Question

1) In many third world, grain-eating countries, middle-aged people go blind. Why do you think this happens?

2) As you go up in altitude, why do your ears feel like they clog up? You yawn to retrieve this feeling, Why does it help?

Answer 1

1) In the grain eating third world countries, the people go blind. The main reason for this blindness is Vitamin A deficiency which is generally associated with less or no dietary intake of preformed vitamin A and its precursors. Most of the people in these countries take staple food (boiled rice, cassava roots, etc) Insufficient dietary intake of vitamin A lead to decreased levels of serum vitamin A, thus lead to blindness.

2) As we go up in altitude, our ears feel like clogged. This is due to the difference in air pressure on either sides of the eardrum. Yawning can help to retrieve this feeling as it opens the eustachian tube and allows air to flow into or out of the middle ear thus balance the pressure on either side of the eardrum.