Cell Lifespans and the Accumulation of Waste

The Hermit "Endure your hunger. Hidden within emptiness lies a truth deeper than any worldly meal."

 

Professor Ohsumi (flustered) "Well... but Master, surely you should at least eat a little something first..."

 

Professor Ohsumi (talking in his sleep) "When you fast, the inner world awakens. Autophagy! Recycling junk proteins! Aaah—!"

 

Professor Ohsumi "In my dream, the hermit and the cells revealed to me the wisdom of an empty stomach."

 

The audience (thunderous applause) "Wow... winning a prize by going hungry — truly, a hermit-grade scientist!"

 

Professor Ohsumi (back in his dream) "Master, this Nobel Prize is thanks to you."

 

The Hermit "A new era is about to begin."

Every Cell Has Its Own Lifespan

Emily "Doctor, I know someone who was diagnosed with cancer, and they started fasting. But shouldn't a cancer patient eat well to keep their strength up?"

 

Dr. Lee "Ah, yes. Fasting can certainly be risky for someone whose strength is already depleted. But for someone who still has reasonable physical reserves, fasting can serve as a process of cleaning out the waste accumulated inside cells, helping to improve overall bodily health."

 

Zoe (startled) "What do you mean by cleaning out the cells? Is there waste inside cells too? And what cleans that waste?"

 

Dr. Lee "Yes, there is waste inside cells — if we define waste as anything that can no longer be used. To understand this, it helps to first appreciate that different tissues in the body have different lifespans. By the way, do any of you happen to know how many cells our body contains?"

 

Susan "A million?"

 

Zoe "Ten billion?"

 

Dr. Lee "Roughly 30 to 50 trillion. Our body is composed of 216 different types of tissues — a kind of biological division of labor. Bone cells, skin cells, nerve cells, and so on each have distinct structures and functions. And these cells also have remarkably different lifespans."

 

Emily "Different lifespans? Aren't cells the same as our own lifespan? Once they're born, don't they stay with us until we die?"

 

Dr. Lee "Haha, no. The average lifespan of a cell is somewhere between 10 and 14 months — but lifespans vary widely. Red blood cells, for example, live about 90 to 120 days. Among the shortest-lived are the epithelial cells of the digestive tract: the lining of the esophagus turns over in about 3 days, and the small intestinal lining in about 7 days. On the other end, neurons and cardiac muscle cells can live for about 50 years."

 

Table 3-1. Lifespan and Volume of Various Cell Types

Cell Type / Tissue	Lifespan (days)	Cell Volume (μm³)
Adipocyte	2,248	600,000
Red blood cell	90	100
Lymphocyte	7–60	200
Neutrophil	1–5.4	300
Pancreatic β-cell	20–30 yrs	1,000
Adrenal cell	455	—
Sperm	3–5 days	30
Oocyte	1	4,000,000
Bone marrow cell	3.2	—
Fibroblast	1–3 yrs	2,000
Monocyte	1–7.4	100–400
Colon cell	3.5	15–25 μm radius
Endometrial cell	13	10–20 μm radius
Esophageal cell	10	—
Cardiomyocyte	25,300	15,000
Skin epithelial cell	64	1–15 μm radius
Renal cell	270	10–30 μm radius
Hepatocyte	327	20–30 μm radius
Lung cell	200	50–100 μm radius, 2,000–3,000
Lung macrophage	81	5,000
Neuron (neocortex)	32,850	4–100 μm radius, 4,000–10,000
Osteoblast	8.3	4,000
Rectal cell	3.5	—
Salivary gland cell	60	8–12 μm radius
Skeletal muscle cell	5,510	10–100 μm radius, 2–3 cm length
Smooth muscle cell	67.5	1–5 μm radius, 20–500 length
Splenic cell	7.8	125
Thyroid cell	3,180	20–250 μm radius
Bladder cell	49	5–250 μm radius

The Longer a Cell Lives, the More Waste Accumulates Inside

Zoe "Wow — so cells differ in shape, function, AND lifespan, all by such large margins."

 

Dr. Lee "Yes, and they also differ enormously in size. The average red blood cell has a volume of about 100 μm³, while a lung macrophage is around 5,000 μm³ — fifty times larger. Osteoblasts are about 4,000 μm³. Cardiac muscle cells are even bigger at 15,000 μm³, and brain cells range from 4,000 to 10,000 μm³. So neurons and cardiac muscle cells are 40 to 100 times larger than red blood cells. And because they live longer, they accumulate proportionally more waste inside."

