We were intrigued by the findings of a study published last month, which suggest a sinister synergy between imbalanced fat intake and the degree of depression and inflammation in older adults.
This prompted us to search the literature for similar investigations. And our hunt uncovered a Dutch study conducted in college students, which produced parallel results.
Aside from the direct evils of depression, this debilitating mood disorder damages memory and mental acuity and promotes inflammation.
In turn, depression-induced inflammation drives a variety of serious health problems, from heart disease, arthritis, and cancer to diabetes and Alzheimer’s disease.
This is why both teams thought it important to detail the degree to which imbalances in dietary fat intake might interact with depression and its insidiously unhealthful handmaiden, inflammation.
Depression, inflammation and dietary fats in older adults
Thanks to prior research, we know that depression activates the body’s inflammatory response system, which yields higher blood levels of the pro-inflammatory immune-system proteins called cytokines.
As the authors of a French review said at the turn of the century, “It has been shown that a dietary increase of polyunsaturated omega-3 fatty acids reduced strongly the production of [pro-inflammatory cytokines]. In contrast, diets with a higher supply of omega-6 linoleic acid [from vegetables oils] increased significantly the production of pro-inflammatory cytokines…” (Colin A et al 2003).
Last month, researchers at Ohio State University set out to examine whether diets high in omega-6 fatty acids and low in omega-3s—in other words, high omega-6/omega-3 intake ratios—add to depression-induced increases in pro-inflammatory cytokines (Kiecolt-Glaser JK et al 2007).
The Ohio group wanted to know whether the excessive intake of omega-6 fatty acids typical of the American diet—which is usually accompanied by inadequate intake of omega-3s—fuels high, depression-driven levels of inflammation even higher.
The three pro-inflammatory cytokines they measured were tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-6 soluble receptor (sIL-6r)… elevated levels of which serve as markers of increased inflammation in the body and are also associated with diverse health problems.
The Ohio State team took blood samples from 43 older adults (average age 67), and the participants’ depressive symptoms—or lack thereof—were assessed by means of a standard test (Kiecolt-Glaser JK et al 2007).
They found that symptoms of depression and high omega-6/omega-3 ratios worked together to drive blood levels of pro-inflammatory IL-6 and TNF-alpha higher than the levels produced by depression or a high omega-6/omega-3 ratio alone.
In addition, while blood levels of TNF-alpha and IL-6 rose in tandem with worsening depression, higher omega-6/omega-3 ratios increased the levels of these cytokines even more.
Study participants who met the test criteria for major depression had higher omega-6/omega-3 ratios and higher blood levels of the three pro-inflammatory cytokines, compared with those who did not suffer from major depression.
As the Ohio researchers said, “Diets with high… [omega-6/omega-3 ratios] may enhance the risk for both depression and inflammatory diseases” (Kiecolt-Glaser JK et al 2007).
Dutch study extends concerns to college-age people
Just as depression does, psychological stress induces increased production of pro-inflammatory cytokines. And, like most Americans, most people in Western Europe eat diets too high in omega-6 fatty acids and too low in omega-3 fatty acids from fish.
Seven years ago, a Dutch team from the University of Maastricht decided to test whether this imbalanced omega-6/omega-3 intake ratio causes the body to produce more pro-inflammatory cytokines than usual in response to psychological stress (Maes M et al 2000).
They recruited 27 university students, and took blood samples a few weeks before a difficult oral examination, one day before the exam, and a few weeks afterwards.
The stress of the exam increased the students’ blood levels of pro-inflammatory cytokines, significantly.
What’s more, blood levels of pro-inflammatory cytokines were highest in the students with the lowest blood levels of omega-3s and in the students with the highest omega-6/omega-3 ratios.
The Dutch scientists came to the obvious conclusion: “The results suggest that increased omega-3 levels may attenuate [reduce] the pro-inflammatory response to psychologic stress” (Maes M et al 2000).
- Kiecolt-Glaser JK, Belury MA, Porter K, Beversdorf DQ, Lemeshow S, Glaser R. Depressive Symptoms, omega-6:omega-3 Fatty Acids, and Inflammation in Older Adults. Psychosom Med. 2007 Mar 30; [Epub ahead of print]
- Colin A, Reggers J, Castronovo V, Ansseau M. [Lipids, depression and suicide] Encephale. 2003 Jan-Feb;29(1):49-58. Review. French.
- Maes M, Christophe A, Bosmans E, Lin A, Neels H. In humans, serum polyunsaturated fatty acid levels predict the response of proinflammatory cytokines to psychologic stress. Biol Psychiatry. 2000 May 15;47(10):910-20.