Everyone is running a marathon, when it gets down to it. The need to revitalize daily life with consumed energy surpassed three squares a day right around the time paying for kids’ graduate school and second mortgages became the American rule rather than the exception. When it comes to refueling—whether running a Sunday 26-mile marathon or the weekly rat race—the requirements for both nutritive fuel carbs, proteins, fats and other energy sources is an inescapable need.
Carbohydrates are the main source of energy used during work and exercise; when intensity ramps up, so does an athlete’s reliance on carbohydrate to fuel muscular contractions. However, the human body, including athletes who train and compete at low intensity, can adapt to a low-carbohydrate diet.
“Ultra-runners” (those who run 50km or farther), for example, can decrease their reliance on carbo-hydrates while dipping into a seemingly endless supply of body fat to support energy needs—all without adversely affecting endurance performance. Yet, during the initial stages of a low-carbohydrate diet—prior to the body making adaptions—endurance and performance will drop due to reduced glycogen stores.
Glycogen is a branched polymeric storage form of glucose carried primarily in the liver and muscles.
Low-impact activity for the long haul affects metabolism differently from intense activity. What works for the endurance athlete will not work for the high-intensity athlete or team sport athlete, who engages in intermittent bursts of all-out effort.
“During anaerobic exercise, there is not enough oxygen available to utilize fat as a primary source of fuel,” says Sally Hara, MS, RDN. “If there is insufficient carbohydrate available, the body will turn to protein, an expensive source of energy and fuel source that is not only inefficient, but also creates ammonia as a byproduct and thus can alter the body’s pH.”
Hara points out that if protein is being burned as a fuel due to insufficient carbohydrate in the diet, there also might not be enough amino acids available for optimal growth and repair of muscle. This can contribute to increased incidence and/or slow recovery of injuries.
Adequate carbohydrates also are necessary for optimal brain functioning. When not adapted to a low-carbohydrate diet, low blood sugar impairs an athlete’s ability to think quickly and clearly.
When it comes to energy, nothing beats the safety and efficacy of carbohydrate. Starches that are modified for rapid digestion are quickly gaining steam, while products using multiple transportable carbohydrates are preferable to those with one type of carbohydrate.
Carbohydrate metabolism requires several micronutrients, so manufacturers can gain product performance and marketing advantages by adding specific micronutrients to sports nutrition products. These products can be aimed at segments of the population most likely to have sub optimal intake of these nutrients, especially vitamins and minerals.
While carbohydrate, in general, is important for exercise, fast-digesting starches are preferential to slow-digesting ones. High-molecular-weight, rapidly digesting modified starches can be beneficial for endurance athletes or those who perform exhaustive bouts of activity more than once per day.
In one study, athletes were glycogen-depleted during a submaximal cycling test, after which they consumed either a high-molecular-weight, rapidly digesting modified starch or a low-molecular-weight glucose polymer made from hydrolyzed cornstarch. Subjects then rested for two hours prior to a 15-minute, all-out cycling test.
The study found the athletes consuming the high-molecular-weight, rapidly digesting modified starch had a significant increase in work output, compared to those consuming the low-molecular-weight glucose polymer. In addition, this high-molecular-weight, rapidly digesting modified starch emptied from the stomach twice as fast as the low-molecular-weight carbohydrate, resulting in a 70% increase in muscle glycogen stores two hours after glycogen-depleting exercise. Fast glycogen re-synthesis is particularly important for athletes who train more than once during a 24-hour period.
Slow-digesting starches are commonly promoted for keeping blood glucose levels blunted and providing long-lasting energy, while increasing fat use during activity and improving performance. However, the research doesn’t support these claims.
One study in trained cyclists found a high-molecular-weight, slow-digesting hydrothermally modified starch consumed 30 minutes before a bout of cycling led to a significantly lower glycemic and insulin response. Such a diet under the same conditions also led to greater fat breakdown, yet no difference in fat oxidation or performance during a submaximal cycling bout compared to maltodextrin.
Although it might sound enticing—steady blood sugar and increased fat breakdown—glucose levels typically return to normal within 20 minutes after an initial insulin spike and subsequent drop from consumption of a high-glycemic carbohydrate pre-exercise with no negative effect on performance.
