Studies indicate link between higher blood levels of omega-3s and reduced risk of dementia, depression, and death among seniors; no mood boost seen in non-depressed elders
by Craig Weatherby
The pile of positive findings that link higher omega-3 intake to healthier aging continues to grow higher.
The results of three new studies—two from France and another from Norway—associate higher blood levels of omega-3s with reduced rates of death, depression, and dementia.
And while a fourth study found that six months on fish oil pills didn’t make non-depressed seniors happier, that wasn’t much of a surprise or disappointment (No one’s ever suggested that omega-3s work like laughing gas!).
Omega-3 and heart researcher William S. Harris, Ph.D. of the University of South Dakota quoted Leonardo DaVinci in an accompanying editorial:
“Learning acquired in youth arrests the evil of old age; and if you understand that old age has wisdom for its food, you will so conduct yourself in youth that your old age will not lack for nourishment.”
Dr. Harris wrote that the results of the new studies “nourish us well” and provide more reasons to cultivate a habit of consuming ample omega-3s from youth onward.
Indeed, the study reported in today’s accompanying article affirms the idea that children benefit when the omega-3 habit begins before birth (See “Child Benefits of Fish Affirmed in Large Study”).
New studies compare seniors’ omega-3 levels with health status
In all three studies, researchers took blood samples from the participants and measured the levels of omega-3s and other fatty acids.
This made the results far more reliable than those from other epidemiological studies.
In most epidemiological studies, participants answer diet questionnaires, and researchers must then estimate omega-3 intake.
Obviously, the results of such studies are less reliable, as they rest on people’s fuzzy memories and on crude estimates of the omega-3 content of participants’ alleged diets.
Blood tests provide a far more accurate measure of how much fish and fish oil people consume, compared with estimates based on people’s answers to questionnaires.
More importantly, use of blood tests to compare omega-3 levels to rates of disease can guide establishment of target omega-3 blood levels, dietary advice designed to help people achieve those target levels, and routine, annual blood tests to monitor omega-3 blood levels.
(See “Recommended daily omega-3 intakes” at the end of this article.)
Our summaries of the three studies follow.
We also relate the negative results of a simultaneously published Dutch study, in which omega-3 supplements failed to enhance elders’ mood.
Study 1: Omega-3 levels and death risk
A team from the Norwegian University of Science and Technology recruited 254 frail, elderly patients and measured their blood levels of EPA, which is one of the two key omega-3s in human cell membranes and in fish fat, the other one being DHA.
After three years, people with the lowest average blood levels of EPA were about 40 percent more likely to die, compared to people with higher levels (Lindberg M et al. 2008).
Omega-3 and heart researcher William S. Harris, Ph.D. of the University of South Dakota made this comment in an accompanying editorial: “… a generalized health benefit arising from a prolonged dietary intake of oily fish … would surprise no one familiar with the omega-3 fatty acid literature.” (Harris WS 2008)
Studies 2 and 3: Omega-3s versus dementia and depression
In two French studies, researchers from France’s counterpart of the U.S. National Institutes of Health (INSERM) compared blood levels of omega-3s with rates of dementia and depression in older French volunteers from Bordeaux who were taking part in the ongoing “Three-City Study”.
French dementia study
In this study, scientists from INSERM examined blood samples from 1,214 participants considered free from signs of dementia, and then followed them for four years (Samieri C et al. 2008).
Over the course of four years, the researchers found that higher blood levels of EPA were associated with a 31 percent reduced risk of developing dementia.
In addition, greater dementia risk was seen in participants whose blood showed higher ratios of omega-6 fatty acids to omega-3 DHA and/or total omega-3s.
We coined the term “omega imbalance” to describe the state of most American’s diets, which contain 20 to 40 times as much omega-6 fatty acids as omega-3s (i.e., ratios ranging from 20:1 up to 40:1 or even higher).
Most researchers say the evidence shows that human bodies evolved in adaptation to prehistoric diets in which omega-6 and omega-6 fats were almost evenly balanced.
(Modern hunter-gatherer societies that live apart from urban cultures still consume diets in which relative intakes of omega-6s and omega-3s approximate prehistoric consumption patterns.)
And most doctors familiar with the evidence say people shouldn’t consume more than four parts omega-6 fats to one part omega-3 fats (i.e., a 4:1 ratio), with a 2:1 ratio being ideal.
