Dietary Supplements and the High-Performance Athlete

Training and nutrition underpin athletic performance, however dietary supplements may play a smaller, but important role. Supplements are very popular in the sporting world; from sports foods that provide additional macronutrients, to powders that may improve alertness. There are so many available, and it can be difficult to know which ones may be beneficial or harmful to an athlete’s health and performance. A new study from the International Journal of Sport Nutrition and Exercise Metabolism summarised the evidence surrounding popular sports supplements and provides guidance for professionals and athletes regarding efficacy, dosage and side effects.

Micronutrients That Often Require Supplementation in Athletes

Common vitamins and minerals play a crucial role in factors that contribute to sports performance such as regulating energy production and creating new cells and proteins. An athlete who is deficient in fundamental nutrients may be more prone to illness and injury or unable to train as effectively. Calcium, vitamin D and iron are three nutrients often lacking in the general population and athlete’s diets.

Calcium & Vitamin D

Calcium and Vitamin D are essential for bone health and important in maintaining immunity and muscle strength. Dairy products are the best source of calcium, while vitamin D is synthesised in the skin from direct contact with sunlight and can also be obtained from some foods.

Athletes may be at risk of insufficient vitamin D during colder seasons where there is less exposure to the sun, while athletes who avoid dairy products are at higher-risk of insufficient calcium intake. It makes sense for athletes to prioritise calcium and vitamin D given the absolute necessity for muscular and bone health in competitive sports.


Suboptimal iron levels may be due to limited intake, choosing foods low in bioavailable iron, or increased iron needs due to rapid growth, high-altitude training or excess loss through sweat, urine or faeces. Female athletes are also more prone to low iron status than males due to blood loss during menstruation.

An athlete who does not obtain adequate iron may notice fatigue, shortness of breath and changes in overall strength, which are essential components for optimal performance.

Sports Foods and Functional Foods

Athletes often have higher macronutrient and electrolyte requirements than the average person, however it can be more challenging to meet needs in certain situations such as during an event or between races. Sports foods can be a convenient source of nutrients like carbohydrates, protein, fat or electrolytes, that help sustain or recover from physical activity by replenishing stores before, during or after an event.

Sports and energy drinks, sports gels and sports confectionary, electrolyte replacement supplements, protein supplements, liquid meal supplements, sports bars and protein enhanced foods are all supported with evidence to improve athletic performance when used correctly. Keep in mind these supplements are often expensive, and everyday foods may be an appropriate option depending on the activity and overall goal.

Supplements That Directly Improve Sports Performance

When someone says ‘sports supplements’, caffeine or creatine are probably the first that come to mind, and for good reasons too. Nitrate, beta-alanine and sodium bicarbonate may also improve performance to some degree depending on the dosage and situation.


Caffeine can increase endorphin release and improve alertness. This stimulant has well-established benefits for both endurance and power athletes of many sporting backgrounds. Dosing appropriately and according to an athlete’s individual tolerance level is key to avoiding side effects such as nausea, anxiety and restlessness.


Creatine is stored in muscles, but this reserve is rapidly depleted during high-intensity exercise. Creatine loading increases muscle stores, therefore improving the rate muscles convert energy to movement. Supplementing with creatine can also lead to greater lean muscle mass, muscular strength and overall power.

However, creatine loading will likely result in water retention, therefore athletes should consider this effect especially for those competing in sports with a lower weight target.


Dietary nitrate supplementation appears to be most beneficial for high-intensity events ranging from 12-40 minutes due to its ability to enhance function of fast-twitch muscle fibres, respiration and blood flow – ultimately improving performance time and levels of exhaustion.

High nitrate foods include leafy green and root vegetables, including

  • Spinach
  • Rocket salad
  • Celery
  • Beetroot

Benefits are usually seen within 2-3 hours after supplementation. Nitrate supplementation may cause stomach upset, so trialling this with a professional before competition day is a must.


