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URL: https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance-HealthProfessional/
Source date: 2024-04-01
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#### Efficacy

#### Safety

The several small studies of athletes described in the previous paragraph who took betaine supplements for up to several weeks found no side effects or safety concerns. However, research has not adequately evaluated the safety of betaine.

#### Implications for use

More research on betaine supplementation to enhance various types of performance, training protocols, and exercise during specific sports is needed before any recommendations for its use can be made [71 ].

### Branched-chain amino acids

Three essential amino acids (EAAs)—leucine, isoleucine, and valine—are the branched-chain amino acids (BCAAs), whose name reflects their chemical structure. BCAAs make up approximately 25% of the amino acids in foods containing complete proteins (including all EAAs) [72 ]; most of these foods are animal products, such as meat, poultry, fish, eggs, and milk (see section on protein ). BCAAs comprise about 14%–18% of the amino acids in human skeletal muscle proteins [73 ].

Unlike other EAAs, the BCAAs can be metabolized by mitochondria in skeletal muscle to provide energy during exercise [74 ,75 ]. The BCAAs, especially leucine, might also stimulate protein synthesis in exercised muscle [72 ,76 ].

The limited research on the potential ergogenic effects of the BCAAs has found little evidence to date that supplements of these amino acids improve performance in endurance-related aerobic events [75 ]. The BCAAs might delay feelings of fatigue or help maintain mental focus by competing with the amino acid tryptophan (a precursor of the neurotransmitter serotonin that regulates mood and sleep) for entry into the brain, but this effect has not been well studied [72 ,74 ,75 ].

The results of several short-term studies lasting about 3 to 6 weeks suggest that about 10–14 g/day supplemental BCAAs might enhance gains in muscle mass and strength during training [1 ]. Overall, however, studies to date provide inconsistent evidence of the ability of BCAAs to stimulate muscle protein synthesis beyond the capacity of sufficient dietary amounts of any high-quality protein to perform this function [76 ].

Furthermore, it is not clear from existing research whether consumption of protein and BCAAs before versus after a workout affects their ability to maximize muscle protein synthesis and reduce protein catabolism [12 ,77-79 ].

Up to 20 g/day BCAA supplements in divided doses appear to be safe [75 ]. For leucine alone, studies suggest an upper safe limit of intake of 500 mg/kg per day in healthy young and elderly men, or about 38 g/day for a man weighing 75 kg (165 lb) [80-82 ].

Studies have not consistently shown that taking supplements of BCAAs or any of their three constituent amino acids singly enhances exercise and athletic performance, builds muscle mass, or aids in recovery from exercise. Consuming animal foods containing complete proteins—or a combination of plant-based foods with complementary proteins that together provide all EAAs—automatically increases consumption of BCAAs (see section on protein ).

This is also true of consuming protein powders made from complete proteins, especially whey, which has more leucine than either casein or soy [78 ].

### Caffeine

Caffeine is a methylated xanthine naturally found in variable amounts in coffee; tea; cacao pods (the source of chocolate); and other herbal/botanical sources, such as guarana, kola (or cola) nut, and yerba mate. Caffeine stimulates the central nervous system, muscles, and other organs such as the heart by binding to adenosine receptors on cells, thereby blocking the activity of adenosine, a neuromodulator with sedative-like properties [83 ,84 ].

In this way, caffeine enhances arousal, increases vigor, and reduces fatigue [13 ,85 ,86 ]. Caffeine also appears to reduce perceived pain and exertion [13 ,85 ]. During the early stages of endurance exercise, caffeine might mobilize free fatty acids as a source of energy and spare muscle glycogen [38 ].

Caffeine is commonly used in energy drinks and shots touted for their performance-enhancement effects [87 ,88 ]. It is also found in energy gels containing carbohydrates and electrolytes as well as in anhydrous caffeine-only pills.

Many studies have shown that caffeine might enhance performance in athletes when they ingest about 2–6 mg/kg body weight before exercise by improving endurance, strength, and power in high-intensity team sports activities [13 ,85 ,89 ,90 ]. For an individual weighing 154 pounds (70 kg), this dose is equivalent to 210–420 mg caffeine. Taking more, however, is unlikely to improve performance further and increases the risk of side effects.

A review of the literature found that caffeine intake affected sport-specific performance (e.g., running, cycling, swimming, and rowing), as measured in time trials. Although 30 of the 33 trials showed positive improvements in performance, the improvements were not statistically significant in half of them [85 ].

