54 yrs. There was no significant difference between different age groups, but the largest proportion of subjects (N=27, 41.5%) was 25-34 years of age (Table 1).
Research Question 1: Using the H[sub2] breath test, what percentage of subjects are lactose malabsorpers by age group? The greater prevalence of lactose maldigestion was seen in the 34-44 years of age group (N=6, 60%)(Table 2).
Research Question 2: Using the H[sub2] breath test, and the evaluation of symptoms 24 hours after the H[sub2] breath test, what percentage of subjects are lactose intolerant by age group? Over half of the maldigesters (60.8%) complained of symptoms in hours following the lactose load (Table 3). As it was predictable subjects 25-34 years of age appeared to the greater overall number of symptoms 24 hrs after the H[sub2] breath test (Table 3).
Research Question 3: what is the frequency of self-reported milk intolerance in relation to lactose malabsorption? Analysis of data was done taking into consideration the self-evaluation of subjects of their capacity to digest lactose. Before undergoing the test, 34 (53.1%) subjects, defined themselves as intolerants to milk. Of the 34 self-reported milk-intolerant subjects, 13 (56.5%) were actually lactose maldigesters and intolerants, and 21 (51.2%) were lactose digesters and tolerant. Thirty (46.9%) subjects defined themselves as tolerant to milk before undergoing the test and from them, 10 (43.5%) were actually lactose maldigesters.
The present study was the first attempt to identify prevalence of lactose maldigestion among Greek-Cypriots. In a self-selected sample representative of the Greek-Cypriot community, 35.4% of the sample was lactose maldigesters. Greek-Cypriots, thus fall into the group of moderate prevalence of lactase deficiency. Fourteen, (21.5%) of the entire study group (60.8% of the maldigesters) reported symptoms that indicate lactose intolerance after an oral load of 25 g of lactose. While prevalence of lactose maldigestion was found to be lower than in previous studies performed in the Mediterranean area, frequency of gastrointestinal symptoms among lactose maldigesters after H[sub2] breath test is compatible to what other studies have reported.
Acquired lactase deficiency may be the cause of gastrointestinal disorders, which coincide with milk consumption, and this may lead to a reduced milk and dairy consumption in those geographical areas where there is a higher prevalence of lactase deficiency. However, it is known that perceived lactose intolerance may lead to avoidance of milk and dairy consumption.
In this study, a clarification of dimensions associated with self-reported lactose intolerance, the real relationship between self-reported lactose intolerance and gastrointestinal symptoms following H[sub2] breath test was attempted. Thirty-four (53.1%) subjects defined themselves as intolerants to milk before undergoing H[sub2] breath test. Of these 23 (35.4%) were lactose maldigesters and 14 (21.5%) of them reported the appearance of symptoms 14 hours after the H[sub2] breath test.
Further investigation regarding subjects’ dietary habits is needed to determine whether these subjects did not consume milk or consumed very low quantities of milk and if their daily calcium intake is significantly low. It must be emphasized that in Greek-Cypriot cuisine, milk and dairy products that contain lactose are used widely and are the main source of calcium intake. In particular, recent prospective studies have suggested reduced calcium intake during adolescence and early adulthood may have a great impact on bone mineral density measurements. This result must induce physicians, dietetic professions and health educators to pay particular attention to dietary calcium intake.
As mentioned above, the percentage of subjects (53.1%) who believed they could not tolerate milk before undergoing the H[sub2] breath test was rather high. From this group, 13 (56.5%) were lactose maldigesters and intolerants, and 21 (51.2%) were lactose digesters and tolerant (Table 4). Although subjects with a major abdominal operation, diabetes mellitus, overt gastrointestinal disease, recent febrile illness, use of antibiotics or laxatives were excluded from the study, further investigation as to why these subjects defined themselves, as intolerants to milk is needed. The possibility of a diagnosis of irritable bowel syndrome or of non-ulcer dyspepsia should be investigated.
Results of this study support that there is a moderate prevalence of lactose intolerance among Greek-Cypriots, and Greek-Cypriots misleadingly think they are lactose intolerant. It is the dietician’s role to be aware of this problem and be also aware of the tests available to detect lactose intolerance.
A positive diagnosis of lactose maldigestion or lactose intolerance does not mean milk and dairy products, and other foods that contain lactose, need to be eliminated from the diet. On the contrary, total elimination of milk and dairy products is unnecessary, nutritionally unwise, and may even increase intolerance to lactose. Moreover milk and dairy products are significant sources of calcium and other essential nutrients like riboflavin, potassium, magnesium, vitamin B12, and high-quality protein. Studies demonstrate that low calcium intake and/or decreased milk consumption compromise intake of other nutrients.
Treatment of lactose intolerance is based on tolerance levels. For this reason, diet should be individualised. Milk and dairy products should first be introduced in small amounts, especially with other foods, and gradually increase the amount as tolerance improves. If intolerance to lactose is severe, patients may need to consume lactose-free products.
There are several limitations to this study. Although the sample was representative of the general population, results should be interpreted with caution, because only a small number of the population was studied. Moreover, absence of any other study on the same population excludes the possibility of comparing results and supporting the validity of these results.
