Rethinking Aging, Toxins, and Mental Health
“Aging is a disease that should be treated like any other” — Élie Metchnikoff
I’m sure many of us have consumed yogurt, a fermented dairy product rich in beneficial bacteria, or probiotics, which has become a trend in Western countries and spread to Asia. Yogurt consumption is believed to have numerous health benefits, from preventing age-related metabolic diseases such as heart disease, diabetes, cancer, to depression.
The yogurt and fermented products market experienced a boom in the early 20th century when Élie Metchnikoff mentioned the connection between commensal bacteria in the digestive tract and the aging process, as well as psychological disorders. Élie Metchnikoff was a Russian zoology expert and a Nobel laureate in Physiology in 1908 for his discoveries regarding the role of macrophage cells in our immune system.
Metchnikoff observed that birds, fish, and reptiles generally have longer lifespans than mammals. Not only do they live longer, but they also tend to remain healthy at ages considered old for mammals. For instance, he believed that some species of eagles could live up to 100 years, while horses lived for about 30 years, and cows only reached a maximum of around 20 years.
When examined from an anatomical perspective alone, there seem to be no significant differences in the respiratory, nervous, and cardiovascular systems between birds and mammals. However, Metchnikoff pointed out a significant difference in the digestive system between the two groups. Mammals have a large, and in fact, the largest, large intestine among all animal types, whereas birds have a shorter and less significant large intestine. According to Metchnikoff, the large intestine in mammals functions primarily as a reservoir for undigested and unabsorbed food remains.
Mammals are animals that evade predators by running around. The presence of a reservoir in the digestive tract allows them to store undigested food remains without having to defecate all the time. Frequent defecation could easily be detected by predators and pose a threat to the animal’s life. The same does not apply to birds. Birds did not need to evolve to develop a large intestine that could serve as a temporary food residue storage because they could easily evade predators by flying.
Metchnikoff argued that there was a price to be paid by mammals for having such long large intestines. The food residues stored in the large intestine became raw material for bacterial putrefaction. Putrefaction releases various toxic substances that enter the bloodstream and can disrupt bodily functions. According to Metchnikoff, this is where the aging process begins. The same toxic substances are also strongly suspected to contribute significantly to psychological disorders such as depression, mania, and neurotic behavior. This theory is known as autointoxication. In Metchnikoff’s era, patients with mental disorders were often treated through surgery to remove their large intestines.
To prevent the putrefaction process that produces harmful toxins, Metchnikoff recommended controlling putrefaction in the large intestine by consuming foods containing beneficial bacteria, such as yogurt. Yogurt contains Lactobacillus bulgaricus and Streptococcus thermophilus bacteria.
Metchnikoff’s autointoxication theory, as described in his book The Prolongation of Life, quickly gained widespread attention and was embraced by many other scientists. Food producers also didn’t want to miss out on the trend and promptly started producing various probiotic foods and drinks. A variety of fermented products claimed as probiotics soon filled store shelves.
The autointoxication theory began to lose followers in the mid-20th century when Sigmund Freud’s psychoanalytic theory gained popularity among scientists as an explanation for psychological disorders.
With the decline of Sigmund Freud’s psychoanalytic theory, the autointoxication theory resurfaced in the early 2000s. Current scientific research has shown that the autointoxication theory is not entirely false. Metchnikoff was wrong in stating that the large intestine only serves as a temporary food residue storage, but he was right that commensal bacteria in the digestive tract play a crucial role in determining both physical and mental health. The term autointoxication has now transformed into metabolic endotoxemia. Metabolic endotoxemia is a significant factor in causing psychological disorders such as depression and anxiety. Furthermore, recent studies have shown that metabolic endotoxemia is closely linked to the risk of developing chronic diseases in old age, such as diabetes, heart disease, cognitive dysfunction, and cancer.