A fast-growing body of evidence links the gross “omega imbalance” in Western diets – especially American diets – to most major diseases, including cancer, heart disease, autoimmune conditions, and dementia. (For more on the dangers of the omega imbalance, see “Report Finds Americans Need More Omega-3s and Less Omega-6s” and search our newsletter archive for “omega-6”.
French depression study
In a companion study, the same team from INSERM examined blood samples from 1,390 Bordeaux residents diagnosed with depression, and analyzed their blood to look for any associations between levels of omega-3s and incidence of depression (Féart C et al. 2008).
Indeed, blood levels of omega-3s were about 16 percent lower in the depressed volunteers, compared with health controls. There were no significant differences in blood levels of any other fatty acids.
When adjusted for potential confounding factors, such as socio-demographic characteristics and health indicators, the found that, in subjects taking antidepressants, blood levels of omega-3s were closely linked to the severity of depression.
The researchers concluded that higher blood levels of omega-3s were associated with a lower severity of depression, especially those taking antidepressants.
Interestingly, compared with healthy controls, the subjects diagnosed with depression were less likely to have high cholesterol levels.
This makes sense, given the considerable evidence that below-normal blood cholesterol levels can lead to mental health problems.
Study 4: Omega-3s don’t lift mood in non-depressed seniors
The findings of a clinical trial published this month—which tested the effects of fish oil supplements on mood among older adults—produced negative results that weren’t very surprising (van de Rest O et al. Am J Clin Nutr 2008).
Researchers from Wageningen University conducted a double-blind, placebo-controlled trial in 302 volunteers aged 65 or older (average 70 years of age), who were not diagnosed as depressed.
The subjects were randomly assigned to consume high doses of omega-3 (1,800 mg per day), lower doses (400 mg per day), or placebo capsules, for six months.
While the volunteers’ blood levels of omega-3s rose in tandem with the omega-3 doses they took, these changes were not associated with any significant change in the mental well-being of the volunteers taking fish oil.
Dr. Harris made this observation in his editorial (Harris WS 2008): “Although one can always suggest that higher doses may have been more effective, it is more likely that what is done is done; at 70 years of age, supplementation is simply unable to materially alter emotion ...”
We suppose the point of the trial was to see whether fish oil would make people who were already in reasonably good mood happier.
The bottom line is that the results do not contradict the large body of evidence linking higher omega-3 intake to reduced risk of depression.
Recommended daily omega-3 intakes: How much is enough?
In his editorial, Dr. Harris concluded that when you considered their results together, these studies “underscore the potential importance of maintaining high dietary omega-3 intakes throughout life.”
And he came to a common sense conclusion: “Together, these findings suggest that dietary habits that include higher… intakes of long-chain omega-3 fatty acids may bring certain health benefits that short-term supplementation cannot provide.”
The question is, how much omega-3 do we need?
Omega-3 and omega-6 fatty acids were once collectively called “vitamin F”, because they cannot be manufactured in the body and must be obtained from foods or supplements.
However, despite their essential nature, obvious health benefits, and general shortage in the American diet, there is no official U.S. recommended daily allowance (RDA) for omega-3s.
(Americans and most other nationalities get more omega-6s than is healthy, from common vegetable oils and foods made with them, so no RDA numbers are needed.)
Experts in the field disagree somewhat on the minimum daily intake of omega-3s, but they agree that most Americans don’t consume nearly enough of them.
The two scientific bodies with the greatest expertise in this area are the U.S. Institute of Medicine (IOM) and the International Society for the Study of Fatty Acids and Lipids (ISSFAL).
The IOM recommends taking 260 (women) to 400 mg (men) of omega-3s per day, while ISSFAL recommends that both genders consume 660 mg of omega-3s per day.
It doesn’t matter whether you get omega-3s by eating fish, by taking fish oil, or both.
Note: by “omega-3s”, both bodies mean the long-chain, marine-source omega-3s (EPA and DHA) found only in fish and fish oil.
People can survive and thrive on short-chain, plant-derived omega-3s (from leafy greens, walnuts, and flaxseed) alone. But the body has to convert plant-derived omega-3s into the long-chain “marine” forms found in human cells and in fish (EPA and DHA), and that conversion rate is very low (two to 10 percent).