 

Susan "I never knew until today that cells differ so dramatically in shape, volume, AND lifespan. The home we live in gets messy if we don't clean it — clutter builds up, work becomes inefficient, and hygiene suffers. That's why I clean every morning. So I'm curious: what causes waste to accumulate inside our cells in the first place?"

Reactive Oxygen Species and Antioxidant Defense

Reactive Oxygen Species from Mitochondria Cause Molecular Aggregation

Dr. Lee "Excellent question. The most important cause is reactive oxygen species, or ROS. To produce energy in the body, what do we need?"

 

Emily "Nutrients."

 

Dr. Lee "Nutrients are like fuel. When we light a wood fire, what do we do?"

 

Grace "We light the wood and gently fan it."

 

Dr. Lee "Exactly — and the reason we fan it is to supply oxygen. Just as wood needs oxygen to burn well, our body needs oxygen along with nutrients to produce energy. Why do you feel suffocated when you can't breathe? Because oxygen isn't being supplied."

 

Zoe "Yes, I read that the French scientist Lavoisier discovered oxygen through his combustion experiments. He showed that a candle flame placed inside a small jar burns at first, but goes out once the oxygen inside is consumed."

 

Dr. Lee "Exactly. When we breathe, oxygen enters through the lungs. Inside the lungs are about a million tiny sacs called alveoli. Through their thin membranes, oxygen passes into the red blood cells of the surrounding capillaries. The red blood cells then deliver oxygen to cells throughout the body. Inside each cell, the oxygen is handed off to organelles called mitochondria. The mitochondria use that oxygen to generate energy, which is stored in molecules of ATP."

 

Dr. Lee "More precisely, cellular energy metabolism using nutrients proceeds through three stages: glycolysis, the TCA cycle, and the electron transport chain (Figure 3-2). Glycolysis takes place in the cytoplasm without oxygen, while the other two stages occur inside the mitochondria and require oxygen."

 

Susan "I understand that mitochondria use oxygen to make ATP. But how does that relate to waste building up inside the cell?"

 

Dr. Lee "Excellent question. When mitochondria use oxygen to produce ATP, about 1 in every 20,000 oxygen molecules becomes a reactive oxygen species. The word 'reactive' here means just that — these molecules react readily with whatever is nearby. If a ROS encounters a gene, it reacts with the DNA and damages its structure, disabling its function. If it encounters a protein, it alters the protein's structure and function. ATP is split into ADP and inorganic phosphate (Pi), releasing energy, and is then reassembled from ADP and Pi using nutrients — this cycle repeats about 1,000 times a day (Figure 3-3). Since the body contains about 40 g of ATP, 1,000 cycles amount to about 40 kg of ATP turnover per day."

 

Figure 3-1. Wood combustion and cellular respiration both combine fuel with oxygen to release energy.

Antioxidant Nutrients and Enzymes Defend Against ROS

Susan "Why are reactive oxygen species so chemically reactive?"

 

Dr. Lee "Simply put, electrons are stable when paired, and ROS are oxygen molecules with unpaired electrons. Even numbers (2, 4, 6, 8) are like paired states, odd numbers (1, 3, 5) like unpaired ones. Electrons carry a negative charge but also spin, generating a magnetic field — a north and south pole. A single unpaired electron is unstable, but when another electron pairs with it and spins in the opposite direction, their magnetic fields cancel out and the system becomes stable."

 

Grace "If 1 in every 20,000 oxygen molecules becomes a ROS, that's actually a tremendous amount being generated."

 

Dr. Lee "Yes, exactly. That's why our body produces antioxidant enzymes. And many plants contain antioxidant compounds that protect us from ROS damage. Among vitamins, vitamin C, vitamin E, and vitamin A act as antioxidants. Adequate intake of these antioxidant vitamins also greatly supports brain development."

 

Zoe "So when ROS are generated and react with proteins, the proteins clump together and lose function. When they react with lipids, the lipids aggregate. When they react with DNA, the genes get damaged and are left unrepaired. THAT is what we call cellular waste."

