Cortisol is a vital hormone that's key to regulating blood sugar and inflammation… and standing up to acute stresses such as fear, injury, and extreme exertion.
Chronically low cortisol levels—a condition known as Addison's disease—were fatal before this hormone was discovered.
But chronically high cortisol levels—which can result from continual stress—is the more common problem, and produces several undesirable outcomes:
Thinning of the skin.
Decreased muscle mass.
Weakened immunity to infections.
Reduced bone formation, increased risk of osteoporosis.
Damage to the brain's hippocampus and losses to learning and memory.
Chronically high cortisol levels kill brain cells (neurons)… which is the chief reason for the brain shrinkage seen in patients suffering from Alzheimer's and other forms of senility.
A few years ago, UCLA research in patients with mild cognitive impairment found that those who had a smaller-than-average hippocampus were more likely to develop full-blown dementia (Apostolova LG et al. 2006).
Cortisol levels rise rapidly in young people placed under stress, but fall back to normal within a few hours after the source of stress is removed.
In contrast, cortisol levels remain high for days in older people, even after the source of stress is gone.
Blood cortisol levels increase with age, and someone aged 65 will have higher average blood levels of cortisol compared with a 25-year-old.
Some anti-aging researchers call cortisol the “death hormone”, because it is associated with old age and disease.
Some studies indicate that fish oils moderate levels of pro-inflammatory cytokines and/or the neurotransmitter norepinephrine, which is a key player in the body's “flight or fight” response to stress.
Five years ago, a small, controlled clinical trial provided the first evidence that fish oil supplements may actually make people feel less stressed (see “Eat Seafood to Ease Stress?”).
Fish oil has also been found to improve body composition in preliminary clinical studies … an outcome attributed to various physiological effects of omega-3s.
Now, the outcomes of two small, controlled clinical trials support the hypothesis that omega-3s possess cortisol-lowering and body-fat-reducing powers.
Gettysburg trial finds improved body composition and cuts in cortisol
Researchers at Pennsylvania's Gettysburg College recruited 44 adults for a six-week trial designed to test the effects of safflower oil and fish oil on people's body composition, metabolic rate, and cortisol levels.
The volunteers were divided in two groups, and each took a daily oil supplement:
Safflower oil—four grams, mostly omega-6 fatty acids
Fish oil—four grams, including 2,400 mg of omega-3 fatty acids (1,600 mg EPA + 800 mg DHA).
In tests performed at the end of the six-week study, members of the fish oil group showed significantly lower cortisol levels.
In addition, the fish oil group shed body fat and gained lean muscle.
There was also a tendency for lower cortisol levels in the fish oil group… as well as a significant correlation between cuts in cortisol and gains in muscle mass… that is, the less cortisol people in the fish oil group had, the more muscle they gained.
As the authors wrote, “…[six] weeks of supplementation with FO [fish oil] significantly increased lean mass and decreased fat mass. These changes were significantly correlated with a reduction in salivary cortisol…” (Noreen EE et al. 2010).
Interestingly, while the results showed beneficial changes in body composition among the fish oil group, there was no difference in total body weight between the safflower and fish oil groups.
Nor were there any rises in resting metabolic rate—which would indicate increased calorie-burning—in either group.
Anglo-Iranian team reports that fish oil lowered cortisol
This study comes from the Anglo-Iranian collaboration that found omega-3 EPA equal to the anti-depressant drug fluoxetine (Prozac) among patients diagnosed with major depression… and that combining them provided results superior to either alone (Jazayeri S et al. 2008; see “Omega-3s Affirmed as Mood Lighteners”).
For their new study, they analyzed blood taken from the 42 patients who'd participated in the prior eight-week trial of EPA and fluoxetine, both before the trial began and after it ended.
The new analysis of the participants' blood showed that cortisol levels dropped in both the omega-3 EPA group and the group that took both EPA and fluoxetine (Prozac).
Some scientists hypothesize that omega-3s might exert anti-depression effects in part by lowering levels of certain pro-inflammatory immune-system proteins (cytokines) associated with depression (IL-1beta and IL-6).
But the volunteers showed no changes in their blood levels of either chemical.
This led the Iranian team to an intriguing conclusion: “These findings suggest that EPA may exert its therapeutic [anti-depression] effects through reduction of cortisol.”
These studies provide good reasons to favor fishy diets… a lighter mood, a healthier body compositions, and healthier aging overall.
Apostolova LG, Lu PH, Rogers S, Dutton RA, Hayashi. 3D mapping of mini-mental state examination performance in clinical and preclinical Alzheimer disease. Alzheimer Dis Assoc Disord. 2006 Oct-Dec;20(4):224-31.
Bhathena SJ, Berlin E, Judd JT, Kim YC, Law JS, Bhagavan HN, Ballard-Barbash R, Nair PP. Effects of omega 3 fatty acids and vitamin E on hormones involved in carbohydrate and lipid metabolism in men. Am J Clin Nutr. 1991 Oct;54(4):684-8.
Bortolotti M, Tappy L, Schneiter P. Fish oil supplementation does not alter energy efficiency in healthy males. Clin Nutr. 2007 Apr;26(2):225-30. Epub 2007 Jan 31.
Couet C, Delarue J, Ritz P, Antoine JM, Lamisse F. Effect of dietary fish oil on body fat mass and basal fat oxidation in healthy adults. Int J Obes Relat Metab Disord. 1997 Aug;21(8):637-43.
Delarue J, Guillodo MP, Guillerm S, Elbaz A, Marty Y, Clèdes J. Fish oil attenuates adrenergic overactivity without altering glucose metabolism during an oral glucose load in haemodialysis patients. Br J Nutr. 2008 May;99(5):1041-7. Epub 2007 Nov 1.
Delarue J, Matzinger O, Binnert C, Schneiter P, Chioléro R, Tappy L. Fish oil prevents the adrenal activation elicited by mental stress in healthy men. Diabetes Metab. 2003 Jun;29(3):289-95.
Hill AM, Buckley JD, Murphy KJ, Howe PR. Combining fish-oil supplements with regular aerobic exercise improves body composition and cardiovascular disease risk factors. Am J Clin Nutr. 2007 May;85(5):1267-74.
Jazayeri S, Keshavarz SA, Tehrani-Doost M, Djalali M, Hosseini M, Amini H, Chamari M, Djazayery A. Effects of eicosapentaenoic acid and fluoxetine on plasma cortisol, serum interleukin-1beta and interleukin-6 concentrations in patients with major depressive disorder. Psychiatry Res. 2010 Jun 30;178(1):112-5. Epub 2010 May 13.
Michaeli B, Berger MM, Revelly JP, Tappy L, Chioléro R. Effects of fish oil on the neuro-endocrine responses to an endotoxin challenge in healthy volunteers. Clin Nutr. 2007 Feb;26(1):70-7. Epub 2006 Oct 18.
Noreen EE, Sass MJ, Crowe ML, Pabon VA, Brandauer J, Averill LK. Effects of supplemental fish oil on resting metabolic rate, body composition, and salivary cortisol in healthy adults. J Int Soc Sports Nutr. 2010 Oct 8;7:31.
- Yehuda S, Rabinovitz S, Mostofsky DI. Mixture of essential fatty acids lowers test anxiety. Nutr Neurosci. 2005 Aug;8(4):265-7