As a nutrition doctor, I know a lot about diet and disease treatment and prevention, but beyond the basics, I didn’t know if there was a diet or supplements that could help (or hinder) my progress.
To get some answers, I reached out to Elizabeth Broad, senior sports dietician for the US Olympic Committee and Jose Antonio, founder of the International Society of Sports Nutrition.
Diet versus supplements
Broad explained that even at the elite athlete level, she always takes the food-first approach to nutrition. She assured me that by eating a healthy and balanced diet, including eating lots of colorful fruits and vegetables, whole grains and adequate amounts of high quality protein including dairy, meat, fish, chicken and eggs, most athletes could get everything that they needed for both training and competing from their diet without turning to supplementation.
The only exceptions were in the case of vitamin D or iron deficiency, both of which can impair performance and often require supplements to restore normal levels in the body. On the other hand, studies of high dose vitamin C and E supplementation suggest that they can actually diminish a person’s response to training, so you are much better off getting those antioxidants — which are important for both training and recovery — from food.
For protein intake, Broad recommended 1.2 to 1.7 g/kg per day (higher than the recommended daily intake of 0.8 g/kg for the average person) to help with recovery and adaptation to training which includes muscle, blood vessel and red blood cell development. She emphasized the importance of distributing protein evenly throughout the day, including at least 20 to 25 grams of protein at breakfast, lunch and dinner and within two hours after training.
Jose Antonio, founder of the International Society of Sports Nutrition, recommends even higher levels (up to 2.2 g/kg to optimize recovery) because, he explained, slightly higher levels of protein can be especially beneficial in athletes looking to improve their body composition (lose fat and gain muscle) since protein tends to be more filling.
However Antonio and Broad agree that training is not the time for strict dieting or calorie cutting, which can impair both training and recovery. They also recommend whey protein as a good choice if you find it more convenient to add in a protein supplement to meet your daily protein needs. Whey protein contains all of the essential amino acids (building blocks of protein) including leucine, which is especially beneficial for stimulating muscle growth.
Regarding the ketogenic diet (low carb, high fat), both Broad and Antonio were not fans. Broad explained that despite the argument that low carb, high fat diets increase the use of fat for fuel during exercise, which seems like a good thing since we all have a lot more stored fat than stored carbohydrates, this type of diet is actually detrimental to mental function, immune function, and offers no performance benefits. In fact, a 2017 study showed impaired performance among elite race walkers following a low carb, high fat diet.
Food and drink during the race
When it comes to eating and drinking during training and races, both Broad and Antonio emphasize the importance of trying out different fueling and hydrating approaches during training to assess your tolerance and performance benefits. This also trains your gut to get used to digesting during exercise.
Some sports drinks and carbohydrate/electrolyte products such as gels and gummies can be a little rough on your digestive system if you aren’t used to them, and different products contain varying concentrations and types of carbohydrates and electrolytes, so take some time to figure out your individual preferences and needs.
If you are training or competing for less than an hour, as long as you have a balanced pre-race meal a few hours beforehand, water is the only thing you need during the workout or race. For sessions or an event longer than 90 minutes, it is important to take in carbohydrates, 30 to 60 grams per hour, in the form of food or supplements to replenish your muscle glycogen stores (sugar stored in your muscles). Glycogen stores are specific to each muscle group, so even if your overall stores of glycogen are high, you can still run out in specific muscles if you don’t take in carbs during longer sessions.
Salt (sodium) supplementation is also important to maintain both mental and physical performance if you sweat a lot or are training or competing in hot weather. According to Broad, there are lots of recipes online to make your own sports drink if you want to customize both the taste and the composition (in addition to saving money). Taste buds change during exercise, she explained, and many people find commercial sports products too sweet.
In terms of performance enhancement for endurance exercise, the only proven supplement is caffeine, which most Olympic endurance athletes use regularly, according to Broad. A 2018 review paper confirms a small but significant effect of 3 to 6 mg/kg of caffeine, but individual tolerance and response varies so it is important to test it out during training if you plan to use caffeine during competition. Broad recommends 1.5 to 6 mg/kg taken one hour before the start of your race, and for longer events, you can take a second, smaller dose about halfway through your 25-mile bike ride (for an Olympic distance triathlon) to give it enough time to kick in during the run.
A 2013 study found that both coffee and caffeine supplements are equally effective, but if you want to make sure to get the correct dose, you are probably better off taking a supplement, according to Broad, as the caffeine level in coffee can vary. Some gels contain caffeine, if you want to try this strategy before or during the race. You can take a caffeine tablet if you don’t use gels.
Some athletes utilize beetroot juice, which increases levels of nitric oxide, a gas that can help increase blood flow, oxygen uptake efficiency and power. A 2017 review showed contradictory findings, but overall the authors concluded that it may have benefits in endurance athletes. But some research suggests this may be negated by caffeine, so the jury is still out on this supplement. Antonio believes in the benefits, but finds the taste terrible. Broad is not convinced, and explained that eating spinach and beets, both good sources of nitrates (which turn into nitric oxide), likely makes this supplement unnecessary.
There are a few other supplements — probiotics, omega-3 fatty acids, curcumin, tart cherry juice and gelatin — that may provide some benefits in overall health and recovery. But supplements are not as carefully regulated as drugs and quality and dosing can vary considerably.
So, food first, along with adequate water intake, is without a doubt your best bet when it comes to improving endurance performance and overall health.