Optimizing Physical Performance: The Science of Nutrient Supplementation

There are many different supplements marketed as performance enhancers in the world of sports nutrition. With athletes trying to find an edge, and opportunistic companies selling the latest fad ingredients, it is very difficult to discern what natural substances are supported by sound scientific evidence and which ones are the flavor of the month. The reality is that many of these “natural” products have little or no evidence supporting their effectiveness or safety. At worst, they may be adulterated with dangerous and banned substances. Despite the pit falls in the world of sports nutrition, good evidence is emerging to show that some nutrients can improve physical performance. This article will discuss the key evidence-based natural nutrients used to optimize performance and dispel common myths regarding sports supplementation.

How Much Protein Do You Need

Of all the nutrients and supplements used for sports performance enhancement, it’s not difficult to argue that protein is most important. It provides essential amino acids that are the building blocks for muscle growth, recovery and repair. In order to optimize protein use, the first question most people have is: how much do I need? The goal is to consume enough protein to offset normal muscle breakdown and recycling as well as to stimulate growth and repair. Currently, the recommended dietary allowance (RDA) for protein in sedentary healthy adults is 0.8 g per kg body weight per day.1 While this may be adequate for most of the population, active people have higher demands on their muscular system and therefore require higher amounts of protein. The current scientific consensus is that endurance and strength athletes need 1.4-2.0 g of protein per kilogram of body weight per day.1 So the average 70 kg male wanting to achieve 1.5 g of protein intake per kg would need to consume 105 g of protein a day.

The biggest concern most people have is whether large amounts of protein may have a damaging effect on their kidneys. Despite this prevailing idea, there is very little evidence to support this concern. The only negative evidence linking large amounts of dietary protein having a detrimental effect on kidney function is from a few animal studies and in patients with kidney disease.2 A number of studies have shown that protein intake has no detrimental effect on kidney function and actually reduces the risk in hypertension, obesity and metabolic syndrome.1 Drinking enough water is a safe practice to help protect the kidneys from damage due to consuming higher levels of protein.

Using Protein Supplements

With numerous sources of proteins becoming available on the market, another key question is: what type of protein is best for athletes? A full spectrum of all essential amino acids is required for muscle health. Animal sources provide a complete source of amino acids, whereas vegetable sources generally lack one or more. This is the reason animal sources such as whey or egg are traditionally considered superior to vegan proteins for building muscle.

The precise protein digestibility corrected amino acid score (PDCAAS) is considered the gold standard measure of protein completeness and how well protein is digested.3 Whey and egg protein consistently have the highest scores in most protein assessment measures, but certain vegan proteins such as soy, rice and pea also score well and are now being used by athletes for muscle growth and recovery. Current research supports whey as the gold standard for muscle building and recovery.1,4 This not only applies to athletes, but also to the aging population which is susceptible to muscle loss. Due to the presence of growth factors, whey protein can prevent the loss of muscle mass and maintain strength in the elderly over and above the effect of simple amino acids.5

In terms of timing, a common recommendation is to deliver amino acids to the muscle during and right after activity, when the ability of muscle to uptake and use amino acids is the highest. One widely accepted idea is that, after exercise a 60-90 minute window exists where the body has an increased ability to utilize carbohydrates and protein. Recent evidence calls this theory into question and now suggests that overall nutrient intake throughout the day may be a better focus.6 It is not recommended to eat a large meal before vigorous exercise because it can cause gastric upset, although a small carbohydrate and protein rich meal or smoothie 60-90 minutes before exercise and within 60 minutes after is still a prudent idea to optimize amino acid delivery.6

Whey protein has some distinct benefits compared to vegan proteins. Whey protein upregulates glutathione production, a powerful cellular antioxidant that prevents cancer formation, protects cells from free radical damage and increases elimination of harmful chemicals.7 Vegan proteins do not increase glutathione to the same degree as whey since they have lower levels of the amino acid cysteine, a key glutathione building block. Whey also has higher levels of Branched Chain Amino Acids (BCAAs). These specific amino acids (leucine, isoleucine, and valine) stimulate muscle growth and maintenance.8 They will be discussed in greater detail later in the article.

Milk Intolerance, Allergies and Whey Protein

Conversely, some people can have a food allergy or sensitivity to animal proteins such as egg, dairy (casein) and whey protein. This is not to be mistaken with lactose intolerance, which is an inability to digest lactose, a sugar found in dairy products. Dairy products, including whey protein, are common food allergens; if a person is sensitive to either the carbohydrate (lactose) component, the protein component, or cannot digest dairy fats properly, then it may promote inflammation and digestive irritation, which can hinder athletic performance and prevent nutrient absorption.9 However, some people may tolerate different forms of whey protein over others and most whey proteins are very low in the fat component. Whey isolate has the non-protein components (lactose) partially or totally removed to “isolate” the whey protein, meaning it contains a higher percentage of protein than concentrate and less carbohydrate calories. Whey protein concentrate contains a very small amount of carbohydrates (lactose) and fats in addition to protein. Whey hydrolysate contains both concentrates and isolates. These proteins have been further broken down for faster absorption and assimilation. Accent 5;

Nutrition Myth Buster: Do amino acids boost growth hormone production?

