Concept: Lactose intolerance
Cows' milk generally contains two types of β-casein, A1 and A2 types. Digestion of A1 type can yield the peptide β-casomorphin-7, which is implicated in adverse gastrointestinal effects of milk consumption, some of which resemble those in lactose intolerance. This study aimed to compare the effects of milk containing A1 β-casein with those of milk containing only A2 β-casein on inflammation, symptoms of post-dairy digestive discomfort (PD3), and cognitive processing in subjects with self-reported lactose intolerance.
European lactose tolerance genotype (LCT -13910 C>T, rs4988234) has been positively associated to body mass indexes (BMI) in a meta-analysis of 31,720 individuals of northern and central European descent. A strong association of lactase persistence (LP) with BMI and obesity has also been traced in a Spanish Mediterranean population. The aim of this study was to analyze a potential association of LP compared to lactase non-persistence (LNP) with BMI in inhabitants of the Canary Islands of Spain using Mendelian randomization.
A major protein component of cow’s milk is β-casein. The most frequent variants in dairy herds are A1 and A2. Recent studies showed that milk containing A1 β-casein promoted intestinal inflammation and exacerbated gastrointestinal symptoms. However, the acute gastrointestinal effects of A1 β-casein have not been investigated. This study compared the gastrointestinal effects of milk containing A1 and A2 β-casein versus A2 β-casein alone in Chinese adults with self-reported lactose intolerance.
Lactose intolerance related to primary or secondary lactase deficiency is characterized by abdominal pain and distension, borborygmi, flatus, and diarrhea induced by lactose in dairy products. The biological mechanism and lactose malabsorption is established and several investigations are available, including genetic, endoscopic and physiological tests. Lactose intolerance depends not only on the expression of lactase but also on the dose of lactose, intestinal flora, gastrointestinal motility, small intestinal bacterial overgrowth and sensitivity of the gastrointestinal tract to the generation of gas and other fermentation products of lactose digestion. Treatment of lactose intolerance can include lactose-reduced diet and enzyme replacement. This is effective if symptoms are only related to dairy products; however, lactose intolerance can be part of a wider intolerance to variably absorbed, fermentable oligo-, di-, monosaccharides and polyols (FODMAPs). This is present in at least half of patients with irritable bowel syndrome (IBS) and this group requires not only restriction of lactose intake but also a low FODMAP diet to improve gastrointestinal complaints. The long-term effects of a dairy-free, low FODMAPs diet on nutritional health and the fecal microbiome are not well defined. This review summarizes recent advances in our understanding of the genetic basis, biological mechanism, diagnosis and dietary management of lactose intolerance.
Impact of short-chain galactooligosaccharides on the gut microbiome of lactose-intolerant individuals
- Proceedings of the National Academy of Sciences of the United States of America
- Published over 3 years ago
Directed modulation of the colonic bacteria to metabolize lactose effectively is a potentially useful approach to improve lactose digestion and tolerance. A randomized, double-blind, multisite placebo-controlled trial conducted in human subjects demonstrated that administration of a highly purified (>95%) short-chain galactooligosaccharide (GOS), designated “RP-G28,” significantly improved clinical outcomes for lactose digestion and tolerance. In these individuals, stool samples were collected pretreatment (day 0), after GOS treatment (day 36), and 30 d after GOS feeding stopped and consumption of dairy products was encouraged (day 66). In this study, changes in the fecal microbiome were investigated using 16S rRNA amplicon pyrosequencing and high-throughput quantitative PCR. At day 36, bifidobacterial populations were increased in 27 of 30 of GOS subjects (90%), demonstrating a bifidogenic response in vivo. Relative abundance of lactose-fermenting Bifidobacterium, Faecalibacterium, and Lactobacillus were significantly increased in response to GOS. When dairy was introduced into the diet, lactose-fermenting Roseburia species increased from day 36 to day 66. The results indicated a definitive change in the fecal microbiome of lactose-intolerant individuals, increasing the abundance of lactose-metabolizing bacteria that were responsive to dietary adaptation to GOS. This change correlated with clinical outcomes of improved lactose tolerance.
Dairy products provide a package of essential nutrients that is difficult to obtain in low-dairy or dairy-free diets, and for many people it is not possible to achieve recommended daily calcium intakes with a dairy-free diet. Despite the established benefits for bone health, some people avoid dairy in their diet due to beliefs that dairy may be detrimental to health, especially in those with weight management issues, lactose intolerance, osteoarthritis, rheumatoid arthritis, or trying to avoid cardiovascular disease. This review provides information for health professionals to enable them to help their patients make informed decisions about consuming dairy products as part of a balanced diet. There may be a weak association between dairy consumption and a possible small weight reduction, with decreases in fat mass and waist circumference and increases in lean body mass. Lactose intolerant individuals may not need to completely eliminate dairy products from their diet, as both yogurt and hard cheese are well tolerated. Among people with arthritis, there is no evidence for a benefit to avoid dairy consumption. Dairy products do not increase the risk of cardiovascular disease, particularly if low fat. Intake of up to three servings of dairy products per day appears to be safe and may confer a favourable benefit with regard to bone health.
