UNDER THE MICROSCOPE:YOU KNOW THE TV ad about relieving feelings of bloatedness by taking a certain probiotic.
Well, recently I reckoned I was feeling a bit bloated so I started to take the recommended probiotic. It made me feel more bloated and I had to stop. Readers will be very relieved to hear that my "bloated" period has now passed!
Probiotics (meaning "for life") are defined as dietary supplements containing beneficial bacteria or yeasts that, when administered in adequate amounts, confer a health benefit on the host. They are extensively advertised and widely consumed. There is evidence that ingestion of probiotics confers various health benefits although it is likely that their benefits are somewhat over-sold. Indeed, recent research has shown that probiotics can even be dangerous under certain circumstances.
The intestine is a large bodily organ and is a very long coiled tube that extends from the stomach to the anus. Food is terminally digested in the intestine and absorbed into the bloodstream. The intestine contains vast numbers of bacteria which, under normal circumstances, provide important services to the body. The average human body contains about 10 trillion (ten thousand, thousand million) body cells plus about 100 trillion micro-organism cells in the gut representing over 500 different species (gut flora). Bacteria make up about 60 per cent of faecal mass.
Useful functions performed by gut flora include training the body's immune system, preventing growth of harmful bacteria, producing vitamins such as biotin and vitamin K, producing hormones that instruct the body to store fat, stabilising intestinal passage, prevention of diarrhoea in infants and children, alleviation of irritable bowel symptoms, improvement of digestive health, and more. If, for whatever reason, the normal healthy balance of bacteria becomes disrupted, ill-health can result. Basically, the idea behind ingestion of probiotic products is to encourage the growth of "good" bacteria and crowd out "bad" bacteria, thereby establishing and maintaining a healthy gut flora.
Probiotics may also help to maintain urogenital health. The vagina, like the gut, has a finely balanced ecosystem. It can be unbalanced by antibiotics, birth control pills or spermicides. Probiotics may help to restore the balance and are said to be helpful in conditions like yeast infection.
The commonest type of bacteria used in probiotic products are lactic acid bacteria (LAB). LAB are widely used in the food industry because they can ferment carbohydrates into lactic acid, producing the characteristic sour taste of fermented dairy foods such as yoghurt. The lactic acid inhibits the growth of various spoilage organisms, helping to prevent gastro-intestinal infections.
Some lifestyles, eg too much alcohol intake, toxic substances, stress and various diseases, tend to disturb the balance of bacteria in our guts, discriminating against the "good" bacteria that work well with the body. Probiotics may well be prescribed in such cases and also after a course of antibiotics.
The informal use of probiotics is very old. Eli Metchnikoff, the 1908 Nobel Prize-winning Russian microbiologist, suggested that ageing results from the activity of certain protein digesting bacteria in the large intestine that release toxic substances from the proteins. It was known that the acidity of fermented dairy products inhibited the growth of these protein digesting bacteria. Metchnikoff also noted the extremely long lives of people in Bulgaria and certain parts of Russia who lived largely on LAB fermented dairy products. He proposed that eating fermented milk would seed the intestine with LAB, increasing intestinal acidity and suppressing the growth of protein digesting bacteria.
The most commonly marketed forms of probiotics are dairy products and probiotic- fortified foods. There is good evidence that various strains of micro-organisms can have beneficial health effects, but specific effects are associated only with specific micro-organisms. Unfortunately probiotics can sometimes be harmful, as described in a study published in The Lancet, February 14th last. Acute pancreatitis is an inflammation of the pancreas and is a serious condition. About 20 per cent of patients develop a complication called necrotising pancreatitis which has a 10-30 per cent mortality rate. This complication is thought to be triggered by an overgrowth of bacteria. It was thought that the prophylactic use of probiotics ("good bacteria") might minimise these complications by keeping the growth of the "bad bacteria" in check. Prof Hein Gooszen, University Medical Centre, Utrecht, performed a double blind, placebo-controlled trial on 296 patients with predicted severe acute pancreatitis - 152 patients received probiotics and 144 received a placebo. Many more patients died in the probiotic group (16 per cent) then in the placebo group (9 per cent). Clearly probiotics is not a safe treatment method in patients at risk of severe acute pancreatitis, and probotiotics can no longer be considered as harmless assistants to intestinal nutrition in severely ill people.
William Reville is associate professor of biochemistry and public awareness of science officer at UCC - http://understandingscience.ucc.ie