Furthermore, fat breakdown, expected when insulin levels are kept low, and fat usage (“burning”), are totally different metabolic scenarios. It must be stressed that just because the fat is available for use doesn’t mean the body will actually use it. In fact, if carbohydrate is available, the body will go for that source of energy first. This is preferential for both athletes training or competing at a high-intensity and persons engaged in intense daily activity.
Sweet as Sugar
Sugar is an important source of energy during exercise or prolonged activity, especially when glycogen stores start dropping and the person needs fuel to continue at the same pace. Further, it is preferential to use multiple types of carbohydrate as opposed to just one.
Each type of carbohydrate uses different intestinal transporters. Therefore, if an athlete consumes a drink composed of one type of carbohydrate, carbohydrate digestion will be limited when the intestinal transporter for that carbohydrate becomes saturated.
Consuming multiple types of carbohydrates together, such as sucrose, fructose and glucose, or maltodextrin, increases the rate of carbohydrate absorption and utilization by the body compared to consuming an isocaloric amount of a single form of sugar. Additionally, consuming multiple types of carbohydrate during exercise could lead to better performance, particularly during long, exhaustive bouts of exercise.
Ribose is a single-unit, 5-carbon sugar the body not only uses as a fundamental component of DNA and RNA, but also as key to the molecule adenosine triphosphate (ATP). ATP is commonly called the “energy currency” of the body since all biochemical and metabolic reactions need it in order to take place. Stores of ATP are limited and cycle quickly, with only a small pool of high-energy molecules in reserve to help regenerate ATP.
Ribose both feeds and regulates ATP synthesis, balancing the supply and demand aspects of energy. In this way, ribose also helps muscles regenerate after energy expenditure. In fact, research shows ATP-depleted muscles prefer ribose.
In formulations, ribose is water-soluble and neutral in odor and flavor. It can be used exactly like sucrose in most formulations, although it is not as sweet as sucrose. Moreover, ribose also is not metabolized the same way as sucrose and so is non-caloric.
Another sugar displaying special functional properties related to energy is the disaccharide isomaltulose. A sucrose isomer derived from beets, isomaltulose has been used as a sugar replacer for improvement of blood sugar balance and lipid metabolism. Its benefit to the former is due to its much slower rate of metabolism compared to sucrose.
Studies reveal isomaltulose can promote higher rates of fat oxidation during activity. This then leads to a preservation of glycogen stores in the muscles, especially for those activities associated with endurance. Other published research points to a possible role isomaltulose can take in augmenting recovery following resistance training and reducing muscle tissue damage.
Consumers recognize B vitamins as “energy” vitamins. To be more accurate, vitamins of this class are better described as catalysts. Thiamin, riboflavin, niacin, B6 and pantothenic acid all are necessary for energy production.
Several minerals, too, including iron, magnesium, copper and zinc, are essential for the metabolism of carbohydrates into energy.
Although there are no nationally representative estimates of pantothenic acid intake, this vitamin is widely distributed in foods naturally, and deficiency is extremely rare.
According to NHANES data—and thanks, in part, to the fortification and enrichment of foods—few people consume below the Estimated Average Requirements (EAR) for thiamin, riboflavin, niacin, vitamin B6 and copper.
However, low calorie intake can put an athlete or highly active person at risk for low thiamin, riboflavin and vitamin B6 status, as well as iron, magnesium and zinc statuses, if only temporarily.
There is a paucity of data examining how consistent, suboptimal intake of individual B vitamins might impact parameters of athletic performance. However, a study of trained male cyclists found dietary restriction of thiamin, riboflavin and vitamin B6 led to a decrease in peak aerobic capacity and peak power. This further emphasizes the importance of adequate B vitamin intake for physical performance.
Iron deficiency is by far the biggest concern, when it comes to many endurance and energy issues because iron carries oxygen to the working muscles.
Iron deficiency is of particular concern for the groups most likely to be deficient, including athletes, highly physically active persons, highly active women, female athletes of all kinds, distance runners, vegetarians and persons with certain digestive diseases, such as celiac disease.
There are three general stag-es of iron deficiency occurs (in order of severity): depletion, marginal deficiency and anemia. Even marginal iron deficiency can impair athletic performance. On the other hand, correction of iron deficiency can improve performance and decrease muscle fatigue.