We think it makes more sense to rely on the ISSFAL recommendation (660 mg per day), because this organization represents the world's leading fatty acid researchers, including some members of the IOM advisory panel.
Dr. Harris and others point to evidence that the risk of sudden cardiac death drops substantially when omega-3s constitute at least 8 percent of the fatty acids in people’s red blood cells (erythrocytes).
He notes that the percentage of omega-3s in red blood cells predicts a person’s risk of sudden cardiac death as well or better than better-known measures such as cholesterol or triglyceride levels (Harris WS 2008):
- Less than 4 percent omega-3s = High risk
- 4-8 percent omega-3s = Intermediate risk
- More than 8 percent omega-3s = Low risk
Unfortunately, routine assessment of what Dr. Harris calls the “omega-3 index” will not become a routine part of annual physicals and examination of heart patients until two criteria are met:
- The value of measuring people’s “omega-3 index” becomes widely accepted.
- Standardized test methods and materials become available in all medical labs and hospitals.
We can only hope that the medical profession acts on the evidence and starts testing patients’ omega-3 levels sooner than later.
- Andersen LF, Solvoll K, Drevon CA. Very-long-chain n–3 fatty acids as biomarkers for intake of fish and n–3 fatty acid concentrates. Am J Clin Nutr 1996;64:305–11.
- Barberger-Gateau P, Raffaitin C, Letenneur L, et al. Dietary patterns and risk of dementia: the Three-City cohort study. Neurology 2007;69:1921–30.
- Block RC, Harris WS, Reid KJ, Sands SA, Spertus JA. EPA and DHA in blood cell membranes from acute coronary syndrome patients and controls. Atherosclerosis 2007;197:821–8.
- Féart C, Peuchant E, Letenneur L, Samieri C, Montagnier D, Fourrier-Reglat A, Barberger-Gateau P. Plasma eicosapentaenoic acid is inversely associated with severity of depressive symptomatology in the elderly: data from the Bordeaux sample of the Three-City Study. Am J Clin Nutr. 2008 May;87(5):1156-62.
- Fontani G, Corradeschi F, Felici A, Alfatti F, Migliorini S, Lodi L. Cognitive and physiological effects of omega-3 polyunsaturated fatty acid supplementation in healthy subjects. Eur J Clin Invest 2005;35(11):691–9.
- Harris WS, Miller M, Tighe AP, Davidson MH, Schaefer EJ. Omega-3 fatty acids and coronary heart disease risk: clinical and mechanistic perspectives. Atherosclerosis 2008;197(1):12–24.
- Harris WS. n-3 Fatty acids and health: DaVinci's code. Am J Clin Nutr. 2008 Sep;88(3):595-6. Harris WS. The omega-3 index as a risk factor for coronary heart disease. Am J Clin Nutr. 2008 Jun;87(6):1997S-2002S.
- Harris WS. Omega-3 fatty acids and cardiovascular disease: a case for omega-3 index as a new risk factor. Pharmacol Res. 2007 Mar;55(3):217-23. Epub 2007 Jan 25. Review.
- Harris WS. The omega-6/omega-3 ratio and cardiovascular disease risk: uses and abuses. Curr Atheroscler Rep 2006;8:453–9.
- Lindberg M, Saltvedt I, Sletvold O, Bjerve KS. Long-chain n–3 fatty acids and mortality in elderly patients. Am J Clin Nutr 2008;88:722–9.
- Samieri C, Féart C, Letenneur L, et al. Low plasma eicosapentaenoic acid and depressive symptomatology are independent predictors of dementia risk. Am J Clin Nutr 2008;88:714–21.
- van de Rest O, Geleijnse JM, Kok FJ, van Staveren WA, Dullemeijer C, Olderikkert MG, Beekman AT, de Groot CP. Effect of fish oil on cognitive performance in older subjects: a randomized, controlled trial. Neurology. 2008 Aug 5;71(6):430-8
- van de Rest O, Geleijnse JM, Kok FJ, van Staveren WA, Hoefnagels WH, Beekman AT, de Groot LC. Effect of fish-oil supplementation on mental well-being in older subjects: a randomized, double-blind, placebo-controlled trial. Am J Clin Nutr. 2008 Sep;88(3):706-13.