High-fat dairy product consumption increases Delta 9c,11t-18 : 2 (rumenic acid) and total lipid concentrations of human milk

Conjugated octadecadienoic acids (18:2, conjugated linoleic acids) have bee n shown to be anticarcinogenic and may influence growth and nutrient partit ioning. The Delta 9c,11t-18:2 isomer (rumenic acid, RA) is most common in b oth food sources and human tissues. To determine if maternal diet can influ ence milk RA concentration, breastfeeding women (n = 16) were enrolled in a 3-wk crossover study. Women initially consumed minimal amounts of food con taining RA during week 1, then were assigned randomly to consume diets rich in high-fat dairy foods (and thus RA) during week 2 or 3. Milk was collect ed by complete breast expression twice during each experimental week. Curre nt and chronic RA intakes were estimated by 3-d dietary records and food fr equency questionnaires, respectively. Estimated chronic RA intakes ranged f rom 49 to 659 mg/d. Dietary RA intake was greater during the high compared to the low dairy period (291 +/- 75 vs. 15 +/- 24 mg/d, respectively; P < 0 .0001). Milk contained more RA during the high than the low dairy period (1 3.5 +/- 0.1 vs. 8.2 +/- 0.4 mu mol/g lipid, respectively; P < 0.0001). Milk lipid concentration was influenced by diet, such that lipid concentration was greater during the high than the low dairy period (46.6 +/- 5.0 vs. 38. 3 +/- 1.6 mg/g milk, respectively; P < 0.05). Additionally, multiple regres sion analyses suggested that body mass index was the primary predictor of m ilk RA and lipid concentrations. In summary, these data indicate that both lipid and RA concentrations of human milk can be influenced by diet.