Concerning caffeine levels in pre-workout supplements
By Katelyn Barnes APD, PhD and Ben Desbrow APD, AdvSD, PhD
Caffeine is a popular, legal, cheap and effective enhancer of sports performance. These features, along with increasing subjective perceptions of alertness, have made caffeine a core ingredient of many pre-workout supplements (PWS). PWS are a relatively new (popularity increased considerably in previous 10 years) class of multi-ingredient dietary supplements promoted to assist with training.
Caffeine’s influence on human health has received considerable scientific attention and this work has generally identified it as a safe substance. However, adverse side effects have been noted at intakes >400mg·day-1. As such, international agencies promote single doses of caffeine <200mg and daily consumption of <400mg for healthy adults (excluding pregnant women). In addition, caffeine’s ergogenic potential has been demonstrated to fall within these safe limits (i.e. 0.5-4.0 mg·kg-1of bodyweight·day-1).
Caffeine content is not commonly stated on the nutrition information panels of PWS. However, according to those that do specify an amount, PWS typically contain ~100-300 mg of caffeine·serve-1. Importantly, dietary supplements are notorious for ingredient variations (either accidentally due to poor manufacturing practices, or intentionally by unscrupulous manufacturers). Thus, PWS consumers may be at risk of exposure to acute caffeine doses (and daily intakes) in excess of safety recommendations. Case study associations with severe adverse events, and accounts of caffeine-related deaths have reinforced safety concerns relating to PWS use. Hence, an independent verification on the caffeine content of PWS was warranted.
This investigation1 aimed to explore the caffeine content of PWS most likely to be consumed within our local context (Australia): Specifically, we sort to;
- Quantify the caffeine content of commonly used PWS in Australia;
- Determine the accuracy of caffeine listed on the nutrition information panel
- Determine the variability in caffeine content within and between batches of the same PWS.
Fifteen caffeine containing PWS were identified as the ‘most popular’ products from a concurrent PWS consumer survey. One container of each PWS was purchased through two leading national online supplement retailers. For the five most popular caffeine containing PWS, a second (online) and third (in store) purchase was made to conduct batch testing (week-to-week variability). High Performance Liquid Chromatography (HPLC) analysis was used to quantify caffeine content of pre-workout supplements. On opening, many of the PWS appeared to demonstrate “layering”, hence each product was tested in samples drawn from the top, middle and bottom of each container. Caffeine·serve-1 was determined from the manufacturer’s recommended serve size. One way ANOVAs were used to detect differences in caffeine content within and between batches. The authors considered the least significant practical difference in caffeine content to be >40mg·serve-1 (~ ½ can of Red BullTM) because this is the smallest amount of caffeine that has been demonstrated to influence (cognitive) performance.
