Learning about the human body is one of the most fascinating topics. But of course, I share that as someone who has a profound love and passion for all things related to studying human health and wellbeing. The study of all biology areas has been my passion and interest for years, and I feel that our body is one of the most important systems that we should learn about to live life in an efficient, effective, and enjoyable way.

Thanks to a recent email with questions from reader Akemi Gaines, we will explore one very fascinating area that deals with our body and its longevity. As part of this article, we will examine why we have to keep eating regularly, how our body deals with old cells and nutrients, and whether it has some sort of recycling system that is capable of optimizing its functions and prolonging our longevity further.

What Happens to Old Cells in Our Body

Question: We are taught we need to eat to get the necessary nutrition and energy. I see the need to renew. But what happens to the old chunk of cells that get replaced with the new? Some cells, like the skin cells, get pushed out, but I guess most of them go into the bloodstream to be excreted in urine or stool. Our bloodstream is both the feeding system of nutrition and the sewage.

Our blood is indeed both the feeding system and the sewage system. Both helpful and harmful molecules and organisms travel via our blood. And similar to our home environment, our blood is either cleaner or dirtier, depending on our habits.

What happens to old cells depends on what cells they are. Some cells have a lifespan of only a few days, while others a few weeks, months, or years. When it comes to skin cells, most of them get sloughed off externally. This is partly why some people like to exfoliate to help remove the old and dead skin cells and allow the new skin to flourish. It is estimated that we lose about 30,000 to 40,000 skin cells every hour! New skin cells grow from within and thus make up our new skin. Old or diseased blood cells are most commonly destroyed by the spleen. They can also be removed through the liver and kidneys, and their byproducts are eliminated in the urine. Most of the cells that pass through and are excreted in the stool are intestinal cells, with cells all along our digestive tract, from the mouth to the anus, being the ones with the shortest lifespan of only a few days, and like skin cells, they get sloughed off. Since they are located internally, they mix in with our food wastes and pass out in our stool.

Many of our cells actually get eaten by other cells, namely ones from our immune system, as they release a signal to be eaten. This is also referred to as a “programmed cell death” or “cell suicide.” Formally, it is known as apoptosis. This is a pretty complex process, but generally speaking, a cell will decide to do this based on many signals that it exchanges between its environment and itself.

The Body’s Nutrient Recycling System

Question: Now this old cell that is getting dumped is no longer good as a cell, but when it’s broken down to a molecular level, it’s a bunch of amino acids and fatty acids, etc., just like any other such building blocks. Can’t we then just recycle these amino acids and lipids back as nutrients to sustain us?

Generally speaking, yes, our bodies have a pretty good recycling system. An individual may recycle and exchange 70% of their cells for new ones each and every year. However, not all is as smooth and simple as we would like it or imagine it to be. There are small organs that make up each of our cells called organelles. One of these organelles is called the lysosome. Lysosomes are like mini digesting factories in that they use their own enzymes to recycle the cell’s own organic material. This is known as autophagy, and it usually goes hand in hand with the process of apoptosis, described above. Any wastes then get transported via the blood to areas (organs) which can expel them out of the body.

During the process of autophagy, a lysosome engulfs another organelle or a small packet of cell contents. The enzymes take apart the substance, and the organic pieces are returned for further use by that cell or another one. This way, many cells can actually continually renew themselves. It has been noted that a human liver cell recycles half of its macromolecules each week (Biology; Campbell & Reece 2002). Macromolecules include things like carbohydrates, fats, and proteins. So this is what happens, but scientists still don’t know exactly how it all happens and makes these processes work. Also, there are apparently many substances that are indigestible to the lysosome. These can cause problems in cells in the long run due to an accumulation of various wastes.

In practical terms, compare this process to recycling an old car. We can definitely use some of the pieces of an old car to make a new car, and some pieces will need to be repaired before they can be re-used. Other pieces, however, will not be able to be used at all, as they either had too much wear and tear or altogether got destroyed beyond any further functional use. In this sense, our bodies do try to reuse and recycle many of their own components. Still, some proteins or carbohydrates, for example, get turned into entirely new chemical components, which the body will have to dispose of and will not be able to reuse again.

