Sat, Jul-14-12, 01:53
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Plan: Muscle Centric
Stats: 238/153/160
BF:
Progress: 109%
Location: UK
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Dr Briffa: Selenium may be vital to your diet
Quote:
From The Times
London, UK
14 July, 2012
Selenium may be vital to your diet
There’s one vital nutrient, of critical importance to our long-term health, that our diet may not be providing enough of, says John Briffa
Many of us make an effort to eat varied, wholesome foods. But there’s one vital nutrient, of critical importance to our long-term health, that our diet may not be providing enough of. Studies show that selenium, a trace mineral, may ward off cancer, protect against thyroid problems and enhance fertility and brain function. Unfortunately, we Brits tend to be chronically deficient in selenium, and our health may be suffering as a result.
Even though selenium is only required in tiny amounts, it is an essential component in more than two dozen “selenoproteins” — substances that play a critical role in the regulation and maintenance of our health (genetic glitches in selenoproteins give rise to an elevated risk of conditions including heart disease and cancer). Studies have linked low selenium levels with a risk of chronic health issues and a heightened risk of several cancers, including those of the lung, bladder and prostate.
We need to be cautious when interpreting the results of these so-called “epidemiological” studies: while higher levels of selenium are linked to a reduced cancer risk, we cannot conclude from this that selenium protects against cancer. It might be, for instance, that individuals with better overall health also eat better diets richer in selenium. It is also possible for disease processes to effectively deplete the body of selenium (in which case, cancer might cause low selenium rather than the other way round).
However, there is evidence that suggests selenium might be genuinely cancer-protective, for men at least. In a seminal study published in The Journal of the American Medical Association, more than 1,300 men and women with a previous history of relatively harmless skin cancer (that is, other than melanoma) were treated with 200 micrograms of selenium or a placebo for about 4½ years.
Selenium supplementation was found to reduce the overall risk of cancer by 25 per cent in men, and more than halved the risk of prostate cancer. The beneficial effects were apparent only in those who started the study with lower selenium levels in their bodies. It seems that the men who benefited from selenium supplementation were the ones who needed it most.
Selenium’s role in health appears to extend well beyond any effects it might have on cancer. For example, selenium supplementation has been found to enhance the function of key elements in the immune system. Other evidence suggests that it is key to male fertility; in one study 100g of selenium daily improved sperm motility in infertile men.
Selenium also plays a role in the functioning of the thyroid gland, which governs our metabolism. In particular, selenium assists the transformation of the main hormone made by the thyroid (T4) into its more active form (T3). Selenium supplementation has also been found to be beneficial in the treatment of the thyroid conditions Hashimoto’s thyroiditis (a common form of low thyroid function) and Graves’ disease (a form of high thyroid function). Not only that but evidence suggests that selenium has some ability to prevent seizures, Parkinson’s disease and dementia.
Certain selenoproteins can protect against processes that are likely to increase the risk of heart disease and heart attacks such as “oxidative damage” of blood fats, inflammation and blood clotting. Higher selenium levels are associated with a reduced risk of heart disease. However, thus far, selenium supplementation has failed to deliver on its promise in the form of reduced risk of cardiovascular disease. Much of this evidence, though, comes from the US, where individuals tend to have good levels of selenium by virtue of a selenium-rich diet.
Selenium supplementation is unlikely to benefit those whose bodies already have enough of it, and some researchers have even sounded caution here. It turns out that the relationship between selenium levels and overall risk of death is U-shaped: in one major study, mortality “bottomed out” at blood levels of 135 micrograms per litre, but mortality rose as levels dropped or increased from this point. Again, the nature of this evidence (epidemiological) makes it difficult to draw firm conclusions from it. However, it seems likely that, as with most things, while too little selenium is a bad thing, too much may well be undesirable too.
One of the reasons Americans have relatively high levels of selenium is due to the wheat in North America being selenium rich. We used to import a lot, but over the past 40 years or so we’ve been reducing this steadily as we rely more on wheat grown closer to home — which is, unfortunately, low in selenium. It is interesting that average body selenium levels in the US approximately coincide with those associated with the lowest risk of death. However, our selenium levels are considerably lower in the UK.
In Britain, we should emphasise selenium-rich foods in our diet, including organ meats (eg, liver and kidney), meat, fish and brazil nuts. The appropriateness of supplementation is likely to depend on your own levels. A recent review in The Lancet medical journal concluded that individuals with selenium levels of 122 micrograms per litre or higher should not supplement. This would count out most Americans but hardly any Britons. For those for whom supplementation is appropriate, daily doses of 100-200 micrograms appear to give the optimum benefits.
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http://www.thetimes.co.uk/tto/healt...icle3474082.ece |
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