Background: Cow milk consumption in childhood has been associated with increased height, which is an important measure of children’s growth and development. Many parents are choosing noncow milk beverages such as soy and almond milk because of perceived health benefits. However, noncow milk contains less protein and fat than cow milk and may not have the same effect on height.Objective: We sought to determine whether there is an association between noncow milk consumption and lower height in childhood and assess whether cow milk consumption mediates the relation between noncow milk consumption and height.Design: This was a cross-sectional study of 5034 healthy Canadian children aged 24-72 mo enrolled in the Applied Research Group for Kids cohort. The primary exposure was the volume of noncow milk consumption (number of 250-mL cups per day). The primary outcome was height, which was measured as height-for-age z score. Multivariable linear regression was used to determine the association between noncow milk consumption and height. A mediation analysis was conducted to explore whether cow milk consumption mediated the association between noncow milk consumption and height.Results: There was a dose-dependent association between higher noncow milk consumption and lower height (P < 0.0001). For each daily cup of noncow milk consumed, children were 0.4 cm (95% CI: 0.2, 0.8 cm) shorter. In the mediation analysis, lower cow milk consumption only partially mediated the association between noncow milk consumption and lower height. The height difference for a child aged 3 y consuming 3 cups noncow milk/d relative to 3 cups cow milk/d was 1.5 cm (95% CI: 0.8, 2.0 cm).Conclusions: Noncow milk consumption was associated with lower childhood height. Future research is needed to understand the causal relations between noncow milk consumption and height.
Controversy persists on the association between dairy products, especially milk, and cardiovascular diseases (CVD). Genetic proxies may improve dairy intake estimations, and clarify diet-disease relationships through Mendelian randomization. We meta-analytically (n ≤ 20,089) evaluated associations between a lactase persistence (LP) SNP, the minichromosome maintenance complex component 6 (MCM6)-rs3754686C>T (nonpersistence>persistence), dairy intake, and CVD biomarkers in American (Hispanics, African-American and Whites) and Mediterranean populations. Moreover, we analyzed longitudinal associations with milk, CVD and mortality in PREDIMED), a randomized Mediterranean diet (MedDiet) intervention trial (n = 7185). The MCM6-rs3754686/MCM6-rs309180 (as proxy), LP-allele (T) was strongly associated with higher milk intake, but inconsistently associated with glucose and lipids, and not associated with CVD or total mortality in the whole population. Heterogeneity analyses suggested some sex-specific associations. The T-allele was associated with higher CVD and mortality risk in women but not in men (P-sex interaction:0.005 and 0.032, respectively), mainly in the MedDiet group. However, milk intake was not associated with CVD biomarkers, CVD or mortality either generally or in sub-groups. Although MCM6-rs3754686 is a good milk intake proxy in these populations, attributing its associations with CVD and mortality in Mediterranean women to milk is unwarranted, as other factors limiting the assumption of causality in Mendelian randomization may exist.
Cow’s milk allergy (CMA) is one of the most common presentations of food allergy seen in early childhood. It is also one of the most complex food allergies, being implicated in IgE-mediated food allergy as well as diverse manifestations of non-IgE-mediated food allergy. For example, gastrointestinal CMA may present as food protein induced enteropathy, enterocolitis or proctocolitis. Concerns regarding the early and timely diagnosis of CMA have been highlighted over the years. In response to these, guideline papers from the United Kingdom (UK), Australia, Europe, the Americas and the World Allergy Organisation have been published. The UK guideline, ‘Diagnosis and management of non-IgE-mediated cow’s milk allergy in infancy-a UK primary care practical guide’ was published in this journal in 2013. This Milk Allergy in Primary Care (MAP) guideline outlines in simple algorithmic form, both the varying presentations of cow’s milk allergy and also focuses on the practical management of the most common presentation, namely mild-to-moderate non-IgE-mediated allergy. Based on the international uptake of the MAP guideline, it became clear that there was a need for practical guidance beyond the UK. Consequently, this paper presents an international interpretation of the MAP guideline to help practitioners in primary care settings around the world. It incorporates further published UK guidance, feedback from UK healthcare professionals and affected families and, importantly, also international guidance and expertise.
The mainstay of treatment of IgE-mediated cow milk allergy (IMCMA) is an avoidance diet, which is especially difficult with a ubiquitous food like milk. Milk oral immunotherapy (MOIT) may be an alternative treatment, through desensitization or induction of tolerance.