| Lactobacillus acidophilus | |
|---|---|
| Lactobacillus acidophilus Numbered ticks are 11 µm apart. |
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| Scientific classification | |
| Kingdom: | Bacteria |
| Division: | Firmicutes |
| Class: | Bacilli |
| Family: | Lactobacillaceae |
| Genus: | Lactobacillus |
| Species: | L. acidophilus |
| Binomial name | |
| Lactobacillus acidophilus (Moro 1900) Hansen & Mocquot 1970 |
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Lactobacillus acidophilus (Latin meaning acid-loving milk-bacterium) is a species in the genus Lactobacillus. L. acidophilus is a homofermentative species, fermenting sugars into lactic acid, which grows readily at rather low pH values (below pH 5.0) and has an optimum growth temperature of 37 °C (98.6 °F). L. acidophilus occurs naturally in the human and animal gastrointestinal tract, mouth, and vagina.[1] Some strains of L. acidophilus may be considered to have probiotic characteristics.[2] These strains are commercially used in many dairy products, sometimes together with S. salivarius ssp. thermophilus and Lactobacillus delbrueckii ssp. bulgaricus in the production of acidophilus-type yogurt.
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Some strains of L. acidophilus have been studied extensively for health effects. Some L. acidophilus strains may be able to survive gastrointenstinal transit, are resistant to bile and low pH, as well as digestive enzymes. They may then be able to adhere to human epithelial cell lines and human intestinal mucus.[3]
A blend of bacterial strains including L. acidophilus NCFM decreased the incidence of pediatric diarrhea. L. acidophilus led to a significant decrease in levels of toxic amines in the blood of dialysis patients with small bowel bacterial overgrowth. At adequate daily feeding levels, L. acidophilus may facilitate lactose digestion in lactose-intolerant subjects.[4]
A University of Nebraska study found that feed supplemented with L. acidophilus L1 and fed to cattle resulted in a 61% reduction of Escherichia coli 0157:H7. Research has indicated L. acidophilus may be helpful reducing serum cholesterol levels.[5]
Antibiotics taken orally will also kill beneficial bacteria, including L. acidophilus. After a therapy that includes antibiotics, patients are occasionally instructed to take an L. acidophilus treatment in order to recolonize the gastrointestinal tract.[3] To that effect, L. acidophilus is often sold in health stores in pill or powder form as a nutritional supplement as well as being available in numerous yogurts. A part of the claims in favor of such treatment refer to attaining a better digestion thanks to a recovered normal intestinal flora. L. acidophilus LA-5 produces bacteriocin CH5 that is both antibacterial and inhibitory against certain yeasts and moulds and is effective against both Salmonella Typhimurium and Campylobacter jejuni.[3] It has been shown to improve bowel regularity and has been shown to have a preventative effect against traveller's diarrhea, as well as antibiotic related bowel issues.[3]
Because of its relation to gut-associated lymphoid tissue (GALT) L. acidophilus LA-5 has been associated with positive effects on the immune system such as increased cytokine, phagocytic activity and antibody production, as well as phagocytosis of Salmonella, and L. acidophilus NCFM has even been shown to reduce incidence of symptoms of fever, cough and runny nose.[3] Anti-inflammatory effects have also been observed in people consuming L. acidophilus NCFM. Additionally L. acidophilus LA-5 has shown to inhibit growth of breast cancer cells, and positive effects on chemotherapy patients.[3] An improvement of lipid metabolism has also been linked to L. acidophilus LA-5.[3]
Animal studies of NCFM have indicated that it reduces intestinal pain by inducing u-opioid and canabinoid receptors in the intestines (of animals), but this effect has not been sufficiently shown in humans yet.[3]
Also, some of the benefits of Lactobacillus acidophilus are the production of vitamin K, and lactase, and some strains may produce bacteriocins such as acidolin, acidophilin and lactocidin .
A study published in the Journal of the American College of Nutrition reported that yogurt containing Lactobacillus acidophilus L1 has the potential of reducing risk for coronary heart disease by 6 to 10% by reducing serum cholesterol concentration.[6]
Although a study that evaluated the effects of Lactobacillus acidophilus on the symptoms of Japanese cedar-pollen allergy achieved positive results, this still needs further research.[7]
There are many types of fermented dairy products that use L. acidophilus including yogurt and some types of cheese. Sweet acidophilus milk is consumed by individuals who suffer from lactose maldigestion and intolerance, which occurs when enzymes (lactase) cannot break down lactose (milk sugar) in the intestine. Failure to digest lactose results in discomfort, cramps and diarrhea.[8] Some bacteria have been shown to improve lactose digestion by providing B-galactosidase, while some L. acidophilus strains have been linked to improvement in symptoms and indicators of lactose indigestion.[3]
| Strain | Brandname | Producer | Proven effect in humans |
|---|---|---|---|
| Lactobacillus acidophilus DDS-1 | Nebraska Cultures[9] | ||
| Lactobacillus acidophilus LA-5 | Chr. Hansen | ||
| Lactobacillus acidophilus NCFM | Danisco |
L. acidophilus is part of the normal vaginal flora.[10] The acid produced by L. acidophilus in the vagina may help to control the growth of the fungus Candida albicans, thus helping to prevent vaginal yeast infections. The same beneficial effect has been observed in cases of oral or gastrointestinal Candidiasis infections. Certain spermicides and contraceptive creams can kill L. acidophilus in the vagina, clearing the path to possible yeast infections.
In general, the ingestion of L. acidophilus is safe. However, people with the following conditions are discouraged from taking L. acidophilus: intestinal damage, a weakened immune system, or with overgrowth of intestinal bacteria.
Some people complain of discomfort or gas. This condition can be overcome when the individual ingests it continuously.[11] Lactose sensitive people may also experience abdominal discomfort from dairy products that include L. acidophilus.
Infections of heart valves with L. acidophilus have also been reported. The risk may be greater in people with artificial heart valves.[12]
Some women have reported burning of the vagina after using vaginal tablets that contain L. acidophilus.[12]