What and how much should I eat?
The science of eating: Nutrition answers all your questions!

When we say 'nutrition', many people think of it as something boring and dull.
Sometimes I wonder if it is really called ‘academic’.
In an age where everything is abundant, you might think that there is no need for diseases like malnutrition that are caused by not eating enough.
However, as we enter an era of excess, a new type of nutritional 'deficiency' is emerging.
Diets that are baseless and claim to be healthy or fit tempt us with plausible names and theories.
"Nutrition Lectures That Are as Fun to Read as a Novel" is a lecture that explains from the basics what a "balanced, good diet" and "nutritious food" are.
It scientifically explains how omnivorous humans should choose and eat food well to sustain life and live a healthy life.
This book explains all knowledge about nutrition, including nutrition, nutrients, and the process of food intake, digestion, absorption, and metabolism, step by step.

Since ancient times, food has been considered the source of life and living, and from this perspective, numerous health and wellness methods have been created.
Not only that, but the treatment also includes diet, which has supported human health and medicine for a long time.
However, these methods remained mostly empirical practices, such as food selection and classification, consumption of certain effective foods, and exclusion of harmful foods, and did not develop into part of life science.
Nutrition, on the other hand, has developed into a discipline that seeks the source of life in food.
As a result, nutrition has been able to scientifically elucidate the relationship between food, life, and health through nutrients by identifying the components that sustain life and clarifying the foods that contain those components.
--- p.21

Protein comes from the Greek word meaning 'first, most important'.
Proteins are made up of amino acids, which contain nitrogen in addition to carbon, hydrogen, and oxygen, and are the main components of organs, muscles, skin, hair, hormones, enzymes, and antibodies.
In other words, the main component that makes up the human body is protein.
Unlike carbohydrates and lipids, which are also energy sources, proteins contain about 16% nitrogen and cannot be replaced by carbohydrates or lipids.
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When blood sugar levels rise after a meal, the satiety center is stimulated by glucose, causing a feeling of fullness.
When the satiety center sends information to the body that it has received sufficient energy, food intake is stopped.
On the other hand, as time passes after a meal and the body's energy is consumed, blood sugar levels drop, and to replenish this, body fat is broken down, releasing free fatty acids.
When the feeding center is excited by the stimulation of free fatty acids in the blood, a feeling of hunger is felt, which soon leads to food intake.
--- p.89

In the liver, bile acids are synthesized from cholesterol, and these bile acids are secreted into the duodenum to aid in the digestion and absorption of lipids.
Bile acids are surfactants with both water-soluble and fat-soluble portions.
These properties allow water and fat soluble substances to mix, contributing to the digestion and absorption of fat.
It acts as a surfactant, so to speak, like soap.
About 95% of bile acids that have completed their function are reabsorbed in the ileum and returned to the liver for reuse (enterohepatic circulation).
About 5% that is not reabsorbed is excreted in the stool.
These metabolisms are the main route by which cholesterol is excreted from the body.
--- p.121

As we age, the efficiency of protein utilization decreases, so we must actively consume protein foods.
Fat is an important nutrient that provides energy efficiently due to its high energy density.
Analysis of nutrient intake in the elderly showed that in addition to protein, intake of antioxidant vitamins such as vitamin C and vitamin E, as well as vitamin D and folic acid also tended to decrease.
To prevent locomotive syndrome (motor phase syndrome), it is emphasized that sufficient intake of calcium, vitamin K, vitamin B6, and vitamin B12 is necessary.
--- p.166

Diabetes is a disease in which blood sugar levels become abnormally high due to insufficient insulin secreted from the pancreas or impaired insulin function.
If this hyperglycemic state persists for a long time, it can cause abnormalities in carbohydrate or fat metabolism, which can lead to complications such as arteriosclerosis, kidney disease, retinopathy, and neuropathy (Figure 3).
The basic principle of a diabetic diet is to keep various metabolic processes, including carbohydrate metabolism, as close to normal as possible, and to prevent complications by preventing the worsening of the disease.
--- p.179

There is no special diet that directly increases the effectiveness of cancer treatment.
However, diet is used as an adjuvant therapy when undergoing cancer treatment such as surgery, radiation therapy, and chemotherapy.
As cancer progresses, symptoms or side effects of surgery, radiation therapy, chemotherapy, etc. can impair the ability to eat, chew, swallow, digest, and absorb food.
As a result, if nutritional status deteriorates, it can impair the effectiveness of various treatments, delay recovery, and lower the patient's quality of life.
Therefore, it is necessary to restore the patient's nutritional status by utilizing various nutritional supplement methods.

--- p.191