Magnesium is another metallic mineral essential for physical function. It is vital for the metabolism of carbohydrates and fats, as well as the production of ATP. For active persons who are taking creatine, to rapidly “recycle” ATP production, magnesium is essential.
Magnesium deficiency can lead to muscular fatigue, muscle cramping, muscular twitching or spasms, numbness and tingling. All of which can result in a substantial drop in energy, and endurance and performance of demanding physical tasks.
Zinc is near the top of the list of minerals in which Americans are often deficient. Zinc is key to multiple metabolic functions, from fertility to immunity to taste and smell. Poor zinc intake can also impair energy production and measures of physical or athletic performance.
Typically, minerals, especially the metal ions, are a challenge to include in any great amount in food and beverage products, since they can adversely affect taste. For this reason, microencapsulated forms often are chosen by processors. Custom premixes can be of value when custom-combining all these supplemental vitamins, minerals and other functional ingredients.
Pep in Their Step
Americans are exhausted, constantly reaching for stimulants that will get them through the busy day, as well as revved up for workouts. The class of natural stimulants most employed are the methylxanthines. These include the two most common, caffeine and theobromine, both of which are classified as non-addictive central nervous system stimulants. (Non-addictive in this case refers to the fact that it poses no physical threat to health, in spite of being mildly addictive [where there are withdrawal symptoms from abruptly ceasing usage].)
Methylxanthines are found in the leaves, seeds and berries of more than 60 plants including tea (Camellia sinensis), coffee (Coffea arabica), yerba maté, guarana and chocolate (Theobroma cacao). The bitter taste serves the plants as a natural pesticide. Methylxanthines bind to adenosine receptors in the central nervous system, leading to a reduction in adenosine activity, and interfering with the chemical messengers that cause sleepiness.
“Caffeine is the most widely consumed psychoactive agent [any substance that affects brain functioning] and most studied ergogenic aid in the history of sports performance,” states Jose Antonio PhD. Antonio also serves as CEO of the International Society of Sports Nutrition. “In low to moderate doses—3-6mg caffeine per kilogram bodyweight—caffeine temporarily increases mental alertness and functioning, while also helping athletes performing long bouts of exhaustive exercise or those who are sleep-deprived feel awake.”
It also has been shown that even smaller doses (0.3mg per kg bodyweight) taken hourly were able to enhance cognitive performance and decrease unintentional sleep episodes in sleep-deprived adults, compared to placebo. Small doses (12.5mg, 25mg, 50mg and 100mg) enhanced cognitive performance and mood in adults with low, moderate and high habitual caffeine intakes.
The central nervous system adapts to regular caffeine consumption by increasing the number of adenosine receptors, so more caffeine is needed to bind to these receptors and achieve the same stimulatory effect. When caffeine consumption is reduced or stopped, the central nervous system will re-adapt by decreasing the number of adenosine receptors.
In addition to its stimulant effects, as a non-selective inhibitor of phosphodiesterase, caffeine increases fatty acid sequestration and decreases reliance on glycogen. “Acute consumption of caffeine can enhance both endurance and strength,” adds Antonio.
Just One Lump, Please
Research supports the beneficial effects of caffeine in athletes, as well. For example, caffeine can enhance performance during maximal endurance exercise, running and triathlon. But for weekend warriors, it also helps in high-intensity activities, like basketball and soccer. Caffeine’s ergogenic effects are greater when consumed in the anhydrous state. In other words, it’s better to eat it than drink it.
Caffeine is completely absorbed about 45 minutes after it is consumed and has a half-life of approximately 3-4 hours in healthy adults. However, many factors affect caffeine metabolism and elimination, including age, genetics, liver function, pregnancy status and use of certain medications.
A person’s tolerance to caffeine can vary, and doses of 250mg-300mg or more can lead to rapid, irregular heartbeat and difficulty sleeping in some individuals. Caffeine consumption could be contraindicated for those with anxiety, cardiovascular disease, hypertension, glaucoma and heartburn. Pregnant women should consume less than 300mg per day.
