The effect of lactose maldigestion on the relationship between dairy food intake and colorectal cancer: a systematic review

The Association of Lactose Intolerance With Colon and Gastric Cancers: Friend or Foe?

Background: Lactose intolerance (LI) appears usually in later ages when the lactase enzyme becomes deficient or absent in the small intestine. Conflicting results have been reported in the literature about the association of lactose intolerance with various gastrointestinal malignancies. Hence, our aim was to study the association between LI, colon cancer (CCa), and gastric cancer (GC) using a large database. Methods: A cross-sectional study was performed using the National Inpatient Sample (NIS) database between 2004 and 2014. We identified adult patients (18-90 years) who were diagnosed with LI (study group) using appropriate International Classification of Diseases, Ninth Revision (ICD-9) codes. The control group comprised patients who did not have a diagnosis of LI. We identified the diagnosis of CCa and GC in both study and control groups using the ICD-9 codes. Univariable and multivariable logistic regression analyses were performed to assess the association between LI, CCa, and GC. Results: The total population comprised 71,360,501 patients, of which 57,909 (0.08%) were diagnosed with LI. LI patients were older (62 vs 51 years) with more females (61.5% vs 60.1%) and less African American patients (11.8% vs 14.3%) (p <0.0001 for all). In addition, LI patients had more smoking (12.4% vs 12%) and obesity (15% vs 8.9%). On the other hand, patients in the LI group had less alcohol use (3.8% vs 4.2%) (p <0.0001). After adjusting for the age, gender, race, smoking, alcohol, obesity, and inflammatory bowel disease, the LI group had a slightly lower rate of CCa (OR 0 .974, 95%CI 0.906-1.048, p = 0.486) and a lower rate of GC (OR: 0.993, 95%CI 0.924-1.068, p =0.853); however, the results were not statistically significant. Conclusion: Patients with lactose intolerance may have a lower risk of colon and gastric cancer. However, these findings were not statistically significant. Further studies are needed to understand this association.

Dairy product consumption and development of cancer: an overview of reviews

OBJECTIVES

To provide a comprehensive systematic overview of current evidence from pooled analyses/meta-analyses and systematic reviews (PMASRs) pertaining to dairy consumption and incident cancer and/or all-cause or cancer-specific mortality.

DESIGN

Overview of reviews.

SETTING

Community setting.

PARTICIPANTS

The unit of analysis is PMASRs. A total of 42 PMASRs was included in this overview of reviews.

INTERVENTIONS/EXPOSURES

Any dairy product consumption (eg, milk, yogurt, etc).

PRIMARY AND SECONDARY OUTCOMES MEASURES

Primary outcome measure is development of any type of cancer. Secondary outcome measures are all-cause mortality and cancer-specific mortality.

RESULTS

From 9693 citations identified, we included 42 PMASRs (52 study reports) published between 1991 and 2017. Thirty-one (74%) of these was pooled analyses/meta analyses, and only 11 (26%) were systematic reviews and meta-analyses. There was a wide variability in the type of study designs included within the other PMASRs, thus contributing to variable and, in instances, divergent estimates of cancer risk for several cancer subtypes. For example, only one systematic review and meta-analysis exclusively included prospective study designs. Most PMASRs were of low to moderate quality based on the Assessing the Methodological Quality of Systematic Reviews (AMSTAR) scores. The median AMSTAR score was 5 (IQR 2-7). Our overview identified conflicting evidence from PMASRs on association between dairy consumption and incident cancers or mortality. Heterogeneity in summary estimates reflected the inclusion of variable study designs and overall low methodological quality of individual PMASRs.

CONCLUSIONS

The association between dairy consumption and cancer risk has been explored in PMASRs with a variety of study designs and of low to moderate quality. To fully characterise valid associations between dairy consumption and risk of cancer and/or mortality rigorously conducted, PMASRs including only high-quality prospective study designs are required.

TRIAL REGISTRATION NUMBER

CRD42017078463.