The participants themselves could be another limitation. This was a self-selected sample. Those who chose to participate could have been lactose maldigesters and that is why they became involved in this study. Also, participants may have become involved in this study to please their physician, or to gain extra attention from medical staff. Subjects’ reliability is also another limitation since subjects were asked to self-report absence or presence of symptoms 24 hours after the H[sub2] breath test.
Lactose intolerance can be confirmed by well-controlled, double blind tests in which neither client nor health professional is aware of the lactose-containing test solution or lactose free-placebo, which was not the case in this study. Under these more controlled conditions, lactose intolerance may appear to be less common than believed.
The long duration of the H[sub2] breath test, as well as the fact that a 10-12 hours fast was involved prior to the test, was definitely a limitation which might have discouraged subjects from participating. Only 3 children participated in the study, possibly for this reason.
This study was a start for further investigation on lactose intolerance in a population considered to have high prevalence of lactose intolerance. Investigating dietary habits of this sample could have revealed that some Greek-Cypriots may be avoiding milk and dairy products because of perceived lactose intolerance, which may lead to inadequate calcium intake. A step further would be investigating of how real and perceived lactose intolerance affects calcium intake and development of osteoporosis.
More research is needed in this area to extend understanding of lactose intolerance among Greek-Cypriots and to acquire the ability to educate Greek-Cypriots on how to cope with lactose intolerance.
The product of this single study is that prevalence of lactose maldigestion among a self-selected sample of Greek-Cypriots is 34.5%. Perceived lactose intolerance among subjects was rather high in comparison to the percentage of subjects who were actual lactose maldigesters and/or lactose intolerants. Lactose digestion capacity should therefore be carefully investigated in all self-reported milk intolerant subjects.
|Demographic information of self-selected Greek-Cypriot subjects participating in a study to determine lactose maldigestion. N=65.|
|Groups||N (%)||N (%)||N (%)|
|Age Group 1 (YRS)||Up to 24||24(36.9)|
|Age Group 2(YRS)||25-34||27(41.5)|
|Age Group 3(YRS)||35-44||10(15.4)|
|Age Group 4(YRS)||45-54||4 (6.2)|
|Weight Group 1||Up to 39||Up to 85.8||2 (3)|
|Weight Group 2||40-49||88-107.8||10(15.4)|
|Weight Group 3||50-59||110-129.8||16(24.7)|
|Weight Group 4||60-69||132-151.8||15(23)|
|Weight Group 5||70-79||154-173.8||10(15.4)|
|Weight Group 6||80-89||176-195.8||8 (12.3)|
|Weight Group 7||90 or more||198 or more||4 (6.2)|
|Lactose Detection using H[sub2] breath test among different age groups of|
|self-selected sample of Greek-Cypriots. (N=65)|
|Age-group||LD (%)||LD (%)||Total|
|Up to 24||18 (75)||6 (25)||24 (100)|
|25-34||16 (59.3)||11 (40.7)||27 (100)|
|34-44||4 (40)||6 (60)||10 (100)|
|45-54||4 (100)||0 (0)||4 (100)|
|Total||42 (64.6)||23 (35.4)||65 (100)|
|Reported severity of symptoms 24 hours after H[sub2] breath test|
|among different age groups in a self-selected sample of Greek-Cypriots. (N=23)|
|Severity of symptoms|
|Age-group||N (%)||N (%)||N (%)||N (%)||N (%)|
|Up to 24||4 (66.7)||1 (16.7)||0 (0)||1 (16.7)||6 (100)|
|25-34||3 (27.3)||4 (36.4)||1 (9.1)||3 (27.3)||11(100)|
|35-44||2 (33.3)||0 (0)||2 (33.3)||2 (33.3)||6 (100)|
|Total||9 (39.1)||5 (21.7)||3 (13)||6 (26.1)||23(100)|
|Lactose detection using H[sub2] breath test among|
|different genders in a self-selected sample of Greek-Cypriots. (N=65)|
|Sex||LD (%)||LD (%)||Total|
|Male||19 (65.5)||10 (34.5)||29 (100)|
|Female||23 (63.9)||13 (36.1)||36 (100)|
|Total||42 (64.6)||23 (35.4)||65 (100)|
|LD= Lactose Detection|
|Lactose detection using H[sub2] breath test among|
|different weight groups in a self-selected sample of Greek-Cypriots. (N=65)|
|Weight||Group||LD (%)||LD (%)||Total|
|Up to 39||Up to 85.8||1 (50)||1 (50)||2 (100)|
|40-49||88-107.8||9 (90)||1 (10)||10 (100)|
|50-59||110-129.8||11 (68.8)||5 (31.3)||16 (100)|
|60-69||132-151.8||9 (60)||6 (40)||15 (100)|
|70-79||154-173.8||4 (40)||6 (40)||10 (100)|
|80-89||176-195.8||5 (62.5)||3 (37.5)||8 (100)|
|90 or more||198 or more||3 (75)||1 (25)||4 (100)|
|Total||42 (64.6)||23 (35.4)||65 (100)|
|LD= Lactose Detection|
|Self-reported intolerance prior to H[sub2] breath test among|
|a self-selected sample of Greek-Cypriots. (N=65)|
|Self reported||LD (%)||LD (%)||Total|
|Negative||20 (48.8)||10 (43.5)|
|Positive||21 (51.2)||13 (56.5)||34 (53.1)|
|Total||41 (100)||23 (100)||64 (100)|