 

Dr. Lee "Exactly. Cells may seem tiny to us, but they're actually more than 1,000 times larger in volume than a microbe. On average, each cell contains 200 to 300 mitochondria. Mitochondria are nicknamed the cell's power plants. Liver cells, which work especially hard, contain 1,700 to 2,200 mitochondria each (Lane, 2005). So even when several or several dozen mitochondria malfunction, the cell often leaves them in place. As damaged mitochondria accumulate, ROS production rises and ATP generation falls — and disease and aging follow (Figure 3-4)."

 

Figure 3-2. Cellular energy production proceeds through three stages: glycolysis, the TCA cycle, and the electron transport chain.

Glycolysis occurs in the cytoplasm without oxygen, producing 4 ATP. The TCA cycle and electron transport chain take place in the mitochondria and produce 32 ATP.

 

Figure 3-3. Consumption and regeneration of ATP.

ATP releases energy by splitting into ADP and inorganic phosphate (Pi). Energy can be understood as movement or change of form.

Cleaning Out Cellular Waste Restores Youth and Vitality

Cleaning Out Cellular Waste Restores Youth and Vitality

Grace "Doctor, if we clean out the waste inside our cells, can the cells truly become young again?"

 

Dr. Lee "Yes. By the way, do you know what percentage of our body is water?"

 

Grace "About 70 percent, I believe."

 

Dr. Lee "Yes, that's right. In children the figure is even higher — about 80 percent of body weight. In adults it's 70 percent, and in the elderly it falls to around 60 percent. Some scientists describe aging as the gradual loss of water from the body."

 

Grace "Why does our water content decrease as we age?"

 

Dr. Lee "It can be inferred that as cellular waste accumulates, it occupies space that would otherwise hold water — so the water content gradually decreases."

 

Grace "Then if we clean out the waste, the water content can rise again, and we can effectively rejuvenate? That would be wonderful."

 

Dr. Lee "Yes. Studies in humans report that body water content increases by about 10 percent during fasting. In experimental organisms commonly used in research — tapeworms, fruit flies, and mice — caloric restriction has been shown to extend lifespan by 20 to 50 percent. In humans, residents of Okinawa who consume about 62 percent of the recommended caloric intake show mortality from cerebrovascular disease, cancer, and heart disease at only 59 percent, 69 percent, and 59 percent of the rates seen in the general population, respectively."

 

Grace "Why does caloric restriction extend lifespan?"

 

Dr. Lee "Excellent question. Scientists cite several mechanisms. Above all, ROS levels decrease. Excessively enlarged fat cells produce both ROS and toxins called adipokines. So when calories are restricted, fat cells shrink, reducing oxidative stress and inflammation. As fat cells and total body fat decrease, cellular sensitivity to nutrients improves, and metabolic efficiency rises. This in turn lowers cardiovascular risk. Less DNA damage means lower rates of cancer and type 1 diabetes. A drop in core body temperature also contributes to longevity. Faster metabolism raises body temperature and shortens lifespan. In fact, vegetarians have been reported to have body temperatures about 0.5°C lower than omnivores."

 

Figure 3-4. Health is maintained when ATP is high and ROS is low.

Conversely, when ATP falls and ROS rises, the body progresses toward disease and death.

When You Fast, Cells Clean Themselves

Grace "So if water content increases during fasting, does that mean fasting actually clears out cellular waste? And could it improve various diseases?"

 

Dr. Lee "Yes. As shown in Figure 3-5, the over-consumption of meat, refined wheat, white rice, sugar, and carbohydrates leads to caloric excess, which then progresses to abdominal obesity, fatty liver, and atherosclerosis. Excess lipids overflow into the bloodstream as hyperlipidemia, and these lipids compete with glucose for oxidation as energy substrates. The unburned glucose accumulates and progresses to diabetes. Diabetes in turn slows microcirculation, leading to necrosis in the optic nerve and the extremities. Where oxygen flow is impaired, inflammation, cancer, and dementia advance more rapidly. So solving the original cause cuts off the entire cascade — and this is one of the core principles of natural healing. In fact, caloric restriction lies at the foundation of essentially every natural healing tradition worldwide."

 

Dr. Lee "Yes, that interpretation is correct. When you fast, the waste inside cells is cleared away. The technical term for this process is autophagy, from auto- (self) and phagy (to eat) — literally 'self-eating.' This was the subject of the 2016 Nobel Prize in Physiology or Medicine."

 

Zoe "Wow — the discovery that fasting cleans out cellular waste won a Nobel Prize? Then there must be plenty of research on autophagy."