Lactose Intolerance, Dairy Avoidance, and Treatment Options

Lactose intolerance refers to symptoms related to the consumption of lactose-containing dairy foods, which are the most common source for this disaccharide. While four causes are described, the most common is the genetically-determined adult onset lactose maldigestion due to loss of intestinal lactase governed by control of the gene by a 14,000 kb promoter region on chromosome 2. Gastrointestinal symptoms from lactose have expanded to include systemic effects and have also been confounded by other food intolerances or functional gastrointestinal disorders. Partly because lactose maldigestion is often interpreted as lactose intolerance (symptoms), focus of therapy for these symptoms starts with lactose restriction. However, withholding of dairy foods completely is not appropriate due to a more favorable impact on health. Industrial efforts to substitute with plant-based products is not completely successful at this time. This narrative article reviews the complexities of the perception of lactose intolerance, its epidemiology, and pathogenesis. Treatments are discussed, including the inappropriateness of dairy avoidance. In conjunction, effects of dairy products on 19 common diseases are reviewed. Different methods of treatment, lactose-reduced products, plant-based dairy substitutes, adaptation, prebiotics, exogenous lactase, probiotics, and some other dietary interventions are further discussed.

Estimating Lactase Nonpersistence Distributions in the Multi-Ethnic Canadian Demographic: A Population-Based Study

Objectives

The lactase persistence/nonpersistence (LP/LNP) phenotypes follow a geographic pattern that is rooted in the gene-culture coevolution observed throughout the history of human migrations. The immense size and relatively open immigration policy have drawn migrants of diverse ethnicities to Canada. Among the multicultural demographic, two-thirds of the population are derived from the British Isles and northwestern France. A recent assessment of worldwide lactase distributions found Canada to have an LNP rate of 59% (confidence interval [CI] 44%-74%). This estimate is rather high compared with earlier reports that listed Canada as a country with a 10% LNP rate; the authors had also noted that biases were likely because their calculations were based largely on Aboriginal studies. We hereby present an alternate LNP prevalence estimate at the national, provincial and territorial level.

Methods

We applied the referenced LNP frequency distribution data to the 2016 population census to account for the current multi-ethnic distributions in Canada. Prevalence rates for Canada, the provinces and territories were calculated.

Results

The national LNP rate is estimated at 44% (CI 41%-47%) after accounting for the 254 ethnic groups, with the lowest rates found in the eastern provinces and the highest rates in the Northwest Territories (57%) and Nunavut (66%), respectively.

Conclusion

Despite the heterogeneous nature of the referenced data and the inference measures taken, evidently, the validity of our LNP estimate is anchored on the inclusion of multi-ethnic groups representing the current Canadian demographic.

Gene-Dairy Food Interactions and Health Outcomes: A Review of Nutrigenetic Studies

Each person differs from the next by an average of over 3 million genetic variations in their DNA. This genetic diversity is responsible for many of the interindividual differences in food preferences, nutritional needs, and dietary responses between humans. The field of nutrigenetics aims to utilize this type of genetic information in order to personalize diets for optimal health. One of the most well-studied genetic variants affecting human dietary patterns and health is the lactase persistence mutation, which enables an individual to digest milk sugar into adulthood. Lactase persistence is one of the most influential Mendelian factors affecting human dietary patterns to occur since the beginning of the Neolithic Revolution. However, the lactase persistence mutation is only one of many mutations that can influence the relationship between dairy intake and disease risk. The purpose of this review is to summarize the available nutrigenetic literature investigating the relationships between genetics, dairy intake, and health outcomes. Nonetheless, the understanding of an individual’s nutrigenetic responses is just one component of personalized nutrition. In addition to nutrigenetic responses, future studies should also take into account nutrigenomic responses (epigenomic, transcriptomic, proteomic, metabolomic), and phenotypic/characteristic traits (age, gender, activity level, disease status, etc.), as these factors all interact with diet to influence health.

Systematic review and meta-analysis of lactose digestion, its impact on intolerance and nutritional effects of dairy food restriction in inflammatory bowel diseases

BACKGROUND

Relationships between inflammatory bowel disease and lactose containing foods remain controversial and poorly defined regarding symptoms, nutritional outcomes, and epidemiologic associations for lactose maldigestion.

