Suboptimal Omega-3 and Iron Blood Concentrations Affect Performance & Function
Two newly published studies demonstrate the importance of measuring blood concentrations of nutrients. Neither of these reports rely upon self-reported dietary intake data combined with food composition databases. Both studies directly examine the relationship between plasma concentrations and performance.
As noted yesterday, low plasma omega-3 concentrations (eicosapentaenoic acid, EPA, and docosahexaneoic acid, DHA) are associated with increased risk of coronary heart disease. Using data from the Singapore Chinese Health Study (participants were 47-83y old), Sun and colleagues compared plasma omega-3 concentrations of α-linolenic acid (ALA), EPA and DHA from 744 individuals who had incident acute myocardial infarction (AMI) episodes with 744 matched controls. AMI cases had significantly lower plasma concentrations of EPA and DHA than controls. Plasma ALA concentrations did not differ between groups. In multivariate analysis, higher plasma EPA and DHA concentrations were associated with an Odds Ratio of 0.62 (P-trend=0.03 for lowest vs highest quartile). The authors write, “These findings support recommendations to regularly consume n-3 PUFAs from both marine-and plant-based foods.”
In the second paper of interest, iron status and cognitive performance were associated in 127 nonanemic young women (18-35y). Hematological indicators of iron status (hemoglobin, red blood cell distribution width, transferrin saturation, ferritin, transferrin receptor, and total body iron) were associated with measures of brain function (attentional network task, Berg card sorting task, Go/no-go task, Sternberg memory search task, and Tower of London task). Better iron status was associated with better performance on tasks of sustained attention and planning ability.
By using clinical measures of nutritional status, significant differences in performance and health outcomes were observed among individuals within “normal nutrient status ranges”. These are not studies comparing deficient vs non-deficient individuals. These studies provide evidence that low (but normal) nutrient status negatively affects performance/health outcomes. These studies provide evidence of the importance of maintaining optimal (sufficient) nutrient concentrations in circulation (blood) to be available to cells and tissues.
This is NOT to say ‘more is not always better’. Iron overload, measured as ferritin concentrations >200 µg/L, has been connected with neural toxicity and reduced memory performance.
Currently, the healthiest approach is to follow the Dietary Reference Intakes (DRIs) for vitamins and elements for your age and sex. Hopefully, the development of affordable, faster, and less invasive technologies will make objective measures of nutrient status possible soon.
Sun Y, Koh W-P, Yuan J-M, Choi H, Su J, Ong CN, van Dam R. Plasma α-linolenic and long-chain omega-3 fatty acids are associated with a lower risk of acute myocardial infarction in Singapore Chinese adults. 2015 J Nutr doi: 10.3945/jn.115.220418
Scott SP, Murray-Kolb LE. Iron status is associated with performance on executive functioning tasks in nonanemic young women. 2015 J Nutr doi: 10.3945/jn.115.223586
Murphy RA, Yu EA, Ciappio ED, Mehta S, McBurney MI. Suboptimal plasma long chain n-3 concentrations are common among adults in the United States, NHANES 2003-2004. 2015 Nutrients doi: 10.3390/nu7125534
CDC. Hemochromatosis (iron storage disease): testing protocol [Internet]. [cited 2015 Dec 10]. Available from: http://www.cdc.gov/ncbddd/hemochromatosis/training/diagnostic_testing/testing_protocol.html