We all know diet is important, but could current food trends actually be bad for our health? Leading endocrinologist and thyroid expert Dr Mark Vanderpump explains why iodine is so important, and how an iodine deficiency could be a serious side-effect of diets such as veganism.
It is, of course, quite natural for people to adopt or experiment with food trends as these get more and more exposure. However two current food trends may be combining as the perfect storm in terms of compromising our health through iodine deficiency.
These are veganism and the increasing popularity of milk substitute drinks like soya, almond and coconut.
Let me first explain about the crucial role that iodine plays in our health.
Iodine and thyroid function
Every cell in your body depends on the efficient production of thyroid hormones for your metabolism. However, your thyroid gland needs iodine in order to convert it to those hormones - commonly referred to as T4 and T3.
In fact we need on average 150 mcg of iodine each day, or 200 mcg in the case of women who are pregnant or breast feeding.
Almost one third of the world's population live in areas of iodine deficiency despite major national and international efforts to increase iodine intake, primarily through the voluntary or mandatory iodisation of salt. Most of these people are in developing countries, but many in large industrialised countries of Europe are also affected.
Iodine deficiency impairs thyroid hormone production and has adverse effects throughout life, particularly early in life as it impairs cognition and growth. In areas where the daily iodine intake is below 50 mcg, a thyroid swelling or goitre is common.
Iodine in pregnancy
Iodine deficiency in pregnancy is extremely serious as it plays a vital role in the development of the unborn baby’s brain and nervous system. This means insufficient levels can result in significant mental impairment and delayed development.
In 2011, I was involved in a study with the British Thyroid Association, in which we measured the urine iodine levels of 664 girls aged 14 years from 9 UK towns. Moderate iodine deficiency (below 50 mcg) was found in 15% and severe iodine deficiency (below 25 mcg) was found in 1%. Extrapolating those figures for the population meant that at least 100,000 babies may have been born with a lower IQ level as a result of lack of iodine.
There has recently been a marked increase in veganism, which is worrying because the main sources of iodine in food are via fish, shell fish and dairy products – all of which are, of course, excluded.
Milk substitute drinks are also contributing to the potential problem of a low iodine diet in our population. Indeed, a recent study showed that the average amount of iodine in milk alternatives is just 1.7% of that in dairy milk at just 2 mcg - remember our average daily requirement is 150mcg.
Unfortunately, too much iodine can also be a problem and, for that reason, the Vegan Society warns against excessive eating of seaweeds (a 7gm serving of which contains 4,500 mcg) and you should also be very careful about taking iodine supplements.
The old saying “we are what we eat” remains as true as ever, so do check out any possible adverse consequences when you make fundamental changes to your diet. There is a very helpful fact sheet about iodine in foods on the British Dietetic society which you might find useful.