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Seafood Mineral May Boost Seniors’ Strength
9/3/2007
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Europeans’ muscle power declined in tandem with rising tariffs on selenium-rich American wheat; Brits' strength linked to fish intake

by Craig Weatherby



One could file this rather strange story under the heading “unintended consequences of import curbs”.


US consumers are up in arms over unwanted lead in paint on Chinese toys, but it’s the absence of imports containing anotherhighly beneficialmetal that’s got European health experts exercised.


Lack of selenium-rich American wheat seems to be sapping European's strength.

Given the new findings and variations in Americans' selenium intake, one has to wonder whether folks on these shores might benefit from upping their intake of the antioxidant, anti-aging metal.

Fortunately, any selenium deficit is readily reversed by taking adequate supplemental doses, or eating ample amounts of ocean fish, which are about the only foods reliably rich in this essential element... see our Selenium Content chart, below.


The backdrop: Selenium nixes mercury, senility, oxidation, and inflammation

Selenium is essential to making an enzyme called glutathione peroxidase, which forms a critical node in the body’s internal antioxidant network. Low levels of glutathione invite chronic inflammation, promote premature aging, and weaken overall immunity.


We’ve reported on two recent studies that linked higher selenium levels to reduced risk of senility. (See “'Seafood Mineral' Selenium May Reduce Risk of Senility” and “Selenium Scores Against Senility… Again.”)


And selenium protects the body from the toxic effects of dietary and environmental mercury. For more on this topic, see “Mercury-Fighting Mineral in Fish Overlooked in Heated Debate.


Selenium levels in Europeans have been falling since the European Union (EU) set tariffs on wheat from the US, where soil selenium levels are much higher. The import duties were imposed in response to massive government subsidy of wheat production under the US farm bill (To read some critiques of the diet-distorting legislation, see “Farm Bill Sets Americans’ Tables for Ill Health”).


Following the import tax on American wheat, average intake of selenium in the United Kingdom dropped a whopping 43 percent, from 60 to 34 micrograms per day, which falls far short of minimum requirements.


Unsurprisingly, higher fish consumption is the best predictor of higher selenium levels among British adults (Bates CJ et al 2007).


Americans are better off selenium-wise, with their average (1.58 nmol/L) and mean (1.56 nmol/L) blood levels rising well above the minimum recommended level (1.25 nmol/L). However, overweight people tend to be more deficient (Niskar AS et al 2003; Kimmons JE et al 2006).


The US Dietary Reference Intake (DRI) for selenium is 55 micrograms (mcg) per day, and the European equivalent is 65 mcg. The safe upper intake limit is 400 mcg per day.


Selenium Levels* in 

Seafood US RDA = 55 mcg


Species Micrograms (mcg) 

per 3.5 oz, cooked 


Sardines

King Salmon

Halibut

Tuna**

Sablefish

King Crab

Silver Salmon

Sockeye Salmon

Sockeye, canned

Scallops


52.7

46.8

46.8

46.8

46.8

40.0

38.0

37.8

34.3

27.9


*micrograms (mcg) of selenium. Source: USDA nutrient database at www.ars.usda.gov/ main/site_main.htm?modecode=12354500


**The USDA database provides no nutrient data for Albacore tuna. Since its diet is similar to that of other tuna. This number is the average for Yellow Fin, Skipjack and Blue Fin tuna.

Selenium seems essential to seniors’ strength

Results from a study by US and European scientists suggest that people who don’t get enough dietary selenium suffer punishing losses of muscle power.


The results flow from a study among 891 Italians aged 65 or older living in either of two towns in the renowned Chianti region. The investigation was conducted by researchers from the Johns Hopkins School of Medicine, the US National Institute on Aging, and the Tuscany Regional Agency (Lauretani F et al 2007).


The Italo-American team found that the average blood selenium levels of all the participants was 0.95 nmol/L, which falls well below the 1.25 nmol/L considered essential for maximum production of "selenoproteins" such as glutathione peroxidase.


And the participants with the lowest blood levels of the metal were much more likely to have weak muscles, compared to those with the highest selenium levels.


The strength deficits suffered by the most selenium-poor people were dramatic:

  • 69 percent weaker in the hips
  • 94 percent weaker in the knees
  • 94 percent weaker in the hands

The scientists reached these results after taking into account potential confounding factors such as age, sex, calorie intake, and body mass index.


More research is required to determine whether increased selenium intake would prevent or reduce age-related decline in muscle strength, and possibly improve muscle strength in people with muscle weakness.


Why should selenium intake affect muscle strength?

The answer to this question could lie in the metal’s role as an essential component of the antioxidant enzyme glutathione peroxidase, which reduces inflammation.


A prior study in the same population, by some of the same researchers, found that lower strength levels correlated with higher inflammation levels. As they wrote then, “Inflammation… is significantly associated with poor physical performance and muscle strength in older persons” (Cesari M et al 2004).



Sources

  • Bates CJ, Prentice A, Birch MC, Delves HT. Dependence of blood indices of selenium and mercury on estimated fish intake in a national survey of British adults. Public Health Nutr. 2007 May;10(5):508-17.
  • Cesari M, Penninx BW, Pahor M, Lauretani F, Corsi AM, Rhys Williams G, Guralnik JM, Ferrucci L. Inflammatory markers and physical performance in older persons: the InCHIANTI study. J Gerontol A Biol Sci Med Sci. 2004 Mar;59(3):242-8.
  • Dietary Reference Intakes (DRIs): Recommended Intakes for Individuals, Elements: Food and Nutrition Board, Institute of Medicine, National Academies. Accessed online September 3, 2007 at http://www.iom.edu/Object.File/Master/21/372/0.pdf
  • Lauretani F, Semba RD, Bandinelli S, Ray AL, Guralnik JM, Ferrucci L. Association of low plasma selenium concentrations with poor muscle strength in older community-dwelling adults: the InCHIANTI Study. Am J Clin Nutr. 2007 Aug;86(2):347-52.
  • Kimmons JE, Blanck HM, Tohill BC, Zhang J, Khan LK. Associations between body mass index and the prevalence of low micronutrient levels among US adults. MedGenMed. 2006 Dec 19;8(4):59.
  • Niskar AS, Paschal DC, Kieszak SM, Flegal KM, Bowman B, Gunter EW, Pirkle JL, Rubin C, Sampson EJ, McGeehin M. Serum selenium levels in the US population: Third National Health and Nutrition Examination Survey, 1988-1994. Biol Trace Elem Res. 2003 Jan;91(1):1-10.

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