The Salt Solution
I was recently discussing sodium intake with a client who has high blood pressure. He raised the question of whether he should be concerned about iodine deficiency if he lowered his salt intake. Great question!
We are looking at two public health measures here, but are they in conflict?
Public health measure number one goes back to 1949 when it was recognised that the iodine content of the Canadian soil was low and so foods grown in Canada were also low in iodine. Iodine is an essential nutrient that the body needs in very small amounts.
Why is it important?
Iodine is a nutrient of great concern because it is important for thyroid health. The thyroid is the master gland of metabolism and helps maintain good health and wellbeing.
When the diet is deficient in iodine, it can lead to an underactive thyroid, which is particularly important for pregnant or lactating mothers. The thyroid hormones are important for normal brain and nervous system development during fetal growth, infancy and childhood. Deficiency can lead to developmental disorders, small stature, miscarriages and infertility.
What was done about it?
To address the deficiency Health Canada mandated the addition of iodine to table salt in 1949, a public health measure that resulted in the virtual elimination of iodine deficiency and the associated developmental delays. Since then, salt sold as table salt in Canada must be fortified with iodine. Manufacturers of Kosher salt, pickling salt, sea salt and gourmet salts are not required to add iodine. More information on iodine, the thyroid and food sources of iodine can be found here.
Public health measure number two targets a reduction of dietary salt intake to address the increasing health concern of high blood pressure. Currently, 2.5 million Canadians have high blood pressure and it is estimated that about one third of those are due to the high salt content of the food we eat. This means that over 800,000 Canadians have treatable and preventable high blood pressure.
Why is it important?
Sodium is a natural part of a healthy diet, and adults need just over half a teaspoon of salt daily, 1500mg, to meet our needs. Children need only 1000-1500mg. Canadian adults currently eat about 3,400 mg per day, more than double our daily need.
What is being done about it?
Health Canada has reached a compromise between what would be ideal and what is realistic. They have set the upper limit of how much we should have (for adults over age 14) at 2,300mg as a more realistic and achievable goal. So a teaspoon a day of salt is more than enough to meet our needs. More information on sodium and maintaining a healthy blood pressure with diet can be found here.
Are these two measures in conflict?
On the one hand we have salt consumption as a vehicle for improving iodine intake and on the other we advise reducing salt intake to improve blood pressure. So returning to the question, can a reduction in sodium intake lead to iodine deficiency, the answer is, probably not.
The reason is that 77% of the sodium we eat comes from processed and restaurant food, and most food companies do not use iodized salt. Reducing processed foods in the diet is the main way suggested to reduce sodium intake. Ironically though, as we, as a society, rely more on processed and restaurant food, our sodium intake may be rising, but our iodine intake may be falling.
Tips to reduce sodium and to include enough iodine in your diet can be found in the links in this article.
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