The fundamentals of any pre-race meal are: carbohydrates, moderate protein, fluids, and electrolytes (sodium is most common electrolyte). For those with sensitive stomachs, less fat and fiber would be beneficial, as well as having a liquid-based breakfast (i.e. smoothies), which is more easily digested.
Thankfully, there are many gluten- and dairy-free options out there today that fit the requirements above:
Gluten-free toast or rice crackers with a couple of eggs
Oatmeal with a scoop of peanut butter (higher in fat and fiber)
Gluten-free cereal with non-dairy milk that has at least 5 grams of protein per serving, such as soy milk
Smoothie made with non-dairy milk or yogurt, adding in fruit or a nut butter (if desired)
Consider dinner for breakfast: A small piece of chicken or fish with rice or a sweet potato
Whole-food protein options are preferred, but if none are available, a non-dairy protein powder such as soy, pea, hemp, etc. can be used.
There’s also the question of how much to eat. The simplest answer is: The longer the wait between breakfast and race time, the more you need to eat. If it is more than three hours, then you can have a good sized meal. If it’s less than two hours, you may do best with a snack or half-meal sized portion. Adequate pre-race fueling is more imperative in longer races, or races where you may be focusing on a PR.
A final thought: Any time your diet becomes restricted (due to a medical condition or personal preference), you need to increase your focus on getting adequate nutrients from those food groups elsewhere, such as finding non-dairy sources of calcium when dairy-free.
Jason Machowsky is a board-certified sports dietitian and certified strength and conditioning specialist at the Tisch Sports Performance Center at Hospital for Special Surgery. In addition to working with a variety of endurance athletes, he serves our nation’s athletes as an active member of the United States Olympic Committee Sports Dietitian Registry. Jason has written a number of Ask the Expert articles for the New York Road Runners, in addition to speaking at the TCS New York City Marathon Expo, the United Airlines NYC Half Experience, and the NYRR Learning Series. He received his Master of Science degree in applied physiology and nutrition from Teachers College at Columbia University.