The phytochemicals in onions improve the working of Vitamin C in the body, for improved immunity.
Onions contain chromium, which assists in regulating blood sugar.
For centuries, onions have been used to reduce inflammation and heal infections.
Raw onion encourages the production of good cholesterol (HDL), thus keeping your heart healthy.
A powerful compound called quercetin in onions is known to play a significant role in preventing cancer.
Onions scavenge free radicals, thereby reducing your risk of developing gastric ulcers.
I dont think there is an upper limit in how many you can have at one time.
Read more:
http://www.care2.com/greenliving/8-great-reasons-to-eat-more-onions.html#ixzz2m21Rh8li