Vegetable oil

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Vegetable_oil

A bottle of peanut oil

Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of edible plants. Like animal fats, vegetable fats are mixtures of triglycerides. Soybean oil, canola oil, grapeseed oil, and cocoa butter are examples of seed oils, or fats from seeds. Olive oil, palm oil, and rice bran oil are examples of fats from other parts of plants. In common usage, vegetable oil may refer exclusively to vegetable fats which are liquid at room temperature. Vegetable oils are usually edible and are generally recognized as safe (GRAS) by the United States Food and Drug Administration (FDA). There is no evidence that seed oils are unhealthy.

Vegetable oils have been used for thousands of years (dating back to at least 6000 BC for olive oil) and were historically important for cooking, lighting, medicine, and industry. Palm oil later becoming a major global commodity during the Industrial Revolution. In the 19th and 20th centuries, scientific advances (like understanding fats and hydrogenation) led to modern products such as margarine and shortening. Oils like soybean and canola became dominant in global markets. Today, vegetable oils are widely used in food, manufacturing (e.g., cosmetics, paints, lubricants), and biofuel, and are produced mainly by pressing or chemical extraction. Global output is rising significantly due to demand, especially for palm oil.

History

In antiquity

Olive oil has been a part of human culture for millennia. Archaeological evidence shows that olives were turned into olive oil by 6000 BC and 4500 BC in present-day Israel. Pagnol, p. 19, says the 6th millennium in Jericho, but cites no source. In ancient Egypt, plant oils including cedar oil, cypress oil, and olive oil were used during the mummification process.

Vegetable oils have been used as lighting fuel for lamps, cooking, medicine and lubrication. Palm oil has long been recognized in West and Central African countries, and European merchants trading with West Africa occasionally purchased palm oil for use as a cooking oil in Europe. It became highly sought-after commodity by British traders for use as an industrial lubricant for machinery during Britain's Industrial Revolution.

Modern history

Palm oil formed the basis of soap products, such as Lever Brothers' (now Unilever) "Sunlight", and B. J. Johnson Company's (now Colgate-Palmolive) "Palmolive", and by around 1870, palm oil constituted the primary export of some West African countries.

In 1780, Carl Wilhelm Scheele demonstrated that fats were derived from glycerol. Thirty years later, Michel Eugène Chevreul deduced that these fats were esters of fatty acids and glycerol. Wilhelm Normann, a German chemist, introduced the hydrogenation of liquid fats in 1901, creating what later became known as trans fats, leading to the development of the global production of margarine and vegetable shortening.

In the United States, cottonseed oil was developed and marketed by Procter & Gamble as a creamed shortening – Crisco – as early as 1911. Ginning mills were happy to have someone haul away the cotton seeds. The extracted oil was refined and partially hydrogenated to give a solid at room temperature and thus mimic natural lard, and canned under nitrogen gas. Compared to the rendered lard Procter & Gamble was already selling to consumers, Crisco was cheaper, easier to stir into a recipe, and could be stored at room temperature for two years without turning rancid.

Soybeans are protein-rich, and the medium-viscosity oil rendered from them was high in polyunsaturates. Henry Ford established a soybean research laboratory, developed soybean plastics and a soy-based synthetic wool, and built a car "almost entirely" out of soybeans. Roger Drackett had a successful new product with Windex. He invested heavily in soybean research, seeing it as a smart investment. By the 1950s and 1960s, soybean oil had become the most popular vegetable oil in the US; today it is second only to palm oil. In 2018–2019, world production was at 57.4 MT with the leading producers including China (16.6 MT), US (10.9 MT), Argentina (8.4 MT), Brazil (8.2 MT), and EU (3.2 MT).

The early 20th century also saw the start of the use of vegetable oil as a fuel in diesel engines and in heating oil burners. Rudolf Diesel designed his engine to run on vegetable oil. The idea, he hoped, would make his engines more attractive to farmers who had a source of fuel readily available. Diesel's first engine ran on its own power for the first time in Augsburg, Germany, on 10 August 1893 on nothing but peanut oil. In remembrance of this event, 10 August has been declared "International Biodiesel Day". The first patent on Biodiesel was granted in 1937. Periodic petroleum shortages spurred research into vegetable oil as a diesel substitute during the 1930s and 1940s, and again in the 1970s and early 1980s when straight vegetable oil enjoyed its highest level of scientific interest. The 1970s also saw the formation of the first commercial enterprise to allow consumers to run straight vegetable oil in their vehicles. However, biodiesel, produced from oils or fats using transesterification is more widely used. Led by Brazil, many countries built biodiesel plants during the 1990s, and it is now widely available for use in motor vehicles, and is the most common biofuel in Europe today. In France, biodiesel is incorporated at a rate of 8% in the fuel used by all French diesel vehicles.

In the mid-1970s, Canadian researchers developed a low-erucic-acid rapeseed cultivar. Because the word "rape" was not considered optimal for marketing, they coined the name "canola" (from "Canada Oil low acid"). The U.S. Food and Drug Administration approved use of the canola name in January 1985, and U.S. farmers started planting large areas that spring. Canola oil is lower in saturated fats and higher in monounsaturates. Canola is very thin (unlike corn oil) and flavorless (unlike olive oil), so it largely succeeds by displacing soy oil, just as soy oil largely succeeded by displacing cottonseed oil.

