Writing in Food and Chemical Toxicology, Netherlands-based researchers report that a daily intake of 19.3 grams of CLA over a three week period does not produce any “clinically relevant effects on markers of liver and kidney function in healthy volunteers”.
CLA (conjugated linoleic acid) is a fatty acid naturally present in ruminant meat and dairy products. Due to changes in the Western diet, average intake of CLA has fallen; if the fat is removed from a dairy product to make a low fat version that will be acceptable to consumers, CLA is removed along with it.
The CLA market is expanding, according to a 2007 Frost & Sullivan report, which said the global market is forecast to reach revenues of US$109.9 million in 2013. Key players in the market include Lipid Nutrition with its Clarinol ingredient and Cognis with its Tonalin ingredient.
Twenty subjects took part in the study, which used 14.6 grams of the cis-9,trans-11 CLA isomer and 4.7 grams of the trans-10,cis-12 CLA isomer. The researchers used CLA provided by Lipid Nutrition, and the mixture was manufactured by NIZO Food Research.
The composition used in the study is similar to the composition in dairy products, and different from the common 1:1 mixed isomers used in dietary supplements or functional foods.
“The present study shows that a daily intake of 19.3 g 80:20 CLA mixture for 3 weeks does not produce clinically relevant effects on markers of liver and kidney function in healthy human volunteers,” wrote the researchers, led by Dr Ingeborg Brouwer. “Therefore, the adverse effects of CLA intake on liver function as reported in multiple studies in mice and hamsters, may be specific for rodents, and may not apply to humans.”
Canadian concerns
Health Canada recently issued a monograph for CLA, about six months it came close to banning the ingredient. The monograph followed letters that were sent to 106 dietary supplements manufacturers last July, after Health Canada decided to pursue concerns that had been raised in some quarters about the body shaping ingredient’s safety and efficacy.
The North American divisions of Cognis Nutrition and Lipid Nutrition both worked closely with their dietary supplement customers selling CLA products in Canada to provide information Health Canada has incorporated into the monograph.
The monograph affirms CLA’s safety but is selective in the kinds of weight management claims it supports.
The new study, by researchers from VU University in Amsterdam, Wageningen University, and Ziekenhuis Gelderse Vallei in Ede, adds to this safety record. After 21 days of supplementation all measures of liver and kidney function were normal, said the researchers.
Industry welcome
John Kurstjens from Lipid Nutrition welcomed the results. Kurstjens told NutraIngredients: “The result of this study confirms what we observed in our own studies with Clarinol CLA that it doesn't affect liver and kidney function in humans.
“This study is done with a very high concentration and mainly one of the two active CLA isomers. The commercial products on the market contain the two active isomers which are necessary for the beneficial effect of CLA for weight management and the advised daily intake dose is much lower than the unrealistic high dose used in this study,” he added.
The results were also welcomed by Cognis Nutrition & Health. David Cai, PhD, regulatory and science manager, told NutraIngredients that the study does add to the totality of compelling evidence supporting the safety of CLA, “because the dose of each CLA isomer used in this study is one of the highest doses reported in clinical studies”.
“Consumers interested in improving their body composition take CLA because they understand it is backed by clinical studies demonstrating its safety as well as its health benefits, [and] we continue to see positive research that supports how CLA safely reduces body fat, maximizes lean muscle and prevents fat cells from refilling,” added Dr Cai.
Dr Cai added that the company’s ingredient had GRAS status in the US, as well as becoming the first CLA to obtain novel food approval in China.
Source: Food and Chemical Toxicology
Volume 48, Pages 587–590
"A high intake of conjugated linoleic acid does not affect liver and kidney function tests in healthy human subjects"
Authors: A.J. Wanders, L. Leder, J.D. Banga, M.B. Katan, I.A. Brouwer