Research: KIECOLT-GLASER and COLLEAGUES,

Listed in Issue 155

Abstract

KIECOLT-GLASER and COLLEAGUES, Department of Psychiatry, Ohio State University College of Medicine, 1670 Upham Drive, Columbus, OH 43210, USA. Kiecolt-Glaser.1@osu.edu  investigated how interactions between polyunsaturated fatty acid (PUFA) levels and depressive symptoms were related to proinflammatory cytokine synthesis.

Background

Depression and stress promote proinflammatory cytokine production. Dietary intakes of omega-3 (n-3) and omega-6 (n-6) PUFAs also influence inflammation; high n-6:n-3 ratios enhance proinflammatory cytokine production, although n-3 has anti-inflammatory properties.

Methodology

Blood samples from 43 older adults (mean age = 66.67 years, SD = 10.09) provided data on PUFAs and tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-6 soluble receptor (sIL-6r). Depressive symptoms were assessed by the Center for Epidemiological Studies Depression Scale.

Results

Depressive symptoms and n-6:n-3 ratios worked together to enhance proinflammatory cytokines beyond the contribution provided by either variable alone, with substantial variance explained by their interaction: 13% for IL-6 and 31% for TNF-alpha, whereas full models accounted for 18% and 40%, respectively. Although predicted cytokine levels were consistent across n-6:n-3 ratios with low depressive symptoms, higher n-6:n-3 ratios were associated with progressively elevated TNF-alpha and IL-6 levels as depressive symptoms increased. Higher levels of sIL-6r were associated with higher n-6:n-3 ratios. Six individuals who met the criteria for major depressive disorder had higher n-6:n-3 ratios and TNF-alpha, IL-6, and sIL-6r levels than those who did not meet the criteria; excluding these six individuals reduced the variance explained by the depressive symptoms and n-6:n-3 ratio interaction.

Conclusion

Diets with high n-6:n-3 PUFA ratios may enhance the risk for both depression and inflammatory diseases.

References

Kiecolt-Glaser JK, Belury MA, Porter K, Beversdorf DQ,  Lemeshow S and  Glaser R. Depressive symptoms, omega-6:omega-3 fatty acids, and inflammation in older adults. Psychosomatic Medicine.  69(3): 217-24 Apr 2007.

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