Chapter 25: Science of Nutrition in Modern Health- Part 1
Understanding the Basics of Nutritional Science !
It's a long read, but for all the subscribers who don't have time to read, you can listen to my Spyderdoc blog audio in the substack app.
One question on everyone's mind is, in this overabundant processed food world, what nutrition should nourish our bodies? Without food, we cannot survive; without survival, we cannot reproduce; without reproduction, humans don't exist. Returning to the million dollar question, What foods are best for me to eat to stay healthy longevity? Let's delve into the question sincerely, as this is more profound and personal. Even though I am looking for answers, I think I wouldn’t solve all queries on nutrition, but I definitely will try to get close.
Without food, we cannot survive; without survival, we cannot reproduce; without reproduction, humans don't exist.
One question that always bothered me was why the tiger or lion, for that matter, any wild animal, is not generally obese. Look around the wild animals and open the famous National Geographic wildebeest migration or the antarctic penguin dance. No matter where you look, you will find one thing the animals eat that is necessary for the body; they might undereat if they don't see the prey but never overeat. This raises the question, why? Why aren't they obese? Do they have extra digestive juices, or are they doing anything other than that they are not obese? They can be underweight if the food is scarce but never overweight or obese.
We are not animals with human touch; we are humans with animals instincts.
Our brains are typically wired in a specific way; evolutionarily, we eat when hungry. Hunger has played a fundamental role in human survival and development. This primary drive for food is essential; intellectual and cultural growth flourish only when food is plentiful. Without hunger, our species might have faced extinction long ago. But what exactly makes us feel hungry? Hunger is driven by a complex neurohumoral (neural and hormonal) process, which I will outline to better explain the mechanisms involved.
Hunger is controlled by a complex hormone system that signals the brain when to eat and when we're full. Some hormonal changes are happening in the brain; these hormones constantly affect the brain with feedback loops. When we are hungry, a hormone called ghrelin is secreted and ignites the brain, making us look for food. Ghrelin is often called the 'hunger hormone' because it stimulates appetite, increases food intake, and promotes fat storage. Do the experiment; when you quit lunch, dinner, or breakfast and are busy with something, you slowly notice a surge in your sharpness and focus. The ghrelin is overflowing at this juncture in the brain, advising the brain to look for food. This is the same hormone hunter-gatherers had and made them look for food(crazy).
Conversely, leptin, released by fat cells, signals when the body has enough energy stored, helping to suppress appetite and promote satiety. Another hormone, GLP-1(famous for Ozempic and Mounjaro for diabetes and weight loss), is released in the gut. It helps control blood sugar levels, reduces appetite after eating, and is implicated in diabetes and weight loss management. These hormones balance energy by coordinating hunger and satiety in response to the body's needs.
As early as 10,000 years ago, we lived in smaller groups, started to create tools, and started farming. This was the beginning of the understanding of the mass production of grains. The communities started to grow into bigger units, where the civilization start to take shape. We improvised large-scale farming and increased crop size to provide larger populations during this time. As the population increased and cities grew, our production capacity also increased. In the last 2000 years, we have had much more complicated complex systems and agricultural farming of trade and transfer of goods. Things have changed dramatically, especially in the last hundred years; it started with wars in the early 20th century; by mid-century, as the wars winded down, there was the industrialization of the food complex mass-producing systems for the populations at large, and this is when the starting of processed food, government programs with fortification became the norm. By the late 20th century, things had shifted to excess consumption of sugars, which was a pivotal moment in the food world. When diet has become not a necessity but a comfort and expectation. Our brain, which evolved to seek out high-calorie foods for survival, now faces an abundance of such foods, leading to overeating. Our stomach, designed to signal fullness, can be overridden by the brain's desire for more, leading to food addiction. This has contributed to the size and current epidemic that we are seeing more than half of the global population being overweight.
This is a fascinating picture of the fed and fasting states, with chemical reactions and the role of energy substrates (glucose and fats).
A Fed State:
During the fed state, as we can see in the above diagram, blood glucose is used in various functions utilizing ATP(energy). From the bloodstream to the liver and skeletal muscle for short-term storage to triglycerol and adipose tissue for prolonged storage.
B Fasting state:
This is how intermittent fasting works. When we stop eating for more than 12 hours, our bodies start knocking on the doors of fat cells, causing us to increase the fatty acids and glycerol, which convert to glucose for energy utilization and also convert to ketones for energy for the brain and skeletal muscle. Cellular energy sources…
To understand how energy storage works and what happens when we eat food, there are macro and micronutrients that we consume at any given time. Food undergoes a complex breakdown process when we eat, beginning in the mouth and continuing through the digestive tract. Enzymes in saliva, the stomach, and the small intestine break down macronutrients—carbohydrates, proteins, and fats—into smaller molecules. The micronutrients include vitamins, minerals etc.