 

Dr. Lee "Yes. As Figure 3-6 shows, research grew sharply starting around the year 2000. Then in 2016, Professor Ohsumi received the Nobel Prize in Physiology or Medicine for his work on autophagy."

 

Figure 3-5. How nutritional excess produces metabolic syndrome.

The various symptoms of metabolic syndrome trace back to nutritional overload. Therefore, weight loss is the central element in healing metabolic syndrome and should come first. The plant-based ketogenic diet supports weight loss while supplying needed nutrients without hunger.

The Five Stages of Autophagy and the Lysosome

The Five Stages of Autophagy

Zoe "Doctor, as you suggested, last week I searched online for autophagy. Yoshinori Ohsumi of Japan won the 2016 Nobel Prize in Physiology or Medicine for it. The citation says he discovered the genes related to autophagy in yeast. But isn't yeast just the microbe used to brew beer and bake bread?"

 

Dr. Lee "Yes. Yeast is widely used in beer-making and bread-making, but although small, it is a eukaryote and therefore widely used in genetic research. A eukaryotic cell has a nuclear membrane that encloses its DNA. Metabolically, yeast also has mitochondria, which allow significant energy production. Remarkably, even when 47 percent of yeast genes are replaced with human equivalents, the yeast still survives."

 

Emily "Why are autophagy-related genes needed in the first place?"

 

Dr. Lee "Genes exist to produce proteins. To understand this, it helps to first see how autophagy unfolds (Mizushima & Komatsu, 2011; Yang & Klionsky, 2010; Glick et al., 2010). As we discussed last time, autophagy is the process of breaking down waste inside the cell. That waste includes damaged mitochondria, aggregated proteins, aggregated lipids, aggregated carbohydrates, and damaged genetic material. When does this internal cleanup actually take place?"

 

Zoe "You said last time, Doctor — that autophagy starts when we go hungry, that is, when we fast."

 

Dr. Lee "Yes. When we don't eat, no nutrients reach the cells from outside. But the cells still need energy to survive, so they begin using nutrients stored inside themselves. The first thing they reach for is the waste that's been sitting there."

 

Susan "But to clean up waste, you need cleaning tools. Are there vacuum cleaners or brooms inside the cell?"

 

Dr. Lee "Excellent question. Yes — cells have cleaning tools. To break down waste, the cell first builds a lipid membrane around it. It's like wrapping a building in scaffolding when you renovate. This is where the autophagy genes — that is, the proteins they produce — come into play. Autophagy proceeds through five stages: nucleation, expansion, maturation, fusion, and recycling (Figure 3-7). Nucleation is the formation of the seed of an isolation membrane. Expansion is the growth of that membrane around the waste. The completed isolation membrane is called the autophagosome — that's the maturation stage. The autophagosome then fuses with a lysosome to form an autolysosome. The names aren't really what you need to remember. The lysosome is essentially a sac containing 50 to 60 different acid hydrolases (Figure 3-8). Think of them as digestive enzymes — like the ones secreted when you eat. These hydrolases break down the aggregated proteins, lipids, carbohydrates, and damaged mitochondria inside the autophagosome. Once digestion is complete, the resulting nutrients are recycled."

 

Susan "Ah, so it's like wrapping scaffolding so passersby don't get hit by falling bricks during renovation?"

 

Dr. Lee "Exactly. Only the waste gets digested, while the rest of the cell stays safe. Building that membrane requires proteins — and proteins are made from genes. The genes carry the information for which proteins to make. So autophagy requires proteins, and the genes that encode those proteins are precisely what Professor Ohsumi discovered, which earned him the Nobel Prize."

 

Figure 3-6. Autophagy-related research.

Studies on autophagy expanded rapidly beginning in the 2000s.

 

Figure 3-7. The five stages of autophagy: nucleation, expansion, maturation, fusion, and recycling.

The Lysosome: A Cellular Sac of 50+ Acid Hydrolases

Zoe "Once a lipid membrane wraps around the waste, does the waste then break down on its own?"

 

Dr. Lee "Excellent question. No, it doesn't break down spontaneously — enzymes are required. Once the lipid membrane wraps the waste, that structure is called an autophagosome. The autophagosome then fuses with a lysosome. The lysosome is one of the cell's organelles — a sac containing a variety of digestive enzymes (Figure 3-8). Cellular organelles are functional units within the cell, just as our body has organs with specialized roles: the heart pumps blood, the brain handles thought, the liver synthesizes enzymes and detoxifies, and the kidneys excrete waste through urine. Just like the body, the cell has its own miniature organs — the organelles. Lysosomes contain 50 to 70 different acid hydrolases."