The production of vegetable oils went up 125% between 2000 and 2020, driven by a sharp increase in palm oil. The global production of vegetable oils went up 130% between 2000 and 2022 to 212 million tonnes in 2022. This is 120 million tonnes more than in 2000, but 3 million tonnes less than the peak observed in 2021. Palm oil registered the largest increase, both absolute and relative, as its production went up 57 million tonnes, or 255%; it overtook soybean oil as the main vegetable oil produced in 2006.

Uses

Culinary

See also: Cooking oil

Many vegetable oils are consumed directly, or indirectly as ingredients in food – a role that they share with some animal fats, including butter, ghee, lard, and schmaltz. The oils serve several purposes in this role:

• Shortening – as in giving pastries a crumbly texture.
• Enriching – adding calories and satisfaction in consumption
• Texture – altering how ingredients combine, especially fats and starches
• Flavoring – examples include olive, sesame, or almond oil
• Flavor base – oils can also "carry" flavors of other ingredients, such as peppers, since many flavors are due to chemicals that are soluble in oil.

Oils can be heated to temperatures significantly higher than the boiling point of water, 100 °C (212 °F), and used to fry foods. Oils for this purpose must have a high flash point. Such oils include both the major cooking oils – soybean, canola/rapeseed, sunflower, safflower, peanut, cottonseed, etc. – and tropical oils, such as coconut, palm, and rice bran. The latter are particularly valued in Asian cultures for high-temperature cooking, because of their unusually high flash points.

Industrial

Vegetable oils are used as an ingredient or component in many manufactured products.

Many vegetable oils are used to make soaps, skin products, candles, perfumes, and other personal care and cosmetic products. Some oils are particularly suitable as drying oils, and are used in making paints and other wood treatment products. They are used in alkyd resin production. Dammar oil (a mixture of linseed oil and dammar resin), for example, is used almost exclusively in treating the hulls of wooden boats. Vegetable oils are increasingly being used in the electrical industry as insulators as vegetable oils are not toxic to the environment, biodegradable if spilled and have high flash and fire points. However, vegetable oils are less stable chemically, so they are generally used in systems where they are not exposed to oxygen, and they are more expensive than crude oil distillate. Synthetic tetraesters, which are similar to vegetable oils but with four fatty acid chains compared to the normal three found in a natural ester, are manufactured by Fischer esterification. Tetraesters generally have high stability to oxidation and have found use as engine lubricants. Vegetable oil is being used to produce biodegradable hydraulic fluid and lubricant.

One limiting factor in industrial uses of vegetable oils is that all such oils are susceptible to becoming rancid. Oils that are more stable, such as ben oil or mineral oil, are thus preferred for industrial uses. Castor oil has numerous industrial uses, owing to the presence of a hydroxyl group on the fatty acid. Castor oil is a precursor to Nylon 11. Castor oil may also be reacted with epichlorohydrin to make a glycidyl ether, which is used as a diluent and flexibilizer with epoxy resins.

Pet food additive

Vegetable oil is used in the production of some pet foods. AAFCO defines vegetable oil in this context as the product of vegetable origin obtained by extracting the oil from seeds or fruits which are processed for edible purposes.

Fuel

Main article: Vegetable oil fuel

Vegetable oils are also used to make biodiesel, which can be used like conventional diesel. Some vegetable oil blends are used in unmodified vehicles but straight vegetable oil, also known as pure plant oil, needs specially prepared vehicles which have a method of heating the oil to reduce its viscosity. The use of vegetable oils as alternative energy is growing and the availability of biodiesel around the world is increasing.

The NNFCC estimates that the total net greenhouse gas savings when using vegetable oils in place of fossil fuel-based alternatives for fuel production, range from 18 to 100%.

Production

Main article: Edible oil refining

The production process of vegetable oil involves the removal of oil from plant components, typically seeds. This can be done via mechanical extraction using an oil mill or chemical extraction using a solvent. The extracted oil can then be purified and, if required, refined or chemically altered.

Mechanical extraction

Oils can be removed via mechanical extraction, termed "crushing" or "pressing". This method is typically used to produce the more traditional oils (e.g., olive, coconut, etc.), and it is preferred by most health-food customers in the United States and in Europe. There are several different types of mechanical extraction. Expeller pressing extraction is common, though the screw press, ram press, and ghani (powered mortar and pestle) are also used. Oilseed presses are commonly used in developing countries, among people for whom other extraction methods would be prohibitively expensive; the ghani is primarily used in India. The amount of oil extracted using these methods varies widely, as shown in the following table for extracting mowrah butter in India:

Method	Percentage extracted
Ghani	20–30%
Expellers	34–37%
Solvent	40–43%

Solvent extraction

The processing of vegetable oil in commercial applications is commonly done by chemical extraction, using solvent extracts, which produces higher yields and is quicker and less expensive. The most common solvent is petroleum-derived hexane. This technique is used for most of the "newer" industrial oils such as soybean and corn oils. After extraction, the solvent is evaporated out by heating the mixture to about 149 °C (300 °F).

Supercritical carbon dioxide can be used as a non-toxic alternative to other solvents.

Hydrogenation

Main article: Fat hydrogenation

Unsaturated vegetable oils can be transformed through partial or complete hydrogenation into oils of higher melting point, some of which, such as vegetable shortening, will remain solid at room temperature.

