Objectives: This study examined the relation of dietary fat intake and blood lipid levels in a young African American and white population with subclinical MRI measures taken at a later age. Methods: Dietary intake was assessed 3 times over 20 years and fasting blood lipids measured x times over 25 years among CARDIA participants who were 18-30 years old at baseline (n=5111). Brain MRI measures were taken at year 25 in a sub-sample (n=690). Spearman partial correlations were used to evaluate relations of dietary intake and blood lipid levels with MRI measurements; analyses were stratified by gender and adjusted for age, race, education, smoking, energy and alcohol intakes, BMI, and intracranial volume. Results: Intakes of energy, alcohol and % kcal from total fat and saturated fat were greater in men than women. Total fat intake was not related to any brain MRI measures. However, both grams and % kcal from saturated fat were inversely related to white matter fractional anisotropy (FA) in men only (r = -0.12; p=0.03 and r=-0.14; p=0.01, respectively). Further, grams and % kcal from saturated fat were positively related to abnormal white matter tissue volume in women only (r=0.13; p=0.01 and r= 0.13; p=0.02, respectively). Omega3 fatty acids were inversely correlated to abnormal white matter (men: r=-0.11; p=0.05, women: r=-0.14; p=0.01). Additionally, omega3 fatty acids were inversely correlated with total ventricle volume in men (r=-0.11; p=0.05), but not in women. In men there were significant inverse correlations between total cholesterol and total brain volume (r=0.12, p=0.03) . Furthermore, there were significant positive correlations between both total (r=0.11, p=0.05) and LDL-cholesterol (r=0.12, p=0.04) and total ventricle volume in men. In women there was a significant inverse correlation between triglycerides and total brain volume (r=-0.12, p=0.03) and normal gray matter (r=-0.15, p<0.01). In addition, there was also a significant inverse relationship between total cholesterol and total brain volume (r=-0.11, p=0.05) in women.
Conclusions: Given these study findings, we conclude that omega3 fatty acid intake and saturated fat may be associated with brain MRI measures in a beneficial and detrimental manner, respectively. Our studies further reveal interesting inverse relations between total and normal gray brain volumes with blood lipids in men and women. Additionally total ventricle volume was positively associated with blood lipids in men. Further research is needed to elucidate the relations of dietary fat intake and blood lipids with brain MRI measures.