How to eat properly when cycling in extreme heat? In the US, we're in the middle of a heat wave. Temperatures are topping 100 degrees F and up in some areas. When touring, how should one's eating and drinking before and during a ride be changed to deal with heat like this? 

If I don't chicken out, I'll be touring this weekend. I've ridden in temperatures like this before, but I'd like to make sure I'm not missing anything obvious. 

The usual way I deal with heat is to drink lots of water, eat properly, reapply sunscreen more often, and don't ride too hard; conserve energy and take a break during the hottest part of the day. (Noon to three, in my experience.) I keep my helmet padding wet, and make sure to eat salty food. However, I'm not sure if I should eat and drink the same kinds of things. 

For during-the-ride food, I've packed dried fruit, nuts, trail mix, energy bars, and I have five water bottles that I keep topped off. 

I'll have a camping load - around 40 pounds of stuff - and I usually keep a pace of around 10mph. 

This ride will be mostly on the roads, in the Pine Barrens of New Jersey, so there won't be all that much climbing. 

Specifically:


Do I stick with protein the night before the ride and carbs after, or does the heat bring different requirements to the table? I'm a vegetarian when away from home, so that restricts what I can eat for my lunch breaks. 
In the past, I've eschewed sports drinks, but is important that I ingest electrolytes? Should I start looking into sports drinks?
It is extremely important that you eat and drink properly when cycling in extremes of temperature.

In Dubai, where riding in the summer means riding regularly in 50c temperatures, this is a major problem. 

Eating is less of a concern than hydration, but you want to avoid dehydrators, like alcohol, in your food. You also want to watch what spices and additives are present in your food, like high salt content, but your standard diet as noted (High protein  the night before, and carbs after a ride and assuming unsalted nuts and trail mix) should be fine to ensure energy. (Too much salt in one go can upset the stomach by drawing water into the gut, especially if you're already dehydrated. So it needs to be in small doses.)

Avoid sugary drinks, stick mainly with water, and electrolyte replacement drinks with low sugar content.

Desert survival expert Marjorie Woodruff recommends drinking a few ounces of water every 1o minutes if water is limited, and a minimum of 1 liter every 45 minutes if water is readily available. Electrolyte replacement s fairly essential, but can be accomplished far more inexpensively using a product like Elete Water because it can be carried easily, and a very small container is an effective add in to about 25 liters of water. It's mostly tasteless, but in our experience here in Dubai, very useful.

Proper clothing is essential. Cover your skin. Do not rely solely on sunscreens, as they do not prevent dehydration, although they are better than nothing. Better yet, do both.

Another essential in hot weather cycling, especially while touring, and deadly essential if touring unsupported is the ability to recognize and understand what is happening when you are affected by heat, and what it feels like.

This article from the Mayo Clinic has a pretty thorough examination of exercise in hot weather, and what the dangers and effect are. 


  How to avoid heat-related illnesses
  
  When you exercise in hot weather, keep these precautions in mind:
  
  Watch the temperature. Pay attention to weather forecasts and heat
  alerts. Know what the temperature is expected to be for the duration
  of your planned outdoor activity.
  
  Get acclimated. If you're used to exercising indoors or in cooler
  weather, take it easy at first when you exercise in the heat. As your
  body adapts to the heat over the course of one to two weeks, gradually
  increase the length and intensity of your workouts.
  
  Know your fitness level. If you're unfit or new to exercise, be extra
  cautious when working out in the heat. Your body may have a lower
  tolerance to the heat. Reduce your exercise intensity and take
  frequent breaks.
  
  Drink plenty of fluids. Dehydration is a key factor in heat illness.
  Help your body sweat and cool down by staying well hydrated with
  water. 
  
  Don't wait until you're thirsty to drink. If you plan to exercise
  intensely or for longer than one hour, consider a sports drink instead
  of water. 
  
  Sports drinks can replace the sodium, chloride and potassium you lose
  through sweating. Avoid  alcoholic drinks because they can actually
  promote fluid loss.
  
  Dress appropriately. Lightweight, loosefitting clothing helps sweat
  evaporate and keeps you cooler. Avoid dark colors, which can absorb
  heat. If possible, wear a light-colored, wide-brimmed hat.
  
  Avoid midday sun. Exercise in the morning or evening, when it's likely
  to be cooler outdoors. 
  
  If possible, exercise in shady areas — or do a water workout in a
  pool.
  
  Wear sunscreen. A sunburn decreases your body's ability to cool
  itself.
  
  Have a backup plan. If you're concerned about the heat or humidity,
  stay indoors. Work out at the gym, walk laps inside the mall or climb
  stairs inside an air-conditioned building. Understand your medical
  risks. Certain medical conditions or medications can increase your
  risk of a heat-related illness. If you plan to exercise in the heat,
  talk to your doctor about precautions.
  
  Heat-related illnesses are largely preventable. 
  
  By taking some basic precautions, your exercise routine doesn't have
  to be sidelined when the heat is on.