Further studies on the iodine concentration of conventional, organic and UHT semi-skimmed milk at retail in the UK

- Organic winter milk was 44% lower in iodine than conventional milk.
- UHT milk was 27% lower in iodine than conventional pasteurised milk.
- The region of England where milk was purchased did not influence iodine content.
- Summer produced milk has a lower iodine content than winter milk.
- Consumption of organic or UHT milk will increase risk of suboptimal iodine status.

Milk is the largest source of iodine in UK diets and earlier studies showed organic summer and winter milk to be significantly lower in iodine than conventional milk. One study also showed UHT milk to have lower iodine concentration. The study on winter and UHT milk was small and accordingly a new study is reported here involving conventional, organic and UHT semi-skimmed milk from four supermarkets over a six-month period in summer and winter in two regions of the UK. The results showed organic milk to be 44% lower in iodine than conventional milk (427 vs. 241 µg/L, P < 0.001) and UHT milk was 27% lower in iodine than conventional milk (427 vs. 314 µg/L, P < 0.001) although the differences tended to be less in the summer. The results indicate that replacement of conventional milk by organic or UHT milk will increase the risk of sub-optimal iodine status especially for pregnant/lactating women.