Hydrogenating vegetable oil is done by raising a blend of vegetable oil and a metal catalyst, typically nickel, in a near-vacuum to very high temperatures, and introducing hydrogen. This causes the carbon atoms of the oil to break double bonds with other carbons. Each carbon atom becomes single-bonded to an individual hydrogen atom, and the double bond between carbons can no longer exist. A fully hydrogenated oil, also called a saturated fat, has had all of its double bonds converted into single bonds. If a polyunsaturated oil is left incompletely hydrogenated (not all of the double bonds are reduced to single bonds), then it is a "partially hydrogenated oil" (PHO). An oil may be hydrogenated to increase resistance to rancidity (oxidation) or to change its physical characteristics. As the degree of saturation is raised by full or partial hydrogenation, the oil's viscosity and melting point increase.

While full hydrogenation produces largely saturated fatty acids, partial hydrogenation results in the transformation of unsaturated cis fatty acids to unsaturated trans fatty acids in the oil mixture due to the heat used in hydrogenation. Partially hydrogenated oils and their trans fats have been linked to an increased risk of mortality from coronary heart disease, among other increased health risks. These concerns have led to regulations mandating the removal of partially hydrogenated oils from food.

Deodorization

In the processing of edible oils, the oil is heated under vacuum to near the smoke point or to about 232 °C (450 °F), and water is introduced at the bottom of the oil. The water is immediately converted to steam, which bubbles through the oil, carrying with it any chemicals that are water-soluble. The steam sparging removes impurities that can impart unwanted flavors and odors to the oil. Deodorization is key to the manufacture of vegetable oils. Nearly all soybean, corn, and canola oils found on supermarket shelves go through a deodorization stage that removes trace amounts of odors and flavors, and lightens the color of the oil. However, the process commonly results in higher levels of trans fatty acids and distillation of the oil's natural compounds.

Occupational exposure

People can breathe in vegetable oil mist in the workplace. The U.S. Occupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for vegetable oil mist exposure in the workplace as 15 mg/m³ total exposure and 5 mg/m³ respiratory exposure over an eight-hour workday. The U.S. National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 10 mg/m³ total exposure and 5 mg/m³ respiratory exposure over an eight-hour workday.

Yield

World production of main vegetable oils by main producers

Typical productivity of some oil crops, measured in tons (t) of oil produced per hectare (ha) of land per year (yr). Oil palm is by far the highest yielding crop, capable of producing about 4 tons of palm oil per hectare per year.

Crop	Yield (t/ha/yr)
Palm oil	4.0
Coconut oil	1.4
Canola oil	0.75
Soybean oil	0.45
Sunflower oil	0.6

Particular oils

For a more comprehensive list, see List of vegetable oils.

The following triglyceride vegetable oils account for almost all worldwide production, by volume. All are used as both cooking oils and as SVO or to make biodiesel. According to the USDA, the total world consumption of major vegetable oils in 2007/08 was:

Oil source	World consumption (million metric tons)	Notes
Palm	41.31	The most widely produced tropical oil, also used to make biofuel
Soybean	41.28	One of the most widely consumed cooking oils
Rapeseed	18.24	One of the most widely used cooking oils, also used as fuel. Canola is a variety (cultivar) of rapeseed.
Sunflower seed	9.91	A common cooking oil, also used to make biodiesel
Cottonseed	4.99	A major food oil, often used in industrial food processing
Palm kernel	4.85	From the seed of the African palm tree
Peanut	4.82	Mild-flavored cooking oil
Coconut	3.48	Used in cooking, cosmetics and soaps
Olive	2.84	Used in cooking, cosmetics, soaps and as a fuel for traditional oil lamps

These figures include industrial and animal feed use. The majority of European rapeseed oil production is used to produce biodiesel, or used directly as fuel in diesel cars, which may require modification to heat the oil to reduce its higher viscosity.

Other significant oils include:

• Corn oil, one of the most common cooking oils, is used for cooking oil, salad dressing, margarine, mayonnaise, prepared goods like spaghetti sauce and baking mixes, and to fry prepared foods like potato chips and French fries.
• Grape seed oil, used in cooking and cosmetics
• Hazelnut oil and other nut oils
• Linseed oil, from flax seeds
• Rice bran oil, from rice grains
• Safflower oil, a flavorless and colorless cooking oil
• Sesame oil, used as a cooking oil, and as a massage oil, particularly in India
• Açaí palm oil, used in culinary and cosmetics
• Jambú oil, is extracted from the flowers, leaves and stem from jambu (Acmella oleracea), contains spilanthol
• Graviola oil, derived from Annona muricata
• Tucumã oil, from Astrocaryum aculeatum is used to manufacture soap.
• Brazil nut oil, culinary and cosmetics use
• Carapa oil, pharmaceutical use and anti-mosquito candle
• Buriti oil, from Mauritia flexuosa, used in cosmetics (skin and hair care)
• Passion fruit oil, derived from Passiflora edulis, has varied applications in cosmetics manufacturing and for uses as a human or animal food.
• Pracaxi oil, obtained from Pentaclethra macroloba, cosmetics use
• Solanium oil, derived from chloroplasts, various applications in cooking

Composition of fats

Properties of vegetable oils
The nutritional values are expressed as percent (%) by mass of total fat.

