The Omega-3 Index: Eat Seafood

“Need” is a funny concept. You don’t need to eat seafood. You don’t need an appendix or legs, either.

Association  of marine omega-3 fatty acid levels with telomeric aging in patients  with coronary heart disease (Farzaneh-Far et al., 2010)

Telomere length is believed to be a biomarker of aging: the shorter your telomeres, the faster you’re aging. In the study, they measured telomere length in white blood cells and EPA+DHA in whole blood at baseline and again 5 years later.

Quartile 1: EPA+DHA = 2.3% of the fatty acids in whole blood.

Quartile 2: 3.3%

Quartile 3: 4.3%

Quartile 4: 7.3%

Potential confounders: quartile 4 was comprised of educated rich white old non-smokers with low levels of inflammation, but the statisticians assured us those variables were controlled for… so there’s  that.

You might be thinking: Bill-man, I don’t feel like getting my Omega-3  Index tested, how much seafood will put me in that fourth quartile?

hold my beer

Factors influencing EPA+DHA levels in red blood cells in Japan (Itomura et al., 2008)

Salmon is roughly 1-2% EPA+DHA by weight, so a standard ~3 ounce  portion has approximately 1-2 grams. Doing this regularly puts you  significantly ahead of the curve.

The impact of age, BMI, and fish intake on the EPA and DHA content of human erythrocytes (Sands et al., 2005)

Omega-3 index in this population: was 4.9% and it increased by ~0.24 units with each additional monthly  serving of fatty fish.  Thus, mathematically, to get from 4.9% to 8% would require 13 additional servings per month. However, biology is not mathematics, and from the figure below it appears that less can do the  same.

>3 servings per week

…and some people just seem “lucky?” 10% without eating seafood?!  Color me skeptical, but these participants specifically were not taking supps…

As one who likes to hedge bets, I’d rather assume those people with a  high Omega-3 Index are either eating pounds of algae daily or  glitches/errors (ie, assume you’re not one of them).

Reminder: why is this important?  

1) Recall the association of Omega-3 Index with telomere length from above. 2) Also, Inverse association between docosahexaenoic acid and mortality in patients on hemodialysis during over 10 years (Terashima et al., 2014).

After adjusting for a plethora of confounding factors, patients with red blood cell phospholipid DHA > 8.1% had a significantly lower risk of all-cause mortality than those with DHA < 7.2%. No effect of EPA.

many studies report omega-3 fatty acids in different samples (whole blood, white blood cells, red blood cell phospholipids). I don’t think this matters very much because over time, they equilibrate.

Blood  EPA and DHA Independently Predict All-Cause Mortality in Patients with  Stable Coronary Heart Disease (Pottala et al., 2010)

27% decreased risk of all-cause mortality in those with total blood levels of EPA+DHA above 3.6% compared to those below it.  3.6%?  According to the data  above, this amounts to about 2 servings/week!

Negative finding? Effects  of omega-3 fatty acid supplementation on neurocognitive functioning and mood in deployed U.S. soldiers: a pilot study (Dretsch et al., 2014)

2.5 grams of EPA+DHA per day (Lovaza) for 2 months: “Although the  results revealed that omega-3 FAs significantly increased the HS-Omega-3 Index (p = 0.001), there were no significant effects on indices  psychological health and neurocognitive functioning by treatment group.  Nevertheless, there was a significant inverse correlation between the  changes in the HS-Omega-3 Index and daytime sleepiness (r = 0.30, p =  0.009). Short-term treatment with 2.5 g of omega-3 FAs did not alter  measures of neurocognition or psychological health, but there was  evidence of a relationship between omega-3 levels and daytime  sleepiness.”

Not too surprising, given that these are fit, healthy subjects… Omega-3 Index increased from 3.5 to 6.7 in the intervention group, and  3.4 to 4.2 in the control group. Not huge increases, possibly because it was supps not seafood (N.B. 2.5 grams/d is roughly equivalent in terms of DHA to a big piece of salmon every day; 30 servings per month).

Also, had the participants been old, unhealthy, and mildly cognitively impaired, I suspect neurocognitive outcomes  would’ve improved…


DHA supplementation improved both memory and reaction time in young adults: a randomized controlled trial (Stonehouse et al., 2013)

Seafood vs. fish oil supps (best product recommendations here)

Comparison  of the effects of fish and fish-oil capsules on the n-3 fatty acid  content of blood cells and plasma phospholipids (Harris et al., 2007)

Participants were assigned to get 485 mg EPA+DHA per day, on average, from either 2 servings salmon or tuna per week or from 1-2 capsules per day.

In red blood cell membranes, DHA increased by 50% in the fish group  and 46% with supps. In plasma phospholipids, DHA increased by 64% in  the fish group and 60% with supps. This basically confirms one of the  aspects of why seafood is better than supps: greater bioavailability of DHA in seafood. It’s not a huge difference, but the whole food is also greater than the sum of its parts: seafood comes with additional benefits not found in supps (eg, iodine, selenium, other micronutrients, etc.).

Fwiw, I try to get some seafood every day. It doesn't have to be huge portions multiple times per day.

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