How old are your body parts?

When asked how old we are, we do not pause and consult our different body parts. When we say our age, we subject ourselves to a host of impressions about what that number means in terms of bodily functions. When we say “20-something,” we tend to associate that with a very high tolerance for any kind and amount of food we eat or drink. As we grow older, we tend to be more careful, as we assume that our body parts have been having regular consistent meetings with each other and agreeing at their common age for a press release. But that attitude is not supported by reality. 

There are people in their 60’s whose hair may be all grey if they have hair at all, or their skin may be all wrinkly, but whose metabolism could beat that of a common 20-year-old.  Patients who are bedridden may have hearts that are so strong even when their kidneys are failing. Some very muscle-fit young people’s immune systems grow to be so vulnerable in their 30’s compared to older people whose muscles may not be taut and strong but could live through a host of allergens and pathogens. These all tell us that while it is much easier for us to see “age” as one solid number, the body parts that make up our bodies age at different rates. A recent study published in Nature Medicine further crystallizes this point. (READ: Japan's silver-haired seniors still punching the time clock)

The research studied people aged 29-75 years old across 2-4 years. They examined a host of things – some of them are the ones we are familiar with in routine tests we undergo – like urine, saliva, and other markers found in blood samples. But they looked at so much more – 10,343 genes, 306 blood proteins, 722 metabolites, and 6,909 microbes including those found in the nose and gut. And while the researchers say this is just the beginning, they think patterns have emerged from their data that so far make it look like that there are 4 clusters inside our bodies where separate aging occur: liver, kidney, metabolic, and immune. They call these “ageotypes.” They said there could be more of these as more studies are done.  

So is this good news or bad news?  

It is good news for those who have been working to make medicine more personalized, which means it is also good for the rest of us and our individually unique bodies. It is also good news to know that while you may have the number known to be “old,” you may have body parts that are not that old. But it is bad news for those who make us all think that “anti-aging” is just all about skin care. It is also bad news for those who insist in treating aging as one monolith of a disease self-combusting at the same rate in each of our inner clocks. Our medical system, including the medical schools we have, largely operate on cookie-cutter templates of human bodies. This has to change to match what we know now about the multi-aging rates of our body systems/parts. 

The study’s findings explain why some people can drink alcohol like bottomless pits most of their lives and still have a “smiling” or at least “uncomplaining” liver while a much younger person can do the same and have a beat-up liver by the time s/he is 30. It also can explain why someone who is almost 70 can eat anything he wants and burn them so fast without causing any spikes in glucose levels. The same for people who have kidneys that give out in their 30’s even when they have not caught a cold in years.  

Knowing what “ageotype” you are may help you be a lot more deliberate in protecting that organ or system which seem to age faster in you. For example, if you found yourself to be the metabolic ageotype, then you should step up on a habit of exercising and calorie-conscious eating. That will serve as your counterpoint to the “original” tendency of your personal metabolism to age and thus, conk out faster than your other body parts. If you are the liver ageotype, then you have to go very easy on your alcohol intake, or have none at all, so that your liver can have much less impetus for damage for which it already has very low threshold for. 

Speaking of aging – even our hair could turn grey so much faster when we are stressed regardless of our age. Another recent study finally found a mechanism why this happens. It has to do with how a substance we naturally release called “noradrenaline” affects the kind of cells that are key to making the pigments that color our hair. When stressed, the amounts of noradrenaline go way beyond the threshold that it carries all those cells, leaving nothing to make those pigments. So when we tell someone who is stressing us that they are responsible for our hair prematurely turning grey or white, we can say we have scientific backing.  

While ageing seems to be inevitable, our bodies apparently do not ride the arrow of a lifetime with all our body parts agreeing what time it is for each them. Like in airports when you have clocks showing what time it is in different cities around the world, so do our body parts tick at different rates. It gives you a better picture of what you can do in your health itinerary if you know those times. – Rappler.com

Maria Isabel Garcia is a science writer. She has written two books, "Science Solitaire" and "Twenty One Grams of Spirit and Seven Ounces of Desire." You can reach her at sciencesolitaire@gmail.com.