In previous articles, we’ve dealt with the issue of iron in vegetarian diets (in Ironing out the facts). Such is the attention that iron gets, you’d be forgiven for thinking that’s the only mineral vegetarians need to think about. Yet, nothing could be further from the truth.

In fact, vegetarians need to get savvy with a number of dietary minerals that can be more difficult to attain when following non-meat, plant-based diets, and in this article we’ll turn our attention to the little known trace mineral selenium.

Don’t let the fact that you only need it in tiny, trace amounts deflect from the fact that it has big implications for health. Getting enough (but not too much) selenium is crucial for optimal health. We need this trace mineral for fertility, thyroid function, a strong immune system, our antioxidant defences, and for cancer prevention. Selenium is not a mineral you would want to fall short on.

Whilst countries like the US get ample selenium in the diet, the UK is a very different story. This is due to the selenium deficient soils of the UK and much of Europe. This means as a population we lack selenium in our diets with intakes significantly below those regarded as optimal for human health.

To be clear this is not an issue specific to vegetarians. Irrespective of whether diets are vegetarian or not, the problem is universal in the UK and one that everybody should be taking more seriously. However, when we consider that good dietary sources of selenium include fish, shellfish, meat, and organ meats, we can see why the risk of selenium deficiency is even more pronounced for vegetarians.

Alas, Brazil nuts, often touted as a selenium superfood, don’t deliver on that promise. Not only are Brazil nuts highly variable in their selenium content (it can be up to a thousand-fold difference!), they also contain undesirable levels of a couple of toxins in the form of barium and radium, a radioactive material. Whilst that shouldn’t put you off ever eating a Brazil nut, it should make you think twice about relying on them as a daily staple.

So what are we to do about the selenium problem? As much as I abide by the idea that we should get everything we need from the food we eat, the reality is that if you live in the UK, you are going to struggle to get enough selenium because it’s missing from the soil, and therefore from our food. The only reliable option is to take a low dose selenium supplement. This applies to everyone, although as we have seen, this is likely to be particularly pertinent to vegetarians. For an average UK adult this should be around 50 mcg per day, although for adult men, given the links between selenium status and prostate cancer risk, it may be more prudent to supplement up to 100 mcg per day.

But please beware of too much of a good thing. The evidence is now clear that too much selenium is as bad as too little. When it comes to selenium, more is definitely not better. The majority of selenium supplements you will find are 200 mcg, which is simply too high for most people. Even the amounts you find in many multivitamin and mineral preparations is too high! As with everything in nature, it is all about balance, and selenium is no exception.