In these studies, performance improvement ranged from a decrease of 0.7% to an increase of 17.3%, suggesting that the caffeine was very helpful to some participants but slightly impaired performance in others. Factors such as the timing of ingestion, caffeine intake mode or form, and habituation to caffeine could also have accounted for the varied effects on performance.

Caffeine supplementation is more likely to help with endurance-type activities (such as running) and activities of long duration with intermittent activity (such as soccer) than more anaerobic, short-term bouts of intense exercise (such as sprinting or lifting weights) [91 ]. Some evidence suggests that caffeine is more likely to improve performance in people who are not habituated to it [85 ].

Limiting caffeine intake to 50 mg/day or abstaining from caffeine for 2–7 days before taking it for an athletic event might maximize any ergogenic effect. However, other evidence shows no habituation effect of caffeine consumption on performance [92 ].

Heavy caffeine use (500 mg/day or more) might diminish rather than enhance physical performance and could also disturb sleep and cause irritability and anxiety [93 ]. Other adverse effects of caffeine include insomnia, restlessness, nausea, vomiting, tachycardia, and arrhythmia [94-97 ]. Caffeine does not induce diuresis or increase sweat loss during exercise and therefore does not reduce fluid balance in the body that would adversely affect performance [13 ,90 ,98 ].

For healthy adults, the U.S. Food and Drug Administration (FDA) states that 400 mg/day caffeine does not usually have dangerous adverse effects [99 ]. The American Medical Association recommends that adults limit their intake of caffeine to 500 mg/day and that adolescents consume no more than 100 mg/day [100 ].

The American Academy of Pediatrics warns that caffeine-containing energy drinks in particular have no place in the diets of children or adolescents and are not suitable for use during routine physical activity [101 ].

Pure powdered caffeine is available as a dietary supplement and is very potent. A single tablespoon contains 10 g caffeine, and an acute oral dose of 10 to 14 g caffeine (approximately 150–200 mg/kg) can be fatal [91 ]. Furthermore, combining caffeine with other stimulants could increase the potential for adverse effects [94 ]. At least two young men have died as a result of taking an unknown amount of pure powdered caffeine [102 ].

Caffeine is easily and rapidly absorbed, even from the buccal membranes in the mouth, and is distributed throughout the body and brain. It reaches peak concentrations in the blood within 45 minutes of consumption and has a half-life of about 4–5 hours [83 ]. For a potential benefit to athletic performance, users should consume caffeine 15 to 60 minutes before exercise [13 ,85 ].

Consumption of caffeine with fluid during exercise of long duration might extend any performance improvements [85 ].

In a position statement, the AND, DoC, and ACSM state that caffeine supplementation reduces perceived fatigue and enables users to sustain exercise at the desired intensity longer [12 ]. The U.S. Department of Defense states that caffeine supplementation at 2–6 mg/kg body weight is linked to enhanced physical performance and the effects of smaller doses usually last longer and are greater in people who do not usually consume caffeine [89 ].

It adds that caffeine could reduce perceived exertion when exercise lasts longer. In a position statement, the ISSN describes caffeine as effective in trained athletes for improving sports performance and notes that supplementation with about 3–6 mg/kg has an ergogenic effect on sustained maximal endurance exercise but not necessarily on strength-power performance [13 ].

The Australian Institute of Sport supports the use of caffeine for improving sports performance in suitable athletic competitions under the direction of an expert in sports medicine, but it notes that more research might be required to understand how caffeine should be used for best results [29 ].

The International Olympic Committee considers caffeine to be a controlled or restricted substance; Olympic athletes may consume it until urinary concentrations exceed 12 mcg/ml [103 ]. The National Collegiate Athletic Association prohibits use of caffeine from any source in amounts that would lead to urine concentrations exceeding 15 mcg/ml [104 ,105 ].

(Consuming about 500 mg caffeine produces a urinary caffeine concentration of 15 mcg/ml within 2–3 hours [106 ].) The World Anti-Doping Agency does not prohibit or limit caffeine use [107 ].

### Citrulline

L-citrulline is a nonessential amino acid produced in the body, mainly from glutamine, and obtained from the diet. Watermelon is the best-known source; 1 cup diced seedless watermelon has about 365 mg citrulline [108 ]. About 80% of the body's citrulline is converted in the kidneys into arginine, another amino acid (see section on arginine ) [30 ].