Type	Processing treatment	Saturated fatty acids	Monounsaturated fatty acids		Polyunsaturated fatty acids				Smoke point
			Total	Oleic acid (ω−9)	Total	α-Linolenic acid (ω−3)	Linoleic acid (ω−6)	ω−6:3 ratio
Avocado		11.6	70.6	67.9	13.5	1	12.5	12.5:1	250 °C (482 °F)
Brazil nut		17.6	26.7	26.1	55.7	0.1	55.6	457:1	208 °C (406 °F)
Canola		7.4	63.3	61.8	28.1	9.1	18.6	2:1	204 °C (400 °F)
Coconut		82.5	6.3	6	1.7	0.019	1.68	88:1	175 °C (347 °F)
Corn		12.9	27.6	27.3	54.7	1	58	58:1	232 °C (450 °F)
Cottonseed		25.9	17.8	19	51.9	1	54	54:1	216 °C (420 °F)
Cottonseed	hydrogenated	93.6	1.5		0.6	0.2	0.3	1.5:1
Flaxseed/linseed		9.0	18.4	18	67.8	53	13	0.2:1	107 °C (225 °F)
Grape seed		9.6	16.1	15.8	69.9	0.10	69.6	very high	216 °C (421 °F)
Hemp seed		7.0	9.0	9.0	82.0	22.0	54.0	2.5:1	166 °C (330 °F)
High-oleic safflower oil		7.5	75.2	75.2	12.8	0	12.8	very high	212 °C (414 °F)
Olive (extra virgin)		13.8	73.0	71.3	10.5	0.7	9.8	14:1	193 °C (380 °F)
Palm		49.3	37.0	40	9.3	0.2	9.1	45.5:1	235 °C (455 °F)
Palm	hydrogenated	88.2	5.7		0
Peanut		16.2	57.1	55.4	19.9	0.318	19.6	61.6:1	232 °C (450 °F)
Rice bran oil		25	38.4	38.4	36.6	2.2	34.4	15.6:1	232 °C (450 °F)
Sesame		14.2	39.7	39.3	41.7	0.3	41.3	138:1
Soybean		15.6	22.8	22.6	57.7	7	51	7.3:1	238 °C (460 °F)
Soybean	partially hydrogenated	14.9	43.0	42.5	37.6	2.6	34.9	13.4:1
Sunflower oil		8.99	63.4	62.9	20.7	0.16	20.5	128:1	227 °C (440 °F)
Walnut oil	unrefined	9.1	22.8	22.2	63.3	10.4	52.9	5:1	160 °C (320 °F)

Seed oil

Seed oils are vegetable oils obtained from the seed (endosperm) rather than other parts of plants. Most vegetable oils are seed oils. Examples are sunflower, corn, and sesame oils.

Claims that seed oils are unhealthy are not supported by scientific evidence.

Used oil

Main article: Yellow grease

A large quantity of used vegetable oil is produced and recycled, mainly from industrial deep fryers in potato processing plants, snack food factories and fast food restaurants.

Recycled oil has numerous uses, including use as a direct fuel, as well as in the production of biodiesel, livestock feed, pet food, soap, detergent, cosmetics, and industrial chemicals.

Since 2002, an increasing number of European Union countries have prohibited the inclusion of recycled vegetable oil from catering in animal feed. Used cooking oils from food manufacturing, however, as well as fresh or unused cooking oil, continue to be used in their animal feed.

Shelf life

Due to their susceptibility to oxidation from exposure to oxygen, heat and light, resulting in the formation of oxidation products, such as peroxides and hydroperoxides, plant oils rich in polyunsaturated fatty acids have a limited shelf-life.

Product labeling

In Canada, palm oil is one of five vegetable oils, along with palm kernel oil, coconut oil, peanut oil, and cocoa butter, which must be specifically named in the list of ingredients for a food product. Also, oils in Canadian food products that have been modified or hydrogenated must contain the word "modified" or "hydrogenated" when listed as an ingredient. A mix of oils other than the aforementioned exceptions may simply be listed as "vegetable oil" in Canada; however, if the food product is a cooking oil, salad oil or table oil, the type of oil must be specified and listing "vegetable oil" as an ingredient is not acceptable.

From December 2014, all food products produced in the European Union were legally required to indicate the specific vegetable oil used in their manufacture, following the introduction of the Food Information to Consumers Regulation.

Urinary tract infection

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Urinary_tract_infection

Urinary tract infection
Other names	Acute cystitis, simple cystitis, bladder infection, symptomatic bacteriuria
Multiple white cells seen in the urine of a person with a urinary tract infection using microscopy
Specialty	Infectious disease Urology
Symptoms	Pain with urination, frequent urination, cloudy urine, feeling the urge to urinate despite having an empty bladder
Causes	Most often E. coli bacteria
Risk factors	Catheterisation (foley catheter), female anatomy, sexual intercourse, diabetes, obesity, family history
Diagnostic method	Based on symptoms, urine culture
Differential diagnosis	Vulvovaginitis, urethritis, pelvic inflammatory disease, interstitial cystitis, kidney stone disease
Treatment	Antibiotics
Frequency	405 million (2019)
Deaths	260,000 (2021)

A urinary tract infection (UTI) is an infection that affects a part of the urinary tract, which includes the bladder, urethra and the kidney. Lower UTIs affect the bladder (cystitis) or urethra while upper UTIs affect the kidney (pyelonephritis). Symptoms from a lower UTI include burning or pain during urination, pain in the lower abdomen and the urge to urinate even when the bladder is empty. Symptoms of a kidney infection are more systemic and include fever or flank pain, usually in addition to the symptoms of a lower UTI. Rarely, the urine may appear bloody. Symptoms may be less clear in very young or old people.

