Kombucha, the controversial life-extender
Drinking kombucha every day may extend your lifespan. This is suggested by an animal study that researchers from the University of Alaska Fairbanks published in Nutrition in 2000. But not all scientists and doctors are enthusiastic about the fermented tea drink.
Kombucha is fermented tea. You can buy it, but you can also make it yourself if you let a mix of bacteria and yeasts ferment black tea with sugar ferment. This mix is called 'scoby', an abbreviation for "symbiotic colony of bacteria and yeast". In prepared kombucha are benign Acetobacter and Gluconobacter bacteria, gluconic acid [no, not glucuronic acid] and yeasts of the Saccharomyces type.
You sometimes read that kombucha no longer contains sugars, because the scoby would convert them into other substances. That is not quite right, says the table below.
According to animal studies, kombucha improves cholesterol levels. [Biotechnology in Animal Husbandry 2011 27(4), p 1749-55.] [Pharm Biol. 2015;53(11):1.] On the internet you will find hundreds of positive anecdotes of kombucha users who feel more vital, sleep better and are less often ill.
Nevertheless, there are cases of consumers who became ill due to kombucha. Sometimes it is not clear why, [MMWR Morb Mortal Wkly Rep. 1995 Dec 8;44(48):892-3;899-900.] sometimes allergic reactions play a role, [J Gen Intern Med. 1997 Oct;12(10):643-4.] sometimes Kombucha bacteria produce toxic amounts of D-lactate [BMJ Case Rep. 2017 Dec 2;2017.] that damage the kidneys [J Intensive Care Med. 2009 May-Jun;24(3):205-7.] or the liver. [S D Med. 2016 Jan;69(1):26-8.]
On the other hand, in toxicological studies kombucha emerges as safe. [Biomed Environ Sci. 2000 Dec;13(4):293-9.] Perhaps many of the reported disease cases are the result of sloppily produced scobies contaminated with Aspergillus fungi. [Crit Path AIDS Proj. 1994-94 Winter;(No 30):31-2.] or of kombucha that has not been produced under sterile conditions.
In 2000, researchers from the University of Alaska Fairbanks published an animal study in which they had a group of mice drink kombucha during their entire life. The researchers gave a control group plain water. The mice in the experimental group were given the equivalent of what people, who want to optimize their health by drinking kombucha, consume daily.
Kombucha prolonged the life of the mice, but only in male animals there was a statistically significant relationship. They lived 5 percent longer than the mice who drank only water. The females in the kombucha group lived only 2 percent longer.
The fermented tea also inhibited the increase in body weight when the animals grew older.
"This would tend to support the claims that drinking the tea-beverage kombucha from the so-called 'mushroom of long life' contributes to longer life", the researchers write.
"Beyond human testimonials, a main effect of increased longevity has not been documented with other species, but could be explored using those who would voluntarily drink the kombucha."
"It is known that simple caloric restriction and weight reduction contributes to longer life in rats and humans and that may be a major mechanism at work in this study."
Nutrition. 2000 Sep;16(9):755-61.
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