The Bible tells us in the Old Testament (in the Book of Wisdom) that God made us in the ‘image of his own eternity’. Was he suggesting that man was born to be immortal? Interpretation of religious scriptures is an age-old problem. Islamic State identifies itself as being more faithful to the codices of the Koran.
Christians can even be broadly defined into three religious groups each of which interprets the book of Genesis in entirely different ways. Literalist Christians see the Bible to be the true voice of God and believe the world really was conjured up in six days. Conservative Christians believe the Bible was written by humans inspired by God and that Genesis did occur but not necessarily within the time frame suggested. Liberal Christians meanwhile see the Bible as a guide for life and take Genesis with a pinch of salt!
Certainly, we all wish that we could at least achieve some sort of longevity and preferably in reasonable health. Immortality is of course quite unlikely unless you are transformed miraculously into a mythological entity like a vampire. The myth of the vampire has been perpetuated by centuries of folklore and most notably by Abraham Stoker’s book ‘Dracula’ published in 1897. Vampires are now a common contemporary reference point (reference ‘Spitting Image’ who cast Priti Patel as one).
But back to some science! Perhaps there really are some hidden secrets to longevity? Certainly, scientists in Japan think so. They believe they may have found a small piece of the jigsaw puzzle. Their findings do not necessarily unlock the door to eternal life, but they do offer an insight as to why centenarians achieve the age they do.
Amazingly their study recruited a total of 106 people who had an average age of 107 years old (they must have been hard to find!). In developed countries, the prevalence of centenarians is about 1 in 6,000. Supercentenarians, those who reach 110 years or more, are much rarer, only about 1 in 7 million people around the world live this long.
They also had a cohort of 112 people who fell within the ages of 85-89 years old and only 47 people who were between the ages of 21-55 years old. Each of these two groups acted as controls. What they then did was study the bacteria that lived in the gut of each of these three groups to observe both what was different and then what they had in common. Why not!
Their investigations suggested that it may be possible to manipulate our gut biomes (the community of bacteria that live there) to produce special bile acids that help ward off illnesses and allow people to live longer. Their research was published in the scientific journal ‘Nature’ on 29th July 2021 while many of us were enjoying a holiday.
The colon (or gut), as an organ, contains 100 billion bacteria per gram (dry weight) and contains as many as 500 separate different species. The gut microbiome has one of the highest bacterial densities in nature. It is a highly dynamic community that has co-evolved with us to help us absorb complex food components. This symbiotic process is amazing but, as the host, it is important to remember that we also need to control the overall balance of bacterial colonization.
We control this balance through our physiology. Factors include intestinal transit time (how fast our food travels through us), a huge variety of enzymes that co-exist with gut bacteria, our diet, and bile produced by our livers. The amount of bile that we release in our intestines changes the types of bacteria that live there. Human liver synthesizes about 200 to 600 mg of bile acids per day. It helps break down fats into forms that can be absorbed.
It also helps us absorb fat-soluble vitamins and remove toxins and metabolic waste. Bile also has a very important role in controlling bacterial populations in our gut.
Bile salts and bacteria have intricate relationships. The composition of bile salts in our intestines is determined by bacteria because they break it down to other useful metabolites. In turn, even the very presence of bile salts helps control populations of certain bacteria in our gut.
A major mechanism of bile acids is that they act almost like a natural detergent and prevent some bacteria from growing. The research in our study appears to suggest that certain specific bacteria, and the specific compounds they produce — known as ‘secondary bile acids’ — could contribute to an overall healthy gut and, in turn, promotes healthy aging.
The gut microbiome is known to play a role in our health and changes as we age. For example, having less diversity in certain types of gut bacteria has been linked with frailty in older adults.
But researchers suspected that people who reach age 100 just might have more of some special gut bacteria that promote good health through the production of secondary bile acids. Surprisingly centenarians in general have a lower risk of chronic diseases and infections compared with other adults who may even be younger.
There were several bacteria that were present in noticeably higher densities in our centenarians. One of these was Alistipies. Alistipes is a species of bacteria that was only discovered in 2003 and consists of 13 species.
There is contrasting evidence indicating that Alistipes may have protective effects against some diseases, including liver fibrosis, colitis, cancer immunotherapy, and cardiovascular disease. In contrast, other studies indicate Alistipes is pathogenic in colorectal cancer and is associated with mental signs of depression.
There was also a large increase in the presence of another genus of bacteria called Bacteroidetes. This is the second most common bacteria in the gut. Bacteroides species make up about 30% of the bacteria in our colon.
Some species of Bacteroides are opportunistic pathogens, but in a balanced gut they are health maintaining, because they are capable of ameliorating inflammation. Research indicates that they could even be promising bacteriotherapeutic candidates for use in clinical and nutritional applications, although more research is required.
Two other species of bacteria that were identified as common in centenarians were Clostridium and Methanobrevibacter species. One of the most enriched species in centenarians was a bacterium called Clostridium scindens, which is important in the production of a secondary bile salt that helps inhibit the growth of dangerous bacteria such as the well-known pathogen Clostridium difficile (or C.diff). Most people never have problems with C. diff.
However, if there is an imbalance in your intestines, C. diff. may begin to grow out of control. The bacteria start to release toxins that irritate and attack the lining of your intestines. This is what leads to symptoms of a C. diff. infection. Various Methanobrevibacter species have similar effects.
Still, much more research is needed to know whether these bacteria are important players in exceptionally long life spans. The current findings only show an association between these gut bacteria and living past 100; they don’t prove that these bacteria caused people to live longer.
Dr. Kenya Honda, a professor in the Department of Microbiology and Immunology at the Keio University School of Medicine in Tokyo who helped publish the study comments; ‘Although it might suggest that these bile-acid-producing bacteria may contribute to longer life spans, we do not have any data showing the cause-and-effect relationship between them.’