In persons with high blood pressure or easily elevated blood pressure, in doses of 200mg-300mg, caffeine can temporarily increase both systolic and diastolic blood pressure, by about 8mmHg and 6mmHG respectively. These levels have been shown to drop to the individual’s normal blood pressure about three hours after consumption.
Caffeine works just fine by itself. But it also has a synergistic effect with other compounds, including glucose and l-theanine. A double-blind, randomized study of healthy young women ages 18-25 found a caffeine-only beverage led to improvement in simple reaction time, and a glucose-only beverage led to improvements in simple reaction time, as measured via one sequential reaction time test and a manual dexterity assembly test. However, the combination of 75g of glucose and 75mg caffeine resulted in sustained attention (sequential reaction time tasks) and verbal memory.
L-theanine contributes by increasing alpha brainwave activity, leading to a dose-dependent, relaxed-yet-alert state 40 minutes after consumption. A randomized, placebo-controlled, double-blind, balanced crossover study found that 150mg caffeine combined with 200-250mg l-theanine led to faster simple reaction time, faster numeric working memory reaction time and improved sentence verification accuracy when compared to caffeine intake alone.
Better make that a mocha latté. The combination of caffeine and theobromine, too, is synergistic. It helps contribute to cocoa’s psychostimulant effects. Theobromine is a less-potent adenosine antagonist and, therefore, a much weaker stimulant than caffeine.
While theobromine is a very weak stimulant, it seems to have additional benefits. “Theobromine has been shown to inhibit the pathways related to adipogenesis [the development of fat cells],” states Antonio. “The half-life for theobromine is about seven hours and, while stimulants often contribute to insomnia, theobromine actually has been shown to enhance sleep duration.”
Fighting fatigue can be accomplished through more than stimulants. Certain peptides and amino acid compounds have exhibited a capacity to hold tiredness at bay in the face of sustained activity. Recent attention has turned to combinations of specific forms of citrulline, arginine, glutamine and alanine as L-alanyl.
A study at the University of Central Florida, published last summer in the Journal of the American College of Nutrition, showed that taking a dipeptide of L-alanyl-L-glutamine during strenuous exercise could “increase endurance and lengthen time to fatigue.” In the study, 12 male athletes ran four one-hour endurance trials on treadmills, followed by a full run to the point of exhaustion. Time to exhaustion was significantly longer following the L-alanyl-L-glutamine ingestion.
In another study, the combination of L-citrulline and L-arginine in an oral supplement led to a more rapid increase in arginine levels in the blood and simultaneously boosted the bioavailability nitric oxide, when compared to supplementation with arginine alone.
Nitric oxide metabolism and regulation is key to mitigation of fatigue, as it increases the flow of oxygen-rich blood to working muscles.
L-citrulline also has demonstrated an ability to enhance nitric oxide levels and action in the presence of the antioxidant compound glutathione. In a placebo-controlled study published last summer in the Journal of the International Society of Sports Nutrition, after a week of oral supplements of the L-citrulline-glutathione combo, nitric oxide levels were enhanced and exercise performance increased.
The study’s principal researcher, Darryn Willoughby, PhD, associate professor of health, human performance and recreation, and the director of the Exercise and Biochemical Nutritional Lab at Baylor University, noted the results indicate glutathione and L-citrulline might “play a role in muscle protein synthesis and muscle performance when combined with resistance exercise.”
Glutathione itself is said to help the body eliminate toxic chemicals, while maintaining cell proteins in addition to its more commonly known function as an antioxidant. Extending the study to animals, the researchers determined the glutathione-L-citrulline complex can enhance nitric oxide across a variety of subjects, not just athletes.
A great deal has been written about the need for protein when it comes to supporting energy needs of athletics and high activity. Dietary protein is broken down into its component amino acids, but overall, when the body is building muscles and tissue, protein is a must.
Easily digestible and metabolized proteins, whether from egg (the highest bioavailability), fish or meat have been classic sources, but dairy and plant proteins have shown themselves to be the most preferred proteins for those consumers needing a quick recharge.
For the growing vegan/vegetarian population, protein isolates from sources such as soy have been the most popular for the longest time. Protein from legumes, especially peas, has gained a great deal of ground in formulations. Recently, a plethora of plant proteins have joined them in the protein toolbox. (See “New Plant Protein Powerhouses, Prepared Foods, September 2015.)
