A Breath of Fresh Air: Perspectives on Inhaled Nutrients and Bacteria to Improve Human Health

Abstract

We propose that the human respiratory system and olfactory pathways sequester airborne nutrients (vitamins, fatty acids, and trace minerals) that are beneficial for health, which we term "aeronutrients." In addition, airborne bacteria, termed "aeromicrobes," have the potential for positive health effects by improving species diversity in the microbiotas of the respiratory and gastrointestinal tracts. These concepts have implications for people living in urban areas or those who have limited access to nature, such as astronauts exposed for long periods to highly filtered air that may be depleted of aeronutrients and aeromicrobes. The possibility that fresh air contributes to human nutrition and health may stimulate a re-evaluation of guidelines pertaining to nutrition and access to natural environments, and will open new avenues of scientific enquiry.

Keywords: aeromicrobe; aeronutrient; gastrointestinal tract; lung; microbiome; nature; nutrition.

FIGURE 1

Routes of entry into the human body by aeronutrients and aeromicrobes. Aeronutrients have 3 primary routes of entry into the body: 1) Inhaled micronutrients are absorbed through the microvessels lining the nasal cavity that drain into several veins that take blood directly to the heart. 2) The olfactory epithelium at the apex of the nasal cavity enables aeronutrients to be transported along olfactory axons into the olfactory bulb and thence to limbic regions of the brain, bypassing the blood–brain barrier. In addition, aeronutrients can diffuse through the fluid-filled spaces surrounding the axons that lead into the cerebrospinal fluid (CSF) of the brain. 3) The lung alveoli are a site of entry for aeronutrients. Capillaries lining the alveoli have a massive absorptive surface that transports aeronutrients directly to the heart. Aeromicrobes have 2 primary routes of entry into the body: 1) Aeromicrobes seed and replenish populations of commensal bacteria in the nasal cavities and respiratory pathways. 2) Aeromicrobes in the oropharynx can enter the gastrointestinal tract by ingestion or by mucociliary clearance to seed the gut microbiome. Dark green circles = aeronutrients; Light green circles = aeromicrobes. CSF, cerebrospinal fluid.