Objective To evaluate the association between fatty acid composition, omega 6/omega 3 ratio and mental retardation.

Methods In a case control study, 31 mentally retarded males (mean age 9.1 yrs) were matched with 31 healthy males for age, BMI and socioeconomic status. The plasma phospholipid fatty acid composition, dietary fatty acids and other nutrients were measured. Logistic and multiple regression analyses were used to evaluate the association between fatty acid composition and mental retardation.

Results The total plasma saturated and polyunsaturated fatty acids were significantly higher and the total monounsaturated fatty acids were significantly lower in cases than in controls. Also, total plasma omega 3 fatty acid and DHA concentrations were significantly lower and Σ omega 6/Σ omega 3 ratio (8.4±3.7 vs. 4.4±1.7, p<0.001) was significantly higher in cases than in controls. The risk of high omega 6/omega 3 ratio was 70% higher in cases than in controls (adjusted odds ratio  = 1.69, 95% CI = 1.25 to 2.29). Thirty eight and 45% of variation in omega 6/omega 3 ratios and total omega 3 fatty acid concentration respectively was explained by mental retardation. There was no significant difference in either total dietary fat or fatty acid composition between cases and control. Dietary carbohydrate and total energy intake were significantly higher in cases than in controls (p<0.05).

Conclusion These results suggest that low total omega 3 fatty acid, particularly, DHA concentration, and increased omega 6/omega 3 ratios may be risk factors for mental retardation in children.