Importance of Iodine
To ensure proper thyroid function, it is very important to evaluate the contribution of various sources of iodine, mostly represented by natural foods, supplements and fortified food products (such as the famous iodized salt).
Food Iodine Content: What does it depend on?
The iodine richest foods are saltwater fish and shellfish; even eggs, milk and meat contain important quantities. Lower and extremely variable concentrations based on the richness of iodine in the soil, are found in vegetables and fruit. In the past, before the introduction of iodized salt, dietary deficits of varying sizes were quite common in those areas where the soils, and inevitably their fruits and the meat of the animals that they drew nourishment from, were particularly poor in iodine. Even water represents a minimal source of the mineral; the richest is the marine one (50 μg / L), while in the United States the average drinking water is only 4 μg / L (WHO, 1988).
The watchword, when we talk about iodine in food, still remains "variability"; just to mention an example, the meat and eggs of a chicken fed with a small percentage of fishmeal contain iodine in concentrations that are clearly higher than the meat of an animal bred in the traditional way.
Iodine in food
| Average iodine content in food | |
| Sea fish | 1220 μg / kg, up to 2.5 mg / kg |
| Clams | 798 μg / kg, up to 1.6 mg / kg |
| Seaweed | 20-8000 mg / kg if dried |
| Sea salt | 1.4 mg / kg |
| Cow milk | 50-200 μg / L |
| eggs | 70-90 μg / kg |
| Wheat and cereals | 47 μg / kg (depending on the soil) |
| Fresh water fish | 30 μg / kg |
| Meat | 50 μg / kg |
| Fruit | 18 μg / kg |
| legumes | 30 μg / kg |
| vegetable | 29 μg / kg |
The contribution provided by iodized salt is associated with that of common foods, guaranteeing the coverage of the daily requirement in the context of a varied and balanced diet. It is a common table salt with iodine salts added; for this reason it maintains the same appearance as traditional salt and has no particular odors or flavors, nor does it obscure the flavor of the foods to which it is added. To avoid as much iodine as possible, it is advisable to consume it raw (add salt after cooking) and store it in a cool place away from light and moisture. Cooking also reduces the iodine content of food, with losses of around 20% for frying, 23% for grilling and 58% for boiling (WHO, 1996).
- from the soil from which they derive (vegetables);
- from the fortification with iodine of feed (milk and derivatives);
- from the environment in which animals destined for food (marine fish) live.
The aforementioned food sources of iodine can only pale before the extraordinary richness of seaweed. Some brown algae classified as Laminariales (kelp seaweed, laminaria japonica, laminaria digitata), contain extraordinarily high quantities of iodine, up to 100-1000 times higher than sea fish.
Recommended contributions
Currently we recommend a daily intake of 150 µg of iodine (in the adult). To ensure a normal development of the child, pregnant and lactating women must take larger amounts, respectively 220 µg / day and 290 µg / day. In kombu, approximately 100, 000 µg of iodine is found on 100 grams (almost 1000 times the recommended intake), while in particularly mineral-rich fish, such as sardine or cod, concentrations do not exceed 250 µg / hg on average.
Excess of Iodine
To date, the toxic levels of iodine have not been exactly specified, also due to the fact that these are many times higher than the adequate doses. It is generally recommended not to exceed 500-1000 µg / day (depending on the dietary habits of the population).
From what has been said, however, it appears evident that the exaggerated consumption of some supplements based on seaweed can be dangerous for health and cause a particular form of hyperthyroidism. The risk increases further if you suddenly change from a diet that is very low in iodine to a substantial dietary supplementation.
