Tag Archives: Omega-3 fatty acid

The false promise of fish oil

24 Jul

I have been blogging a lot about diet lately and I should move onto other topics, but I think this Washington Post story is important:

“People in the United States spend about $1.2 billion annually for fish oil pills and related supplements even though the vast majority of research published recently in major journals provides no evidence of a health benefit.”



More evidence against fish oil

14 Apr

A good review in The New York Times:

“There’s a major disconnect,” Dr. Grey said. “The sales are going up despite the progressive accumulation of trials that show no effect.”

Here is Dr. Greger on the topic:

‘Put all the studies together, and there’s no justification for the use of omega 3s as a structured intervention in everyday clinical practice or for guidelines supporting more dietary omega-3’s. So what should doctors say when their patients follow the American Heart Association advice to ask them about fish oil supplements? Given this and other negative meta-analyses, “our job as doctors should be to stop highly marketed fish oil supplementation in all of our patients.”’


Walnut consumption and cognitive function

6 Mar

There is a folk belief that eating walnuts improves memory. Here is a study published in The Journal of Nutrition, Health, and Aging offering evidence for this claim.

“Abstract: Objective: To examine the association between walnut consumption and measures of cognitive
function in the US population. Design: Nationally representative cross sectional study using 24 hour dietary recalls of intakes to assess walnut and other nut consumption as compared to the group reporting no nut consumption. Setting: 1988-1994 and 1999-2002 rounds of the National Health and Nutrition Examination Survey (NHANES).

Population: Representative weighted sample of US adults 20 to 90 years of age. Main Outcome Measure: The Neurobehavioral Evaluation System 2 (NES2), consisting of simple reaction time SRTT), symbol digit substitution (SDST), the single digit learning (SDLT), Story Recall (SRT) and digit symbol substitution (DSST) tests. Results: Adults 20-59 years old reporting walnut consumption of an average) of 10.3 g/d required 16.4ms less time to respond on the SRTT, P=0.03, and 0.39s less for the SDST, P=0.01 SDLT scores were also significantly lower by 2.38s (P=0.05). Similar results were obtained when tertiles of walnut consumption were examined in trend analyses. Significantly better outcomes were noted in all cognitive test scores among those with higher walnut consumption (P < 0.01). Among adults 60 years and older, walnut consumers averaged 13.1 g/d, scored 7.1 percentile points higher, P=0.03 on the SRT and 7.3 percentile points higher on the DSST, P=0.05. Here also trend analyses indicate significant improvements in all cognitive test scores (P < 0.01) except for SRTT (P = 0.06) in the fully adjusted models.

Conclusion: These significant, positive associations between walnut consumption and cognitive functions among all adults, regardless of age, gender or ethnicity suggest that daily walnut intake may be a simple beneficial dietary behavior.”

This study has some clear limitations. It is correlational not experimental and cannot demonstrate a cause and effect relationship between walnuts and cognitive function. In addition, it is based on self-report walnut consumption, a measure that might not be accurate.

You can find Seth Roberts posts on walnuts here.



Krill oil shortens mouse life span

2 Sep

Beware of the claims made on behalf of the various fish oil products. Here is a recent study suggesting that krill oil (a popular fish oil supplement) shortens the life span of mice. From the abstract:

“Taken together, the results do not support the idea that the consumption of isolated ω-3 fatty acid-rich oils will increase the life span or health of initially healthy individuals.”


Mercury slows nerve transmission

17 Jun

Since fish is often recommended as a “brain food,” I feel a special responsibility to point out that fish should not be considered a safe source of omega-3 fatty acids. Here is a video by Dr. Greger describing recent research on the effects of mercury on the nervous system:


The prudent course of action is to consume plant sources of omega-3-fatty acids, such as ground flax seeds.

Dr. Greger: Fish oil is snake oil

6 Feb

In Dr. Greger’s latest evaluation of fish oil he states:

“Advice to eat oily fish or take fish oil to lower risk of heart disease, stroke, or mortality is no longer supported by the balance of available evidence.”

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Low blood levels of omega-3 fatty acids linked to poor cognitive performance

18 Oct

A paper published in PLOS, reports on a study of 493 schoolchildren between the ages of seven and nine. The researchers took took blood fatty acid profiles of the children and assessed several cognitive and behavioral variables.

Their conclusion:

“In these healthy UK children with below average reading ability, concentrations of DHA and other Omega-3 LC-PUFA were low relative to adult cardiovascular health recommendations, and directly related to measures of cognition and behavior. These findings require confirmation, but suggest that the benefits from dietary supplementation with Omega-3 LC-PUFA found for ADHD, Dyspraxia, Dyslexia, and related conditions might extend to the general school population.”

One strength of this study was its use of an objective measure of Omega-3. Most previous studies have relied on dietary self report.

Here is a link to Dr. Greger’s videos on omega-3 fatty acids.



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