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Core Knowledge


Supplements 101


With thousands of supplements on the market, it's increasingly challenging to differentiate between snake oil and proven health and performance boosters. Supplements can include vitamins, minerals, proteins, and fiber, among others.

They can be used to boost the immune systems, decrease heart attack risk and high levels of stress, and can also increase energy levels, alleviate pain, and reduce symptoms from diseases like fibromyalgia, osteoporosis, and Alzheimer's disease. Supplements have also been used to increase athletic performance.

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The supplement industry is very under-regulated, so you can't always trust that the label is telling the truth about what's inside. It's important to make sure that your supplement is third-party tested through a company such as NSF International, Informed Choice, or United States Pharmacopeia. This helps ensure that you're actually getting what you paid for, but keep in mind that this doesn't mean the product actually works. Buying supplements from a company that has an established record of ethical business conduct is one step that can decrease the likelihood of getting unclean supplements.

Athletic Performance and Supplements

Athletes and Serious Exercisers

Athletes and serious exercisers may benefit from supplementation, but the decision of which supplements to includes should be made on case-by-case basis according to a person's needs. We recommend that you consult with a sports medicine physician and/or a registered dietitian with expertise in sports nutrition before using supplements.

Athletes Under 18

We don't recommend performance-enhancing supplements for athletes under the age of 18. College, high school, professional, and Olympic athletes should pay special attention to guidelines regarding supplements established by sports governing bodies like the NCAA, the NFL, and the World Anti-Doping Agency. If athletes choose not to follow these guidelines, they may loose eligibility or experience other penalties by their affiliated schools.

Aging Athletes and Exercisers

Dietary needs change with age, so certain supplements can be beneficial for older athletes and exercisers can be beneficial. For example, between 50-90 percent of people ages 51-70 are vitamin D deficient. In this case, a supplement may help. Always check with your doctor before supplementing.

"Food First" Approach to Supplements

At Core Performance, we follow a “food-first” approach to supplements. Nutritional goals should be reached first by eating and drinking healthy foods and fluids. When there are dietary deficiencies or ways to improve performance by taking legal, ethically administered/safe supplements, these choices are recommended with care. To learn more about choosing healthy, natural, and minimally processed foods, read "How to Eat Clean." 


Vitamins are organic substances, both water-soluble (like vitamin C and B-complex vitamins) and fat soluble (vitamin A, D, E and K), and help regulate metabolism, control tissue growth, and protect cells. Vitamins A, C, E, and beta-carotene serve necessary protective functions as antioxidants, which can reduce the potential for free radical damage (oxidative stress),and may help protect against heart disease, cancer, and degenerative diseases.

Minerals are essential to life and provide structure in the formation of bones and teeth and help regulate the macronutrients glycogen, fat, and protein.

A multivitamin with antioxidants can be used to complement a healthy diet, helping to supplement nutrients that you may not get through fresh foods sufficiently.

Vitamin D

Vitamin D is a group of fat-soluble prohormones obtained from sun exposure, food, and supplements. Vitamin D is naturally produced by the human body when exposed to direct sunlight. Season, geographic latitude, time of day, cloud cover, smog, and sunscreen affect UV ray exposure and vitamin D absorption. People with limited sun exposure should include good sources of vitamin D in their diet.

Sources of vitamin D:

  • Vitamin D-fortified milk
  • Salmon
  • Sardines
  • Mackerel
  • Cod liver oil

An average American diet has 100 IU per day. Adequate intake has been defined as 200 IU/day from infancy to 50 years old, 400/day for individuals ages 51-70, and 600/day for those over 70 years old. However, the American Academy of Pediatrics argues that these recommendations are insufficient and instead recommends a minimum of 400 IU, even for infants. People with a high risk of deficiency should aim for 1000 IU of vitamin D daily.

Vitamin D deficiency is a world-wide epidemic affecting all age groups in all populations, even athletes and those otherwise considered healthy are at risk. Recent estimates show that ore than 50 percent of the global population is at risk of deficiency. If you're concerned about your vitamin D status, talk to your doctor about ordering a vitamin D blood test.


Calcium is necessary to build and maintain strong, dense bones. Approximately 99 percent of the body's calcium is stored in the bones and teeth, according to the National Institutes of Health Department of Dietary Supplements. Long-term calcium deficiency can lead to rickets, poor blood clotting, and osteoporosis.

Calcium sources include:

  • Dairy products like milk and cheese
  • Seaweeds, nuts, and seeds
  • Blackstrap molasses
  • Beans, quinoa, and amaranth
  • Oranges, figs, and dandelion leaves
  • Collard greens, okra, rutabaga, broccoli, and kale
  • Fortified products such as orange juice and soy milk

If you aren't getting the calcium you need from food, a supplement can help. Calcium carbonate is the most common and least expensive calcium supplement.