For many years, research has been focused on naturally stimulating human growth hormone (HGH) production since levels decline with age. Glycine is one amino acid that attracted special attention after two studies in the 1970’s found it increased growth hormone in prepubescent children.8,9 However, these results were never replicated and the original studies used intravenous glycine. Therefore, oral supplementation most likely does not have any substantial impact on growth hormone levels. However, recent studies have shown that resting growth hormone responses increase with oral ingestion of L-arginine (with a dose range of 5-9 g of arginine). Within this range there is a dose-dependent increase and higher doses are not well tolerated. Most studies using oral arginine have shown that arginine alone increases the resting growth hormone levels at least 100%, while exercise can increase growth hormone levels by 300-500%. The combination of oral arginine plus exercise attenuates the growth hormone response, however, and only increases growth hormone levels by around 200% compared to resting levels.9

The following study adds to the evidence that that glutamine boosts growth hormone levels. In a randomized, double-blind, placebo-controlled trial of 42 healthy middle-aged and elderly adults, the subjects consumed either a placebo or 5 g of a nutritional supplement composed mainly of glutamine, glycine, and niacin. The supplement was ingested twice daily for three weeks. At baseline and at the study’s end, the investigators analyzed the participants’ blood. Ingesting the supplement led to a 70% increase in serum growth hormone levels compared to placebo, leading the researchers to conclude that an oral mixture of glutamine, glycine, and niacin can enhance growth hormone secretion in healthy adults.9

Branched Chain Amino Acids (BCAAs) and Muscle Growth

BCAAs are specific amino acids that have the most significant role in stimulating protein synthesis since they upregulate enzymes that are responsible for muscle growth.10 BCAA’s make up about 25% of animal protein and occur in a 2:1:1 ratio (leucine: isoleucine: valine) in nature. High quality supplements should reflect this ratio. BCAA supplementation also prevents damage to muscle during exercise. One randomized, placebo controlled study found that those subjects that used BCAAs during and after strenuous exercise had less muscle soreness and faster recovery than those subjects that took placebo.11 In addition to supporting muscle growth, studies also show that BCAAs aid in the maintenance and production of glycogen, which is responsible for muscle energy and is a stored source of fuel during exercise.11 They may also help to delay the onset of fatigue and maintain mental function in aerobic exercise, because BCAAs can compete with tryptophan (a calming amino acid) in the brain.12 Some evidence also suggests that BCAAs maintain immune function in athletes. There is no substantial evidence that BCAAs improve performance, but they do improve recovery in both resistance and aerobic athletes. Due to their muscle protective mechanism and the fact that BCAA plasma levels peak about 30 minutes after ingestion, they should be supplemented before and after exercise in divided doses.

Leucine, in particular, is the most studied of the three BCAAs since it signals the synthesis of protein and glycogen in the muscle (anabolism, or building), and it also appears to modulate the secretion of insulin or its actions on muscle cells. Glycogen is a quick energy supply for working muscles. Post-workout glycogen storage has traditionally been thought to be increased only by consuming a good amount of simple carbohydrates immediately post-exercise. Studies have gotten mixed results when examining the effect of combining protein or BCAAs with carbohydrates for elevated post-exercise glycogen synthesis. The more muscle glycogen stores can be increased, the more energy is available for the next exercise session, resulting in better performance. In terms of protein anabolism, the importance of leucine is demonstrated by the fact that when all amino acids are supplemented except leucine, protein synthesis decreases by 40%.

The Amino Acid L-Carnitine

L-carnitine is an amino acid that plays a central role in the breakdown of fatty acids and their subsequent transport into the mitochondria to be used in the production of cellular energy.13 L-carnitine has been studied to address conditions such as angina, heart damage, peripheral vascular disease, diabetes, chronic fatigue syndrome, kidney failure and athletic performance. A number of studies using human subjects have found that L-carnitine supplementation reduces damage to muscle and decreases muscle soreness, especially after exhaustive exercise when oxygen is limited.14 The primary mechanisms responsible for the positive results are the increase in energy formation in the mitochondria, the reduced build up of lactic acid and free radical damage to muscle cells. A new mechanism being explored is that L-carnitine improves blood flow in areas with poor oxygen levels, which can be beneficial for those doing intense exercise and for those with conditions such as diabetes or peripheral artery disease.14 Despite the positive effects on muscle recovery, L-carnitine supplementation does not appear to improve performance markers such as strength and speed directly.13 Some studies do show that oral carnitine reduces fat mass, increases muscle mass, and reduces fatigue, which may contribute to weight loss in some people. Additionally, disorders of fatty acid oxidation and metabolism typically are associated with primary and secondary forms of carnitine deficiency.15

Nutrition Myth Buster: Does drinking coffee before a workout improve performance?

