Salt is one of those things in the world that is so ubiquitous as to feel almost forgettable. If you think about it at all, it’s probably in the context that salt is delicious, but also that salt causes high blood pressure, and you should eat less of it.
This is true, but salt is a balancing act. A person’s salt intake needs to be in the goldilocks zone between too much and too little. Getting enough salt is vital to human health, and without it, you would not be able to survive. Salt is necessary for us to balance fluids in our bodies, and it helps nerves to fire. Indeed, the effects of being salt deficient are quite striking. In one study (McCance, 1936), researchers had three college-age volunteers eat a low-sodium diet and lie under heat lamps for two hours a day to sweat the salt out of their bodies. The results that they report are quite striking. Quoting directly from McCance, 1936:
As the deficiency developed, all three subjects lost weight. Their cheeks fell in and they began to look ill. People who had no idea that they were being used as experimental animals commented on their appearance. [...] Physical symptoms predominated in the case of R. A. M. *(one of the test subjects) but all experienced them to some degree. A mild breathlessness at first and sense of fatigue gave place later to general exhaustion and distress on the least exertion. [...]
And when the researchers describe the experiences of the volunteers who were allowed to have salt with a meal again, the results are similarly striking.
R. A. M. found his sense of flavour returned before he had finished his first salt meal. About an hour later he felt hot all over, he experienced a deep-seated pricking and tingling in his extremities and was conscious of bounding pulsation. In a few hours he was much more comfortable in mounting the stairs, and by evening was "no longer aware of his legs as he moved about the room."
Although it’s one of only four ingredients in a lean sourdough, we probably spend less time thinking about salt than any of the others. I want to dedicate this post to diving into the question of whether iodized salt should be used in sourdough baking by examining its effects on the fermentation process, flavor, and health benefits.
Should I Use Iodized Salt in Baking?
Iodine deficiencies are associated with a wide array of adverse health effects, including goiter, hypothyroidism, and increase risk of pregnancy loss and infant death (Pearce et al., 2016). For this reason, over 100 countries now have universal salt iodization laws for household salt and/or salt used in processed food.
This leads to the question, should we use iodized salt in our bread baking? There are two primary reasons given for not using iodized salt in baking:
- The iodine imparts a taste to the bread
- The iodine has some effect on fermentation and/or gluten formation
Both of these seem like reasonable concerns, so let’s take a few seconds to discuss each one.
Can I Taste Iodine in my Baking?
A recent review of the effects of adding iodized salt to foods (Blankenship et al. 2018) reported on 11 other studies on the effects of adding iodine to bread, including studies on the effects of iodizing all commercial breads in Australia (Charlton et al., 2013), which noted
"No subjective effects on quality reported after 3 years of national distribution"
in Denmark (Rasmussen et al., 2007)
"No subjective effects on reported quality after National distribution since 2000"
and in Belgium (Vandevijvere, 2012)
"44% of bakeries use iodized salt. No subjective effects on reported quality after national distribution since 2009"
Empirical studies aside, the concentration of iodine in typical bread can be estimated. In the U.S., salt is typically iodized to a level of 0.045 mg/g (that is 0.045 mg of iodine per gram of salt). Most bread recipes call for approximately 2% salt by weight. Putting these numbers together, one kilogram of dough contains approximately 20 g of salt, and therefore 0.9 mg of iodine.
In one study, researchers enriched potatoes and rice to an iodine level of 400 mg/kg and found that blind taste testers could not identify the iodized foods any better than would be predicted by chance. Although this study was not carried out specifically on bread, the iodine levels employed were orders of magnitude higher than those which our back-of-the-envelope calculation found would be present in homemade bread. Given this, it seems like a safe assertion that iodine is not detectable through taste in homemade sourdough.
Does Iodine Affect Fermentation?
Here, things become a little less clear-cut. Searching the internet for any keywords related to iodization and fermentation reveals a ubiquitous belief that using iodized table salt will slow down fermentation.
However, despite this conventional wisdom, Müller et al. (2018) found that the presence of iodine when fermenting sauerkraut made no difference to the quality of the sauerkraut that was created, and as noted by Sandor Katz in The Art of Fermentation:
... having had the opportunity to ferment vegetables with every possible kind of salt handed to me by workshop organizers, I have observed that lactic acid bacteria seem tolerant of a wide variety of salts, including iodized table salt, and are not particularly picky
Thus, I was unable to find definitive evidence one way or the other, or studies specifically on bread fermentation. In summary, there is a wide-ranging belief that iodine harms fermentation, contrasted with the one study I was able to find (Müller et al., 2018), and the writings of a widely respected fermentation teacher.
This leaves me with only one option, to say: try it! If you are not getting the results you want, maybe try switching from iodized to non-iodized salt. It may (or may not!) make a difference.
References
- Blankenship, J. L., Garrett, G. S., Khan, N. A., De-Regil, L. M., Spohrer, R., & Gorstein, J. (2018). Effect of iodized salt on organoleptic properties of processed foods: a systematic review. In Journal of Food Science and Technology (Vol. 55, Issue 9, pp. 3341–3352). Springer Science and Business Media LLC. https://doi.org/10.1007/s13197-018-3277-9 Charlton, K. E., Yeatman, H., Brock, E., Lucas, C., Gemming, L., Goodfellow, A., & Ma, G. (2013). Improvement in iodine status of pregnant Australian women 3years after introduction of a mandatory iodine fortification programme. In Preventive Medicine (Vol. 57, Issue 1, pp. 26–30). Elsevier BV. https://doi.org/10.1016/j.ypmed.2013.03.007
- McCance R. A., Experimental sodium chloride deficiency in man. (1936). In Proceedings of the Royal Society of London. Series B - Biological Sciences (Vol. 119, Issue 814, pp. 245–268). The Royal Society. https://doi.org/10.1098/rspb.1936.0009
- Müller, A., Rösch, N., Cho, G.-S., Meinhardt, A.-K., Kabisch, J., Habermann, D., Böhnlein, C., Brinks, E., Greiner, R., & Franz, C. M. A. P. (2018). Influence of iodized table salt on fermentation characteristics and bacterial diversity during sauerkraut fermentation. In Food Microbiology (Vol. 76, pp. 473–480). Elsevier BV. https://doi.org/10.1016/j.fm.2018.07.009
- Pearce, E. N., Lazarus, J. H., Moreno-Reyes, R., & Zimmermann, M. B. (2016). Consequences of iodine deficiency and excess in pregnant women: an overview of current knowns and unknowns,. In The American Journal of Clinical Nutrition (Vol. 104, pp. 918S-923S). Elsevier BV. https://doi.org/10.3945/ajcn.115.110429
- Rasmussen, L. B., Ovesen, L., Christensen, T., Knuthsen, P., Larsen, E. H., Lyhne, N., Okholm, B., & Saxholt, E. (2007). Iodine content in bread and salt in Denmark after iodization and the influence on iodine intake. In International Journal of Food Sciences and Nutrition (Vol. 58, Issue 3, pp. 231–239). Informa UK Limited. https://doi.org/10.1080/09637480701198117
- Vandevijvere, S. (2012). Sodium reduction and the correction of iodine intake in Belgium: Policy options. In Archives of Public Health (Vol. 70, Issue 1). Springer Science and Business Media LLC. https://doi.org/10.1186/0778-7367-70-10
