High iodised salt intake linked to thyroid nodules and cancer
What it found
In a large study of people in Hunan, China, eating more than 5 g of iodised salt a day was linked to a higher chance of thyroid nodules and thyroid cancer.
Most people in the study ate more than that.
What they found
Studies in people
Thyroid nodules common
Among the 51,637 people, 40.25% had thyroid nodules and 0.76% had thyroid cancer. Only 3.59% ate less than 5 g of iodised salt a day.
More than 5 g linked to nodules
People who ate more than 5 g of iodised salt a day were more likely to have thyroid nodules. The link stayed even after accounting for other factors.
More than 5 g linked to cancer
People who ate more than 5 g of iodised salt a day were also more likely to have thyroid cancer. This link remained after accounting for other factors.
Age and salt together
People over 60 who ate more than 5 g of iodised salt a day had the highest chance of thyroid nodules. For thyroid cancer, the risk was higher only when daily iodised salt exceeded 5 g.
Physical activity may offset risk
People who were physically active and ate more than 5 g of iodised salt a day did not have a higher chance of thyroid nodules than inactive people who ate less salt. A similar pattern was seen for thyroid cancer.
Education may offset risk
People with a postgraduate education or higher who ate more than 5 g of iodised salt a day had a lower chance of thyroid nodules than those with high school education or below who ate less salt. This was not seen for thyroid cancer.
What the authors conclude
“Daily intake of more than 5 g of iodized salt increased the risk of thyroid nodules and thyroid cancer, while increased physical activity and education level reduced the risk of thyroid nodules and thyroid cancer caused by iodized salt intake.”
Also in their conclusions
- They conclude that daily intake of more than 5 g of iodised salt increases the risk of thyroid nodules and thyroid cancer.
- They advise that increased physical activity and education level reduce the risk of thyroid nodules and thyroid cancer caused by iodised salt intake.
- They strongly recommend moderate exercise and say that limiting salt is imperative.
How it was done
It is still debated whether eating too much iodised salt raises the risk of thyroid nodules and thyroid cancer. The authors wanted to give a scientific basis for advice on daily iodised salt intake and for preventing these thyroid problems.
They looked back at health check data from 51,637 people in Hunan, China, between 2017 and 2019. Everyone had a thyroid ultrasound and a urine test, and answered a questionnaire. Daily iodised salt intake was estimated from a spot urine sample.
What it can’t tell you
- This was a retrospective study, so it can show links but cannot prove that high iodised salt intake causes thyroid nodules or cancer.
- The study was done in one region of China, so the results may not apply to other populations.
- The number of thyroid cancer cases was small (390), which may affect the reliability of the results.
Who paid
- Conflicts
- The authors declare that they have no conflict of interest.
- Authors work at
- the Third Xiangya Hospital of Central South University, China
The paper
- Title
- Analysis of the correlation between high iodized salt intake and the risk of thyroid nodules: a large retrospective study
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Wang Y, Wang J, Chen Z, et al (2021). Analysis of the correlation between high iodized salt intake and the risk of thyroid nodules: a large retrospective study. BMC cancer. doi:10.1186/s12885-021-08700-zFree full textPubMed 34493230DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error