Originally Posted by Dave Cutter

I read somewhere once years ago that doctors actually receive training on what people might mean when they use terms like "light headed". Since I am not a doctor.... I missed that training. So... I am going to overlook that part of your post (because it might require a doctor) and just respond to what jumps out at me.

People don't tend to get up at night to rehydrate and a half cup of milk on cheerios isn't a lot of hydration ether. A 20 mile ride before breakfast shouldn't be a problem for most people... as far as nutrition is concerned. But not hydrating is a common problem with cyclists. Often the breeze created by our speed makes it "feel" like we remain a lot dryer than we do. Cyclist sweat bunches.

Include a big glass of juice (or juice drink), coffee, or water with breakfast (or as soon as you get up). Then... rehydrate more often while cycling. Instead of taking on large amounts of fluids at one time. I use a "4 mile rule". A small drink of water (I often take green tea with me instead) every four miles... thirsty or not.