The most common cause of infection is E. coli, though other bacteria or fungi may sometimes be the cause. Risk factors include being female, sexual intercourse, diabetes, using a catheter, and family history. Additional factors that have been found to increase the risk of infection include urinary retention (delaying urination), insufficient water intake, use of spermicides as a contraceptive method, and poor genital hygiene.

Kidney infections usually occur when a bladder infection spreads, but may also come from bacteria in the blood. Diagnosis in young healthy women can be based on symptoms alone. In those with vague symptoms, diagnosis can be harder because bacteria may be present even if there is no infection.

In uncomplicated cases, UTIs are usually treated with a short course of antibiotics. Resistance to many of the antibiotics used to treat this condition is increasing. In complicated cases, a longer course or intravenous antibiotics may be needed. If symptoms do not improve in two or three days, further diagnostic testing may be needed. People with bacteria or white blood cells in their urine but no symptoms usually do not need antibiotics. For people with recurrent infections, methenamine may be prescribed. Postmenopausal women may also be offered vaginal estrogen replacement. If these do not work, preventative antibiotics can be considered.

Approximately 400 million UTI cases occur each year. They are more common in women than men, and are the most common bacterial infection in women. Up to 10% of women have a urinary tract infection in a given year, and half of women have at least one infection at some point in their lifetime. They occur most frequently between the ages of 16 and 35 years. Recurrences are common. Urinary tract infections have been described since ancient times with the first documented description in the Ebers Papyrus dated to c. 1550 BC.

Signs and symptoms

Urine may contain pus (a condition known as pyuria) as seen from a person with sepsis due to a urinary tract infection.

The most common symptoms of a UTI are burning with urination and having to urinate frequently (or an urge to urinate) in the absence of vaginal discharge and significant pain. These symptoms may vary from mild to severe and in healthy women last an average of six days. Some pain above the pubic bone or in the lower back may be present. People experiencing an upper urinary tract infection, or pyelonephritis, may experience flank pain, fever, or nausea and vomiting in addition to the classic symptoms of a lower urinary tract infection. Rarely, there may be blood or visible pus in the urine.

Children

In young children, the only symptom of a urinary tract infection (UTI) may be a fever. Because of the lack of more obvious symptoms, when girls under the age of two or uncircumcised boys less than a year old exhibit a fever, a culture of the urine is recommended by many medical associations. Infants may feed poorly, vomit, sleep more, or show signs of jaundice. In older children, new onset urinary incontinence (loss of bladder control) may occur. About 1 in 400 infants of one to three months of age with a UTI also have bacterial meningitis.

Elderly

Urinary tract symptoms are frequently lacking in the elderly. The presentations may be vague and include incontinence, a change in mental status, or fatigue as the only symptoms. Delirium can co-occur with UTIs in elderly people. Some present to a health care provider with sepsis, an infection of the blood, as the first symptoms. Diagnosis can be complicated by the fact that many elderly people have preexisting incontinence or dementia. Rarely, for UTIs associated with urinary catheters, the urine turns purple (purple urine bag syndrome).

It is reasonable to obtain a urine culture in those with signs of systemic infection who may be unable to report urinary symptoms, such as when advanced dementia is present. Systemic signs of infection include a fever or increase in temperature of more than 1.1 °C (2.0 °F) from usual, chills, and an increased white blood cell count.

Cause

Uropathogenic Escherichia coli (UPEC) cells adhered to bladder epithelial cell

Pathogenic E. coli from the gut is the cause of 75% of uncomplicated UTIs, and 65% of complicated UTIs. Rarely they may be due to viral or fungal infections. Healthcare-associated urinary tract infections (mostly related to urinary catheterization) involve a much broader range of pathogens including: Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa and Enterococcus faecalis. These species can form biofilms and colonise catheters. In sub-Saharan Africa, Staphylococcus aureus, which typically occurs secondary to blood-borne infections, is more common.

Chlamydia trachomatis and Mycoplasma genitalium can infect the urethra but not the bladder. These infections are usually classified as a urethritis rather than urinary tract infection.

Intercourse

In young sexually active women, sexual activity is the cause of 75–90% of bladder infections, with the risk of infection related to the frequency of sex. The term "honeymoon cystitis" has been applied to this phenomenon of frequent UTIs during early marriage. In post-menopausal women, sexual activity does not affect the risk of developing a UTI. Spermicide use, independent of sexual frequency, increases the risk of UTIs. Diaphragm use is also associated. Condom use without spermicide or use of birth control pills does not increase the risk of uncomplicated urinary tract infection.

Anal intercourse may increase the risk of UTI in men and in women if followed by vaginal sex.

Although sex is a risk factor, UTIs are not classified as sexually transmitted infections (STIs).

Sex

Women are more prone to UTIs than men because, in females, the urethra is much shorter and closer to the anus. As a woman's estrogen levels decrease with menopause, her risk of urinary tract infections increases due to the loss of protective vaginal flora. Additionally, vaginal atrophy that can sometimes occur after menopause is associated with recurrent urinary tract infections.