METHODS

A literature review was performed using Pub Med, Cochrane library and individual references, to extract data on lactose maldigestion prevalence in inflammatory bowel diseases. A meta-analysis was done using selected articles, to determine odds ratios of maldigestion. Information was collected about symptoms, impact on pattern of dairy food consumption, as well as the effects of dairy foods on the course of inflammatory bowel diseases.

RESULTS

A total of 1022 articles were evaluated, 35 articles were retained and 5 studies were added from review articles. Of these 17 were included in meta-analysis which showed overall increased lactose maldigestion in both diseases. However increased risk on sub analysis was only found in Crohn's in patients with small bowel involvement. Nine additional studies were reviewed for symptoms, with variable outcomes due to confounding between lactose intolerance and lactose maldigestion. Fourteen studies were evaluated for dairy food effects. There was a suggestion that dairy foods may protect against inflammatory bowel disease. Nutritional consequences of dairy restrictions might impact adversely on bone and colonic complications.

CONCLUSIONS

Lactose maldigestion in inflammatory bowel disease is dependent on ethnic makeup of the population and usually not disease. No bias of increased disease prevalence was noted between lactase genotypes. Intolerance symptoms depend on several parameters besides lactose maldigestion. Dairy foods may decrease risks of inflammatory bowel disease. Dairy restrictions may adversely affect disease outcome.

The Diverse Forms of Lactose Intolerance and the Putative Linkage to Several Cancers

Lactase-phlorizin hydrolase (LPH) is a membrane glycoprotein and the only β-galactosidase of the brush border membrane of the intestinal epithelium. Besides active transcription, expression of the active LPH requires different maturation steps of the polypeptide through the secretory pathway, including N- and O-glycosylation, dimerization and proteolytic cleavage steps. The inability to digest lactose due to insufficient lactase activity results in gastrointestinal symptoms known as lactose intolerance. In this review, we will concentrate on the structural and functional features of LPH protein and summarize the cellular and molecular mechanism required for its maturation and trafficking. Then, different types of lactose intolerance are discussed, and the molecular aspects of lactase persistence/non-persistence phenotypes are investigated. Finally, we will review the literature focusing on the lactase persistence/non-persistence populations as a comparative model in order to determine the protective or adverse effects of milk and dairy foods on the incidence of colorectal, ovarian and prostate cancers.

Adaptation to Lactose in Lactase Non Persistent People: Effects on Intolerance and the Relationship between Dairy Food Consumption and Evalution of Diseases

Dairy foods contain complex nutrients which interact with the host. Yet, evolution of lactase persistence has divided the human species into those that can or cannot digest lactose in adulthood. Such a ubiquitous trait has differential effects on humanity. The literature is reviewed to explore how the divide affects lactose handling by lactase non persistent persons. There are two basic differences in digesters. Firstly, maldigesters consume less dairy foods, and secondly, excess lactose is digested by colonic microflora. Lactose intolerance in maldigesters may occur with random lactose ingestion. However, lactose intolerance without maldigestion tends to detract from gaining a clear understanding of the mechanisms of symptoms formation and leads to confusion with regards to dairy food consumption. The main consequence of intolerance is withholding dairy foods. However, regular dairy food consumption by lactase non persistent people could lead to colonic adaptation by the microbiome. This process may mimic a prebiotic effect and allows lactase non persistent people to consume more dairy foods enhancing a favorable microbiome. This process then could lead to alterations in outcome of diseases in response to dairy foods in lactose maldigesters. The evidence that lactose is a selective human prebiotic is reviewed and current links between dairy foods and some diseases are discussed within this context. Colonic adaptation has not been adequately studied, especially with modern microbiological techniques.

