Jan 29, 2015
Burst of Energy

It seems like almost every athlete is using energy supplements for a pick-me-up. Here’s what you need to know about how these products work and the ingredients you may find in them.

By Dr. Kris Clark

Kris Clark, PhD, RD, FACSM, is the Director of Sports Nutrition and an Assistant Professor at Pennsylvania State University, where she coordinates nutrition planning for more than 800 varsity athletes. She can be reached at: [email protected].

Tim just got out of his last class of the day and needs to be on a soccer field across campus in 45 minutes dressed and ready to practice, but right now he’s feeling low on energy. Jessica is headed out on her longest training run of the season and isn’t sure what to bring with her for fuel. Alex worked on a school project with classmates all morning, rode the team bus for two hours to the game, and when halftime rolls around, he isn’t sure he’ll be able to sustain his level of play.

What can these athletes do for a quick boost? Though there is no replacement for food-based fuel combined with properly timed nutrient consumption, a fast-acting energy supplement might be the answer.

But advice on energy supplements is not as straightforward as it might seem. Should all three of these athletes use the same supplement? What about the delivery method? Would a gel, bar, chew, or shake be best? And when should they be taken?

Along with good food choices throughout the day, I regularly recommend energy supplements to the Penn State athletes I work with. Most supplements are small and can be easily carried in a backpack or gym bag, or kept in a locker. The convenience factor, along with the advantage of an energy edge, has made them popular among athletes in many sports. The keys are knowing which energy supplements to use and when.


While the combination of ingredients and how they are packaged varies, the goal of each energy supplement on the market is the same: to boost an athlete’s energy level. There are two basic ways supplements can safely do this.

The first is with carbohydrates. Just as foods that contain carbohydrates improve energy levels, so do carbohydrate-containing supplements. The single most important source of energy for athletes, carbohydrates provide the fastest and most efficient method of fueling muscle contractions for any type of exercise.

During digestion, carbohydrates are broken down into smaller sugars–glucose, fructose, and galactose. These sugars are then absorbed into the bloodstream where they are immediately used as muscle fuel.

Any sugars not needed by the muscles right away gets stored as glycogen–a complex carbohydrate energy reserve. The muscles and liver can generally store up to 1,800 calories worth of glycogen for future use. That’s about two to three hours worth of fuel. And any extra glucose beyond the 1,800 calories is stored as fat.

When blood glucose levels start to drop during exercise, the stored glycogen is called upon. Because of its immediate accessibility in the muscles and liver, these glycogen stores are tapped for short, intense bouts of exercise like sprinting and weight lifting. Endurance exercise, like a long run sustained at a slow pace, is eventually fueled by the extra glycogen being stored as fat.

Carbohydrate-containing supplements are generally made for long-duration exercise. If an athlete has a lengthy preseason practice, they are a great choice as they will effectively elevate blood sugar for energy while exercising.

The second way to safely boost energy levels is with caffeine. Research suggesting that caffeine enhances performance is plentiful, so it’s no surprise many manufacturers use it as a main ingredient in their energy supplements. Studies have shown small but worthwhile improvements in both short-term, intense aerobic exercise lasting four to eight minutes as well as prolonged high-intensity aerobic exercise lasting 20 to 60 minutes. However, the stimulant’s effect on strength and power (weightlifting) exercises and sprints lasting less than 90 seconds is unclear.

Greater alertness, attentiveness, and an overall sense of increased energy have also been attributed to caffeine use. Recent evidence suggests that low intake levels–one to three milligrams per kilogram of body weight–are ideal and best consumed an hour before and/or during exercise. I recommend athletes look for drinks, bars, gels, and sport beans with up to 100 milligrams of caffeine per serving.

It’s important to note that caffeine is a central nervous system stimulant and can cause jitteriness in athletes not acclimated to using it. It may not be for everyone, so if you recommend a supplement with caffeine to an athlete, make sure they are aware of this possible side effect. Several companies that manufacture energy supplements also offer reduced or caffeine-free alternatives.

