Estimation of conjugated linoleic acid intake by written dietary assessment methodologies underestimates actual intake evaluated by food duplicate methodology

Conjugated linoleic acids (CLA) are conjugated isomers of linoleic acid, wh ich may promote health with regard to cancer, heart disease, diabetes, bone formation, growth modulation and immunity. The c9,t11 isomer of CLA, rumen ic acid (RA), is the major isomer present in the diet. However, dietary int akes of CLA and RA by humans have not been examined rigorously, nor has the relationship between dietary CLA or RA and health (e.g., body composition) . Three-day dietary records (DR) were collected from adult men (n = 46) and women (n = 47) and analyzed using a nutrient database modified to contain total CLA and RA. Simultaneously, 3-d food duplicates (FD) were collected t o determine analytically individual fatty acid intakes, including those of total CLA and RA. Chronic total CLA and RA intakes were estimated using a s emiquantitative food-frequency questionnaire (FFQ). Body composition was es timated using body mass index and percentage of body fat. Total CLA intake was estimated from FD to be 212 +/- 14 and 151 +/- 14 mg/d (mean +/- SEM) f or men and women, respectively; RA intake was estimated to be 193 +/- 13 an d 140 +/- 14 mg/d for men and women, respectively. In general, CLA and RA i ntakes estimated by DR and FFQ were significantly lower than those estimate d by FD. Body composition was not significantly related to dietary total CL A or RA intake. In conclusion, results suggest that DR and FFQ methodologie s are not reliable estimators of individual total CLA and RA intakes and ma y underestimate total CLA and RA intakes of groups. Intake of total CLA and RA was found to be significantly lower than that suggested previously by o thers.