Although endogenous lactase activities remain unchanged during lactose feeding, lactose-malabsorbers frequently report experiencing fewer and less severe GI symptoms as feeding progresses. This would suggest that some adaptive mechanisms relating to lactose processing occur during prolonged intake of lactose.
In one of the first studies to demonstrate adaptation to lactose feeding, Johnson et al. In addition, when challenged with the maximum tolerated dose of lactose, 4 of these subjects exhibited no increase in breath H 2 concentration Subsequent investigations have produced similar findings: lactose-malabsorbing individuals show decreased breath H 2 concentrations after a lactose challenge following a lactose-feeding period 68—71 Table 2.
Although these reports have reported none or only minor improvements in GI symptoms, the findings imply that colonic microbes adapt to the presence of lactose in the colonic lumen. Interestingly, these bacterial taxa do not produce H 2 during carbohydrate fermentation, which likely explains the observed reduction in breath H 2 concentrations after lactose feeding These results suggest that when dietary lactose reaches the colon, it stimulates the growth of lactose-fermenting bacteria, but whether this reduces intolerance symptoms to lactose is still a matter of debate.
Studies have shown decreased flatulence during a lactose challenge following a lactose-feeding period, possibly because of microbial changes leading to reduced colonic gas production 68 , Colonic adaptation is also supported by a study showing that supplementing lactose-intolerant individuals with a prebiotic increases the proportion of lactose-fermenting bacteria, which leads to decreased abdominal pain when lactose is reintroduced in the diet 75 , Taken together, however, these studies mainly report only minor improvements in 1 intolerance symptom with no changes in other GI symptoms 68 , 70 , Moreover, Briet et al.
Another explanation could be individual differences in the composition of microbiota that contribute to GI symptom development after lactose intake. Nevertheless, these studies show that lactose feeding increases the proportion of intestinal bacteria capable of hydrolyzing lactose and decreases colonic H 2 production, trends that might lead to some alleviation of intolerance symptoms in lactose-malabsorbers. This colonic adaptation to lactose feeding appears to be reversible, i.
However, despite colonic adaptation, the nutritional benefit of lactose for these individuals would still remain low compared with lactase-persistent individuals.
Intervention studies investigating colonic adaptation in humans after a lactose-feeding period. Studies that have measured changes in endogenous lactase activity after an intervention period consistently show a lack of enzyme induction, suggesting that lactose intake does not affect an individual's lactase activity. Although these studies are scarce and have relatively few subjects, data from cross-sectional studies support the theory of purely genetic regulation.
However, a few questions remain open. Firstly, the existing intervention studies have mainly been conducted on subjects from populations with a high prevalence of hypolactasia. This implies that most of the subjects in these studies are genetically homozygous for lactase deficiency, meaning that their ability to express lactase might have already been compromised permanently.
Perhaps extending these analyses to include genetic polymorphisms with varying lactase activities would produce a wider range of outcomes.
Secondly, considering that the age of onset for hypolactasia varies extensively between populations, it would certainly be of interest to investigate the genetic or epigenetic factors that trigger the downregulation of lactase expression at a certain age in different populations.
Contrary to endogenous lactase, the capacity of colonic microbes to process lactose can adapt to increased flux of lactose into the colonic lumen. Colonic adaptation occurs mainly in lactase-deficient individuals and is possibly responsible for the increased tolerance to lactose after a lactose-feeding period, but this matter is still being debated and requires more detailed investigations. Nevertheless, in lactose-malabsorbing individuals, withdrawing lactose from the diet might lead to the loss of adaptation and subsequently lower the threshold for intolerance symptoms when lactose is reintroduced.
Overall, however, it remains unclear if lactose intake leads to colonic adaptation in all lactose-malabsorbers and what are the possible differences between adapters and nonadapters. In addition, the microbial alterations contributing to colonic adaptation after lactose feeding should be investigated more thoroughly. The sole author was responsible for all aspects of this manuscript and declares no conflict of interests.
This review was funded by the Foundation for Nutrition Research. The funder had no role in the literature search, data gathering, and interpretation, and had no say in the final content of this manuscript. Lactose and lactase—who is lactose intolerant and why? J Pediatr Gastroenterol Nutr. Google Scholar. Lactose malabsorption and intolerance: a review. Food Funct. Lactase non-persistence and lactose intolerance. Curr Gastroenterol Rep.
Simoons FJ. Primary adult lactose intolerance and the milking habit: a problem in biologic and cultural interrelations. Am J Dig Dis. Review article: lactose intolerance in clinical practice—myths and realities.