Chronic prostatitis in the forms of chronic prostatitis/chronic pelvic pain syndrome and chronic bacterial prostatitis (not acute bacterial prostatitis or asymptomatic inflammatory prostatitis) may cause recurrent urinary tract infections in males. Risk of infections increases as males age. While bacteria is commonly present in the urine of older males this does not appear to affect the risk of urinary tract infections.

Urinary catheters

Urinary catheterization increases the risk for urinary tract infections. The risk of bacteriuria (bacteria in the urine) is between three and six percent per day, and prophylactic antibiotics are not effective in decreasing symptomatic infections. The risk of an associated infection can be decreased by catheterizing only when necessary, using aseptic technique for insertion, and maintaining unobstructed closed drainage of the catheter.

Male scuba divers using condom catheters and female divers using external catching devices for their dry suits are also susceptible to urinary tract infections.

Others

A predisposition for bladder infections may run in families. This is believed to be related to genetics. Other risk factors include diabetes, being uncircumcised, and having a large prostate. In children UTIs are associated with vesicoureteral reflux (an abnormal movement of urine from the bladder into ureters or kidneys) and constipation.

Persons with spinal cord injury are at increased risk for urinary tract infection in part because of chronic use of a catheter, and in part because of voiding dysfunction. It is the most common cause of infection in this population, as well as the most common cause of hospitalization.

Pathogenesis

Bladder infection

The bacteria that cause urinary tract infections typically enter the bladder via the urethra. However, infection may also occur via the blood or lymph. It is believed that the bacteria are usually transmitted to the urethra from the bowel, with females at greater risk due to their anatomy. After gaining entry to the bladder, E. coli are able to attach to the bladder wall and form a biofilm that resists the body's immune response.

About half of the recurrent infections have the same strain as the first infection. This implies that there is a reservoir of the pathogen somewhere in the body. Potential locations of these reservoirs are the gut or vaginal microbiome, or even the bladder itself. Bacteria that cause UTIs have been found in all three locations.

Diagnosis

Multiple bacilli (rod-shaped bacteria, here shown as black and bean-shaped) shown between white blood cells in urinary microscopy. These changes are indicative of a urinary tract infection.

In straightforward cases, a diagnosis may be made and treatment given based on symptoms alone without further laboratory confirmation.

Urine analysis

In complicated or questionable cases, it may be useful to confirm the diagnosis via urinalysis. For instance, a nitrate test can diagnose some UTIs, as a subset of bacteria produce this. Not all bacteria do, however, so a negative test does not exclude a UTI. Other dipstick values useful for diagnosing UTIs are high pH (some bacteria split urea), the presence of blood, and or leukocyte esterase. Another test, urine microscopy, looks for the presence of red blood cells, white blood cells, or bacteria.

Urine culture is deemed positive if it shows a bacterial colony count of greater than or equal to 10³ colony-forming units per mL of a typical urinary tract organism. Antibiotic sensitivity can also be tested with these cultures, making them useful in the selection of antibiotic treatment. As symptoms can be vague and without reliable tests for urinary tract infections, diagnosis can be difficult in the elderly.

Classification

A urinary tract infection may involve only the lower urinary tract, in which case it is known as a bladder infection. Alternatively, it may involve the upper urinary tract, in which case it is known as pyelonephritis. If the urine contains significant bacteria but there are no symptoms, the condition is known as asymptomatic bacteriuria. If a urinary tract infection involves the upper tract, and the person has diabetes mellitus, is pregnant, is male, or immunocompromised, it is considered complicated. Otherwise if a woman is healthy and premenopausal it is considered uncomplicated. In children when a urinary tract infection is associated with a fever, it is deemed to be an upper urinary tract infection.

Children

To make the diagnosis of a urinary tract infection in children, a positive urinary culture is required. Contamination poses a frequent challenge depending on the method of collection used, thus a cutoff of 10⁵ CFU/mL is used for a "clean-catch" mid stream sample, 10⁴ CFU/mL is used for catheter-obtained specimens, and 10² CFU/mL is used for suprapubic aspirations (a sample drawn directly from the bladder with a needle). The use of "urine bags" to collect samples is discouraged by the World Health Organization due to the high rate of contamination when cultured, and catheterization is preferred in those not toilet trained.

Some, such as the American Academy of Pediatrics recommends renal ultrasound and voiding cystourethrogram (watching a person's urethra and urinary bladder with real time x-rays while they urinate) in all children less than two years old who have had a urinary tract infection. However, because there is a lack of effective treatment if problems are found, others such as the National Institute for Health and Care Excellence only recommends routine imaging in those less than six months old or who have unusual findings.

Differential diagnosis

In women with cervicitis (inflammation of the cervix) or vaginitis (inflammation of the vagina) and in young men with UTI symptoms, a Chlamydia trachomatis or Neisseria gonorrhoeae infection may be the cause. These infections are typically classified as a urethritis rather than a urinary tract infection. Vaginitis may also be due to a yeast infection. Interstitial cystitis (chronic pain in the bladder) may be considered for people who experience multiple episodes of UTI symptoms but urine cultures remain negative and not improved with antibiotics. Prostatitis (inflammation of the prostate) may also be considered in the differential diagnosis.

Hemorrhagic cystitis, characterized by blood in the urine, can occur secondary to several causes, including infections, radiation therapy, underlying cancer, medications, and toxins. Medications that commonly cause this problem include the chemotherapeutic agent cyclophosphamide with rates of 2–40%. Eosinophilic cystitis is a rare condition where eosinophiles are present in the bladder wall. Signs and symptoms are similar to a bladder infection. Its cause is not entirely clear; however, it may be linked to food allergies, infections, and medications among others.