Why We Have to Eat Food Regularly

Question: I read Aubrey de Grey’s Seven Causes of Aging and Death – which are: undesirable mutation/slowdown of DNA, proteins, etc., and the accumulation of junk in and around the cells. I understand the need to get rid of the old cells, but when cells break down, the leftover building blocks on the molecular level are just that — building blocks. An amino acid is an amino acid, whether we get it from foods or it’s our own old cell recycled. Food is just someone else’s old cells (whether they are animal or plant-based.) So the problem is we don’t have such a recycling system in our body?

Aubrey de Grey is the co-founder of the SENS Research Foundation, whose research and expertise is precious to consider for a better understanding of this topic. I remember I saw Aubrey’s TED talk — A Roadmap to End Aging, a few months ago, and it really got me intrigued about a few things when it comes to longevity. I personally believe that our bodies can last much longer than a mere 6o to 80 years, about a quarter of which at least is spent dealing directly with disease and disabilities of all kinds.

Our cells cannot use everything they receive and thus find ways to release, store or recycle as needed, similar to when we eat and go to the bathroom to expel waste or filter blood through our kidneys. The food that we eat creates our whole body and is a larger reflection of what happens when nutrients come into cells and create them. Many nutrients can be used again during these processes, as I explained in the answer above, but others are either too used up, indigestible, or just plain junk and no longer usable. In this sense, we cannot think that we can perpetually work with what we have, as sooner rather than later, we will be in a deficient state of some sort.

When we eat, yes, we are essentially ingesting either plant cells or animal cells, which our body then breaks down to use for nutrients and other beneficial substances. And yes, some of those cells will actually be physically old and problematic, especially when it comes to animal-based foods, but we should not confuse the word “old” here with food being simply the cells the organism is made of. So more often than not, we are eating usable materials from plants and/or animals, not actually old materials that are used out or subject to destruction.

Similarly, an amino acid is not necessarily kept as the exact amino acid it was. When it comes to proteins and the numerous amino acids that make them up alone, the body maintains a regular pool of amino acids that can be re-arranged based on the body’s needs, and is one of the biggest reasons why we don’t have to eat all essential amino acids in one meal, or even one day. Given the nature of chemistry, often just one less or more carbon, hydrogen, or any other element in a compound makes all the difference as to what that compound or molecule is, does, and how it behaves. What goes into our bodies and how our bodies change that substance are often two very different things. Chemical reactions are also often one-way, meaning that we cannot get back the original, perhaps desired, substance. So while our body does try to recapture and recycle as much back as it can on a daily basis for optimal efficiency, mostly via our liver and kidneys, it just cannot reuse or recreate everything for the reasons explained above. This is why we need to eat regularly to replenish those things that get used up, burned up, changed, or destroyed.

Question: So if we can develop an inner recycling system, we wouldn’t need to eat so much?

As mentioned above, we do have a pretty good recycling system in our bodies. Still, there are simply many substances, molecules, and compounds that get used up and chemically changed and thus cannot be re-used in the way we’d like to imagine, as new nutrient molecules of carbohydrates, proteins, fats, vitamins, or minerals. For the simplest example to help understand why this is so, just imagine burning wood in a fire. When that wood burns up into ash, yes, you have much of the same atoms and elements that were originally present in the original wood. Still, now having undergone a chemical reaction, they are in new forms that are not equivalent to how they were in the wood pre-burning. Put another way, you cannot make wood out of ashes. This simple example helps you understand why molecules cannot be re-used perpetually and need to be replenished accordingly in order to get a desired function or outcome.

For example, we eat macronutrients (carbs, fats, protein) and micronutrients (vitamins, minerals) each day. These nutrients get used to build new things, supply us with energy, and initiate a whole slew of various chemical reactions. The majority of these substances get chemically changed in the body to be compatible with the specific part of the body or task they need to be working at or doing. Once these substances get changed and/or wear out, in most cases, it is inefficient or simply impossible for the body to to re-build them back into being the original molecule they were and which our body needs. A seemingly small chemical change oftentimes makes a big difference to the function and destiny of that molecule.

Therefore, speaking on a purely scientific or medical level, we need to eat regularly to replenish our body and all the substances that are used up or destroyed. However, a person will generally need less food the less damage is done within the body, the more nutrient dense food they eat, and the more efficient and optimized their body is.

The recycling system that we have is there and is good, but it cannot fully compensate for the daily usage of our body’s systems, which includes all sorts of stresses, traumas, and toxins. Of course, if we were to consider this topic metaphysically, then we open ourselves up to a whole new level of potential and possibility that can surpass the need for food and offer us advanced healing and longevity.