Aliment Pharmacol Ther. Food and Agriculture Organization of the United Nations. Milk and milk products , [Internet]. Google Preview. Systematic review: effective management strategies for lactose intolerance. Ann Intern Med. Lactose intolerance symptoms assessed by meta-analysis: a grain of truth that leads to exaggeration.
J Nutr. The genetically programmed down-regulation of lactase in children. Identification of a variant associated with adult-type hypolactasia.
Nat Genet. An upstream polymorphism associated with lactase persistence has increased enhancer activity. World J Gastroenterol. Can primary hypolactasia manifest itself after the age of 20 years? A two-decade follow-up study. Scand J Gastroenterol.
World-wide distributions of lactase persistence alleles and the complex effects of recombination and selection. Hum Genet. Differences in DNA methylation and functional expression in lactase persistent and non-persistent individuals. Sci Rep. Lactase nonpersistence is directed by DNA-variation-dependent epigenetic aging. Nat Struct Mol Biol. The role of colonic metabolism in lactose intolerance. Eur J Clin Invest. Quantitative measurement of lactose absorption.
Identification of bacteria with beta-galactosidase activity in faeces from lactase non-persistent subjects. Colonic fermentation may play a role in lactose intolerance in humans. Lactose malabsorption and intolerance: pathogenesis, diagnosis and treatment. United Eur Gastroenterol J. Plimmer RHA. On the presence of lactase in the intestines of animals and on the adaptation of the intestine to lactose. J Physiol. Adaptation of intestinal lactase in the rat. The stimulation of lactase by feeding lactose.
How is lactose intolerance diagnosed? Some tests can help your doctor check for lactose intolerance. These may include: Lactose tolerance test. This test checks how your digestive system absorbs lactose. You will be asked not to eat or drink anything for about 8 hours before the test.
This often means not eating after midnight. For the test, you will drink a liquid that contains lactose. Some blood samples will be taken over a 2-hour period.
These will check your blood sugar blood glucose level. Hydrogen breath test. You will drink a liquid containing a lot of lactose. Your breath will be checked several times. High levels of hydrogen in your breath may mean you are lactose intolerant. Stool acidity test. This test is used for infants and young children.
It checks how much acid is in the stool. If someone is not digesting lactose, their stool will have lactic acid, glucose, and other fatty acids. Foods to Avoid if You Have IBS While lactose intolerance and irritable bowel syndrome IBS are two different conditions, both can cause similar symptoms for people who drink milk or eat milk products.
Read More. How is lactose intolerance treated? Here are some tips for managing lactose in your diet: Start slowly. Health Conditions Related to Genetic Changes Lactose intolerance At least nine LCT gene mutations cause congenital lactase deficiency, also called congenital alactasia. More About This Health Condition. Molecular genetics of human lactase deficiencies. Ann Med. Molecular differentiation of congenital lactase deficiency from adult-type hypolactasia. Nutr Rev. Check that your baby is gaining weight and growing normally.
If all this is okay, speak to an Australian Breastfeeding Association counsellor, lactation consultant or child health nurse, to check if your baby has a lactose overload. This is common in the early weeks and can happen when a baby is taking in more milk than they can digest easily. Breastfeeding advice is helpful in this situation.
If the situation is more complex, such as if your baby has poor weight gain or blood in their bowel motions, then this needs further investigation.
See your GP. Vomiting is not a symptom of lactose intolerance in babies. Note that vomiting in the early weeks of life is quite normal, as long as the baby is not distressed by it and they are keeping down sufficient milk to gain weight and grow normally. Most people with lactose intolerance can handle small amounts of lactose, such as a glass of milk, which contains 8—10 grams of lactose. Some helpful tips include:. This page has been produced in consultation with and approved by:.
Children may feel stomach pain for a range of reasons and may need treatment. Adoption can give a secure family life to children who can? Severe allergic reactions anaphylaxis and asthma attacks need urgent emergency first aid. In an emergency, always call triple zero Allergy occurs when the body overreacts to a 'trigger' that is harmless to most people.
Allergies to insect stings and bites range from milder allergic reactions to life-threatening, severe allergic reactions anaphylaxis.
Content on this website is provided for information purposes only. Information about a therapy, service, product or treatment does not in any way endorse or support such therapy, service, product or treatment and is not intended to replace advice from your doctor or other registered health professional.
The information and materials contained on this website are not intended to constitute a comprehensive guide concerning all aspects of the therapy, product or treatment described on the website. All users are urged to always seek advice from a registered health care professional for diagnosis and answers to their medical questions and to ascertain whether the particular therapy, service, product or treatment described on the website is suitable in their circumstances.
The State of Victoria and the Department of Health shall not bear any liability for reliance by any user on the materials contained on this website. Skip to main content. Home Allergies. Lactose intolerance. Actions for this page Listen Print.
0コメント