Selenium - Antioxidant Series Part 4

This week’s Friday Five antioxidant is selenium.  This mineral is a nutrient most people don’t hear much about, yet it contributes a lot to our general health and wellbeing.  Read on to find out more.

Antioxidant wheel

1 What is it?

Selenium is believed to support our hormone production, in particular in the thyroid gland.  It may also be important for both male and female fertility, heart health, and during pregnancy (see point 4 below regarding required intake).  This mineral also has antioxidant properties.

2 How does selenium help us as and antioxidant?

At a basic level, selenium helps to reduce oxidative stress by helping us to manage the amount of free radicals in our bodies.  Looking more closely at this, we need it to produce the antioxidant enzymes glutathione peroxidase, thioredoxin reductase and iodothyronine deiodinases (yep, I struggle to say these too).  Low levels of these enzymes in blood tests may help highlight low selenium.

You have probably heard about ‘bad’ LDL cholesterol.  Well, LDL cholesterol becomes a greater issue for heart health if it becomes oxidized.  Some scientists suggest that selenium compounds help to reduce this oxidation and, in turn, potentially reduce the risk of associated heart disease.  There are also studies that suggest the mineral may have a further role in the recovery of the heart following blood supply problems.

There is increasing evidence that selenium may have a further role in reducing the incidence of some types of cancer.  The mechanism for this benefit is not yet understood.  It is possible that the mineral’s antioxidant properties help to reduce DNA damage, which is associated with the development of cancer.

There are also tentative studies that show a link between selenium and the immune system, including a lower response to the polio vaccine (this can contribute to a higher risk of contracting the virus).  The benefits for the immune system, are also seen in selenium’s effect on thyroid antibodies which contribute to autoimmune thyroiditis (this may occur with hyperthyroidism or hypothyroidism).

3 Signs of deficiency

While the list below may be caused by a lot of different health conditions, they are all potential signs of selenium deficiency:

  • Muscle weakness
  • Fatigue
  • Mental fog
  • Hair loss
  • Weak immune system

Deficiency is not thought to be common, but the risk is increased if you are undergoing kidney dialysis, have HIV, or have a digestive disorder affecting the small intestine as your absorption of the nutrient may be reduced.  Selenium levels are not typically tested in the UK, however there are tests available if required.

4 How much do we need?

Being a trace element, we do not need large amounts of selenium.  In fact having too much can also contribute to health problems, such as:

  • Hair loss
  • Brittle nails
  • Fatigue
  • Digestive issues
  • Joint pain

Extreme long-term toxicity in humans is very rare, however signs may include neurological problems, kidney failure and heart attack.

Don’t assume experiencing any of these symptoms means you have excess selenium however, each can have many different causes.  If you have concerns about the symptoms, please seek medical advice.

It is worth noting that these problems are generally associated with excess intake due to supplement use rather than food (however, it is not clear if this is due to the focus of the studies) and should dissipate once the supplements have been stopped.   While selenium may be included in general health supplements, selenium-specific supplements in particular should only be used when there is a specific health need and under supervision.  If you have an excess level of selenium you may notice a garlic-like odour on your breath, or a metallic taste in your mouth – do not rely on these signs for diagnosis and consult your doctor with any concerns.

The UK daily recommended intake of selenium is 75mcg for males aged 19 years and over, and 60mcg for females aged 19 years and over.  Lactating parents should increase their intake by 15 mcg per day (assuming no other influential health concerns).  No increase is recommended during pregnancy over the normal daily intake.

Overall selenium intakes should not exceed 400mcg per day, for people over the age of 19 years.

While diet is an important source of selenium, we may also be exposed to it though environmental exposure, including some workplaces (for example ceramic, glass or semiconductor manufacture).  This increased exposure may contribute to problems of toxicity.

5 Sources

The best dietary source of selenium is Brazil nuts. Just one nut may well contain enough to meet your daily recommended intake*, so do not eat more than 2-3 Brazil nuts on a regular basis!

Other good sources of the mineral include*:

  • Green vegetables (yes, them again – they do keep coming up on these nutrient source lists don’t they?!)
  • Shiitake and button mushrooms
  • Fish and seafood (especially oysters, halibut and yellowfin tuna)
  • Beef and poultry
  • Eggs
  • Seeds
  • Wholewheat bread
  • Beans
  • Cottage cheese

*The exact amount of selenium in food can be significantly affected by the environment in which it grows.

Important

If you are considering taking nutritional supplements, please consult with a suitably qualified professional to ensure the supplement is appropriate for you.  This is especially important if you have any health conditions or are taking medications.

Alible Nutrition Nutritional Therapy services consider health conditions and medications prior to providing advice regarding foods or supplements.  I cannot give individual advice outside the consultation process.

Are you getting enough?

To find out if you are getting enough selenium in your diet, or have a specific health condition that could be supported by better nutrition, take a look at my Nutritional Review or Nutritional Therapy services and choose the best one for you.  Or, you can request a call for more information!

References/Further Reading