Selenium

Selenium is a trace element that is essential for a wide range of biochemical functions within the body. It plays an important role in our immune system and in reproduction. It also helps to prevent damage to cells and tissues.

The RNI for adults is 75μg a day for men and 60μg a day for women. High intakes of selenium can be toxic. The Expert Group on Vitamins and Minerals (EVM) set a safe upper limit for selenium intake at 450µg per day, in North America the upper level of tolerable intake is set slightly lower at 400µg per day (SACN, 2013).

Selenium intake varies widely around the world, mainly due to the differences in the availability from the soil. Selenium is less readily taken up by plants growing in more acidic, impervious soils (Fordyce, 2005). This makes it difficult to make food composition tables and estimates of dietary intakes may be of limited reliability for determining actual intakes (SACN, 2013). The UK is reported as having low selenium intakes with an average adult intake of 48µg per day from food sources or 51µg including supplements (SACN, 2013). If your food is grown in soil that has low selenium levels it could be a problem regardless of dietary preference. Because European soil and plants are relatively poor sources of selenium, farmed animals are often supplemented with it (Hoeflich et al., 2010). If you are concerned about getting enough, you could cut out the middleman and take a supplement.

According to the NDNS, teenagers and adults are estimated to have average selenium intakes below the RNI. Only boys and girls aged 1.5-10 years had an average intake above the RNI (which is 15-30µg per day for this age group). It should be noted however, that the selenium dietary reference values were set on very limited data and caution should be exercised when using the RNI to infer the adequacy of selenium intake in the population (Bates et al., 2014).

The research on vegan diets and selenium has produced mixed results (de Bortoli and Cozzolino, 2009; Hoeflich, 2010; Fayet, 2014). It is well-documented how a well-balanced vegan diet offers a wide range of beneficial health effects. However while a not well-balanced vegan diet (chips and beans), may still be preferable to not well-balanced meaty diet (chips and burgers), it may be low in certain nutrients such as selenium. A vegan diet is not fool-proof, some common sense is required. 

Food (100g) Selenium (μg)
RNI: 60μg/day for women and 75μg/day for men
Brazil nuts 85-690
Green or brown lentils, dried, boiled 40
Mushrooms, fried in corn oil 12
Red kidney beans, canned 6
Mung beans, boiled 5
Soya milk  4

Table 7.0 The selenium content of selected foods.

Source: FSA, 2002

The main plant-based sources of selenium in the UK diet are bread and cereals. Table 7.0 shows how Brazil nuts provide a very rich source of selenium. The amount contained in 100g of Brazil nuts can range from 85-690µg per 100g (FSA, 2002). Consuming just two Brazil nuts a day for 12 weeks can increase the amount of selenium in the blood by over 60 per cent (Thomson et al., 2008). Including Brazil nuts in the diet could avoid the need for supplements.

Nuts are a healthy, nutritious food that provide an excellent source of vitamin E and magnesium. People who eat nuts also have higher intakes of folate, beta-carotene, vitamin K, calcium, phosphorus, copper, selenium, potassium and zinc. Nuts provide valuable phytochemicals and their antioxidant power is similar to that of broccoli and tomatoes. Eating 42g (a generous handful) of mixed nuts a day can reduce the risk of heart disease (King et al., 2008).