How much iodised salt do vegans need?

[Jebus]

I'm guessing it's probably less than a teaspoon per day but I'd be grateful if anyone can share some insight as I have so far been unable to find an answer to this question. It is important to get this right as too much sodium is probably never a good thing.

[brimstoneSalad]

Salt, being water soluble, is easily flushed from the body. It doesn't matter too much how much you eat (although eating it without drinking enough is a problem). It increases water retention a little, but only right after you eat it. For some people at high risk of stroke and heart attack, this slight increase in blood pressure is enough to send them over the line. For most people, it's harmless.
Reduction of saturated fat and cholesterol is what will do long term benefit (and eating it do long term harm). Salt, in terms of the epidemiology, seems to be fine as long as you don't go crazy with it. Try to keep it under 7 grams a day (only easy to exceed if you're eating a lot of processed food, or pickled veggies).

Check the label of the salt you have for the daily recommended amount for iodine. It probably varies by country and brand.
Seaweed is another source of iodine, if you want to avoid salt. But as salt is delicious and as far as I can tell harmless in moderation for most people, I'd just say go with the salt.

[cornivore]

That can depend on how much you sweat and what else you eat (raw vs cooked, etc).

The results of the study suggest that loss of iodine through profuse sweating may lead to iodine deficiency...
—Electrolyte loss in sweat and iodine deficiency in a hot environment

We conclude that in areas of iodine deficiency in which millet is a major component of the diet, its ingestion may contribute to the genesis of endemic goiter.
—Antithyroid and goitrogenic effects of millet

Excess dietary iodine: In genetically susceptible individuals, increased consumption of Iodine can act as a trigger for thyroiditis.
Dietary Factors... Various Possible Toxicants Involved in Thyroid Dysfunction: A Review

Generally it would be recognized as safe to go up to the recommended daily value of sodium with iodized salt, and also use it for electrolyte replacement.

Conclusion
The benefits of iodine repletion outweigh the risk of thyroid auto-immunity, hence global iodine sufficiency should be ensured.

[cornivore]

The same kind of thing is said about taking multivitamins, where the benefits usually outweigh the risks. Those may contain iodine too, so maybe you wouldn't want it to be in both (or it's probably best to have both kinds of salt, in case you want to replace the sodium and iodine lost in sweat, sometimes, and not take another multivitamin just for that).

[Jebus]

I put about a third of a teaspoon of iodized salt in my nut mix. On days when I don't eat nuts I take a kelp supplement.

[cornivore]

It seems that for pregnant women, taking a prenatal vitamin with iodine and using iodized salt would be recommended.

Iodine deficiency is the world's single greatest cause of preventable mental retardation. It is especially damaging during the early stages of pregnancy and in early childhood. —Household use of iodized salt in rural area

When salt is tested it doesn't all have exactly the same amount of iodine, and this decreases with shelf life too (something like 20% per year). It sounds like we'd have to eat more than a tablespoon (or 3 teaspoons) of iodized salt per day for a while to have a problem with that (there's supposedly 150mcg per 1/2 to 3/4 of a teaspoon, which is adequate for adults).

A review of case reports show that iodine intake of less than 1000 mcg/day is safe for most people.—Iodised salt is safe

The upper intake for adults is listed as 1100mcg, or much less for children: Iodine Fact Sheet for Health Professionals

[cornivore]

It's recommended to use iodized salt on foods after cooking, as iodine is lost during that process.

Losses during boiling, roasting, deep frying and microwave cooking were found to be 40.23%, 10.57%, 10.40% and 27.13% respectively. From the obtained results, authors have concluded that the loss of iodine depends upon type of cooking method and time of addition of salt during cooking.

Thus, to prevent iodine losses while cooking, it is advisable to sprinkle salt on food after cooking (wherever possible) rather than adding salt while cooking as is done traditionally in India. Further, storage of salt in hot and humid condition near the cooking area should be avoided.
—Effect of different cooking methods on iodine losses

[cornivore]

I put about a third of a teaspoon of iodized salt in my nut mix.

Speaking of salting dry foods, I got the impression that salt could end up being irritating, if not mixed with water, after I tried supplementing a pinch of coarse sea salt as a snack throughout the day. I was just looking this up too, and technically that doesn't have to do with pH, because salt is neutral, as it doesn't react with water. However this doesn't mean it is isotonic or non reactive in the mouth, etc.

Human toxicity excerpts

Oral administration of concentrated salt solutions causes irritation of the orogastric mucosa.

The GI effects of oral salt administration include swollen tongue, nausea, vomiting, diarrhea, abdominal cramps, and thirst.

Hypertonic salt solutions can produce ... a distinctive microscopic lesion of the kidney ... parenchymatous dehydration produces a shrinking which is most conspicuous in the convoluted tubules of the renal cortex. Some experimental evidence suggests that similar hypernatremic syndromes may be produced with normal salt diets if water intake is restricted.