Prevention

A number of behaviors are recommended to prevent UTIs from recurring. They include urinating after sex, avoiding douching, wiping from front to back after defecation, and wearing breathable underwear. It is unclear how much these help; clinical guidelines typically regard the evidence as weak. NICE also recommends not holding up urine frequently and drinking sufficiently. There is lack of evidence surrounding the effect of tampon use. In those with frequent urinary tract infections who use spermicide or a diaphragm as a method of contraception, they are advised to use alternative methods.

Using urinary catheters as little and for as short a time as possible, in addition to appropriate care of the catheter when used, prevents catheter-associated urinary tract infections. They should be inserted using sterile technique in hospital; however, non-sterile technique may be appropriate in those who self-catheterize. The urinary catheter set up should also be kept sealed. Evidence does not support a significant decrease in risk when silver-alloy catheters are used.

Medications

For peri-menopausal or postmenopausal women with recurrent infections, topical vaginal estrogen has been found to reduce recurrence. For other people, or if topical estrogen does not work sufficiently, a single dose of antibiotics after a triggering event (like intercourse) can be considered. Methenamine is another medication used for prevention. As an antiseptic, antibiotic resistance does not develop against it.

European guidelines, including the UK guidelines, recommend a prolonged course of daily antibiotics after other options are proven ineffective or inappropriate. Where possible, the choice of antibiotic should be informed by a recent culture and the results of a susceptibility test. The American Urological Association recommends continuous antibiotics as one of many first-line options for recurrent UTIs.

Antibiotics following short-term urinary catheterization decrease the subsequent risk of a bladder infection. A number of UTI vaccines are in development as of 2025.

Children

Low-dose antibiotics slightly reduce the risk of recurrent UTIs in children. However, the benefit is small; many children stop having repeat infections without antibiotics, and antibiotic use can increase the likelihood that future UTIs will be resistant to treatment. Circumcision of boys has been observed to exhibit a strong protective effect against UTIs, with some research suggesting as much as a 90% reduction in symptomatic UTI incidence among male infants, if they are circumcised. The protective effect is even stronger in boys born with urogenital abnormalities.

Dietary supplements

Cranberry products can reduce the risk of UTIs in certain groups (women with reoccurring UTIs, children, and people having had clinical interventions), but not in pregnant women, the elderly or people with urination disorders. They can also be used as an adjuvant to antibiotics and other standard treatments. Some evidence suggests that cranberry juice is more effective at UTI control than dehydrated tablets or capsules. Cranberry supplements are high in sugar content, which may worsen the risks associated with UTIs in patients with diabetes mellitus.

D-mannose is often marketed as a dietary supplement that prevents UTIs; however, there is little evidence supporting its use. A randomised controlled trial compared daily d-mannose with a placebo (fructose) among women with recurrent urinary tract infections over 6 months. D-mannose offered no benefit over placebo in reducing UTIs.

Certain probiotics might help reduce UTI recurrence, but evidence is weaker than for cranberries.

Treatment

The mainstay of treatment is antibiotics. Fosfomycin can be used as an effective treatment for both UTIs and complicated UTIs, including acute pyelonephritis. The standard regimen for complicated UTIs is an oral 3 g dose administered once every 48 or 72 hours for a total of 3 doses or a 6 grams every 8 hours for 7 days to 14 days when fosfomycin is given in IV form. Gepotidacin was approved for medical use in the United States in March 2025. It is the first new antibiotic approved in the US for UTIs in nearly 30 years.

Phenazopyridine is occasionally prescribed during the first few days in addition to antibiotics to help with the burning and urgency sometimes felt during a bladder infection. However, it is not routinely recommended due to safety concerns with its use, specifically an elevated risk of methemoglobinemia (higher than normal level of methemoglobin in the blood). Paracetamol may be used for fevers. There is no good evidence for the use of cranberry products for treating current infections.

Uncomplicated

Uncomplicated infections can be diagnosed and treated based on symptoms alone. Antibiotics taken by mouth such as nitrofurantoin, pivmecillinam, or fosfomycin are typically first line. Fosfomycin may be used as a single dose, whereas nitrofurantoin and pivmecillinam require a 3 to 5 day course. Cephalosporins, amoxicillin/clavulanic acid, or a fluoroquinolone may also be used. Antibiotic resistance to bacteria that cause UTIs has been increasing, and trimethoprim/sulfamethoxazole is now only recommended in areas with low E. coli antibiotic resistance.

The Food and Drug Administration (FDA) recommends against the use of fluoroquinolones, including a Boxed Warning, when other options are available due to higher risks of serious side effects, such as tendinitis, tendon rupture and worsening of myasthenia gravis. The Infectious Diseases Society of America noted concern of generating resistance to this class of medication. Amoxicillin-clavulanate appears less effective than other options. For simple UTIs, children often respond to a three-day course of antibiotics. The combination sulopenem etzadroxil/probenecid (Orlynvah) was approved for medical use in the United States in October 2024.

Women with recurrent simple UTIs are over 90% accurate in identifying new infections. They may benefit from self-treatment upon occurrence of symptoms, with medical follow-up only if the initial treatment fails.