And though the World Anti-Doping Agency removed caffeine from its list of prohibited substances in 2004, the NCAA’s doping threshold is 15 micrograms per milliliter of urine. A moderate amount of caffeine (up to six milligrams per kilogram of body weight) will not raise urinary caffeine levels, but it’s good for athletes to be aware not to consume too much.

Hundreds of popular energy supplements combine carbohydrates and caffeine for an optimal energy boost. I tell athletes to look for supplements with 25 to 30 grams of carbohydrates and no more than 100 milligrams of caffeine. There are a number of products that contain these optimal levels.

When combining carbohydrates and caffeine, athletes should consume the supplement 30 to 60 minutes prior to exercise. This will give the body the time it needs to digest and absorb the carbohydrates. If pressed for time, consuming a liquid supplement is best because carbohydrates in liquid form are immediately transported into the bloodstream, quickly elevating blood sugar.


If carbohydrates and caffeine are all that an energy supplement needs, why do these products also have so many other ingredients on their labels? One answer is that manufacturers want their supplements to be unique and capture the attention of potential users.

For example, caffeine is a drug derived from a variety of sources, including cocoa, coffee beans, herbs, and tea leaves. By using a variety of plant sources, a supplement may appear more “natural” than if it contained a basic caffeine powder or extract.

Manufacturers may also include other ingredients that have health benefits beyond an energy boost to separate themselves from their competitors. Here is a guide to some of these ingredients and what they do:

Guarana: This South American bush produces potent caffeine-rich seeds. When compared to coffee beans, which contain anywhere from one to 2.5 percent caffeine, guarana seeds contain four to eight percent more per serving. Guarana is reputed to be a stimulant that increases mental alertness, fights fatigue, and increases stamina and physical endurance.

Yerba mate: Another South American plant, “mate” is a source of caffeine when the leaves are brewed for tea. Its caffeine content is low compared to coffee or guarana seeds and is Generally Recognized as Safe (GRAS) by the Food and Drug Administration (FDA).

Creatine: A calorie-free, nitrogen-containing substance naturally occurring in very small amounts in humans, creatine helps supply energy to muscle cells by producing adenosine triphosphate (ATP), which transports chemical energy within cells for metabolism. Extensive research shows that daily doses between five and 20 grams have no negative health effects on adults.

Coupled with weight training, the benefits of ingesting creatine appear to be increased muscle mass and weight gain. But taking a supplement containing creatine just before a workout will not improve energy levels unless the product also contains carbohydrates and/or caffeine. Benefits from creatine come from daily use over time, and it is considered more of a training aid than an immediate energy-enhancing agent.

Taurine: This non-essential amino acid (a building block of protein) is necessary for normal skeletal muscle functioning, but humans can produce enough of it naturally by eating a wide variety of protein sources. The amount of it present in energy supplements will not harm the body.

Branched-chain amino acids: Including leucine, isoleucine, and valine, these essential amino acids must come from diet and/or supplements because unlike taurine, the body cannot manufacture them. Some believe their consumption aids in gaining lean muscle mass.

L-Carnitine: Produced in the body by the amino acids methionine and lysine, L-carnitine is required to help shuttle fatty acids into the cells to be used as an energy source. Manufacturers include it in energy supplements because it gives the impression that it burns fat, though this hasn’t been proven.

Inositol: A substance made naturally in the body, inositol is added to energy supplements because of its potential link to cell membrane integrity. The amount found in energy products will not harm the body.

B vitamins: These water soluble and essential vitamins must come from diet or supplements. They play a role in breaking down carbohydrates, fat, and protein so they can serve as energy sources for working muscles. Athletes should have no problem eating foods with plenty of B vitamins since they’re plentiful in dairy, grain-based foods, and meats. Since B vitamins will be excreted in urine if excess amounts are consumed, there is no risk associated with consuming extra B vitamins found in energy supplements.

