This research was conducted to evaluate the knowledge and purchasing behaviour of consumers regarding lactose-free foods. Study data were collected from 1882 individuals with the help of a questionnaire form. Attitudes towards animal welfare, healthy nutrition and gastrointestinal symptoms were also evaluated. The majority (86.6%) of the participants reported that they had heard of the concept of lactose-free foods before, but more than half (67.0%) did not report buying them because of their higher costs compared to regular products and lack of sufficient information. Not causing gas/bloating (32.5%) and being healthier (28.3%) were shown to be the most significant motivational factors in purchasing lactose-free foods (P < 0.05). The factors affecting purchase of lactose-free products were education, employment status, history of having a food intolerance test and animal welfare perception together with higher scores from the gastrointestinal symptom rating scale, and attitude scale for healthy nutrition (P < 0.05). Body mass index was not found to be an effective factor determining purchase intention. The results provide a general overview of consumers, however, further studies on other demographic groups are needed.

The aim of this review was to present various topics related to lactose intolerance with special attention given to the role of fermented foods and probiotics in alleviating gastrointestinal symptoms. Lactose intolerance is a common digestive problem in which the human body is unable to digest lactose, known as milk sugar. Lactose intolerance can either be hereditary or a consequence of intestinal diseases. Recent work has demonstrated that fermented dairy products and probiotics can modify the metabolic activities of colonic microbiota and may alleviate the symptoms of lactose intolerance. We suggest that, lactose free dairy products could be recommended as alternatives for the alleviation of lactose intolerance and for the promotion of human health and wellness.

Clinical manifestations of lactase (LCT) deficiency include intestinal and extra-intestinal symptoms. Lactose hydrogen breath test (H2-BT) is considered the gold standard to evaluate LCT deficiency (LD). Recently, the single-nucleotide polymorphism C/T− 13 910 has been associated with LD. The objectives of the present study were to evaluate the agreement between genetic testing of LCT C/T− 13 910 and lactose H2-BT, and the diagnostic value of extended symptom assessment. Of the 201 patients included in the study, 194 (139 females; mean age 38, range 17–79 years, and 55 males, mean age 38, range 18–68 years) patients with clinical suspicion of LD underwent a 3–4 h H2-BT and genetic testing for LCT C/T− 13 910. Patients rated five intestinal and four extra-intestinal symptoms during the H2-BT and then at home for the following 48 h. Declaring H2-BT as the gold standard, the CC− 13 910 genotype had a sensitivity of 97 % and a specificity of 95 % with a κ of 0·9 in diagnosing LCT deficiency. Patients with LD had more intense intestinal symptoms 4 h following the lactose challenge included in the H2-BT. We found no difference in the intensity of extra-intestinal symptoms between patients with and without LD. Symptom assessment yielded differences for intestinal symptoms abdominal pain, bloating, borborygmi and diarrhoea between 120 min and 4 h after oral lactose challenge. Extra-intestinal symptoms (dizziness, headache and myalgia) and extension of symptom assessment up to 48 h did not consistently show different results. In conclusion, genetic testing has an excellent agreement with the standard lactose H2-BT, and it may replace breath testing for the diagnosis of LD. Extended symptom scores and assessment of extra-intestinal symptoms have limited diagnostic value in the evaluation of LD.

This trial was designed to assess the effect of live probiotic consumption on leucine assimilation from fresh and pasteurised yoghurt in volunteers with different lactose digestibility. Thirty-three volunteers (mean age 32, s.d. 7 years) participated in this parallel single-blind study (16 of them with moderate lactose intolerance). Breath samples were taken before and at 15 min intervals over 3-h after the ingestion of fresh and pasteurised yoghurt extrinsically labelled with (1-13C)leucine. The 13C enrichment in breath was measured by isotopic rate mass spectrometry and mathematically converted to a percentage of assimilated leucine (100-%13C-dose in breath) and the assimilation kinetic constant (min− 1). The 13C-leucine assimilation was statistically higher after the fresh yoghurt intake than after the pasteurised product intake (P = 0·032) while the kinetic constant of assimilation was slower in intolerance status (P = 0·014) although a product-related effect (P = 0·445) was not found. In conclusion, fresh yoghurt intake resulted in higher short-term leucine assimilation, while lactose intolerance appears to negatively affect the assimilation rate of leucine from dairy products. These findings offer new insight on acute in vivo amino acid assimilation in the presence of probiotics and moderate lactose intolerance.

Transit kinetics and survival rates of a bacterial species from yoghurt (i.e. Streptococcus thermophilus strain FBI3) were examined in different digestive compartments of gnotoxenic and human-microbiota-associated mice. The production of the lactose-hydrolysing enzyme (i.e. β-galactosidase) was also investigated within the digestive tract, using a chromosomal reporter system based on luciferase genes from Photorhabdus luminescens under the control of the plac promoter. In both mice models, S. thermophilus cells transited within 2h from the stomach to the caecum–colon compartment of the digestive tract where they displayed a survival rate of nearly 100%. In gnotoxenic mice, luciferase activity was found to increase in the second half of the small intestine and in the caecum–colon compartment when lactose was added to the drinking water provided to the animals. In human-microbiota-associated mice drinking lactose, luciferase activity was similarly increased in the second half of the small intestine but was drastically reduced in the caecum–colon compartment. This feature could be ascribed to the presence of the resident human microbiota.