Age-related drop in antioxidant, anti-mercury mineral linked to increased risk of cognitive decline and dementia; seafood is the richest source
by Craig Weatherby
Last month, we reviewed the widely overlooked connection between selenium and mercury, and its highly encouraging implications for seafood safety.
Most ocean fish are high in selenium, which binds to mercury in the body, thereby preventing it from damaging brain and other tissues. In fact it’s been hypothesized that fish are high in selenium because they need to neutralize the mercury that occurs naturally in their environment, mostly from seabed geothermal vents.
This link may explain why people who eat copious amounts of ocean fish and comparatively large amounts of methylmercury—such as the 600-plus children in the landmark Seychelles Islands study—seem to suffer no mercury-related problems (See “Mercury-Fighting Mineral in Fish Overlooked in Heated Debate”).
And the results of a study from France suggest that the brain benefits of seafood extend beyond those attributed to omega-3 fatty acids.
As the French authors said, “The real importance of selenium in the brain and the capacity of the brain to manage selenium depletion is just beginning to be explored. Molecular biology has recently contributed to the recognition of selenium and selenium-dependent enzymes as modulators of brain function” (Akbaraly NT et al 2007).
Mental declines linked to age-related slump in brain selenium levels
The new findings flow from analysis of data from a nine-year study among elderly residents of the town of Nantes in Western France.
The data came from an investigation called the Etude du Vielissement Arteriel (EVA). Between 1991 and 1993, researchers recruited 1,389 men and women born between 1922 and 1932, who were examined for physical health and cognitive function upon enrolling in the study.
The subjects’ blood selenium levels were also measured at the beginning of the study, again between 1993 and 1995, and for the last time after nine years had passed.
After controlling for the effects of time, gender, education level, blood selenium levels at the outset, and major health factors, the analysis showed that the participants whose selenium levels dropped over the course of the study had a higher risk of cognitive decline.
Significantly, the extent of the subjects’ mental decline correlated with the drop in selenium.
And among the participants whose selenium levels rose, the risk of cognitive decline was greatest among those whose selenium counts went up the least.
Selenium’s role in body’s own “antioxidant network” called key
Selenium is an essential component in critical antioxidant enzymes the body uses to neutralize the free radicals generated by normal metabolism and by external influences, from pro-inflammatory foods to pollutants.
The brain contains large amounts of selenium, which also plays a role in the synthesis of thyroid hormones that affect mental performance.
As the authors concluded, “These results are in agreement with the effect of antioxidant supplementation observed in some long-term studies and the lack of effect after a 6-month period in patients with mild Alzheimer’s disease… The preventive effect of selenium supplementation at a nutritional level needs to be evaluated with large scale-studies” (Akbaraly NT et al 2007).
We certainly need more research, but it can’t hurt to make sure you’re getting plenty of the overlooked anti-mercury, antioxidant mineral from seafood and multivitamin supplements, right now.
- Akbaraly NT, Hininger-Favier I, Carriere I, Arnaud J, Gourlet V, Roussel AM, Berr C. Plasma selenium over time and cognitive decline in the elderly. Epidemiology. 2007 Jan;18(1):52-8.
- Berr C, Balansard B, Arnaud J, Roussel AM, Alperovitch A. Cognitive decline is associated with systemic oxidative stress: the EVA study. Etude du Vieillissement Arteriel. J Am Geriatr Soc. 2000 Oct;48(10):1285-91.
- Berr C, Richard MJ, Roussel AM, Bonithon-Kopp C. Systemic oxidative stress and cognitive performance in the population-based EVA study. Etude du Vieillissement Arteriel. Free Radic Biol Med. 1998 May;24(7-8):1202-8.