Selenium Deficiency
May Increase Risk of
Chronic Disease
Antioxidants, Minerals & Vitamins for
Supporting Bone & Joint Health, Cancer Risk
Reduction, Cardiovascular Health, Cognitive &
Mental Function, Diabetes, Immune System
Functioning are the Topics of Important New
Nutritional Healthcare Research
Ensuring adequate intakes of selenium may reduce the
risk of age-related diseases such as cancer and heart
disease, says a new review that supports "Bruce Ames'
Triage Theory."
By analyzing data from hundreds of published articles,
Joyce McCann, PhD, and Bruce Ames, PhD, from
Children's Hospital Oakland Research Institute
(CHORI) report that selenium-dependent proteins
considered essential to ensuring an organism survives
until it reaches reproductive age are largely more resistant
to selenium deficiency than non-essential selenoproteins.
The new data adds to an earlier analysis of triage theory
with vitamin K, published in the American Journal of
Clinical Nutrition (2009, Vol. 90, pp. 889-907).
Evolutionary Mechanisms
Dr Ames' theory works by understanding that natural
selection favors short-term survival over the long-term;
The researchers hypothesized that our short-term
survival is achieved by prioritizing the allocation of scarce
micronutrients. In other words, to stop us falling over from
a lack of iron in the heart, for example, iron is pulled from
non-essential sources.
The triage theory is a way of "measuring the insidious
damage going on over time", he said. The theory was first
proposed in 2006 (PNAS, Vol. 103, Pages 17589-94) to explain why age-related diseases like heart disease,
cancer, and dementia may be unintended consequences
of mechanisms developed during evolution to protect
against episodic vitamin and mineral shortages.
By analyzing the activity and concentrations of 12
selenoproteins, five of which were classified as essential
and seven as non-essential, the doctors found that the
activity and levels of non-essential selenoproteins were
preferentially lost when the organism was moderately
selenium deficient.
"Results of the analysis are largely supportive of the
theory, suggesting that, among all selenoproteins,
dysfunction of those that are nonessential is likely to
be the major contributor to increased disease risk due
to selenium deficiency," they explained.
Indeed, the non-essential selenoprotein Dio2 has
previously been linked to a wide range of diseases or
conditions, including osteoarthritis, while Gpx1 may
protect against DNA damage, and ultimately cancer risk,
Gpx2 may exert ant-inflammatory effects, and Gpx3 has
been implicated in improved cardiovascular health.
They also now report that current recommendations for
selenium intake, based on maximizing blood activities
of the selenium enzyme glutathione peroxidase (GPx)
may be insufficient, given that an essential selenium-
dependent protein called Sepp1 was found to be more
sensitive to selenium deficiency than Gpx3.
"The fact that Sepp1 is more sensitive to Se deficiency
than Gpx3 in human plasma has important implications
for estimating the percentage of the population that is
modestly selenium deficient,"
"Since the current [US] RDA (55 micrograms per day,
roughly corresponding to 100 micrograms per liter of
plasma selenium) is based on the sensitivity of Gpx3
in plasma, Sepp1 is expected to be at suboptimal
levels, even in some individuals meeting current
selenium intake recommendations.
"Based on these findings, it recently was suggested that
recommended selenium intake levels should be raised
from 55 to 75 micrograms per day," they added.
Selenium and Cancer
Selenium is a trace element that occurs naturally in the
soil and is absorbed by plants and crops, from where
it enters the human food chain - either directly or
through consumption of meat and other products from
grazing animals.
The mineral is included in between 50 and 100 different
proteins in the body, with multifarious roles including
building heart muscles and healthy sperm. However,
cancer prevention remains one of the major benefits of
selenium, and it is the only mineral that qualifies for a
Food and Drug Administration (FDA)-approved
qualified health claim for general cancer reduction
incidence.
Europe versus America
The study is of added importance in Europe where
selenium levels have been falling since the EU imposed
levies on wheat imports from the US, where soil
selenium levels are high. As a result, average intake of
selenium in the UK has fallen from 60 to 34 micrograms
per day, leading to calls from some to enrich soil and
fertilizers with selenium to boost public consumption.
Selenium-enriched fertilizers are used in Finland.
The European recommended daily intake (RDI) is 65
micrograms. The recommended EC Tolerable Upper
Intake Level for selenium is 300 micrograms per day.
Source: FASEB Journal Published online
"Adaptive dysfunction of selenoproteins from the
perspective of the triage theory: why modest selenium
deficiency may increase risk of diseases of aging"
Editor's Note: This article is not intended to provide medical advice,
diagnosis or treatment.
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