Vitamins, minerals and amino acids
Selenium
The selenium in your blood; the value mainly follows recent intake, and a deficiency is unusual in the Netherlands.
Everything about this testWhat it measures
Selenium is a trace element. It protects cells against damage (antioxidant) and is needed for the thyroid to work. In the blood, selenium is mostly found in proteins, especially selenoprotein P, which carries selenium to the tissues. This analysis measures the total selenium in the blood; this value mainly follows the intake from food and supplements in the preceding period.
- A low selenium intake, for example with a very one-sided diet, long-term artificial nutrition or a severe bowel disease
- Too much selenium from supplements or a lot of Brazil nuts
High
A raised selenium is almost always caused by supplements or by regularly eating a lot of Brazil nuts. According to the Netherlands Nutrition Centre (Voedingscentrum), a handful of Brazil nuts already gives you more than the tolerable upper limit of 255 micrograms per day for adults. Going over that limit once causes no symptoms. With too much selenium over a long period, loss of hair, nails and teeth, skin damage and symptoms of the nervous system can develop.
Low
A low selenium can fit a low intake. According to the Netherlands Nutrition Centre (Voedingscentrum), it is not known how often this occurs in the Netherlands, and people who eat mainly plant-based or organic food are at greater risk of a low intake, because the amount of selenium in plant products depends on the soil. The value can also fall temporarily during inflammation or a serious illness, without there being a deficiency. Symptoms of a true deficiency, such as muscle pain, muscle weakness and heart disorders, are rare.
If your result is abnormal
With a low selenium, the GP looks at your diet and at diseases that reduce absorption, and repeats the measurement if needed once there is no more inflammation. With a raised selenium, the GP asks about the use of supplements and Brazil nuts.
Reliability
The test is mainly used in hospital for a specific question, such as long-term artificial nutrition. The blood value mainly follows recent intake and says little about the stores in the tissues. The Health Council of the Netherlands, following EFSA, uses selenoprotein P as the best measure of selenium status, and notes that its link with health has also not been studied enough.
Limitations
- Supplements and Brazil nuts raise the value within a short time.
- Inflammation or a serious illness can temporarily lower the value.
- Laboratories measure in serum, plasma or whole blood with different reference values; this makes results hard to compare.
How common is this
According to the Netherlands Nutrition Centre (Voedingscentrum), selenium deficiency does not normally occur in the Netherlands, but it is not known how often a (too) low intake occurs. People who eat mainly plant-based or organic food are at greater risk of a low intake. Too much selenium occurs mainly with supplement use; according to the Health Council of the Netherlands, eating Brazil nuts can also exceed the upper limit.
Who is this useful for
Useful when a severe deficiency is suspected, for example with long-term artificial nutrition or a severe bowel disease, and with long-term use of selenium supplements. In healthy people, including those eating plant-based, the result says little, because the blood value mainly follows recent intake. The advice of the Netherlands Nutrition Centre (Voedingscentrum) to vary your diet with foods such as fish and different kinds of nuts applies regardless of the result.
Downsides and risks
- A low result can lead to taking selenium supplements on your own; staying above the tolerable upper limit of 255 micrograms per day for a long time can be harmful.
- Because the meaning of a slightly abnormal value is unclear, the result can cause unnecessary worry.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results