Understanding the digestion process and how the glucose molecule turns into the powerhouses in mitochondria to produce energy as ATP(energy molecule) is essential. It can be very scientific, but I will make it simple. This is essential for future chapters to understand food energy balance and how we become overweight, obese, have metabolic dysfunction, etc. One must understand the fundamental mechanisms and make more cautious decisions when consuming food.
Every molecule we ingest is converted into energy that the body uses. All cells and tissues need energy to function properly, whether for movement, growth, or repair. The process of how our bodies convert food into energy is genuinely remarkable. For example, even while writing a blog, many cells simultaneously generate the energy needed. When we immediately consume more nutrients than the body needs, it stores the excess energy at the cellular level, primarily as glycogen or fat, to be used later. This efficient system helps the body manage its energy balance.
The ideal amount of carbohydrates to consume is less than 100 grams per day, especially for people with metabolic dysfunction, fatty liver, prediabetes, and diabetes and people who want to lose weight.
Also, moving after eating helps muscles absorb glucose better and minimize its presence in the bloodstream.
Glucose Metabolism(inside cell)…
Inside the cells, glucose is processed through a series of steps to produce energy molecules that fuel the body’s activities. Excess glucose is stored as glycogen in the liver and muscles for short-term energy. Any additional glucose beyond glycogen storage is converted into triglycerides in the liver and stored in adipose (fat) tissue for long-term energy. The liver plays a crucial role in maintaining energy balance by regulating blood glucose levels, releasing glycogen when needed, and converting excess nutrients into fat. Adipose tissue stores triglycerides that can be broken down into fatty acids and used as fuel during fasting or low-energy periods. This system ensures the body has a continuous supply of energy, with the liver storing up to 100 grams of glucose for immediate use and 300 grams for muscle use. Once glycogen stores are full, excess glucose is converted into fat for long-term storage.
Glucose enters inside the cell from absorption of food in the intestine —>GLUT transporters enter the cells—> Undergoes breakdown of glucose(glycolysis) in the cytoplasm—> Broken down to pyruvate releasing some energy ATP and NADH —> Pyruvate enters Mitochondria and converts to Acetyl CoA—>Krebs Cycle generates ATP/NADH/FADH2—> NADH and FADH2 carry electrons to the ETC in the mitochondrial membrane producing large number of ATP—> this is how energy is utilized.
In fat metabolism, stored triglycerides are broken down into free fatty acids and glycerol through lipolysis. These fatty acids are transported to cells, where they undergo beta-oxidation in the mitochondria to produce acetyl-CoA, which then enters the Krebs cycle(enzymatic reaction within mitochondria) to generate ATP (energy). If there is excess energy, acetyl-CoA can be converted back into fatty acids via lipogenesis and stored as triglycerides in adipose tissue for later use.
Elevated triglyceride levels can indicate excess energy storage and may signal early stages of prediabetes.
In protein metabolism, dietary proteins are broken down into amino acids, used to build tissues but can also be converted into energy. During this process, the nitrogen group is removed through deamination, producing urea as waste. The remaining carbon skeleton can be converted into glucose for energy or enter the Krebs cycle to produce ATP. Some amino acids are also converted into acetyl-CoA, fueling energy production, especially when glucose is unavailable.
We understand nutrition science better by examining cellular physiology and mechanisms as above. Our bodies are meant to thrive even when we sustain hardships. We are not meant to decay but to flourish and have a full life. Again, as I said earlier, if we provide the optimal environment for our bodies, we heal and prosper. Remember the Hunter-gatherers, around 10000BC? They were hunting and eating food at times once or twice a week. Insulin, a building hormone, helps store food for future availability as it helps them tremendously. In the present times, we continue to store food as our bodies think of future starvation(however, that never happens), which is our protective mechanism. The same hormone in excess is present-day diabetes, causing premature morbidity and mortality. The next chapter will look into the mechanisms of healthy eating and unhealthy patterns. Let's also look at the clinical nutritional studies in the next blog…
Suman Manchireddy MD FACP FHM, Internal Medicine, Leesburg, VA.
Email : Care@ReliantMD.com
Disclaimer: This is purely informational and educational purposes only, seek medical advise prior to starting any testing or treatment regimen. The data presented here is researched extensively and has been condensed for a broader audience.
References…
Stroke Revisited: Diabetes in Stroke - Glucose Metabolism
Textbook of Physiology by Ganong
Textbook of physiology by Guyton
WHO
TERRIFIC!!! I'm right there with you. We monitor our carb intake and try to spend more and more time in autophagy through either diet and IF or exercise (when I don't have two cracked bones in my foot from dropping a 45lb plate from waist high while loading the reclining squat machine). Eagerly looking forward to the next installment. THANK YOU for all of your work.