Beta-alanine is used to increase skeletal muscle carnosine content (a protein used to soak up by-products produced during exercise). This can assist with improving exercise capacity and performance for sustained high-intensity exercises, continuous or intermittent, from 30 seconds to 10 minutes in duration.

Benefits may only be minor, but potentially valuable in highly competitive continuous or intermittent sports. Meanwhile, side effects can include rashes, tingling or numbness.

More research is needed to provide practical dosing advice that is specific to certain sports, so professional guidance from an Accredited Sports Dietitian is recommended.

Sodium Bicarbonate

Sodium Bicarbonate acts as a blood buffer and helps to flush metabolic by-products from muscle tissue during exercise.

As a result, this can help sustain high-intensity exercise performance. Fortunately, potential side effects such as stomach upset can be managed through dietary changes.

Supplements That Indirectly Improve Performance

There are also supplements can indirectly effect sports performance by influencing factors that contribute to this such as enhancing immunity, assisting with training capacity, and contributing to beneficial physique changes like an increase in muscle mass.


Supporting immune health in athletes is important to prevent sickness during training and competition while the body is under constant physical stress. There is moderate evidence to support the use of vitamin D, probiotics and vitamin C for immunity in athletes.

However, supplements including the following do not support immunity in athletes:

  • Bovine Colostrum
  • Zinc
  • Glutamine
  • Echinacea

Caution should be taken with Vitamins C and E, as high doses of these antioxidants have been found to hinder exercise-induced training adaptions on a cellular level (especially in in endurance athletes).

Training Capacity, Recovery and Injury Management

Training capacity, recovery and injury management are important factors that contribute to performance growth and overall physical health leading up to competition.

Creatine Monohydrate may improve recovery from muscle damaging exercises, while Beta-hydroxy beta-methylbutyrate (HMB) may produce minor improvements in muscle strength and recovery.

However, similar results from HMB could probably be obtained through a balanced diet containing adequate protein. Meanwhile, omega 3-fatty acids, vitamin D, gelatine and vitamin C/collagen and anti-inflammatory supplements like curcumin are not supported with sufficient evidence to guide recommendation for training capacity, recovery or injury management.

Physique Changes: Lean Muscle and Fat Mass

Changes in lean muscle mass or fat mass can make all the difference on competition day. Lower muscle mass can limit strength, while additional fat might mean an athlete exceeds their weight category.

When dietary intake is suboptimal, protein and leucine supplementation may be an appropriate method to meet an athlete’s needs and promote lean mass gain and potential fat loss. However, optimising dietary protein intake first is ideal, and protein supplementation in-excess of an athlete’s needs is unnecessary and unlikely to lead to additional benefits.

Additionally, pyruvate, chromium, green tea, alpha-lipoic acid, conjugated linoleic acid (CLA), konjac fibre, omega-3 polyunsaturated fatty acids and chitosan supplements have little to no effect on reducing fat mass.


There is a lot to consider when adding a sports supplement into an athlete’s routine. It is important to ensure athletes are following a balanced meal plan tailored to their needs prior to supplementation so they can maintain good health through high impact sports and intense training programs. Supplements should also be trialled well before event day to ensure dosage aligns with expected results, and side effects can be controlled.

It is also crucial to perform a risk analysis weighing the benefits of the supplement with the risk of potential doping due to contamination. One in ten supplements sold are contaminated with some form of prohibited steroid or stimulant which could be detrimental to an athlete’s career.

Fortunately, there are quality assurance programmes set in place to help athletes manage the potential of inadvertent doping violation. Products that carry the ‘Informed Sport’ logo are much safer for athletes to take as these have undergone rigorous manufacturing audits and are batch-tested for banned substances. You can visit their website and download the latest list of Informed-Sport certified products to clarify certification.

Speak with one of our Accredited Sports Dietitians at Sunshine Coast Dietetics for further supplementation guidance and dosing advice that is tailored to your body and athletic goals.