Do you need supplements?

Meyken Houppermans, PhD. CrossFit Level 3 Trainer
Founder and Head Coach
Sport supplements are popular among CrossFitters to improve performance, enhance recovery, gain muscle mass, lose body fat, increase energy, delay fatigue, and restore nutrients. Despite the lack of evidence of their effectiveness. Taking supplements is not without risk.

Dietary supplement to treat malnutrition

Dietary supplements can be of great use to treat malnutrition in developing countries with limited access to adequate nutrition. Inadequate nutrition and micronutrient deficiencies are prevalent conditions that can have irreversible health effects, and affect mortality and morbidity.

Examples of supplementation in cases of malnutrition are vitamin A and iron in developing countries where women of reproductive age, infants and children often have deficiencies; folic acid, iron, calcium and iodine in developing and developed countries for reproductive-aged women or those who are pregnant; and calcium and vitamin D for elderly.

Dietary supplement to enhance health and performance

In developed countries, adequate nutrient intake can usually be achieved through awell-balanced diet. 

Lack of evidence

Supplementation might not confer additional health benefits of performance, except among individuals with increased requirements for example because of certain diseases,or among athletes with a temporary deficiency syndrome.

The evidence on the effectiveness supplementation such as multi-vitamin and mineral supplements in relation to the prevention of diseases, the enhancement of immune system, or the improvement of performance is inconclusive and research results are limited.

Despite this lack of evidence, over the last twenty years the use of dietary supplements and sports supplements has grown, especially since the COVID-19 pandemic due to a global trend to prevent and treat disease without drugs. Sports supplements are more and more used by recreational athletes for several reasons such as to improve performance, enhance recovery, gain muscle mass, lose body fat, increase energy, delay fatigue, and restore nutrients.

Dietary and sports supplements are easily available in supermarkets and online because of limited legislation compared to prescribed supplements and medication. Research shows, the dietary supplement industry is huge and supplements are produced with minimal regard for safety, quality, and efficacy by multinationals who make large profits.

Placebo effect

Research has shown that in over 60% of supplements aimed at hormone regulation, muscle strengthening, fat burning and gaining more energy, the food label does not reflect what and how much is actually in there and the supplements contain substances indicated as doping. A food label should display all ingredients; mention it is not a replacement for a wholesome meal plan; should contain info on advices dosage; and cannot have medical claims.

In many cases, the effect is only a placebo effect. Nevertheless, many athletes use orhave used supplements. Why is that?

Often we start to take something or do something, when we’re in a dip. For example when our training is not going how we planned or how we would like to see it. And then, we come out of that dip and attribute the progression to whatever we did or took during the dip. When actually,  dips are a natural part of life. And the causality between the progression and whatever you took is often hard to find. So often, a supplement has a placebo effect.

Some sport supplements are particularly popular among recreational athletes:

Magnesium and zinc

Magnesium and zinc are supplements often adviced to and taken by athletes, because a shortage in magnesium might lead to muscle cramps and fatigue. There is no clear evidence for this statement. Zinc is often used because zinc is required for muscle build and immune function.

In the general population a shortage in magnesium hardly happens. There are hardly any cases of shortage, only sometimes zinc in people who eat vegan.

Magnesium is in grains, greens, nuts and fish. An overdose does happen, due to supplements. This leads to gut problems.

Zinc is in meat, cheese, grains, fish and nuts, although zinc in nuts, legumes and grainsis not absorped well because of the high fiber content of these products. An overdose happens, due to supplements. And this can lead to a shortage in copper. Copper is needed for immune system.


Calcium is important for functioning of the nervous system, that signals to muscles, and is needed for muscle contraction. Research shows calcium supplements have a different effect compared to dairy as source of calcium. Calcium supplements or dairy?  

Supplements beneficial for performance

A wholesome diet with whole grain products, lean animal and/or plant based protein, lots of colorful vegetables, some fruit, nuts and seeds, optionally dairy, and unsaturated fats, all in moderate amounts, provides everything the body needs to function optimally. Besides eating minimally processed foods (How artificial is your food?), timing of meals is relevant for health and performance.