Läs produktdeklarationen på ActiQs

Supplement Facts
Serving Size: 1 tablet (4.4 g) (makes 16 fl-oz/475 ml prepared)
Servings Per Container: 12
	Amount Per Serving	%Daily Value*
Calories	10	
Total Fat	0 g	0%
Total Carb	4 g	1%
Total Sugars	2 g	
Incl 2 g added sugars		4%
Vitamin A (as retinyl acetate)	112.5 mcg	13%
Vitamin C (as ascorbic acid)	10 mg	11%
Vitamin D (as ergocalciferol)	5 mcg	25%
Vitamin E (as d-alpha tocopherol acetate)	2 mg	13%
Vitamin B6 (as pyridoxal-5 phosphate)	0.25 mg	15%
Folic Acid (as folic acid)	136 mcg DFE	34%
Calcium (as calcium carbonate)	15 mg	<2%
Magnesium (as magnesium oxide)	15 mg	4%
Chloride (as Himalayan Sea Salt)	75 mg	3%
Sodium (as Himalayan Sea Salt, sodium carbonate)	100 mg	4%
Potassium (as potassium bicarbonate)	150 mg	3%
Organic Green Tea Extract (containing 40 mg caffeine)	41 mg	†
*Percent Daily Values (DV) are based on a 2000 calorie diet. 
†Daily Value (DV) not established.

Dextrose, citric acid, natural flavors, beet powder color, stevia leaf extract, avocado oil, riboflavin (for color).

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Supplement Facts
Serving Size: 1 Vegetarian Capsule
	Amount per Serving	% Daily Value
CoffeeGenic®
Green coffee extract (bean) [std. to 50% chlorogenic acids]	400 mg	**
**Daily Value not established.

Vegetable cellulose (capsule).
Each serving contains approximately 12 mg of caffeine (the amount found in 1/4 cup brewed green tea).

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Do you drink coffee or tea first thing in the morning, hoping the caffeine in it will jump-start your day? Do you follow it up with more coffee, an energy drink, or other caffeinated beverages throughout the day?

According to medical experts, including here at the FDA, caffeine can be part of a healthy diet for most people, but too much of it can have negative effects and large amounts may pose a danger to your health. Depending on factors such as body weight, medications you may take, certain medical conditions, and individual sensitivity, “too much” can vary from person to person. Be aware of the level of caffeine in your diet and look out for signs when it’s too much.

Daily Caffeine Consumption for Most Adults

For most adults, the FDA has cited 400 milligrams* a day — that's about two to three 12-fluid-ounce cups of coffee — as an amount not generally associated with negative effects. However, there is wide variation in both how sensitive people are to the effects of caffeine and how fast they eliminate it from the body.

Certain conditions tend to make people more sensitive to caffeine’s effects, as can some medications. If you are concerned about a condition or medication, or if you’re pregnant, trying to become pregnant, or breastfeeding, we recommend talking to your health care provider about whether you need to limit caffeine consumption.

“Energy Drinks” and Children and Teens

Medical experts advise against energy drinks for children and teens because of the levels of sugar and caffeine, according to the American Academy of Pediatrics.*

Too much caffeine in children and teens can cause increased heart rate, heart palpitations, high blood pressure, anxiety, and lead to sleep problems, digestive problems and dehydration.

The Dietary Guidelines for Americans say that drinks containing caffeine should be avoided for children younger than age 2 and beverages that contain no added sugars should be the primary choice for children and teens. These include water and unsweetened fat-free or low-fat milk — including low-lactose or lactose-free options or fortified soy beverage — and 100% juice within recommended amounts.

Talk with your health care professional about your child’s or teen’s caffeine consumption.

*Children Should Avoid Drinks with Sugar, Caffeine, AAP News, December 1, 2023

Caffeine May Be in Products You May Not Expect

Coffee, tea, and chocolate are well-known sources of caffeine, but it can also show up in products you may not expect.

Typical Caffeine Content in 12-fluid-ounce Drinks*

Drink Type
Typical Caffeine Amount

caffeinated soft drink
23 to 83 milligrams

green tea
37 milligrams

black tea
71 milligrams

coffee, regular brewed non-specialty
113 to 247 milligrams

energy drink
41 to 246 milligrams

*Caffeine content adapted from Assessing dietary exposure to caffeine from beverages in the U.S. population using brand-specific versus category-specific values, Food and Chemical Toxicology, June 2015

The amount of caffeine in specific products, and container sizes, can vary. If you have questions about a product, contact the manufacturer.  You can find more information about caffeine levels in food and beverages on U.S. Department of Agriculture Food Data Central.