The biggest trend in protein power for the active set in recent years has been that of dairy proteins, especially whey/whey protein hydrolysate. Whey is one of the most heavily studied proteins, as far as sports formulations go, and can boast a wealth of support for its efficacy in helping the daily active, athletes and the highly active competitive athletes maintain energy and rebuild muscle.
A recent study (industry-sponsored) of 18 top-class Danish runners from Team Denmark taken during a week-long, twice-daily training session compared two groups of the athletes; one receiving a carbohydrate and electrolyte sports drinks before and after each training session; the other consuming a high-quality whey protein hydrolysate before each session, and both a sports drink and the whey protein hydrolysate afterward. Both groups received isocaloric diets, otherwise.
Results revealed the subjects in the whey protein hydrolysate group performed better in a final 4km run than the sports drink-only group. In fact, the whey group enjoyed a mean improvement of 17 seconds, while experiencing less muscle damage in comparison to the beverage-only group.
Challenges of including high levels of protein can be off flavors, chalky textures (for plant proteins) and solubility issues in certain beverage formulations. Ingredient technologists and masking technologists have been able to overcome most of these challenges, however.
Whether using protein, lipids, carbohydrates, botanicals or supplemental vitamins, manufacturers of energy products have a vast portfolio of ingredients and expertise to expand options beyond beverages and bars. Gummies, chews and even savory crackers and other snacks are making their way to retail shelves with the promise of more efficient energizing for every level of activity.
In a recent lecture on choline, exercise performance and muscle health, Donald Layman, PhD, professor emeritus of health and nutrition at the University of Illinois, pointed to how muscle health is important for more than just athletic performance—it is critical to overall health in the long run.
While acknowledging that routine daily exercise “increases energy expenditure, helps maintain body composition and controls body weight,” Layman explained that “we often forget that good nutrition choices are essential for optimal muscle performance.”
Choline, a catalytic nutrient often classed with the B vitamins, is a crucial compound in multiple metabolic processes, including muscle function. However, it’s estimated that more than nine in 10 Americans are not getting enough choline in their diets.
Choline supports other metabolic functions involved in activity and physical exertion, such as the nervous system that sends signals to exercising muscles. Specifically, choline is part of the neurotransmitter, acetylcholine. Acetylcholine is the signal that stimulates muscle contraction, which supports muscle movement and performance.
When muscles are active, nitric oxide is produced and expands arterial walls. This increases the flow of oxygen-rich blood to those muscles. However, nitric oxide has a rapid turnover, needing to be replaced every second. Choline supports optimal nitric oxide function.
Choline also is an essential part of phosphatidylcholine, a compound that makes up about 50% of the phospholipid membrane that protects every cell in the body, controlling nutrient uptake into muscles, as well as transferring the signals that trigger contraction.
A deficiency in choline will alter muscle metabolism, increasing the amount of fat within the individual muscle fibers. As this fat accumulates, it can lead to formation of large fat droplets. Changes in the composition of the muscle fibers can negatively impact the way muscles function during exercise.
Results of a recent study of healthy adults, reported in The American Journal of Clinical Nutrition, showed that “a diet deficient in choline caused muscle damage and fatty liver in 77% of men and 80% of postmenopausal women.” It also noted that “10% of adults experienced fatty liver and muscle damage, even when consuming the Adequate Intake levels of choline.” The study also revealed that “consuming adequate or higher amounts of choline reversed these conditions for everyone.”
Other exercise studies with choline have focused on use during prolonged activities like marathons. The athletes in these studies were shown to suffer from loss of acetylcholine after intense training or competition. In fact, Layman stressed, it also is known that “choline losses occur after exercise of only an hour; and could occur with a long run, cycling or a competitive tennis match.”
Layman further states, “It is clear that choline deficiency has adverse effects on muscle health, including fat metabolism and muscle function. Choline supplementation can provide benefits for endurance athletes, such as marathon runners, as well as more casual athletes, by preventing the adverse health effects associated with choline deficiency. Adequate intake of choline from food or dietary supplements is essential for good health and physical performance for everyone.”
Note: This segment was derived from a Choline Information Council (www.cholinecouncil.com) report on a recent lecture by Donald Layman, PhD.