Supplements for Endurance Training

Endurance exercise can be physically demanding on the body, thus sleep and nutrition both play important roles for health, performance, and recovery. With a busy lifestyle and work schedule, it can often feel overwhelming trying to maintain a well-balanced diet and you may wonder if supplements are needed to help with your training sessions. The short answer is no, supplements aren’t necessary. In general, healthy diet can be sufficient. Supplements should only be used to supplement, or complement your diet regimen, and should never be used in replacement of a real whole foods diet. Supplements are generally not recommended unless prescribed by a medical health professional, but if you choose to take supplements, here are a few things to keep in mind:

1. Not all supplements are safe.

Although supplements are regulated by the FDA, the FDA does not test or approve them before they are sold on the market. There have been ongoing concerns with supplements contaminated with materials such as metals, toxins, and dioxins.

2. Do your research.

Don’t be fooled by packaging designs and promising health claims! Many supplements may claim to improve various health conditions and athletic performance without having any actual scientific evidence to back it up.

3. Supplements may be contraindicated with medications or exacerbate pre-existing health conditions.

Supplements can also cause unwanted interactions or alter the efficacy of medications. For example, Ginseng is promoted as a supplement to enhance immunity and overall health, however, studies have shown it reduces the effects of blood thinners and may your raise blood pressure if you are on diuretics. Garlic supplementation is believed to improve cardiovascular health and cholesterol levels; however, studies have shown it can cause hypoglycemia in certain individuals, which is particularly dangerous for runners who are diabetic.

There are hundreds of supplements available on the market, and it can be confusing trying to navigate where to start. Here are some common supplements that you may have come across for endurance training:

Running/Energy gels

Running gels are one of the most commonly used supplements for endurance training. Studies have shown running gels to effectively help maintain blood glucose levels and prevent runners from “bonking,” in other words, prevent the body from quickly depleting its glycogen stores. This is critical for runners, since glycogen depletion is what usually causes the feeling of fatigue and decreases endurance and performance during runs. Running gels are often sold as small packets of liquid or gummy candies and contain 20-40 grams of carbohydrates in the form of glucose and fructose. Some gels may also contain electrolytes or caffeine (read the packaging carefully, especially if you’ve already had caffeine beforehand!) Isotonic gels are typically pre-mixed with water, while energy gels need to be taken with water. Although all gels have their own directions, it is generally recommended to take 1 gel 15 minutes before exercise, and an additional gel every 45 minutes during exercise. Running gels may cause side effects of stomach upset, nausea, vomiting and or diarrhea if your body cannot tolerate simple sugars in high amounts at one time. If you decide to give energy gels a try, experiment with them early on in your training program, the last thing you want is to feel sick from the gels on race day.

Branched chain amino acids (BCAAs)

BCAAs are made up of essential amino acids leucine, isoleucine, and valine. “Essential” means that these amino acids need to be obtained through your diet, and your body cannot produce them on its own. It has been suggested that BCAA supplementation can improve fitness performance, increase muscle growth, and reduce muscle breakdown, soreness, and fatigue. However, there is inconsistent evidence to prove such benefits. BCAAs are sold in liquid, powder, and pill form, and can be quite expensive. The most cost-effective way to obtain BCAA’s is through your diet with an adequate amount of protein foods including meat, fish, and milk.

Protein Powder

Protein is a macronutrient that contains essential amino acids needed for muscle building and repair after training sessions. The word macro means your body needs to obtain it in larger amounts compared to other nutrients such as vitamins and minerals. It was previously believed that protein intake within the first 1-2 hours after training was the most efficient way to stimulate muscle repair, and supplement companies promoted protein powder as an easy way to ingest protein within this “anabolic window,” however, studies now show that the anabolic window can last up to 24 hours. Most importantly, protein powder is not required if you are eating enough protein foods throughout the day. Good source of protein includes animal meat, fish, dairy, eggs, tofu, legumes, seeds, and nuts. Plant based protein sources may not contain all the essential amino acids, however if you are eating a variety of whole foods such as fruits, vegetables, starches and grains, different incomplete protein foods combined can make up a complete source of protein that is needed for muscle building.


Creatine is a non-essential amino acid that is naturally produced within the body for ATP (energy) production when converted into a substance called “phosphocreatine.” Studies have shown creatine to improve performance, but mainly in high intensity, short duration movements, such as sprints or weightlifting. There are few studies supporting creatine as a useful supplement for long distance running. Your body will generally produce and store 1-2 grams of creatine in your muscles per day, and a diet with animal protein will also provide your body with an additional 1-2 grams of creatine.


Glutamine is a non-essential amino acid that is naturally produced within the body to serve as a substrate, or molecule that works alongside enzymes for various biochemical reactions. Glutamine supplementation has been historically known to aid in recovery for individuals who are critically ill with burns, gastrointestinal diseases, or infections, however when it comes to athletic performance, there are inconsistent findings. Some studies have demonstrated Glutamine to reduce muscle breakdown and soreness, while other studies have shown no proven effect. According to the National Institutes of Health, there is not enough research to recommend glutamine as a supplement to enhance athletic performance improvement. Instead, a diet with animal protein and dairy products will provide enough glutamine required by the body.

Antioxidants (Vitamin C, Vitamin E, Coenzyme Q10)

Aerobic metabolism from exercise can increase the production of free radicals and cause oxidative damage to our cells. Antioxidants are believed to neutralize free radicals and reduce soreness induced muscle damage and inflammation within the body. However, there is currently little evidence to show improvement of muscle growth and endurance performance with antioxidants in the form of supplements. Rather it is recommended to obtain antioxidants through whole foods including fruits and vegetables, which also contain many other beneficial nutrients that a supplement cannot provide, this includes vitamins, minerals, water, and fiber.


Caffeine is a chemical that is naturally found in coffee, tea, and chocolate. It works as a stimulant by blocking adenosine receptors within the body. Blocking adenosine receptors results in increased alertness and wakefulness, and reduces feelings of lethargy. Modest amounts of caffeine can reduce fatigue and improve endurance training. Typically, 3-6 milligrams per kilogram of body weight 60 minutes before exercise may increase aerobic performance by 1-8%. Too much caffeine however (doses of 500 milligrams or higher) show no further benefits and may actually decrease your endurance performance. Over consumption of caffeine may cause side effects [PB1] of increased heart rate, light headedness, jitteriness, anxiousness, gastrointestinal alterations, insomnia, increased blood pressure, and potential development of high caffeine tolerance.

It is always recommended to notify your physician or dietitian before starting on any supplementation. Before trying a new supplement, do your research to ensure you are buying from a safe, reputable brand, and that you are fully aware of any side effects it may cause. It is also recommended to first try any new supplement in a serving size smaller than recommended dose, just in case you have any adverse reactions to it.

For any questions or nutrition counseling, please contact Maria Dinh, RD, MS or Rachel Golaszewski MS, RD at


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