Category Archives: selenium

Choosing the Best Supplements: Part Two

In Part One I discussed some guidelines to help ensure that you are getting the best out of your supplements. Read on for more pointers.

Mineral Bioavailability
There isn’t much point in taking a supplement in a form that your body cannot use. Mineral bioavailability simply refers to the proportion of a mineral that is actually absorbed into the blood to be used by the body.

A ‘bioavailable’ mineral must be soluble in the intestine so that it can be absorbed. Minerals should be bound to different compounds to aid their absorption. This binding, or ‘chelation’, helps the mineral to survive the acid environment of the stomach and pass through into the small intestine for absorption.

If the mineral is bound too tightly, or not tightly enough, it can be released at the wrong time.  This is why the ‘form’ of the mineral is an important consideration.

Generally inorganic forms of minerals – carbonates, sulphates and oxides are not well absorbed. On the other hand, organic forms such as citrates, gluconates, aspartates and amino-acid chelates are more bioavailable.

Better quality minerals, i.e. those that are in a bioavailable, organic form do tend to be more expensive. However, cheaper supplements may be a false economy if they are poorly utilised by the body. Choosing a supplement becomes a case of weighing the cost of the supplement against its bioavailability. For example, in the New Optimum Nutrition Bible, Patrick Holford (1) explains that iron amino acid chelate is four times better absorbed than other forms, making it worth the additional cost.

Holford lists the most bioavailable forms of each mineral. All of the following forms are the most readily available to the body. In descending order (the very best first), he lists:

A multi-mineral supplement including Chronium, Calcium, Magnesium, Iron, Zinc, Manganese and Selenium.

Calcium – amino acid chelate, ascorbate, citrate, gluconate, carbonate

Magnesium – amino acid chelate, ascorbate, citrate, gluconate, carbonate

Iron – amino acid chelate, ascorbate, citrate, gluconate, sulphate, oxide

Zinc – picolinate, amino acid chelate, ascorbate, citrate, gluconate, sulphate

Manganese – amino acid chelate, ascorbate, citrate, gluconate

Selenium – Selenocysteine or selenomethionine, sodium selenite

Chromium – Picolinate, polynicotinate, ascorbate, gluconate

Tablets or Capsules?
Deciding between capsules or tablets is often a personal preference. Those who find tablets difficult to swallow often favour easy-to-swallow capsules. Sensitive individuals also tend to prefer capsules which are more likely to be free from fillers or binders. On the other hand, tablets can be compressed meaning that a higher dosage can be delivered in a single pill. They also allow for ‘sustained-release’ formulas. This can be useful for water-soluble vitamins such as Vitamin C, where absorption is better when given as a steady release formula rather than in a single dose.

For very sensitive individuals or for the delivery of light-sensitive nutrients such as coenzyme Q-10, capsules are the best choice. There are of course advantages to both types of supplements, which are listed below.

Capsules Tablets
Superior protection against oxygen and light Low cost
No need for fillers and binders Allows for sustained-release formulas
Odorless and tasteless Can fit more ingredients in through compression
Less gastrointestinal irritation Can be notched to divide the dose

Quality Assurance
The simplest way to be certain of the quality of a supplement is to check that it is GMP certified. Good Manufacturing Practice (GMP) is an assurance of quality of manufacture. While medical drugs are held to these strict standards, it is not currently a legal requirement for food supplements in the UK. However, most reputable supplement companies voluntarily submit their products to GMP certification. This compliance requires thorough record keeping, quality testing, and standards consistent with the manufacture of drugs.


1. Holford, P (2004) Patrick Holford’s New Optimum Nutrition Bible. London: Piatkus.


Selenium, an essential trace mineral that may help reduce the risk of certain cancers

Selenium isn’t a mineral that receives a lot of press attention, however it is an essential trace element that is incredibly vital to our health.  I first became aware of the importance of selenium for optimal health when I was studying for my MSc in Nutritional Medicine at the University of Surrey.  My professor at that time, Margaret Rayman, was (and is) a leading scientific researcher in the field of selenium.  At the time I was studying (2000-2002) there was a lot of research linking low selenium intakes to increased prostate cancer risk in men.  A very recently published paper (1) has now found that low selenium intakes seem to be tied to throat and stomach cancers too.  This is a preliminary study and further research is certainly required before any firm conclusions can be drawn.

Selenium acts as an important antioxidant in the body and this may account for part of the role it plays in cancer prevention.  As an antioxidant selenium may also be useful in preventing conditions related to inflammation such as pancreatitis, rheumatoid arthritis, systemic inflammatory response syndrome, asthma and cardiovascular disease, to name but a few.  It is also vital for a healthy immune system and plays a role in fertility in men and women.  In men it is vital for good sperm motility and in women selenium appears to be vital in very early pregnancy (2)

With regards the potential cancer protective role of selenium the antioxidant role may not be the only way that selenium acts.  Selenium also seems to act at the DNA level on specific genes in a variety of complicated ways (2)

As well as the requirement of selenium for antioxidant defence there is evidence that selenium:
* Is needed for thyroid function
* Is required by the immune system
* Has important antiviral effects
* Is needed for reproduction
* Enhances mood
* Reduces the risk of cancer
* Protects against mercury toxicity

The effect of selenium and its importance is most observable in populations where selenium status is low. The amount of selenium in the soil where food is grown determines its selenium content.  This is important here in the UK since our soils are very low in selenium.  The UK RNI (reference nutrient intake) for selenium is 75mcg/d for adult men and 60mcg/d for adult women.  However in the UK selenium intakes are estimated to be 39mcg/d which is very low and probably inadequate for most individuals (3).  Selenium intakes in the UK have fallen over the last 25 years largely due to the decrease in imports of high selenium wheat from the USA and Canada.  Plant foods are generally low in selenium in the UK/Europe where soil selenium levels are low (2).

