Lactobacillus acidophilus
Encyclopedia
Lactobacillus acidophilus (Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 meaning acid-loving milk-bacterium) is a species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 in the genus Lactobacillus
Lactobacillus
Lactobacillus is a genus of Gram-positive facultative anaerobic or microaerophilic rod-shaped bacteria. They are a major part of the lactic acid bacteria group, named as such because most of its members convert lactose and other sugars to lactic acid. They are common and usually benign...

. L. acidophilus is a homofermentative species, fermenting sugars into lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

, 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
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....

, mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

, and vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

.
Some strains of L. acidophilus may be considered to have probiotic
Probiotic
Probiotics are live microorganisms thought to be beneficial to the host organism. According to the currently adopted definition by FAO/WHO, probiotics are: "Live microorganisms which when administered in adequate amounts confer a health benefit on the host"...

 characteristics. These strains are commercially used in many dairy products, sometimes together with S. salivarius ssp. thermophilus and Lactobacillus delbrueckii ssp. bulgaricus
Lactobacillus bulgaricus
Lactobacillus delbrueckii subspecies bulgaricus is one of several bacteria used for the production of yogurt. It is also found in other naturally fermented products...

in the production of acidophilus-type yogurt.

Health effects

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.

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 amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...

s 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.

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
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

 0157:H7
Escherichia coli O157:H7
Escherichia coli O157:H7 is an enterohemorrhagic strain of the bacterium Escherichia coli and a cause of foodborne illness. Infection often leads to hemorrhagic diarrhea, and occasionally to kidney failure, especially in young children and elderly persons...

. Research has indicated L. acidophilus may be helpful reducing serum cholesterol
Cholesterol
Cholesterol is a complex isoprenoid. Specifically, it is a waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes...

 levels.

Antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

s 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. 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
Digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....

 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.
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.

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. 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.
An improvement of lipid metabolism has also been linked to L. acidophilus LA-5.

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.

Also, some of the benefits of Lactobacillus acidophilus are the production of vitamin K
Vitamin K
Vitamin K is a group of structurally similar, fat soluble vitamins that are needed for the posttranslational modification of certain proteins required for blood coagulation and in metabolic pathways in bone and other tissue. They are 2-methyl-1,4-naphthoquinone derivatives...

, and lactase
Lactase
Lactase , a part of the β-galactosidase family of enzymes, is a glycoside hydrolase involved in the hydrolysis of the disaccharide lactose into constituent galactose and glucose monomers...

, and some strains may produce bacteriocin
Bacteriocin
Bacteriocins are proteinaceous toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain. They are typically considered to be narrow spectrum antibiotics, though this has been debated...

s 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
Coronary heart disease
Coronary artery disease is the end result of the accumulation of atheromatous plaques within the walls of the coronary arteries that supply the myocardium with oxygen and nutrients. It is sometimes also called coronary heart disease...

 by 6 to 10% by reducing serum cholesterol concentration.

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.

Used for lactose intolerance

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. 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.

Strains with described health effects

StrainBrandnameProducerProven effect in humans
Lactobacillus acidophilus DDS-1 Nebraska Cultures
Lactobacillus acidophilus LA-5 Chr. Hansen
Chr. Hansen
Chr. Hansen A/S is a global company based in Denmark which produces natural ingredients to the food, beverage, dietary supplements, and agricultural industries. The company is a leading supplier of food cultures, probiotics, enzymes and natural colors...

 
Lactobacillus acidophilus NCFM Danisco
Danisco
Danisco A/S is a Danish bio-based company with activities in food production, enzymes and other bioproducts as well as a wide variety of pharmaceutical grade excipients. It was formed in 1989 from the largest Danish industrial merger ever of the two old C.F...

 

Vaginal flora

L. acidophilus is part of the normal vaginal flora
Flora (microbiology)
In microbiology, flora refers to the collective bacteria and other microorganisms in an ecosystem . While the term microflora is widely used, it is technically a misnomer since the word root flora pertains to the kingdom plantae...

. The acid produced by L. acidophilus in the vagina may help to control the growth of the fungus Candida albicans
Candida albicans
Candida albicans is a diploid fungus that grows both as yeast and filamentous cells and a causal agent of opportunistic oral and genital infections in humans. Systemic fungal infections including those by C...

, thus helping to prevent vaginal yeast infections. The same beneficial effect has been observed in cases of oral or gastrointestinal Candidiasis
Candidiasis
Thrush redirects here. For the hoof infection see Thrush .Candidiasis or thrush is a fungal infection of any of the Candida species , of which Candida albicans is the most common...

 infections. Certain spermicides and contraceptive creams can kill L. acidophilus in the vagina, clearing the path to possible yeast infections.

Side effects

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
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

, or with overgrowth of intestinal bacteria.

Some people complain of discomfort or gas. This condition can be overcome when the individual ingests it continuously. 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.

Some women have reported burning of the vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

after using vaginal tablets that contain L. acidophilus.

External links

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