The BRAT diet is a diet for patients with gastrointestinal distress such as diarrhea, dyspepsia, and/or gastroenteritis. The BRAT diet consists of foods that are exceptionally bland and low in fiber. Low-fiber foods were recommended as it was thought that foods high in fiber cause gas and possibly worsen gastrointestinal upset.
An acronym, BRAT is a mnemonic for bananas, rice, apple sauce and toast, the staples of the diet. Extensions to the BRAT diet include BRATT (with tea), BRATTY (with tea and yogurt), and BRATCH (with chicken, often boiled). Sometimes the "T" represents tapioca.
In addition to dietary restrictions, medical professionals recommended that all patients, regardless of age, intake plenty of fluids to prevent dehydration, along with oral rehydration solutions to replace the depleted electrolytes to avoid salt imbalance. Severe, untreated salt imbalance can result in "extreme weakness, confusion, coma, or death."
Nutritional analysis 
The American Academy of Pediatrics states that most children should continue a normal, age appropriate diet. The foods from the BRAT diet may be added, but should not replace normal, tolerated foods. Sugary drinks and carbonated beverages should be avoided. The BRAT diet is no longer routinely recommended by nutritionists at the Seattle Cancer Care Alliance (SCCA) to patients who have had stem cell transplants and have diarrhea due to Graft-versus-host disease as long-term use can lead to nutritional deficiencies. BRAT is nutritionally incomplete and may be deficient in energy, fat, protein, fiber, some vitamins and calcium. Cultured foods, rice water, coconut water and soluble fiber foods/supplements are more effective at treating ongoing diarrhea in conjunction with tolerated foods and beverages.
A well-balanced diet is not always best during diarrhea. The intestinal mucosal cells are damaged in common viral enteritis, and are not able to properly absorb nutrients until they regenerate, which requires about 48 hours. Many clinicians feel that restricting food intake during this time, especially difficult to digest substrates such as fats and proteins, helps to shorten the duration of the diarrhea (and also nausea and vomiting) that results from the enteric insult. Thus the usual recommendation for clear liquids, especially those that replace the salts lost in diarrhea and vomiting. Sports drinks and bouillion are ideal for this. The brain can only use glucose as a fuel (and, normally to a lesser degree, ketone bodies), so the sugars in sports drinks and hard candy may help to ward off the mental confusion that can accompany the illness. If sugars are restricted, the body's natural mechanism is to break down muscle tissue to generate glucose, as fat cannot be broken down into glucose. Once the nausea has resolved, and hunger returns, the BRAT diet can supply carbohydrates which are easier to metabolize by the weakened intestine than are fats and proteins. The BRAT diet can also serve as a test diet, since if symptoms return or worsen that is a sign that the diet was advanced too soon. Studies have found, however, that incorporating foods from the BRAT diet may reduce the severity of diarrhea. The BRAT diet was never meant to be exclusive; the need for salt replacement should always be kept in mind. It was only designed to give patients some idea of what they could try as they advance their diet, so as to avoid a relapse. Apple sauce provides pectin, as does toast with grape jelly.
In 2007, Debora Duro and Christopher Duggan reported that bananas and rice have been shown to have a positive effect on the bowels, but recommended caution in using the diet. In vitro research has found that rice may offer anti-secretory benefits. In studies of choleric patients, rice-based oral re-hydration solutions help decrease stool volume and stop diarrhea sooner. Duro and Duggan referenced a meta-analysis that looked at thirteen studies. The banana’s high content of amylase-resistant starch has been shown to protect the gastrointestinal mucosa in animals and reduce symptoms of non-ulcer dyspepsia and peptic ulcer in people. Amylase-resistant starch is broken down into short-chain fatty acids in the colon, a process that may reduce water and electrolyte losses and benefit GI symptoms. Duro and Duggan cite one study in which adding pectin or bananas to the diet significantly decreased stool weight and stopped diarrhea much sooner, compared with a rice diet alone.
Adding rice, bananas, or pectin to the diet during diarrhea may be beneficial, but Duro and Duggan point out that the BRAT diet is not nutritionally complete and may be deficient in energy, fat, protein, fiber, vitamin A, vitamin B12, and calcium. Duro and Duggan also say that food restriction does not benefit diarrhea and actually causes individuals to suffer from diarrhea for longer periods of time, based on randomized clinical trials.
Medical attention is required when on the BRAT diet if there is any blood or mucus present in the diarrhea, if the diarrhea is severe or if it lasts longer than 3 days.
Additionally, other medical professionals advise first aid treatment for gastroenteritis by briefly limiting the diet to bland, easy-to-digest foods and plenty of liquids (including oral rehydration therapy, e.g. oral pediatric electrolyte solutions sold at retail).
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