Nutrition Hotline

This issue's Nutrition Hotline discusses the stability of iodine in iodized salt over time and whether or not lack of sleep leads to weight gain.

QUESTION:"I make sure we use iodized salt a few times per week to get iodine. If it takes us over a year to go through a container of salt, is the iodine content of the salt the same a year later?" D.W., via e-mail

ANSWER: The Salt Institute estimates that nearly 70% of the table salt sold in the U.S. is iodized. Iodine is added to salt to protect people from iodine deficiency which can result in thyroid problems and poor growth and development in infants and children. Interestingly, almost none of the salt used to produce processed foods is iodized. This is believed to have led to lower intakes of iodine in the U.S. The iodine content of iodized salt is quite stable. Even under extreme conditions, which included being stored in woven polypropylene bags that allowed contact with moisture and air, the iodine content of iodized salt remained high over a six month period in one study1. Another study found that iodine content of iodized salt was stable for more than a year.2


1 Maramac CC, Tengco LW, Rayco-Solon P, et al. 2007. Stability of iodine in iodized fresh and aged salt exposed to simulated market conditions. Food Nutr Bull 28(4):412-8.

2 Ranganathan S, Karmarkar MG, Krupadanam M, et al. 2007. Stability of iodine in salt fortified with iodine and iron. Food Nutr Bull 28(1):109-15.

QUESTION:>"I've watched my weight creep up, little by little, over the years. I try to eat healthy and have been vegan for the past five years. Because of work and family responsibilities, I know I don't get as much sleep as I should. Somewhere I heard that a lack of sleep could lead to weight gain. Is there any truth to that?" M.R., via e-mail

ANSWER:> If you're not getting enough sleep, you're not alone. Studies suggest close to a third of adults in the U.S. sleep less than 6 hours a night. At least 7 hours of sleep is recommended. Weight gain has been reported in people sleeping less than 5 or 6 hours a night. There are several possible causes of this weight gain1. Lack of sleep can affect the levels of hormones that control hunger, leading to an increased food intake. If you're awake more, you have more time to eat which can lead to overeating. Unfortunately, that extra time awake is often not used for exercise. Physical activity is often less during periods of sleep deprivation, possibly due to fatigue. Lack of sleep seems to lead to an increased consumption of high-fat foods and to a decrease in impulse control. This decrease in impulse control makes it more likely that you'll eat, even if you're not hungry. If you are able to lose weight but aren't getting enough sleep, you're more likely to lose muscle than fat. Getting enough sleep is an important part of a healthy lifestyle.


1 Shlisky JD, Hartman TJ, Kris-Etherton PM, et al. 2012. Partial sleep deprivation and energy balance in adults: an emerging issue for consideration by dietetics practitioners. J Acad Nutr Diet 112(11):1785-97.