Colorectal cancer and nonfermented milk, solid cheese, and fermented milk consumption: a systematic review and meta-analysis of prospective studies

Colorectal cancer is the second most prevalent cancer worldwide. A systematic review and meta-analysis of prospective studies was conducted to examine the association between intake of different types of dairy foods during adulthood and the development of colorectal cancer, specifically comparing nonfermented milk, solid cheese, and fermented milk. Seven databases were systematically searched and 15 cohort studies selected for inclusion, involving over 900,000 subjects and over 5200 colorectal cancer cases. Meta-analysis resulted in an overall relative risk of colon cancer of 0.74 (95% confidence interval 0.60-0.91) in men consuming nonfermented milk (highest intake category averaging 525 g/day). No association was found between consumption of nonfermented milk and rectal cancer in men or nonfermented milk and colon or rectal cancer in women. No protective association was found between consumption of solid cheese or fermented milk and colorectal cancer. Reasons for the differences in the impact of nonfermented milk, solid cheese, and fermented milk in the colon are discussed. This meta-analysis supports the inverse association between nonfermented milk consumption and risk of colon cancer in men, and provides an evidence base to assist in the formulation of dietary guidelines involving dairy foods.

Latitude, sunshine, and human lactase phenotype distributions may contribute to geographic patterns of modern disease: the inflammatory bowel disease model

Countries with high lactase nonpersistence (LNP) or low lactase persistence (LP) populations have lower rates of some "western" diseases, mimicking the effects of sunshine and latitude. Inflammatory bowel disease (IBD), ie, Crohn's disease and ulcerative colitis, is putatively also influenced by sunshine. Recent availability of worldwide IBD rates and lactase distributions allows more extensive comparisons. The aim of this study was to evaluate the extent to which modern day lactase distributions interact with latitude, sunshine exposure, and IBD rates. National IBD rates, national distributions of LP/LNP, and population-weighted average national annual ultraviolet B exposure were obtained, estimated, or calculated from the literature. Negative binomial analysis was used to assess the relationship between the three parameters and IBD rates. Analyses for 55 countries were grouped in three geographic domains, ie, global, Europe, and non-Europe. In Europe, both latitude and ultraviolet B exposure correlate well with LP/LNP and IBD. In non-Europe, latitude and ultraviolet B exposure correlate weakly with LP/LNP, but the latter retains a more robust correlation with IBD. In univariate analysis, latitude, ultraviolet B exposure, and LP/LNP all had significant relationships with IBD. Multivariate analysis showed that lactase distributions provided the best model of fit for IBD. The model of IBD reveals the evolutionary effects of the human lactase divide, and suggests that latitude, ultraviolet B exposure, and LP/LNP mimic each other because LP/LNP follows latitudinal directions toward the equator. However, on a large scale, lactase patterns also follow lateral polarity. The effects of LP/LNP in disease are likely to involve complex interactions.

Lactose intolerance

Declining ability to digest lactose is normal after childhood, and some degree of adult intolerance is common in many populations.

However, this does not mean that everyone with low lactase levels cannot tolerate any lactose. Most people with LI can tolerate fermented dairy (e.g. cheese, yoghurt). Any dairy avoidance treatment for LI should be individualised, reassessed periodically, and avoid underconsumption of key nutrients such as calcium.

Differential impact of lactose/lactase phenotype on colonic microflora

BACKGROUND

The ability to digest lactose divides the world's population into two phenotypes that may be risk variability markers for several diseases. Prebiotic effects likely favour lactose maldigesters who experience lactose spilling into their colon.

OBJECTIVE

To evaluate the effects of fixed-dose lactose solutions on fecal bifidobacteria and lactobacilli in digesters and maldigesters, and to determine whether the concept of a difference in ability to digest lactose is supported.

METHODS

A four-week study was performed in 23 lactose maldigesters and 18 digesters. Following two weeks of dairy food withdrawal, subjects ingested 25 g of lactose twice a day for two weeks. Stool bifidobacteria and lactobacilli counts pre- and postintervention were measured as the primary outcome. For secondary outcomes, total anaerobes, Enterobacteriaceae, beta-galactosidase and N-acetyl-beta-D-glucosaminidase activity in stool, as well as breath hydrogen and symptoms following lactose challenge tests, were measured.