So how much calcium do you need? The Institute of Medicine recommends that adults age 19-50 need 1000 mg/day, while adults over 51 should aim for 1200 mg/day.

Omega-3 Fatty Acids

Omega-3s are found in fatty fish like salmon or tuna, walnuts, and flaxseed. Diets high in omega-3s have been found to help control inflammation and protect the heart. Consider taking a fish oil supplement that has 1-3 g of EPA and DHA, as recommended by The American Heart Association. Make sure to check the label of your supplement and take enough to get to that 1-3 grams of EPA + DHA, not total fish oil.

For more information on omegas, read "The Complete Guide to Omega Fatty Acids."


Probiotics are "good" bacteria that have been linked to increased immunity, a healthy digestive system, reduced fatigue, and general well-being. While there hasn't been a direct link to athletic performance, the benefits probiotics have on the entire body may in turn benefit performance.

Foods high in probiotics include:

  • Yogurt
  • Non-baked cheese
  • Kefir
  • Miso
  • Tempeh
  • Sauerkraut
  • Kim chi
  • Soy beans and other soy products

While getting probiotics from food is preferred, it can be challenging because a lot of probiotic benefits can be lost in the processing used to increase a food's shelf life. If you experience consistent stomach problems like gas and bloating, consult your doctor about using a probiotic supplement.

Digestive Enzymes

Digestive enzymes are proteins secreted by the salivary glands, stomach, pancreas, and small intestine. They help break down large macronutrients into smaller, more easily digested, forms of these nutrients, which can help increase energy, growth, and overall health.

A poor diet, stress, aging, and a body with a disease can affect natural processes internally, resulting in poor digestion, less efficient absorption of food, and decreased energy and immunity. Even worse, undigested or poorly digested food can damage the digestive tract. Supplementation can help reverse these negative affects.

Look for plant-based digestive enzymes, which have been shown to withstand the harsh conditions of the digestive tract. Start by taking one to three digestive capsules (depending on the size of your meal) immediately before eating. A quality digestive enzyme supplement should provide a mixture of:

  • Proteolytic (enzymes that breakdown proteins)
  • Lipolytic (enzymes that breakdown fat)
  • Carbolytic enzymes (enzymes that breakdown carbohydrates)

Digestive enzymes, especially proteolytic enzymes, when taken on an empty stomach, can be absorbed into the blood stream, helping to manage inflammation and increase circulation leading to enhanced nutrient delivery and removal of waste. This may prove beneficial for recovery from strenuous activity, as well as injury.

Performance-Enhancing Supplements


Creatine is a naturally-occurring compound that can be produced by the human body and plays a role in energy metabolism. Creatine helps replenish our most immediate fuel (intramuscular ATP) used in short intense bouts of exercise like sprinting and weight lifting.

Creatine supplementation is a way to maximize intramuscular stores of this compound, which has been shown as an effective means to increase performance. Creatine supplementation may lead to slight weight gain (consisting of water and potentially lean tissue), but it doesn't appear to reduce performance, and more often than not isn't connected to improvements in performance. Five grams per day of creatine monohydrate accompanied by ~30 g of carbohydrate is a commonly recommended dosage for improving performance.

Read "The Complete Guide to Creatine," for more tips.

Essential Amino Acids (EAA)

Essential Amino Acids are the building blocks used to build blocks of proteins. While the body produces some EAA on its own, it may rely on the diet or other outside sources for some (or higher quantities) of these. When we're stressed, like during exercise, EAAs are mobilized and used for protein synthesis and energy metabolism. If this doesn't happen, the body breaks down muscle for energy.

Sources of EAAs include a combination of complete proteins (primarily animal sources) combined with incomplete proteins (rice and beans) or through supplementation. Supplementing with EAA in combination with carbohydrate immediately post-exercise has been shown as an effective means of promoting muscle protein synthesis. There is also some evidence to show that the same combination used prior to exercise may be effective at promoting increases in muscle protein synthesis.

Take ~6-9 g of EAA (20 g of whey protein that contains ~9 g of EAA) combined with ~30-60 g of carbohydrate immediately post-exercise (depending on the intensity and duration) for optimal recovery and muscle protein synthesis. For more tips on post-workout nutrition, click here.


Leucine is an essential amino acid that you can only get from food or supplements. It's used as fuel for the body and helps build muscle after strenuous exercise. Unlike other amino acids, it can stimulate muscle growth on its own and it has been shown to help reduce muscle protein breakdown.

