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Organic acids play an active role in keeping the intestines healthy

You may have already heard of the word “organic acid”. Organic acids are known as sour ingredients in foods. Typical organic acids are citric acid present in citrus fruits and dried plums, acetate which is the main component of vinegar and malic acid which gives acidity to apples and wine. In recent years, many functionalities about them have been discovered.

There is an expression that the intestine is healthy when the pH value (indicator of acidity and alkalinity) in the intestine is mildly acidic and that the intestinal environment deteriorates when the value is in alkaline. This is related to the tendency of the intestinal environment to become acidic because of the functions of organic acids. Among the intestinal bacteria, lactic acid bacteria and bifidobacteria, which are classified into good bacteria, can produce organic acids such as lactic acid and acetic acid. These organic acids keep the intestinal pH value below 6 and remain there in a mildly acidic environment. In fact, many bad bacteria such as pathogenic Escherichia coli, salmonella, and dysentery, which are called pathogenic bacteria, cannot survive in a mildly acidic environment. Therefore, keeping the intestinal environment in mildly acidic with organic acids can help to prevent infection.

The advantage of keeping the intestines in a mildly acidic environment with organic acids is that it allows to increase the absorption rate of minerals. Minerals are essential nutrients for the body, albeit in trace amounts. In Japan, many children and women are found in a state of calcium and iron deficiency. Therefore, we must get an adequate amount of minerals from our diet.

Minerals are not well absorbed when the intestinal environment is deteriorated. Intestinal pH levels are also involved in this absorption process. Minerals are easily dissolved in a mildly acidic environment and then are absorbed into the body through the intestines. Organic acids promote the mineral absorption by keeping the intestinal environment mildly acidic. There are many other research reports on the function of organic acids, such as being energy sources for cells of the large intestine, suppression of cancer cells, suppression of cholesterol synthesis, and promotion of blood circulation.

Ingestion of lactic acid and pyruvic acid enhances intestinal immunity

It was reported in a scientific journal Nature in 2019 that organic acids such as lactic acid and pyruvic acid produced by gut microbiota can activate the intestinal immune response. There are many types of immune cells in the intestine. Macrophages, which are innate immune cells in the small intestine, play a role in catching and exterminating pathogenic bacteria and viruses that have entered the intestine.

According to this paper, the immune response of the subject mice, which ingested lactic acid or pyruvic acid against Salmonella, a type of pathogenic bacterium, has been enhanced and their resistance to Salmonella has increased. The detailed mechanism about how innate immunity works has been unknown up until now, but this study has revealed the mechanism of immune enhancement by the ingestion of lactic acid and pyruvic acid.

Fermented foods also contain many types of organic acids

Fermented foods are the key to the efficient intake of organic acids in our daily diet. As I wrote at the beginning, vinegar and wine also contain organic acids. In addition, lactic acid bacteria are involved in the fermentation processes of miso and soy sauce. Therefore, lactic acid is present in them. The reason why pickles are sour is that lactic acid bacteria produce lactic acid, acetate, malic acid, etc. during the fermentation period. Organic acids are not broken or reduced by cooking, if you use an appropriate amount of fermented foods and fermented seasonings in cooking, you can get a good level of organic acids from your daily diet.

Nowadays, many people are paying attention to measures against infectious diseases. Fermented foods containing organic acids can be indispensable foods for enhancing the immune responses.

Nature 566, 110-114 (2019)

Credit to: Muneaki Takahata Ph.,D.