Lactose is the main carbohydrate found in milk and dairy products and is digested by the enzyme lactase into its absorbable components - glucose and galactose - which are then used as fuel by the body.
Lactose maldigestion occurs when insufficient amounts of the enzyme lactase are available in the gut to digest lactose. This results in undigested lactose passing into the large intestine where it can be fermented by the bacteria in the colon causing adverse gastrointestinal symptoms in some individuals, such as flatulence, diarrhoea and abdominal pain.
This problem is known as lactose intolerance and is defined as “the occurrence of symptoms after persons with clinically diagnosed lactose maldigestion consume a trigger amount of lactose”.
Although the lactose content of yogurt is naturally lower than milk, research has shown that the lactose that is present in yogurt is better tolerated by individuals with low production of lactase (hypolactasia) than lactose in an equivalent quantity in milk.
This may be due to several factors including the activity of live bacteria in the yogurt or the digestive action of other enzymes on lactose such as bacterial β-galactosidase. The increased viscosity of yogurt compared with milk has also been suggested as a potential explanation, as this may result in slower emptying from the stomach and thus a longer transit through the gastrointestinal tract, which in turn may improve the absorption and reduce the amount of lactose present in the colon.
Whatever the explanation, the science consistently shows that yogurt is well tolerated by individuals who have lactose intolerance.
This is important, since those suffering from lactose maldigestion or intolerance often exclude all dairy foods from the diet which can lead to poor calcium intake.
Hard cheeses such as cheddar are also naturally lower in lactose than milk and can be well tolerated by those who have difficulty digesting lactose.
Interestingly, studies have suggested that even in subjects with lactose intolerance, consumption of small amounts of any dairy food, if combined with a meal, is often well tolerated and regular consumption may even reduce symptoms.
Obesity is an increasing public health problem in the UK, with one in five adults now classed as obese.
Fears about weight gain are often cited as a reason to cut down on the consumption of milk and dairy products. However, contrary to popular belief, research has shown that people who consume milk and dairy foods are likely to be slimmer than those who do not.
Studies have also shown that consumption of milk and dairy foods as part of a calorie controlled diet is associated with increased weight loss, particularly form the abdomen.
This is particularly beneficial since excess fat around the trunk region of the body is associated with greater risks to health.
The precise mechanisms involved are unclear but studies suggest they are likely to involve calcium found in milk, yogurt and other dairy foods. The evidence also suggests that calcium from dairy sources has a substantially greater effect than calcium from supplements.
Probiotics can be defined as live bacteria which are beneficial to human health. Fermented dairy products such as yogurt have the ability to support the viability of probiotic cultures and therefore provide a suitable vehicle for their delivery into the body, and are easily incorporated into the diet.
Non pathogenic (non-harmful) intestinal bacteria play an important role in the normal functioning of the gut and improve resistance to disease; however factors such as changes in lifestyle, diet, increased stress and consumption of antibiotic medications can all lead to changes in the balance of gut bacteria (microflora).
Reduced numbers of beneficial bacteria such as Lactobacilli and Bifidobacteria and increased numbers of harmful or pathogenic bacteria often result, this may cause minor health complaints and infections and may pre-dispose individuals to a number of life threatening diseases such as bowel cancer and inflammatory bowel disease.
In these situations probiotics can exert a positive effect on health by redressing the balance of health-promoting and pathogenic bacteria in the gastrointestinal tract.
The micro-organisms most commonly used as probiotics are lactic acid bacteria such as Lactobacilli and Bifidobacteria which are both found naturally in the gut. Numerous health benefits have been connected with the use of probiotics including:
Diarrhoea often results from disturbances to the natural balance of gut microflora through infection with pathogenic strains of bacteria.
The treatment of diarrhoea with probiotics has traditionally been one of the main application areas for probiotics.
The best documented evidence exists for shortening the duration of a form of diarrhoea in children known as “rotavirus diarrhoea” by selected probiotic strains.
Prevention and treatment of diarrhoea after the use of antibiotics, particularly in the elderly, has also been connected with certain probiotic strains e.g. L. acidophilus, L. bulgaricus and B. longum.
Unfortunately many of the trials in this area have been poorly controlled and used low numbers of subjects. Therefore further studies with improved design are needed to determine the full effect of probiotics on the treatment of diarrhoea.
The immune system is responsible for protecting us from infection and disease, however
many sub groups of the population may have weak immune function such as infants, the elderly, surgical patients, trauma victims, people under stress and HIV positive individuals which reduces their natural protection from illness.
Probiotics have been connected to improved immune function in these groups, and the results of human studies indicate that yogurt containing probiotic strains of bacteria can enhance immunity and reduce the incidence of conditions such as cancer, gastrointestinal disorders and symptoms of allergy although further research is required.
Inflammatory bowel disease
The term Inflammatory Bowel Disease (IBD) includes disorders such as Crohn’s disease, ulcerative colitis and pouchitis.
These conditions are usually chronic (long term) and go through periods of exacerbation followed by periods of remission throughout the life of sufferers.
The cause of the disease is unclear, but several theories suggest it may be due to abnormal responses to certain bacteria in the gut.
The current treatment for IBD involves suppression or modulation of the immune system with steroid medications in order to induce remission, or surgery to remove the diseased section of the bowel. However both treatments result in numerous complications for the patient.
At present treatments do not address the contribution of the intestinal bacteria (microflora) to the condition, which is an area where probiotic intervention may prove beneficial.
In theory, probiotics have the potential to reduce the immuno-inflammatory responses induced by bacteria that may be responsible for damage to the intestines seen in this condition.
Several well designed trials support this theory including three trials which have found treatment with the probiotic Esherichia coli Nissle 1917 to be as effective as the standard drug treatments for maintaining remission in ulcerative colitis.
Additional studies have found benefits with supplementation of mixtures of several probiotics in inducing remission and preventing relapse of pouchitis, ulcerative colitis and Crohn’s disease.
Some practitioners now believe that the evidence is strong enough to prescribe certain probiotics for treatment of inflammatory bowel disease as an alternative to current drug treatments. However most feel that further investigations are required to determine the full therapeutic potential of probiotics before changes are made to current treatment procedures.
Irritable bowel syndrome
Irritable bowel syndrome (IBS) is a gastrointestinal condition characterised by abdominal pain, bloating, excessive gas, constipation and diarrhoea.
The type and severity of symptoms experienced varies widely between individuals and, in general, the condition is poorly understood.
No test currently exists for IBS and therefore it can only be diagnosed by excluding the presence of other gastrointestinal abnormalities.
IBS sufferers are commonly found to have abnormal gut bacteria (microflora) and this is thought to contribute to the development of the disease.
For this reason, the use of probiotics to redress these abnormalities has been suggested as a potential treatment.
To date, there have been few studies involving probiotics and IBS, possibly because IBS sufferers are a very diverse group and are therefore difficult to study.
The studies that have been conducted so far have produced conflicting results, some with very real improvements in symptoms and some with no change.
Although the use of probiotics in the treatment of IBS is currently not justified; more research in this area is certainly warranted because abnormalities seen in the gut bacteria (microflora) of IBS sufferers suggest that a probiotic approach will ultimately be justified.