Sodium chloride at concentrations much above that in tears causes a stinging sensation on contact with the eye. Solutions up to 10% do not alter the permeability of the corneal epithelium, but solutions more dilute than 0.9% sodium chloride cause increased permeability.

Another thing they mention is that children can be especially sensitive to excessive salt intake.

A surprisingly small amount of salt intake can result in a fatal outcome. We report two cases of severe salt intoxication in two girls, aged 20 and 7 months, who presented with severe hypernatremia. Both had seizures after accidental salt ingestion. In the first case, salt instead of sugar was inadvertently added to two yogurts, leading to hypernatremia and convulsions. In the second case, a mistake in the preparation of salt-saturated water as an oral rehydration solution provoked seizures, coagulopathy and longitudinal venous sinus thrombosis. Both cases developed encephalic death.

SIGNS AND SYMPTOMS/ Fatal salt poisoning has occurred in children following the inadvertent substitution of table salt for sugar in infant formulas and the administration of salt as an emetic. Symptoms are generally seen within hours of oral ingestion and include seizures, obtundation, coma, and cardiorespiratory arrest. Serum sodium levels may be greater than 180 mEq/L. Such high levels of sodium create a large osmotic gradient between the extracellular fluid (ECF) and Intracellular fluid (ICF), leading to extreme cellular dehydration and brain injury. Autopsy studies of children dying from salt poisoning have shown capillary and venous congestion of the central nervous system, subarachnoid and parenchymal hemorrhage, and dural sinus occlusion.

An estimated dose of more than 400 mEq/kg resulted in brain injury and death in a 2 year old child given a salt water solution to induce emesis.

Using salt as an emetic seems to be dangerous for persons of any age.

Although a plethora of reports on life-threatening complications of salt emesis has been published since the early 1960s, salt is still used to induce emesis in cases of intoxication in the clinical as well as in the domestic setting.

The case of a 63-year-old female nursing home inhabitant who accidentally ingested the anti-epileptic medication of another nursing home inhabitant is described. After telephone instructions from a specialist in internal medicine, caregivers forced the woman to vomit by means of saline solution and digital manipulation. This caused not only substantial hypernatriemia but also aspiration pneumonia, from which the woman died after short hospitalization. The potential toxicity by major electrolyte shifts in terms of hypernatriemia following administration of sodium chloride solution is well known; this measure is medically contraindicated for the induction of vomiting.

Saturated solutions of kitchen salt have been used by paramedics to provoke vomiting in two patients: a 50-years-old woman and a 44-years-old man. According to anamnesis patients received respectively around 330 and 500 g of dissolved kitchen salt. In both cases bloody emesis and bloody diarrhea, alteration of consciousness and low blood pressure were noted. Maximum blood sodium level was 177 and 173 mmol/L respectively. Due to signs of gastrointestinal bleeding gastric endoscopy was performed in both cases, which demonstrated widespread damage of gastric mucosa. Normalization of electrolyte disturbances and improvement of patients' status was achieved with intravenous infusion of 5% glucose. Both patients have been discharged to further outpatient treatment after 10-days hospitalization.

I think the "widespread damage of gastric mucosa" may also be a risk of eating salted dry foods, over a long period of time, if a drink is not ingested with those, at least. "Hypernatremia is the clinical term for an excessive concentration of sodium relative to water in the body." So, how much salt is needed depends on that in particular (which would be variable).

They say potassium iodide "should be used with extreme caution, if at all, in patients with tuberculosis and is contraindicated in the presence of acute bronchitis". Beyond that, the iodine present in various dietary supplements has been known to cause thyroid storm. FDA figures also reveal "much iodine concentration variability in cakes and breads, with unusually high values in several samples" . . . Although dietary deficiencies might still be more common: "U.S. rates of iodine intake have declined due to increased consumption of processed foods lacking in iodized salt and suggests a reemergence of iodide deficiency in the U.S." . . .

[cornivore]

By the way, gargling could be risky, whether or not concentrated salt mixtures were swallowed...

Hypermagnesemia-induced fatality following epsom salt gargles: "We report a fatal case of chronic Epsom salt gargles for halitosis that produced a serum magnesium of 23.6 mg/dL (9.8 mmol/L) and resulted in coma".

Fatal hypernatremia from exogenous salt intake: "We describe a 41-year-old man who had seizures and hypernatremia after ingestion of a supersaturated salt water solution intended for gargling... and died 3 days later. Review of the literature revealed 10 adult and 20 pediatric cases of hypernatremia attributable to exogenous intake of salt".

I suppose that if serum magnesium could be raised by gargling, then so could iodine. Also, a salt water mouthwash is not recommended for those with high blood pressure, so rinsing would be similar to gargling.

[cornivore]

Another thing I hadn't read before is that "stomach cancer is more common in Japan due to its high-salt diet"...