RESULTS

Lactose maldigesters had a mean change difference (0.72 log10 colony forming unitsg stool; P=0.04) in bifidobacteria counts compared with lactose digesters. Lactobacilli counts were increased, but not significantly. Nevertheless, reduced breath hydrogen after lactose ingestion correlated with lactobacilli (r=-0.5; P<0.001). Reduced total breath hydrogen and symptom scorestogether, with a rise in fecal enzymes after intervention, were appropriate, but not significant.

CONCLUSIONS

Despite failure to achieve full colonic adaptation, the present study provided evidence for a differential impact of lactose on microflora depending on genetic lactase status. A prebiotic effect was evident in lactose maldigesters but not in lactose digesters. This may play a role in modifying the mechanisms of certain disease risks related to dairy food consumption between the two phenotypes.

Determinants of geographic patterns of diseases: interaction of lactose/lactase status and sunshine exposure

Geographic patterns of diseases depend on multilayered causes. However, the division of the world's population into two phenotypes regarding lactose digestion and sunshine exposure to fixed areas of the globe are two relatively slow changing variables. It is hypothesized that it is a vectorial interaction between these two variables that provide a backbone to risk modification of many diseases. Lactase non persistence status tends to follow sunshine exposure particularly in Europe but Lactase persistence status is also been shown to be related to pastoral life styles in spotty regions of Africa, Middle East and China. Current emphasis of research favours the modifying role of vitamin D and sunshine. Nevertheless it was demonstrated that national digester/nondigester status has mathematical relationships to geographic distribution of some diseases. These relationships are also similar to that described for the effects of latitude through sunshine and vitamin D. This observation raises a question as to how each one affects disease outcome. In this paper lactose/lactase interactions are first reviewed for eight exemplary diseases. Based on population findings and corroborative meta-analyses gleaned from the literature 6 types of interactions may be classified. Then in a preliminary fashion lactose digester and maldigester status are related to relative annual sunshine exposure. Further the relative national annual sunshine exposure is evaluated to outcomes of the same exemplary diseases. The patterns related to sunshine reflect that obtained with national lactase status proportions and also corroborate a literature review. However, correlations are weak to moderate and only ovarian cancer reached conventional statistical significance. Because these comparisons are based on modest number of national data firm conclusions cannot be made. However, it is argued that evolutionary pressures exerted by regional sunshine exposure may have had influence on a number of relevant genetic polymorphisms in parallel with lactase status. Furthermore influences of ancestral herding and dairy food consumption also may have exerted independent influences on either lactose phenotype. As such both discussed variables are postulated to exert parallel as well as independent effects on modifying geographic disease patterns. These could partly explain both north to south and west to east directional changes.

Impact of lactose containing foods and the genetics of lactase on diseases: an analytical review of population data

Dairy foods (DFs) contain complex ingredients that could affect different diseases. The control of lactose digestion phenotypically divides populations into those who can [lactase persistent (LP)] and those who cannot [lactase nonpersistent (LNP)] assimilate lactose. LNP subjects, however, can adapt to lactose intolerance through intestinal bacteria. The DF/LNP status interactions may function as disease risk modifiers. We evaluated the relationship between DF and LNP with colorectal, breast, prostate, ovarian, lung, and stomach cancer and inflammatory bowel diseases (IBD; Crohn's disease and ulcerative colitis). Yearly per capita DF consumption, LNP national prevalence, cancer mortality, and incidence of IBD were obtained from several sources. A negative binomial regression model was used to derive incremental risks. There were statistically significant (P <or= 0.05) increases in risk for colorectal and prostate cancer and ulcerative colitis with DFs and a statistically significant decreased risk for stomach cancer. There were trends (P<0.1) for lung and ovarian cancers and Crohn's disease. As LNP prevalence increased, stomach cancer risk increased, whereas risks of all other conditions decreased (P<0.01). In 3 cancers (prostate, ovarian, and breast), meta-analyses of case-based studies support ecological data. In colorectal cancer, on the contrary, meta-analyses of case-based studies suggest protection. The possible importance of distinguishing LNP/LP status in studies is discussed.