SCIENTIFIC PAPER:

Milk Consumption and Lactose Intolerance in Adults

INTRODUCTION

Lack of lactase in the body is the cause of Lactose Intolerance (LI) due to Lactase Deficiency (LD), often leading to symptoms like abdominal cramps, diarrhea and flatulence. Patients thus have to exclude lactose in their diet, which can cause nutrition-related diseases.

This article discusses the relationship between milk consumption and LI in adults, and also how lactase activities are affected by milk consumption behaviors.


SUBJECTS AND METHODS

Subjects
- 182 subjects.
- Age: 20-70 years old, without milk protein allergies, gastrointestinal/pulmonary diseases.
- Selected via cluster random sampling method, from various parts of Sichuan.
- Do not have any antibiotic treatment 15 days prior to experiment.

Questionnaires
Milk consumption habits of subjects, (how often and how much milk was consumed), and any effects that occur after consumption were obtained through questionnaires which were created and tested out on. The responses were then used to find out the accumulative milk intake (AMI) of the subjects by multiplying 365 with amount of milk consumed per sitting, frequency of consumption per day and duration of milk consumption. In the questionnaire, subjects were divided into groups of various frequencies of milk consumption.

Identification of Subjects with Lactose Intolerance
Subjects have to go through a challenge dose whereby they are given 25g of lactose to digest in their body. Fecal and gaseous samples were then collected and analysed.

Hydrogen breath test (HBT) was performed to all subjects to determine lactase activities. Changes in hydrogen values collected at the end of the test (ΔH) were calculated. If the ΔH >1.786mg/m³ (equivalent to 20 ppm) or fecal lactose was positive, then that subject is said to have LD.

Subjects with LD were to determined to have LI if they have symptoms (flatulence, abdominal pain and diarrhea) and how severe they are after the challenge dose.

Statistical Analyses used to categorise subjects:
- χ² test: Analyze differences in the milk consumption behaviours in subjects.
- Correlation between severity of symptoms and AMI calculated by rank correlation analysis.
- Statistical significance for all tests: P<0.05.


RESULTS

Milk Drinking Behavior and Prevalence of Lactose Intolerance in Adults
Results showed that those who do not consume milk is more likely to suffer from LI than those who consume milk every day since it has the highest chi-squared value (χ² =21.452).

Severity of LI Symptoms and AMI in Adults
AMI and severity of symptoms (4 different levels: lactose tolerant, LD, LI without diarrhea, LI with diarrhea) were shown to vary inversely. The more milk an individual consumes, the less severe the symptoms (r = –0.2884).

Effects of Milk Drinking Behaviors on Lactose Intolerance in Adults

In all subjects, single factor analysis was used to study variables (educational background, frequency of milk intake, amount of milk consumed per sitting) related to milk consumption habits, which gave a significant statistical significance of P<0.1. This was further analysed using binary logistic regression, that concluded the frequency of milk consumption and amount of milk consumed per sitting are variables that affect LI, but not educational background.


DISCUSSION

Results obtained above are rather accurate as they can be supported by findings from other papers, experiments and surveys.

Results also suggest that individuals having difficulty digesting lactose can gradually tolerate the sugar by introducing more lactose. This induces metabolic changes to the body in the long run, since severity of symptoms varies indirectly with amount of milk consumption, which could be supported by external researches done on the same topic. This explains why the Chinese have higher percentage of LI, due to less lactose consumption in their dietary habits, compared to populations from other countries.


REFERENCE

Qiao Rong, Huang ChengYu, Du HuiZhang, Zeng Guo, Li Ling and Ye Sheng. 2011, Milk Consumption and Lactose Intolerance in Adults, Biomed Environ Sci, 24(5), p.512‐517.