IL-6 and TNF-a are two of a family of six cytokines that, when stimulated, produce an inflammatory response to a stressor such as an injury or infection, said study co-author Ron Glaser, professor of molecular virology, immunology and medical genetics and director of the IBMR.
“You need this good inflammation for an initial response, but if it stays up, and inflammation becomes chronic, then you’ve got a problem,” Glaser said. “Our research and studies done by others have shown that these two cytokines are clearly related to overall health - and when they’re elevated in the blood, that is not good for overall health. So the more ways we can find to lower them, the better.”
Statistically, there was no significant difference in lowered inflammation between the two doses, but each dose clearly produced cytokine reductions that differed significantly from the placebo group.
“These data support the idea that a higher dose of omega-3 is not necessarily better than a lower dose in terms of prevention of inflammation,” said Martha Belury, professor of human nutrition at Ohio State and a co-author of the study.
However, levels of omega-3 fatty acids in participants’ blood increased according to which dose they consumed, which improved their ratio of omega-6 fatty acids to omega-3 fatty acids. The current typical American diet contains between 15 and 17 times more omega-6 than omega-3, a ratio that researchers suggest should be lowered to 4-to-1, or even 2-to-1, to improve overall health.
“Scientists tend to agree that the best way to gauge a person’s omega-3 status is to see whether that ratio goes down,” Belury said. “That’s what we saw in this study, and it was achieved through supplementation. We wanted participants to maintain normal diets and simply add this modest amount of oil to their existing diet. We expected and we found that their blood plasma omega-3 fatty acids went up in a dose-responsive manner.”
The Food and Drug Administration considers daily omega-3 supplementation of up to 3 grams to be “generally regarded as safe.” The doses in this study were within those safety parameters, but the researchers did not extend their findings to make a general recommendation about omega-3 supplementation.
“Although omega-3 fatty acids cannot take the place of good health behaviors, people with established inflammatory diseases or conditions may benefit from their use,” Kiecolt-Glaser said.
The researchers also sought to determine whether omega-3 fatty acids could reduce depression symptoms, but participants had relatively few symptoms to begin with so no significant reductions were seen. Depression is also associated with chronic inflammation, but research hasn’t yet fully defined the mechanisms behind that relationship.
This work was supported in part by grants from the National Institutes of Health. OmegaBrite, a company based in Waltham, Mass., supplied the supplements as an unrestricted gift but did not participate in the study design, results or publication.
Additional co-authors, all at Ohio State, include Rebecca Andridge of the Division of Biostatistics; William Malarkey of the IBMR and the departments of Psychiatry and Internal Medicine; and Beom Seuk Hwang of the IBMR and biostatistics.