Care is needed with supplementation since high doses of selenium can build up in the body and are toxic to health.  I would suggest not taking more that 100mcg/d.  I also do not recommend taking selenium as a single nutrient supplement since nutrients interact in complex and synergistic ways.  If you are taking a multi-vitamin and mineral supplement check to see that it contains selenium, if not then consider switching to a multi-formulation that does contain selenium.  Unfortunately dietary sources of selenium are few in the UK.  Brazil nuts (just 4-6 a day) and fish contain the highest concentrations in the diet of the UK population.  Some selenium rich flours are available to buy for cooking with

(1)Steevens J et al.  2009.  Selenium status and the risk of esophageal and gastric cancer subtypes: the Netherlands cohort study.  Accepted Manuscript, 14 December 2009.  Gastroenterology.  DOI: 10.1053/j.gastro.2009.12.004
(2) Rayman, M.P. 2000.  The importance of selenium to human health.  The Lancet 356: 233-241.
(3) BNF (British Nutrition Foundation).  2001.  Briefing Paper: Selenium and Health.

Written by Ani Kowal


Nutrition and diet for prostate protection – Part I

Broccoli, of all things, drew me into writing about prostate problems!  It is being consistently branded as a ‘superfood’ and recently a study found that eating just a few portions of broccoli each week could really go far to protect men from prostate cancer(1).

The most common prostate problem in men over 50 years of age is benign (non harmful/cancerous) enlargement of the prostate gland, known as Benign Prostatic Hypertrophy (BPH).  This noncancerous condition tends to cause an impediment in the flow of urine and often an increased frequency of urination, especially at night.  Sometimes men also experience a difficulty in urinating or a weak flow stream. 

BPH is the most common cause of prostate enlargement, however, prostate cancer can cause similar symptoms and so it is ALWAYS important to visit a GP in the first instance before deciding to follow any natural guidance for BPH.  The good news is that BPH responds very well to nutritional approaches (any programme may take 6-8 weeks to produce results).

Today I am going to talk about BPH and prostate cancer prevention as both are linked to similar nutrients and dietary advice.  It is important to talk about prostate cancer as it is the most frequently diagnosed non-skin cancer within the male population of western countries.

Back to the broccoli!  Multiple studies have linked the eating of diets rich in fruit and vegetables to a reduced risk of prostate cancer, however the broccoli study(1) is the first human trial which investigated the mechanisms behind the positive results.  Amazingly the broccoli seemed to be switching on genes in the body which prevent cancer developing and switching off genes which usually help cancer to spread.  Broccoli is a cruciferous vegetable, as are brussel sprouts, cauliflower, cabbage, rocket, watercress and horseradish.  Cruciferous vegetables contain compounds called isothiocyanates, responsible for the bitter taste, these are likely to be providing the cancer-prevention benefit.  

Other studies have also suggested that consuming one or more portions of broccoli per week can reduce the risk of prostate cancer(2).  Different fruits and vegetables probably work through different mechanisms (for example through their anti-oxidant potential) and so providing a wide variety in the daily diet will confer the best protection to health!

One nutrient that is gaining attention for its cancer preventative prospects is Selenium.  Here in the UK many of us will not obtain much selenium from our diets because our soils are fairly deficient and so agricultural crops contain less selenium than from elsewhere in the world.  Since reducing our wheat imports from the USA our selenium intakes have dropped.  One sure fire way to provide ourselves with enough of this essential mineral is to eat Brazil nuts!  These nuggets are packed with selenium and just 5-6 a day would be beneficial!  A review paper has just been released(3) which assessed several observational and supplement studies that support a preventative effect of selenium against prostate cancer. 

Evidence suggests that selenium acts via multiple mechanisms and pathways, most-notably through its anti-oxidative and anti-inflammatory effects.  Selenium is an integral constituent of many hundreds of enzymes which work in most cells throughout the body and so it is not surprising that it shows anti-cancer potential.  Although larger-scale trials are needed it is, in my opinion, necessary that we make sure that our diets contain adequate amounts of this nutrient.  It is an essential mineral that the body cannot do without and so it seems prudent to at least provide the minimum amounts needed for health.  If you are not a regular consumer of Brazil nuts then you may wish to consider a supplement.  However, single nutrient supplements are not something that I recommend.  If you already take a multi-vitamin and mineral supplement check to see if it contains Selenium.  There is no current recommendation but many health professionals recommend at least a minimum of 35µg (micrograms) a day and no more than 200 µg a day (selenium in high doses can be toxic).  Many multivitamin-mineral supplements provide 75µg. 

Check back later in the week for part II

(1)Traka M, Gasper AV, Melchini A, Bacon JR, Needs PW, et al. Broccoli Consumption Interacts with GSTM1 to Perturb Oncogenic Signalling Pathways in the Prostate. PLoS One, 3(7): e2568 DOI: 10.1371/journal.pone.0002568
(2)Joseph MA et al.  2004.  Cruciferous vegetables, genetic polymorphisms in glutathione S-transferases M1 and T1, and prostate cancer risk.  Nutr Cancer 50:206-213
(3)Peters U & Takata Y.  2008.  Selenium and the prevention of prostate and colorectal cancer.  Mol Nutr Food Res.  Sep 2 [EPub ahead of print]

Written by Ani Kowal