Nevertheless, some supplements can be useful. For example decades ago when we all had iodine deficiencies leading to dysfunction of the mental and physical development in children, the Dutch government diseased to add iodine to bread. (Dutch standards on vitamins and minerals). Additionally, certain (sports) supplements seem to have certain verifiable beneficial effects in certain cases:


There is no clear scientific evidence that caffeine stimulates performance, at least not in all cases and all athletes. The evidence seems to depend on the doses, the population, the habitual consumption of caffeine, and the type and duration of the exercise.

What is known it that caffeine peaks 60 minutes after intake and half-time is 2-10 hours. In general, caffeine seems to improve cognitive functioning, meaning focus, psychomotor skills and memory.

In endurance athletes some studies show an improvement of 10-20% in time to exhaustion. In strength athletes, some studies show improvements in performance in short training sessions of 5 minutes at 100% of VO2Max. These benefits occur only when taking a caffeine supplement, not when drinking caffeine.

In general a healthy and non-pregnant adult can take up to 400 mg of caffeine per day safely, with a maximum of 200 mg of caffeine at one time. Caffeine supplements often contain high levels of caffeine. Within Europe there is no legislation on the maximum amount of caffeine in food supplements.

Too much caffeine can have adverse effects such as headaches, increased heart rate, hypertension, gastrointestinal problems, restlessness and sleep problems.


There are some indications that creatin can have a positive effect on short-term maximal, and explosive efforts of an interval nature such as weightlifting or short sprints, but only in men. Creatin may increase muscle strength a little bit, but it is no guarantee for success.

Creatine often leads to weight gain due to fluid retention, and in some cases to intestinal discomfort. Furthermore, the use of a creatine supplement can interfere with the body's own production of creatin and, moreover, taking additional creatin has no effect in about 30% of the users.

Supplements beneficial for overall health

Supplement cannot replace a wholesome diet. Nevertheless, two supplement that can support overall health:

Fish oil

Omega 3 has an anti- inflammatory effect. Omega 6 on the other hand, such as in sunflower oil increases inflammation.

It is recommended to take omega 3 supplements if fish is excluded from a diet. Furthermore, sometimes omega 3 supplements are a better source of omega 3 compared to fish, because farmed fish often hardly contains any omega 3, because it is fed with grains.

Vitamin D

Vitamin D is needed to absorb calcium from the diet and is important for growing and maintaining strong bones and teeth, for proper muscle function and the immune system. It is recommended for all adults in The Netherlands to take a 10micrograms vitamin D supplement.

Supplements with health risks

Too high dose

The accuracy of food labels of vitamin supplements and herbal supplements cannot be guaranteed. This increases the risk of a too high dosage, not without risk. For example, a too high dose of vitamin B6 can lead to neuropathie and a too high dose of vitamin A can lead to intoxination.

Herbal supplements

Herbs such as huperzia serrata, tabernanthe iboga or ashwagandha are also known to be harmful. Some herbal supplements are prohibited by law, such as supplements containing the herbs kava kava and ephedra. A too high dose of silverclover can lead to liver inflammation. Furthermore sometimes herbal supplements such as kurkuma, ginseng and green tea can contain toxic substances such as led.

Furthermore, herbal supplements such as CBD oil, St. John's wort and Valerian can weaken or intensify the effect of a medication, which can lead to health risks.

Pre- and post workout supplements

Some pre-and post workout supplements, may contain substances that are on the dopinglist. They also sometimes contain too much of certain substances for example DMAA (dimethylamylamine) or sibutramine, increasing the risk of hypertension or increased heart rhythm. The substance is banned in Europe because its safety has not been established.


In most cases supplements are not necessary. Taking supplements is not without risk. Because of the limited research on the effectiveness and the lack of legislation, the user is not 100 percent guaranteed that the product is safe, effective, and contains what it says on the food label. What is guaranteed, however, is that in most cases a wholesome diet provides sufficient nutrients to function optimally and additional supplementation might be in place but only after a medical checkup by a health professional.

Create your own health!©


Picture retrieved from Genetic Literacy Project. April 2024.

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