For mild to moderate uncomplicated UTIs, antibiotics may be completely avoided initially, following discussion with the patient. For instance, ibuprofen can be recommended while a culture is performed to confirm diagnosis and to test how susceptible the infection is to various antibiotics. Delaying or avoiding antibiotics leads to a longer recovery period, but many UTIs do resolve without antibiotics. The risk of progression to a kidney infection is higher than with antibiotic use, but remains low. A 'wait-and-see' antibiotic prescription can be provided. Overall, this strategy substantially reduces antibiotic use.

Complicated

Complicated UTIs are more difficult to treat and usually requires more aggressive evaluation, treatment, and follow-up. It may require identifying and addressing the underlying complication. Increasing antibiotic resistance is causing concern about the future of treating those with complicated and recurrent UTI.

Cefepime/zidebactam (Zaynich) was approved for medical use in the United States in May 2026.

Asymptomatic bacteriuria

Those who have bacteria in the urine but no symptoms should not generally be treated with antibiotics. This includes those who are old, those with spinal cord injuries, and those who have urinary catheters. Pregnancy is an exception and it is recommended that women take seven days of antibiotics. If not treated it causes up to 30% of mothers to develop pyelonephritis and increases risk of low birth weight and preterm birth. Some also support treatment of those with diabetes mellitus and treatment before urinary tract procedures which will likely cause bleeding.

Pregnant women

Urinary tract infections, even asymptomatic presence of bacteria in the urine, are more concerning in pregnancy due to the increased risk of kidney infections. During pregnancy, high progesterone levels elevate the risk of decreased muscle tone of the ureters and bladder, which leads to a greater likelihood of reflux, where urine flows back up the ureters and towards the kidneys. While pregnant women do not have an increased risk of asymptomatic bacteriuria, if bacteriuria is present they do have a 25–40% risk of a kidney infection. Thus if urine testing shows signs of an infection—even in the absence of symptoms—treatment is recommended. Cephalexin or nitrofurantoin are typically used because they are generally considered safe in pregnancy. A kidney infection during pregnancy may result in preterm birth or pre-eclampsia (a state of high blood pressure and kidney dysfunction during pregnancy that can lead to seizures). Some women have UTIs that keep coming back in pregnancy. There is insufficient research on how to best treat these recurrent infections.

Pyelonephritis

Pyelonephritis is treated more aggressively than a simple bladder infection using either a longer course of oral antibiotics or intravenous antibiotics. Seven days of the oral fluoroquinolone ciprofloxacin is typically used in areas where the resistance rate is less than 10%. If the local antibiotic resistance rates are greater than 10%, a dose of intravenous ceftriaxone is often prescribed. Trimethoprim/sulfamethoxazole or amoxicillin/clavulanate orally for 14 days is another reasonable option. In those who exhibit more severe symptoms, admission to a hospital for ongoing antibiotics may be needed. Complications such as ureteral obstruction from a kidney stone may be considered if symptoms do not improve following two or three days of treatment.

Prognosis

With treatment, symptoms generally improve within 36 hours. Up to 42% of uncomplicated infections may resolve on their own within a few days or weeks.

15–25% of adults and children have chronic symptomatic UTIs including recurrent infections, persistent infections (infection with the same pathogen), a re-infection (new pathogen), or a relapsed infection (the same pathogen causes a new infection after it was completely gone). Recurrent urinary tract infections are defined as at least two infections (episodes) in a six-month time period or three infections in twelve months, and can occur in adults and in children.

About 10–20% of children with upper urinary tract infection, which involves the kidney (pyelonephritis), will go on to develop scarring of the affected kidney. Then, 10–20% of those who develop scarring will have an increased risk of hypertension in later life. Recurrent UTIs are a rare cause of further kidney problems if there are no underlying abnormalities of the kidneys, resulting in less than a third of a percent (0.33%) of chronic kidney disease in adults.

Epidemiology

Urinary tract infections occur almost four times more frequently in females than in males. Urinary tract infections are the most frequent bacterial infection in women. They occur most frequently between the ages of 16 and 35 years, with 10% of women getting an infection yearly and more than 40–60% having an infection at some point in their lives. Recurrences are common, with nearly half of people getting a second infection within a year.

Pyelonephritis occurs between 20 and 30 times less frequently. They are the most common cause of hospital-acquired infections accounting for approximately 40%. Rates of asymptomatic bacteria in the urine increase with age from two to seven percent in women of child-bearing age to as high as 50% in elderly women in care homes. Rates of asymptomatic bacteria in the urine among men over 75 are between 7–10%. 2–10% of pregnant women have asymptomatic bacteria in the urine and higher rates are reported in women who live in some underdeveloped countries.

Urinary tract infections may affect 10% of people during childhood. Among children, urinary tract infections are most common in uncircumcised males less than three months of age, followed by females less than one year old. Estimates of frequency among children, however, vary widely. In a group of children with a fever, ranging in age between birth and two years, 2–20% were diagnosed with a UTI.

Veterinary medicine

Domestic cats are less susceptible to bacterial urinary tract infections than domestic dogs.

History

Urinary tract infections have been described since ancient times with the first documented description in the Ebers Papyrus dated to c. 1550 BC. It was described by the Egyptians as "sending forth heat from the bladder". Effective treatment did not occur until the development and availability of antibiotics in the 1930s, before which time herbs, bloodletting and rest were recommended.