Dear Monique,
I just finished reading large sections of your book, which I find fantasticand will highly recommend to friends. With regards to supplements, onethat I take, but did not see mentioned is conjugated linoleic acid (CLA).Any thoughts on whether this is needed in a reasonably healthy diet? Iam an 80 kg, 46-year-old competitive road racer.
Best regards,
ChrisHi Chris,
At this point there is no reason to add conjugated linoleic acid toa healthy diet or training diet as based on the current research. CLA hasbeen studied fairly extensively, but mostly in animals.  In theseanimal studies CLA appears to reduce body fat stores, while preservinglean body mass. CLA supplements are usually accompanied with photographsof the taut abdominal six-pack. Some manufacturers also promote CLA asreducing the risk for diabetes and certain types of cancer. However, whetherit can do the same in humans is the still the subject of ongoing researchand currently the human data is less than conclusive.What is CLA?
You may be surprised to learn that CLA is a mixture of polyunsaturatedfatty acids which are actually natural trans fats. Trans fats have receivedmuch deserved attention as the latest culprits in promoting increased levelsof blood cholesterol.  However, the trans fats found naturally insome foods are different than the manufactured form found in processedfoods and won’t raise blood cholesterol as these hydrogenated oils can.These natural trans fat are also not included for the purposes of nutritionalregulations and labeling.Food sources of CLA include animal foods like whole milk, cheese, beef,lamb, veal, poultry, and eggs. Food products of grass fed animals are goodsources and contain much more CLA than those from grain fed animals. Infact, pasture grazed cows may have 3 to 5 times more CLA in their milkthan cows fed hay.There are about 28 possible types of CLA, each one with a slightly differentarrangement of chemical bonds. The type most commonly found in meat anddairy products is the cis 9, trans-11 CLA form, which appears responsiblefor promoting muscle growth. Another form, the trans-10, cis-12 form seemsto help prevent fat storage.The average diet provides about 50 to 300 milligrams of CLA a day. Switchingfrom grain-fed to grass-fed products can greatly increase your CLA intake.Because many sources of CLA are also high in saturated fat and increaseyour risk for heart disease, the best way to boost your CLA dietary intakeis to switch from grain-fed to grass-fed products.
 
CLA Supplements
Supplements often contain manufactured sources of CLA, so they likelycontain fatty acids different from these natural sources, but many do containa mix of the these two forms mentioned above. There is still some debateabout which of the fatty acids are really the most beneficial, so whethera manufactured supplement is as good as natural CLA or which supplementis the best has not been conclusively determined.CLA Research
Dozens of animal studies conducted over two decades have establishedthat CLA can dramatically reduce body fat stores, while preserving leanmuscle mass. Animal studies have also found that CLA may protect againstcertain types of cancers.Human data is far less conclusive. Several clinical trials have shownthat CLA can lead to some reduction in body fat both in normal weight andoverweight people, after anywhere from 4 to 12 weeks of supplementation.Study doses ranged from two to four grams of CLA daily.  On the flipside, other studies found no beneficial body fat changes at all with supplementation.Some studies showing a beneficial effect from CLA supplementation havealso included a calorie restricted diet in the study design. Weight lossresult may not always be very impressive. In one study, subjects lost only2 to 4 lb. of weight per year, an amount of weight loss that could be achievedwith consistent training and sensible dietary adjustments in one month.While these human results are not overly impressive, one recent animalstudy has raised some concerns regarding the side effects of CLA supplementation.This study found that CLA caused mice to accumulate excessive amounts offat in their livers. Some animal studies have also found that CLA may raiseinsulin levels.The Current CLA Bottom Line
For now CLA supplements are not recommended due to conflicting studyresults in humans and possible side effects. As far as food sources areconcerned, don’t increase intake of fatty animal foods to obtain more CLA.But you can consume more grass fed beef which increases CLA intake withoutadding more saturated fat.
Monique

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Monique Ryan, MS, RD, LDN is a nationally recognized nutritionistwith over twenty-two years of experience and is owner of Personal NutritionDesigns, a Chicago based nutrition consulting company that provides nutritionprograms for endurance athletes across North America (www.moniqueryan.com).Monique consults with the Chicago Fire Soccer Team, and was the nutritionistfor Saturn Cycling from 1994 to 2000. She has also consulted with the Volvo-CannondaleMountain Bike Team, the Gary Fisher Mountain Bike Team, and the RollerbladeRacing Team. Monique has consulted with USA Cycling, and was a member ofthe Performance Enhancement Team for the Women’s Road Team leading to the2004 Athens Olympics. She has also provided nutrition consultation servicesto USA Triathlon for coaching clinics, athlete clinics, and for the residentathlete team and was a member of the USAT Performance Enhancement Teamfor the 2004 Athens Olympics. Monique is the author of "SportsNutrition for Endurance Athletes," 2nd edition (March 2007), from VeloPress,which provides sports specific nutrition for road cycling, mountain biking,running, triathlon, swimming, rowing, and adventure racing. She is alsoauthor of "PerformanceNutrition for Winter Sports" (PeakSports Press), "Performance Nutritionfor Team Sports" (PeakSports Press), and "Complete Guide to Sports Nutrition."Monique is a regular contributor to VeloNews, Inside Triathlon,Outside, and ACE Fitness Matters. As part of the FeedZonecolumn, Monique will answer selected questions online. Please sendyour questions to RyanWebQA@aol.com.