 

Zoe "I get 'hydrolase' — an enzyme that breaks things down. But what does 'acid hydrolase' mean?"

 

Dr. Lee "The 'acid' part means the enzymes are activated under acidic conditions. The 'hydrolase' part means that water molecules are used in the breakdown reaction."

 

Grace "So for the lysosome to become acidic, hydrogen ions must be pumped into it?"

 

Dr. Lee "Yes, exactly. 'Acidic' means a high concentration of hydrogen ions (protons). And pumping protons into the lysosome consumes ATP. Do you remember when I said that fasting can be dangerous for those who are physically weak?"

 

Grace "Yes, I remember. You said to fast only when the body has reserves of strength."

 

Dr. Lee "Exactly. For cellular waste to be broken down, the acid hydrolases must be activated, and that requires ATP to drive proton transport. In a frail person, ATP may be insufficient, so the cellular cleanup can stall. The undigested toxins can then make health worse rather than better. Max Gerson, the famous figure in natural healing, struggled exactly with this problem — toxins released during fasting. At the time, the sponge effect of dietary fiber and its detoxifying role had not yet been studied."

 

Zoe "So even cleaning requires energy. And once the lysosomal hydrolases break down the waste, can the products be reused as nutrients?"

 

Dr. Lee "Excellent question. Aggregated proteins are broken down into amino acids. Aggregated carbohydrates are broken down into glucose. Damaged DNA is broken down into nucleotides. These basic units are identical to the nutrients we obtain from food."

 

Zoe "Ah — so it's like dismantling an old wall back into bricks, then using those bricks to build a new house?"

 

Dr. Lee "Yes, a beautiful analogy. The recycled nutrients can be used both as energy substrates and as building blocks for new cellular structures."

 

Figure 3-8. Activation of acid hydrolases in the lysosome.

ATP energy is required to drive hydrogen ions into the lysosome.

Phagocytes, Zombie Cells, and Macrophages

When the Body Is Full, Cells Stop Cleaning and Leave Waste Behind

Susan "Doctor, can lysosomes also break down microbes that have invaded the body — back into basic units?"

 

Dr. Lee "Yes. Among immune cells, the very first line of defense — innate immunity — consists of phagocytes (Murphy & Weaver, 2017). Dendritic cells and macrophages are the classic examples (Underhill & Goodridge, 2012). They engulf invading microbes to defend the body, and the engulfed microbes are then broken down to basic units by the lysosome's hydrolases."

 

Grace "That must be why people say to fast when you're sick. Dogs and animals in nature stop eating when they're ill."

 

Dr. Lee "Exactly. When you don't eat, immune cells become hungry and patrol the body more aggressively, hunting down microbes (Figure 3-9). Experiments show that a single macrophage can engulf up to 12 other cells. So even macrophages stop hunting when they're full. Notably, eating saturated fat slows macrophage activity."

 

Grace "So digesting cellular waste and activating phagocytes is essentially reversing aging — a true rejuvenation process?"

Zombie Cells and the Macrophages That Devour Invaders

Emily "I remember you said the average cell lifespan is 8 to 14 months. Does that mean macrophages eat cells at the end of their lifespan and recycle them as nutrients?"

 

Dr. Lee "Yes. The classic example is red blood cells. As I mentioned, red cells live 90 to 120 days. When the cell membrane begins to deteriorate and they can no longer function, macrophages engulf them and split them into heme and globin. The iron from the heme molecule is recovered and reused in the body. The body needs about 10 mg of iron per day, of which 9 mg is recycled by macrophages and only 1 mg has to come from food (Andrews, 2008)."

 

Emily "Wow — the body really is a master of recycling."

 

Dr. Lee "Haha, you could say that. The body recycles many of its nutrients through autophagy, hydrolysis, and similar processes. So when this recycling falters, waste accumulates, water content drops, and cellular structure and function deteriorate. We call that aging — or disease. In a sense, aging IS the accumulation of waste inside cells. And there's one concept we can't leave out: zombie cells and macrophages."

 

Zoe "Zombies are dead people who attack the living, right? So zombie cells would be dead cells that affect the body?"

