The research, published online ahead of print in JAMA Internal Medicine, is the latest in a series of articles in the journal addressing the caffeine content in energy products and comes as the sector faces heightened scrutiny.
It found that the “majority of caffeine-containing supplements had inaccurate labels”, co-author and assistant professor of medicine at Harvard University Dr Pieter Cohen told us.
He added: “Many were not even compliant with the lenient laws regulating supplements.
“Single servings of these supplements could supply as much caffeine as found in four sodas or three cups of coffee and could exposure our troops to risks especially when combined with energy drinks and significant physical exertion.”
The authors identified the most popular dietary supplements sold as capsules (excluding drinks and gels) on military installations labeled as containing caffeine or herbal ingredients known to naturally contain caffeine - but without caffeine listed on the label.
The quantity of caffeine per serving in the supplements was determined by high-pressure liquid chromatography with UV absorbance after solvent extraction, and the results compared with the caffeine content listed on the label.
All analyses were performed by NSF International.
Only 9 out of 20 products listed an accurate amount of caffeine on the label
31 supplements met the inclusion criteria, of which 20 products listed caffeine on the label.
Analysis of the 11 supplements containing herbal ingredients that naturally contain caffeine revealed they contained minimal amounts (0-3 mg per serving).
Of the 20 products listing caffeine on the label, only nine listed an accurate amount of caffeine (within 10% more or less than the amount listed on the label), however.
Meanwhile, caffeine amounts listed on the label of five of the 20 products “varied widely” from chromatographically determined levels, with ranges from 27% to 113% of the labeled quantity.
Products without the amount of caffeine labeled contained 210 to 310 mg per serving
The other six products listed caffeine as an ingredient without providing an amount on the label. All six contained high amounts of caffeine, ranging from 210 to 310 mg per serving, said the authors.
“The law regulating the manufacturing and sales of dietary supplements in the United States has loopholes that allow manufacturers to avoid listing the quantity of caffeine on the label.
“Our… analyses… found that less than half of the analyzed supplements’ labels provided clinically useful information regarding caffeine content.
A limitation of the study was that only one sample of each supplement was tested, acknowledged the authors.
“Future research would need to determine if our findings are representative and if caffeine content varies from one sample to another.”
Military personnel cannot determine if a supplement can be safely combined with other products containing caffeine
But they added: “Our findings are consistent with prior research demonstrating that commercially available dietary supplement labels do not provide sufficient information in respect to caffeine content.
“Given the lenient legal framework and inaccurate labels, military personnel are unable to determine if a supplement can be safely combined with other products or foods containing caffeine.
“This is of increasing concern, as caffeine intake in the form of energy drinks has significantly increased over the past decade, and a recent Centers for Disease Control and Prevention study found that 45% of service members consume energy drinks on a daily basis.”
To ensure consumer safety, they conclude, “accurate information on caffeine content should be provided on all dietary supplement labels”.
FDA: 400mg of caffeine a day poses no particular risks for most healthy adults
There is a consensus among health professionals that for most healthy adults, consuming 400mg or less of caffeine daily poses no particular risks.
The Food and Drug Administration (FDA) also made this clear in its responses to two letters sent by senators Dick Durbin, D-IL and Richard Blumenthal, D-CN, asking the agency to probe the safety of energy beverages.
This didn’t stop the pair from sending a third letter to FDA with the same request late last year.
However, New York-based attorney Marc Ullman of Ullman, Shapiro & Ullman told us earlier this month that he is not expecting sweeping new rules from the FDA.
“I just don’t see the mechanism that justifies action from FDA within our legal and regulatory framework.”
CRN: There is nothing unique about the caffeine in supplements, but it's not labeled when you buy a coffee
Council for Responsible Nutrition (CRN) regulatory counsel Rend Al-Mondhiry told us: "The five products that state inaccurate caffeine levels would be considered adulterated and out of compliance with the law, so that is unfortunate. It's a GMP testing issue."
She added: "We are ready to engage in a dialogue with the FDA about caffeine, but we need to remember that caffeine is a safe ingredient, and one of the most studied ingredients. Also, there is nothing unique about the caffeine in supplements, but it's not labeled when you buy a coffee."
Rules on caffeine use
While caffeine is generally recognized as safe (GRAS) in cola-type beverages up to 0.02% or 200ppm (or 71mg/12oz) - a level the FDA says is also relevant to other soda products, this stipulation does not apply to dietary supplements.
Currently, supplement manufacturers are not required to list the amount of caffeine in their products if it is part of a proprietary blend. So 5-Hour Energy, for example, which is marketed as a supplement, lists caffeine as part of an 1,870mg 'energy blend' that also includes other ingredients such as taurine.
Source: JAMA Internal Medicine
Published online ahead of print, January 7, 2013. doi: 10.1001/jamainternmed.2013.3254
“Caffeine Content of Dietary Supplements Consumed on Military Bases”
Authors: Pieter A. Cohen, MD, Selasi Attipoe, MA, John Travis, BS, Mark Stevens, MD and Patricia Deuster, PhD, MPH