Writing in the journal Food and Chemical Toxicology, Wayne Doyle and his colleagues from Saint Mary’s College of California said that the increasing popularity of energy drinks among young people meant it was important to assess their effects on relevant human tissues.
The biologists cited a range of studies showing that energy drinks led to better cognitive function, improved athletic performance improved and mood, stopped blood pressure increases under stress and raised pain tolerance.
“On the other hand, studies have shown that use of energy beverages led to minimal memory gains, decreased heart rate, increased diuresis and natriuresis, and increased arterial pressure,” the scientists wrote, citing work by Bichler et al. (2006) and Riesenhuber et al. (2006).
Noting clinical cases of adverse cardiovascular and neurological effects due to excessive caffeinated drink intake (Reissig et al. 2009), Doyle et al. wrote: “The contradictory effects of energy beverages observed by the various studies make it necessary to further examine their safety.”
Scratch wound healing assay
The team said there were few studies correlating to energy beverages and changes in cellular function (the only study they found was Worthley et al. 2010), adding that their research was the first to examine the effects of energy drinks on the cellular morphology of multiple cell types.
Using in vitro assays, they examined the effects of two energy beverages on mesenchymal and epithelial tissues and neuronal (nerve) cells.
Doyle et al. described one of the drinks chosen as a “leading canned beverage” with caffeine, taurine, (glucose metabolite) glucuronolactone, vitamin B complexes, glucose, Asian ginseng, (amino acid) L-carnitine and guarana.
The second drink chosen was a concentrated beverage with caffeine, taurine, glucuronolactone, vitamin B complexes and citicoline. This last is a naturally occurring brain chemical that has been used to treat Alzheimer’s Disease.
“Our results showed that treatment of epithelial and mesenchymal with either energy beverage resulted in dose-dependent delay in wound closure, in a scratch wound healing assay,” Doyle et al. wrote.
Discussing their results, the biologists wrote that in rat embryonic fibroblast cells, treatment with the energy beverages led to decreased lamellipodia formation.
As cytoplasm extensions, lamellipodia allow cells to move along the substrate, and are important in wound repair. Cytoplasm itself is a gel-like substance (principally water) within the cell membrane that holds the cell’s internal structures, with the exception of the nucleus.
Caffeine, taurine, glucose…
Doyle et al. also found decreased lamellipodium proliferation and viability; whereas in MDCK (Madin-Darby Canine Kidney epithelial cells) energy beverage treatment resulted in actin (a protein) disorganization but did not affect cell proliferation.
This suggested that the mechanisms underlying wound healing might be different in the two cell types, the team wrote, while they found that the healing delays could not be mimicked by treatment of caffeine, taurine and glucose alone or in various combinations.
Furthermore, treatment of chick forebrain neuronal cultures with energy beverages resulted in a dose dependent inhibition of neurite outgrowth.
Summing up their findings, Doyle et al. wrote: “Our results showed that acute exposure to energy beverages results in changes to cytoskeletal processes in mesenchymal, epithelial and neuronal cells.
“In addition, our study characterized the interactions between the major ingredients of energy beverages – caffeine, taurine and glucose, and showed that the effects seen with the energy beverages were not solely due to the presence of caffeine, taurine and glucose or their combinations,” they added.
“Our results underscore the need to use the complete beverage rather than the major ingredients, and to fully characterize the combinatorial effects of all ingredients in the energy beverages.”
Title: ‘The effects of energy beverages on cultured cells’
Authors: W.Doyle, E.Shide, S.Thapa, V.Chandrasekaran
Source: Food and Chemical Toxicology, July 20 2012 (published online ahead of print) http://dx.doi.org/10.1016/j.fct.2012.07.008