Published On: Wed, Jul 25th, 2018

Why vegans need to know about iodine and selenium

Heather Russell from The Vegan Society tells us about these essential nutrients.

why do vegans need iodine

Protein, calcium, iron and vitamin B12 regularly crop up in conversations about vegan nutrition. You’re less likely to find yourself chatting about iodine and selenium, but they’re worth a mention as every vegan should ensure adequate intakes of these nutrients.

Why they’re important

Let’s start with iodine. Your thyroid gland uses it to make hormones that control how fast your cells work. You need a steady supply of iodine as dietary deficiency can lead to an underactive thyroid gland. It’s also important to avoid consuming an excessive amount of iodine because this can lead to thyroid disorders. It’s critical to optimise iodine status during pregnancy, breastfeeding and childhood due to the role of this nutrient in brain development.

Selenium is part of lots of enzymes. Your body makes these substances in order to speed up reactions. It’s important to avoid both dietary deficiency and an excessive intake of selenium. Too much can cause selenosis, and even a mild form of this condition can result in the loss of skin, hair and nails.

Daily targets

In the UK, the recommended adult iodine intake for is 140mcg (micrograms) per day. However, the World Health Organization recommends 250mcg for pregnancy and breastfeeding in countries where salt is not routinely iodised, including the UK. The recommended daily intakes of selenium are 60mcg for women and 75mcg for men. The difference is due to the assumption that people with a higher body weight require a higher intake.

Iodine and selenium in vegan diets

There’s no easy way of establishing exactly how much iodine and selenium you get from the plant foods in your diet; it depends on where the plants were grown. Generally, plant foods provide low amounts of these nutrients, with some exceptions.

Seaweed contains a lot of iodine. However, there are several issues to consider. Firstly, like all plant foods, the iodine content is variable, and there is huge variation between different types. The daily upper limit for iodine can easily be exceeded by eating kelp and other types of seaweed. Spikes and long term increases in iodine intake have been linked to thyroid problems. Also, some seaweeds are contaminated; like hijiki which contains a high level of arsenic.

Arguably, supplementation is the best way to ensure a reliable intake of iodine and avoid deficiency. This is why The Vegan Society’s VEG 1 supplement contains it. If you don’t want to supplement your iodine intake, consuming 4g of a seaweed called nori might provide the recommended daily intake. However, please note this option is not advisable during periods of development: pregnancy, breastfeeding and childhood. Iodine supplements aren’t suitable for everyone, so it’s a good idea to speak to a health professional before using one.

A vegan diet can be really heart-healthy, but like everyone else, you need to keep an eye on salt because of the link with high blood pressure. Public health authorities recommend cutting down, so adding iodised salt to your vegan diet is not a good idea.

Brazil nuts contain an unusually high amount of selenium. The content varies due to variable soil content, but eating just two a day might meet your body’s need. Bear in mind that it’s fairly easy to consume an excessive amount of selenium by eating a lot them. Alternatively, you could use a supplement to guarantee a reliable intake. The Vegan Society’s VEG 1 supplement also contains this nutrient.

Takeaway tips

Arguably, supplementation is the best way to ensure a reliable intake of iodine. Don’t want to use a supplement containing iodine? One and a half to two sheets (4g) of nori might provide the recommended daily intake. Two Brazil nuts daily or a supplement will optimise your selenium status.

If you want to know more, check out resources at www.vegansociety.com/nutrition.


About the author 

Heather Russell is passionate about eating well and keeping fit. She trained to be a dietitian to combine her love of science with a desire to help people, and she loves food! She worked in the NHS from 2010-16, and is now using her dietetic skills to support the work of The Vegan Society.

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