Oxygen-A Critical, but Overlooked, Nutrient.

Area of Science:

• Physiology
• Nutritional Science
• Biochemistry

Background:

• Gaseous oxygen (O2) is indispensable for aerobic respiration and ATP production.
• Oxygen is not traditionally classified as a nutrient due to its respiratory, rather than gastrointestinal, absorption.
• This classification overlooks O2's fundamental role in sustaining life and growth.

Purpose of the Study:

• To re-evaluate the classification of oxygen (O2) within nutritional science.
• To argue that the route of substance entry into the body does not preclude it from being a nutrient.
• To highlight the physiological and molecular consequences of oxygen deficiency (hypoxia).

Main Methods:

• Literature review and conceptual analysis of O2's role in metabolism.
• Comparison of O2's definition against standard nutrient criteria.
• Examination of physiological responses to varying oxygen levels, including gene expression changes.

Main Results:

• Oxygen meets the definition of a nutrient, providing essential nourishment for life and growth.
• Oxygen deficiency (hypoxia) occurs in various conditions, from high altitudes to specific tissues and diseases.
• Hypoxia triggers metabolic shifts to anaerobic glycolysis and activates hypoxia-inducible factor-1 (HIF-1).

Conclusions:

• Oxygen (O2) is a critical, yet overlooked, nutrient essential for aerobic life.
• Nutritional science should incorporate oxygen into its scope, recognizing its fundamental role.
• Understanding oxygen's nutrient status has implications for treating hypoxia-related conditions.