Ultimately the human body, just as the body of all other living organisms and nature as a whole, is very efficient and will always seek the path of least resistance. This includes having the need for regular nutrient input rather than trying to convert old compounds into new materials. If we work against this system, for example, by not eating, the body will then be forced to work more with what it has (i.e., old substances) until it wears and uses even those out, at which point we would die from various function, organ, and system breakdown.

How We Can Prevent Aging

According to my own research, understanding, and theories on aging, I resonate with Aubrey de Grey’s 7 Causes of Aging, which are:

  1. Cell loss (i.e., tissue atrophy, shrinking tissue)
  2. Proliferation of unwanted cells (i.e., cancerous cells)
  3. Mutations in mitochondria
  4. Death-resistant cells/mutations in the nucleus, such as chromosomal mutations
  5. Tissue stiffening from protein cross-links
  6. Accumulation of “junk” outside of cells
  7. Accumulation of “junk” inside of cells

Out of these seven reasons, he claims that junk that builds up inside and outside of the cells throughout our lives is the biggest contributor to aging. This alone can give good merit to all the focus on detoxifying our bodies today. Bottom line, if we are interested in longevity and extending our life, but even more importantly in assuring the best quality of life, then it goes without saying that we should focus on keeping our bodies clean. This means avoiding and minimizing physical, chemical, mental, and emotional stressors and toxins as much as possible and having good lifestyle habits that regularly help remove waste from our cells, tissues, organs, and bodies. This means at the very least having proper, daily bowel movements and skin that is not blocked by any substance, such as antiperspirants, to be able to sweat freely. In addition, drinking enough pure water each day, doing breathing exercises, regular physical activity, eating a cleansing plant-based diet, maintaining healthy body weight and not being overweight, and spending plenty of time in nature for exposure to fresh air and natural sunlight.

Let’s break it down further with a convenient example. A common meal can vary between eating a processed burger or pizza versus a plant-based chili or whole-meal salad. The former choices are not only filled with “junk” to begin with, but they will also lead to the creation of a lot of internal junk for our bodies, given that they contain substances which the body will have trouble digesting and using, and which are toxic to it by their very nature. A diet that is high in such foods is much more indicative of faster aging. The second set of choices, on the other hand, provides lots of quality nutrients, cleansing, and healing substances with minimal problems, which ultimately increases the quality and likelihood quantity of our lifespan. For best longevity, the cleaner, purer, and healing the diet is, the less junk accumulates in and around our cells.

This does not only apply to diet. This also applies to the water we drink, the air we breathe, and the products we use. It even applies to our thoughts. I don’t mean one has to have “pure” thoughts like religions might like us to believe, but pure or clean with respect to negative and destructive or positive and constructive thoughts. Today, we know that our thoughts generate all sorts of chemical reactions and emotional feedback loops that can be very helpful or harmful on a cellular and whole system level. A lot of undesirable emotional and chemical reactions result in cellular damage and junk in our bloodstream and body, which our cells then have to work harder to try to clean up and out.

Finally, this conversation would be incomplete without further mentioning the idea of detox. In the past few decades, various forms of detox have become very popular. While some are superficial fad and hype, a result of clever marketing, true and effective detox protocols, like fasting, can be constructive and beneficial. It allows our bodies to “catch up” and optimize its innate cleaning system that is very capable of getting rid of a lot of the “junk” that not only ages us but also leads to various diseases.

One of the easiest, effective detox strategies that we can do is make sure that there is a 12 hour period of no eating between our last meal of the day and our first meal of the next day. For example, if your last food item was eaten at 7 pm, you would not eat anything again till 7 am the next day. This allows for proper digestion and our body’s natural cleansing system to kick in, which it is most capable of doing during the time we sleep, which is when we are not assaulting or stressing it further with anything. This also coincides with why most healthy people have one or more bowel movements first thing in the morning or sometime in the morning hours. This is all part of healthy and optimized cleaning and elimination.


I hope you have enjoyed gaining some new perspective about how incredible your body is and why it is so worth it to support it properly via your lifestyle habits and choices. While it is exciting to talk about lengthening the human lifespan and optimizing our body’s functions, the most important thing that I hope you take away from this discussion is to actively work on the quality of your health and wellbeing each day. When we work with, rather than against our body, we are the ones who gain the most benefit and reap the best rewards for optimal health and wellbeing.