Clearing up confusion over iodine in milk

Cow’s milk is not a natural source of iodine. It is fortified, at the cow, notes Dale Vince of the Green Britain Foundation

You report that scientists say moving even partly from dairy products to vegan alternatives could lead to deficiencies in iodine and other micronutrients if the substitutes are not fortified (Swapping from dairy to plant-based milk, cheese and yoghurt ‘could lead to micronutrient deficiencies’, 4 November).

To be clear, cow’s milk is not a natural source of iodine. It is fortified, at the cow. As the paper published in the Lancet Planetary Health explains, iodine is in milk because it is added to cattle feed. The vitamin B12 is there because cobalt is added to the feed so the cow’s gut bacteria can make it. Britain has been doing this for decades. If fortification is the answer, and the paper’s authors say it is, then fortify plant milk. It’s better for us and the planet than cow’s milk.

The study assumes that every plant product on the shelf is bought in equal measure, but they’re not, and the most popular brands are fortified with iodine. This means that the study’s deficiency figures are overstated.

Dairy is one of the heaviest climate burdens on our plates, and most of humanity can’t digest it past childhood anyway. Moving away from it is the right direction. The answer to a fortification gap is fortification, not telling teenage girls to put dairy back in the fridge. We need to leave cow’s milk for baby cows. Dale Vince Founder, Green Britain Foundation