Energy or protein bars, ice cream, chewing gum, dietary supplements, and over-the-counter medications are some of the products that may have caffeine as an added ingredient.

It’s important to know if a product has caffeine, especially if you’re sensitive to it, limiting your intake, or giving the product to children or teens.

There’s no difference in the way your body handles or the safety between the caffeine that occurs naturally in coffee and tea, for example, and what’s added to a product, so be sure to consider all sources of caffeine in your diet.

“Decaffeinated” Does Not Mean Caffeine-free

Decaffeinated coffees and teas have less caffeine than their regular counterparts, but still contain some caffeine. For example, decaf coffee typically has 2 to 15 milligrams in an 8-fluid-ounce cup. If you react strongly to caffeine in a negative way, you may want to avoid these beverages altogether.

Check the Product Label and Other Tips to Watch Caffeine Intake

All packaged foods are required to list caffeine in the “list of ingredients” when it is added to products as a stand-alone ingredient.

When a packaged food contains an ingredient – such as chocolate chips – that inherently contains caffeine, then caffeine will not appear on the list of ingredients. However, the caffeine-containing ingredient (for example, chocolate) will be listed.   

Many packaged foods, including beverages and dietary supplements containing caffeine, voluntarily provide information on the label as to how much caffeine they contain. 

Restaurants and other retail food establishments serving food and drinks are not required by law to tell you how much caffeine is in the products they serve. The FDA encourages you to ask retailers if their products have caffeine and if so, how much.

Take care the first time you consume a new packaged food or beverage containing added caffeine if the amount of caffeine in the food is not declared on the label.

If you’re used to drinking caffeine-containing beverages every day, and want to cut back, it’s best to do so gradually. Caffeine withdrawal isn’t considered dangerous but can be unpleasant.

Be Aware of How Much Caffeine Is in “Energy Drinks”

The name “energy drink” was developed by the food industry to describe certain beverages. Generally, “energy drinks” have 54 to 328 milligrams of caffeine per 16 fluid ounces, with a few brands containing 41 to 246 milligrams of caffeine per 12 fluid ounces. Most energy drinks in the U.S. have the total amount of caffeine from all sources, such as other ingredients that may have caffeine, like guarana, listed on the label.

The FDA does not have a regulation specific to “energy drinks.” All of the general regulations about the safe use of ingredients apply to these beverages.

Pure and Highly Concentrated Caffeine Products

The FDA estimates toxic effects, like seizures, can be observed with rapid consumption of around 1,200 milligrams of caffeine, or less than 1/2 teaspoon of pure caffeine.

Pure and highly concentrated caffeine products can have serious health consequences, including death. In the mid-2010s, pure or highly concentrated caffeine products emerged on the market. They were often marketed in bulk packaging with up to thousands of servings per container, which required consumers to measure out a safe serving from what can be a toxic or even lethal amount of bulk product. The FDA took action to protect consumers from these products. However, some products containing pure and highly concentrated caffeine remain on the market. Consumers should exercise caution when using such products.

Signs of Consuming Too Much Caffeine

Too much caffeine can cause a variety of symptoms:

increased heart rate

heart palpitations

high blood pressure

insomnia or sleep disruptions

anxiety

jitters

upset stomach

nausea

headache

Talk with your health care professional about your caffeine consumption if you have any of these symptoms.

FDA Oversight of Products with Added Caffeine

By law, food companies are responsible for making sure any use of caffeine in their products is safe. Caffeine, like any substance added to food, must be safe under the conditions it’s expected to be used, including the amount expected to be consumed.

The FDA monitors the marketplace to help ensure caffeine is safely used in the products we regulate. We’ll act when needed, including collaborating with the Federal Trade Commission when marketing claims made by a company become a health and safety issue.

Additional Information

A 2017 systematic review of health outcomes associated with caffeine intake by the Institute for the Advancement of Food and Nutrition Sciences confirmed the safety of the 400 milligrams a day level for most adults. The research was structured to meet gold standards for systematic reviews outlined in the National Academies of Science, Institute of Medicine 2011 publication, “Finding What Works in Health Care — Standards for Systematic Reviews”

Content current as of:

08/28/2024

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