Many people like to drink a coffee or another caffeinated beverage before their workout in the hopes it will boost their performance. Caffeine has been intensely studied as a potential sport performance aid. The summary of the research suggests it improves focus in intense and mentally demanding exercise. It also appears to reduce the use of muscle glycogen (an energy source) in endurance athletes. Additionally, it may help promote the recovery of glycogen after exhaustive exercise.16 The evidence shows a moderate improvement in performance for endurance sports, but really does not apply to resistance athletes. It is important to note that most studies used dry caffeine extract and the same effects were not achieved when coffee was used in the trials. The typical doses used were 3-6 mg of caffeine per kg body weight (equal to approximately 210-420 mg for an average 70 kg male). As a reference, a typical medium (14 oz) coffee contains 140 mg of caffeine.16 In summary, drinking a coffee before an aerobic workout should be beneficial although the same cannot be said for resistance training. In terms of fat loss and increasing the metabolism, at least one study showed that caffeine/coffee stimulates the metabolic rate in both control and obese individuals; however, this was accompanied by greater oxidation of fat (use of fat as an energy store) in the control group only. 17

Other Nutrients That Improve Sports Performance

Astaxanthin is a unique and powerful antioxidant that is being studied for a wide variety of conditions including eye fatigue, cardiovascular disease, and diabetes.18 Astaxanthin appears to also improve muscle function after exercise since it may protect cells and mitochondria from free radical damage. It may also reduce lactic acid formation, which reduces muscle soreness, allowing athletes to perform exercise longer.18 To support this theory, a number of studies in human subjects have shown astaxanthin supplementation improves both resistance and endurance performance.19,20 One study supplemented athletes with 4 mg of astaxanthin for six months leading to an improvement in the number of squats in just three months.20 D-Ribose is a naturally occurring sugar that has been studied in heart failure, fibromylgia and exercise performance as a way to improve muscle energy production. A double blind, placebo-controlled trial looked at the effects of supplemental ribose on body composition and exercise performance in 20 male bodybuilders. They were given 10g/day of D-ribose for four weeks while on a strength training program. The results showed an improvement in the total work performed and in bench press strength.21 More research is needed to confirm this effect, as a number of other studies have found that supplementation with D-ribose had no effect on exercise performance; although they used a lower dose (less than 3 g).

Colostrum is the first milk (before normal milk is produced) secreted by mammals when a baby is born that is very rich in immune and growth factors. Many athletes suffer from poor immunity as a result of intense training, making colostrum an attractive supplemental option. The evidence suggests that colostrum helps maintain intestinal barrier integrity, immune function, and reduces the chances of suffering upper respiratory tract infection symptoms in athletes undertaking heavy training.22,23 The latest evidence suggests colostrum may improve lean body weight (compared to whey protein) and helps maintain testosterone levels during exercise.24

Nutrition Myth Buster: Is creatine harmful or helpful?

Creatine is one of the most studied sport performance supplements. Numerous studies have found it to be safe and beneficial for increasing high -intensity exercise capacity and lean body mass during training.25,26,27 Supplementation studies with creatine have found that subjects experience a 10-15% improvement in strength and anaerobic performance, and increased muscle size gains.26 Creatine provides the building blocks to produce a type of rapidly used energy called phosphocreatine which allows a person to train harder. Other emerging areas of research include looking at creatine in other diseases and injuries (i.e. Alzheimer’s disease, muscular dystrophy, concussions, etc.) that could benefit from improved energy production. In summary, creatine can be used to improve strength, muscle size and reduce exercise fatigue. It’s recommended for athletes who compete in short duration, high intensity sports like football, volleyball or weight lifting, but there is little benefit for endurance athletes such as runners or cyclists.

What You Need To Know

It is now well established that a balanced diet and appropriate supplementation can enhance sports performance. Protein is an essential dietary component, and whey protein in particular offers several health benefits. Branch chained amino acids are essential amino acids that improve recovery times from both resistance and aerobic activity, as does the amino acid L-carnitine. Other nutrients that improve sports performance include astaxanthin, D-ribose and colostrum.

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