While leucine can be found in foods like meat, eggs, dairy, and soy products, supplementation is a good way to reap the benefits. If you choose this supplement, incorporate 1-2 g of free form L-leucine into your post-workout shake every day to benefit from its muscle-building and performance enhancing ability. For shake ideas, check out "5 Simple Post-Workout Shakes." 


Beta-hydroxy-methylbutyrate (HMB) is a metabolite of leucine that has been linked to the promotion of muscle growth and the reduction of muscle protein breakdown. The use of this metabolite is debatable. Some research has shown it to be beneficial in trained and non-trained individuals, while other studies have shown that it has no effect. We use it at Athletes’ Performance and Core Performance in combination with proper diet and training protocols. It's recommended to supplement with 3 g of HMB per day to see benefits.


Beta-alanine is a non-essential, naturally-occurring amino acid. Beta-alanine may boost muscle mass, decrease muscular fatigue, and decrease time to fatigue in both strength and aerobic training. While most research supports these benefits, some studies have shown this supplement to have no benefits. More research is needed, but divided doses of 3.2 to 6.4 g per day has been shown to increase levels of carnosine, which has in some studies has been linked to increased performance.


Carbohydrates are the body’s main fuel of choice. Carbohydrate stored in the body are called glycogen and help balance energy levels. When athletes say they "hit a wall," they're running low on glycogen. Supplements like sports gels, sports drinks, and sports beans are used to boost energy, increase endurance, and positively affect performance.

Carbohydrate supplements are important for anyone who wants to gain an edge on their competition. Consumption of carbohydrates can delay time to fatigue and help increase intensity, reps, and duration.

The key to using carbohydrate supplements is to make sure that you're replacing the amount of glycogen being lost without overdoing it. A rule of thumb: Consume 1 g of carbohydrates/per kilogram/per hour for aerobic activity. Upset stomach is a possible side-effect of using these supplements, so make sure that you practice with your carbohydrate of choice prior to competition or race (nothing new on game day). Also, make sure the product you're using has two different types of carbohydrate: sucrose and glucose. This will also lessen the chance of an upset stomach.


The most plentiful non-essential amino acid in the body under normal conditions, glutamine is considered essential under physiological stress since it's a fuel source for immune system cells. The estimated daily intake of glutamine through protein-rich foods is approximately 3 to 6 g per day, and more for athletes who consume higher protein diets. Largely synthesized in skeletal muscle and released into the blood during exercise, it plays a number of important physiological roles, including increasing cell volume and stimulating protein and glycogen synthesis. Despite this, there is no compelling evidence to support glutamine supplementation in terms of increasing lean body mass, improving muscular performance, or decreasing exercise-induced stress and susceptibility to infections. Supplementation with glutamine is considered safe but not effective, and getting it through food is your best bet.


Arginine is a conditionally essential amino acid involved in protein synthesis that's been suggested to have ergogenic potential. The main interests in arginine are its role in the secretion of endogenous growth hormone, its involvement in the synthesis of creatine, and its role as a precursor to nitric-oxide. Arginine is a popular supplement among those wishing to improve exercise performance and body composition. While the theory is there, the available evidence to support claims in healthy athletes is limited and data is conflicting. More research is needed to evaluate the role of arginine supplementation on exercise performance and training adaptations in healthy and diseased populations before conclusions can be drawn.


Caffeine can be an ergogenic aid for performance but it’s specific to the type of activity and also individual responses. Caffeine can enhance alertness, maximize endurance activities, and also potentially optimize glycogen resynthesis during the recovery phase of exercise. The research is inconsistent when looking specifically at strength and power activities. When consumed in low-to-moderate doses (3-6/mg/kg) 30 to 60 minutes prior to exercise it can be effective at enhancing performance. Higher dosages show no further benefit. Athletes should also take into consideration that they may not respond well to caffeine pre-workout (i.e. they may encounter diarrhea or jittery sensations that are distracting) so they should practice prior to game day to be safe.

Take-Home Message

When starting any new supplement, you need to be strategic when adding it into your daily routine and consistent with taking it. We highly recommend that you:

  1. Have a legitimate reason to consider dietary, performance-enhancing, or recovery-enhancing supplements.
  2. Make your decision based on information from reputable, scientific sources. Also make sure the health professional recommending the product doesn't have a vested interest in the products being discussed or sold.

Tags: Supplements


  1. Institute of Medicine
  2. Bob Calvin MS, RD, LD, CSCS, performance nutritionist, Athletes’ Performance/Core Performance
  3. Danielle LaFata, MS, RD, performance nutritionist, Athletes’ Performance/Core Performance
  4. Simin Levinson, MS, RD, performance nutritionist, Athletes’ Performance/Core Performance