Ginkgo biloba: An herb primarily touted for its effect on memory performance, supplement manufacturers claim ginkgo biloba improves blood flow and oxygen delivery to the brain and subsequently better helps deliver nutrients.

Glucuronolactone: A naturally-occurring substance that is part of all connective tissue, glucuronolactone is used in energy products by manufacturers under claims it will detoxify the blood. Studies have shown that levels up to 1,000 milligrams per serving is safe.

None of the ingredients listed are “bad” for an athlete to consume, as long it’s not in excess. A lot of choosing which energy supplement to take will be based on personal preference. For some, it has to do with taste and texture. I know athletes who can’t seem to get the gels down, but love the chews and beans–and vice versa.

Consider a reasonable investigation of any energy product before suggesting them to your athletes because all products are not created equally. Take into account the ingredients on the nutrition facts label, but keep in mind that the NCAA, which partners with the organization Drug Free Sport, takes a hard line in this area: No supplement is a safe supplement. Contaminated products do exist, which means ingredients may be present in a product without being identified on the nutrition facts label.


While the athletes I work with use energy supplements often, I also advise them that the best solution to a lack of energy is through whole foods. In a pinch, an energy supplement may work very well, but there are nutrients and vitamins in foods that are important and cannot be found in supplements.

Colorful plant foods, fruits, and vegetables contain highly potent antioxidants that supplements don’t. Broccoli, tomatoes, carrots, brussels sprouts, cantaloupe, peaches, strawberries, and blueberries are just a few examples of foods loaded with plant chemicals that protect cellular membranes and also provide good carbohydrates for energy.

Energizing the mind and body through food takes some forethought and planning on the athlete’s part, and for many, this is tough. Keeping in mind that food must be completely digested, absorbed, and metabolized in the muscle cell to become usable energy, here are some simple suggestions.

Three hours before a workout, an athlete should eat a complete meal that contains carbohydrates, protein, and fats. A good mid-day meal would be a turkey and cheese sandwich with lettuce and tomato on whole wheat bread, a salad or piece of fruit, a cup of yogurt, and a glass of milk. An example of a good breakfast three hours prior to a workout is eggs (prepared any way), pancakes with syrup or a bowl of cereal with milk, 100-percent juice or a piece of fruit, and a glass of milk.

If an athlete only has one hour before a practice or game, they should focus on foods heavy on carbohydrates because they are easily digested and available for use faster than proteins and fats. Examples include a bagel or whole wheat bread with jelly and a banana, dry cereal, a sports bar, an energy gel and a half a sports bar, or crackers with honey and jelly and a piece of fruit. All of these possibilities can also include a sports drink with carbohydrates in it.

Not long ago, an athlete on campus reached out to me for advice. Her story illustrates perfectly how the right food choices can make a big impact on performance.

It was a Friday afternoon in January and the athlete, a swimmer, was practicing with the rest of the team in Florida over the holiday break. She sent me three separate text messages listing everything she’d eaten that day, and the fourth message said, “doc–what should i eat next? we practice at 4 & thats gonna be a killer?”

I looked at the clock, saw that she had two and a half hours before practice–just enough time to eat and digest food–and called her. I recommended half of a peanut butter and jelly sandwich, a large handful of pretzels, and at least 16 ounces of a sports drink containing at least 100 milligrams of caffeine. Her text back to me later that night read, “did so good tonight second fastest in the group including the guys love u girl thanks again.”

Carbohydrates were key for the athlete to get immediate energy. She also went into the practice session hydrated so that she wasn’t risking low energy levels due to dehydration.

Athletes need to understand that their diet throughout the entire day and not just right before a practice or game is important. Energy levels should be fueled by food all day long for optimum performance. In addition, energy supplements can add an extra boost when time is tight or planning ahead is not possible.

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