 

Dr. Lee "Yes. Do you have any idea how many cells our body produces over a lifetime?"

 

Zoe "If a cell lives about a year and we live 80 years, then we'd produce about 80 times the number of cells in our body."

 

Dr. Lee "That's one way to estimate it. But of the roughly 37 trillion cells in our body, about 20 to 25 trillion are red blood cells — about 84 percent. And red cells live only 90 to 120 days. So the actual figure isn't 80 times but about 500 times. Even at 100 years of life, that's roughly five times the body's cell count dying every year. We have to clear away that many dead cells every year."

 

Zoe "Wow — so the saying that you have to keep your blood clean to stay healthy isn't empty wisdom. And since red cells turn over every 3 to 4 months, even a few months of careful living should improve health noticeably."

 

Dr. Lee "Exactly. That's why traditional devotional prayer in Korea is called the Hundred-Day Prayer. Even our ancient Dangun myth describes the bear and the tiger spending a hundred days in a cave, eating only mugwort and garlic in a fasting practice in order to become human."

 

Figure 3-9. Microglia of the brain (yellow) engulfing a dead neuron — a zombie cell — shown in purple.

The microglia detects the dead brain cell and digests it completely within 166 minutes.

Two Kinds of Specialized Phagocytes: Circulating Monocytes and Resident Tissue Phagocytes

Emily "So zombie cells are dead cells that haven't been cleaned up and are still hanging around the body. And these zombie cells must cause problems."

 

Dr. Lee "Yes. The professional cleanup cells that specialize in removing dead cells are called macrophages. Phagocytes are divided into specialized and non-specialized phagocytes. The specialized ones are further divided into those that circulate in the blood and those that reside in tissues."

 

Dr. Lee "Tissue-resident phagocytes are also called the mononuclear phagocyte system or the reticuloendothelial system. Specialized phagocytes go by different names depending on where they reside: Kupffer cells in the liver, type II alveolar cells in the lungs, microglia in the brain, renal interstitial macrophages in the kidney, splenic macrophages in the spleen, osteoclasts in bone, and Langerhans cells in the skin (Hume, 2008). Monocytes circulate in the blood, and when they encounter activating signals, they transform into giant macrophages. It's a bit like a person turning into the Hulk under stress."

 

Dr. Lee "Experiments show that a single macrophage can engulf at most about 12 dead cells. Once a macrophage is full, it stops eating — even if dead cells are still present. Long-chain saturated fat in particular slows macrophage activity. This is one of the reasons to reduce meat intake."

 

Dr. Lee "Yes, the rejuvenation process is closely tied to cellular cleanup (López-Otín et al., 2013). So fasting once a year to clear out cellular waste is generally a good idea."

Ketones, Autophagy, and the Practice of Fasting

Ketones Rise During Fasting and Promote Autophagy

Zoe "You mentioned that fasting triggers autophagy. And in our last session, you said ketones rise during fasting. What's the relationship between rising ketones and autophagy?"

 

Dr. Lee "Excellent question. We'll go deeper later, but in short: rising ketones promote autophagy. Ketones aren't just an energy substrate — they also serve as signaling molecules that activate autophagy. Figure 3-10 shows the trajectory of my own ketone levels during a 10-day fast. By day 2, ketones had already risen to about 4 mM. This was likely because I have a low body weight relative to my height, and I had already been on a ketogenic diet for several days beforehand. In that state, autophagy was likely proceeding rapidly inside my cells."

 

Figure 3-10. Changes in ketone bodies and blood glucose during a 10-day fast.

Hunger Subsides 2 to 3 Days into a Fast

Zoe "I know a yoga practitioner who fasts once a month without fail. I now realize they fast precisely to clear out the body's waste so they can practice yoga in a better state. From now on, when I feel hungry, I can think of it as my body and zombie cells getting cleaned up."

 

Dr. Lee "Exactly. You may feel hungry, but after about 2 days the hunger fades. The hypothalamus suppresses appetite. Meanwhile, phagocytes patrol every corner of the body, hunting down zombie cells, cancer cells, and various lurking microbes and viruses, breaking them down for use as nutrients. There's a Russian proverb:

"A one-week fast heals diseases of the body.
A two-week fast heals diseases of the mind.
A three-week fast heals diseases of the soul."

That's all for today, everyone. See you next time."

References