Does wearing sunglasses cause anaemia?

Yes it can, and to tell you how it does I need to introduce to you two nutrients. 

1. Folic Acid; it is one of the vitamin in the B complex group. Among it's many functions one very important is the role it plays in manufacture of red blood cells (RBC's are small cell's in your blood that transport oxygen, Anaemia is a fancy name for their deficiency)

2. Vitamin D; Body produces its own vitamin D from cholesterol in the presence of ultraviolet light (UV).

Like you can see, our body needs the UV light for Vitamin D production, but the same UV light is quite deadly for Folic acid and can destroy it. So the body has to hit a balance between the UV light it receives, not too much not too less. To maintain this balance it pulls a pretty neat trick. 

Introducing Melanin; Melanin is a pigment that gives our skin its colour, most importantly it is body's natural sunscreen, blocking the UV rays. The amount of Melanin is controlled by the boss of all glands,the Pituitary. Whenever you are exposed to sunlight, the Pituitary gland goes into an overdrive, cranking up melanin production to protect the body's Folic Acid reserves. When you come into a shady area, it reduces melanin production to keep Vitamin D manufacture unaffected (which needs UV). So how does the pituitary, which is located in a dark corner of the brain, know whether there is sunshine or not? It has its own spy-cam,

your eyes. When sunlight falls on the optic nerve, it triggers the pituitary to produce melanin or reduce it when there is no sunlight. So when you wear those fancy sunglasses and walk in sunlight, your pituitary thinks

that you are still in the shade. Melanin production is still at the shade levels. However, the UV light is now destroying your Folic acid en masse. Over a period, your Folic acid reserves deplete, which leads to a fall

in RBC production leading to anaemia. Phew! So next time you think you have anaemia, and pop in that iron supplement, try popping out those Ray-Ban's. Your doctor never told you this did he/she?