Nutrition and Food Choices Overview

Nutrition

• Nutrition is the study of how the body uses nutrients for energy, growth and regulation at the cell, tissue, and whole-body levels.
• It encompasses food composition, ingestion, digestion, absorption and transport of nutrients and functions, and disposal of byproducts of metabolism.
• The science of nutrition is evolving with more evidence-based research to replace older questionnaires and correlational studies that lack data precision and reliable variables.

Food Choices

• Individual responses to food vary, so a "one-size fits all" approach seldom works; identifying diets tailored to individual needs is essential.
• Animal activism, climate issues, and religious beliefs often influence dietary choices and can lead to confusion and diversion from preventive health promotion.
• Randomized Clinical Trials are valuable; they allow for more control and give superior quality data when studying the effects of specific foods/nutrients on health or disease.

Composition of the Human Body

• The human body is formed of approximately 27 elements.
• The most common elements are Oxygen, Carbon, Hydrogen and Nitrogen which comprise 63%,18%, 9% and 3% respectively.
• Water constitutes 55-65% of body mass, and protein and lipids together contribute about 30-40%
• Nucleic acids, carbohydrates, and other organic molecules make up the remaining 1%, and minerals account for 5%.

Introduction to Macronutrients

• Carbohydrates: Made of carbon, hydrogen, and oxygen, primarily used as fuel (starch and sugars).
• Lipids: Fats and oils are essential for various bodily functions (energy storage, insulation, cell signaling, etc), also carrying fat-soluble vitamins (A, D, E, K); the primary lipids are triacylglycerols, and phospholipids.
• Proteins: Organic compounds composed of amino acids; used in various cellular processes (structure, function). Of particular importance are amino acids such as leucine, tryptophan, methionine, valine and phenylalanine, isoleucine, threonine.

Introduction to Micronutrients

• Minerals: Essential inorganic substances in health (macrominerals like calcium, sodium, chloride, potassium, etc.), and micro(trace) minerals, like iron, zinc etc
• Vitamins: Organic substances that facilitate important chemical reactions in the body; vitamins are classified into fatsoluble and water-soluble vitamins.

Digestion and Absorption

• Digestion begins in the mouth (chewing and saliva); the stomach further mixes food.
• The small intestine is where most digestion and absorption happens, using enzymes and digestive juices; this is supported by accessory organs such as the pancreas.
• The large intestine absorbs water and electrolytes, and stores indigestible material prior to excretion.

Importance of Water

• Water is essential, and we can survive longer without other nutrients than water.
• It facilitates various bodily functions and a key component of the body's transport system.
• It is divided into compartments like intracellular, extracellular (interstital and plasma) and transcellular fluids.

Brain Metabolism

• The brain has a high metabolic rate, relying primarily on glucose for energy.
• The blood-brain barrier restricts fat usage, therefore the brain strongly relies on glucose for its energy needs.
• Insulin does not affect the amount of glucose absorbed in the brain but plays a role in other parts of the body.

Homeostasis of Glucose

• Normal glucose levels are maintained through the interplay of insulin, glucagon, and other hormones,
• Insulin promotes glucose uptake by cells, while glucagon increases glucose levels
• Glucose homeostasis is influenced by both hormonal and neural controls.

The Glycemic Index (GI)

• Glycemic index (GI) measures how quickly a food causes an increase in blood sugar levels.
• Glycemic Load (GL) is similar but accounts for portion size.
• Foods with high GI can trigger large rises blood sugar and influence related comorbidities.

Fiber in the Diet

• Fiber is any carbohydrate that cannot be digested or absorbed by the human body.
• It has many beneficial effects on digestion and health overall including cholesterol reduction and gut health.
• Types of fiber include soluble and insoluble types which serve different functions.

Importance of the Gut Microbiota

• The gut microbiota contains a diverse and vast collection of microorganisms.
• This community plays essential metabolic roles (production of certain vitamins).
• Gut-microbiota is influenced by the food choice, and these changes may cause significant issues.