Salt: Don't Ban It Entirely

Salt is bad for blood pressure but good for brain development, researchers say

By Jeanie Lerche Davis
WebMD Weight Loss Clinic - Feature

Reviewed By Brunilda Nazario

Pass the salt: Who hears that anymore? Salt's been nearly banished, and rightly so. Too much salt affects blood pressure -- and not in a good way. But for some people, cutting back has a downside.

Take stock of the facts.

Too little salt -- iodized salt, that is -- is dangerous, too. It's the iodine in iodized salt that helps the body make thyroid hormone, which is critical to an infant's brain development.

A little salt is essential to good health. Healthy adults should consume salt and water to replace the amount lost daily through sweat and to achieve a diet that provides sufficient amounts of other essential nutrients.

The American Heart Association and NIH advise adults to get no more than 2,400 milligrams of sodium daily. That's about 1 teaspoon of salt. Just think how salty your favorite snacks taste. Eat too many salty foods (even soft drinks have sodium), and you easily go overboard.

Truth About Iodized Salt

Is the salt in your kitchen salt iodized? Most people don't know. "Most people buy just whatever one their hand grabs... and until about five years ago, it didn't really matter," says Glen Maberly, MBBS, MD, an endocrinologist and professor of international health in the Rollins School of Public Health at Emory University School of Medicine in Atlanta.

Yet getting too little iodine -- called iodine deficiency -- is a serious issue. Iodine is an essential mineral for the production of thyroid hormones. Too little iodine in a pregnant women's diet can affect the development of the fetus' brain and can cause cretinism, an irreversible form of physical and mental retardation. Iodine deficiency during infancy can also result in abnormal brain development and impaired intellectual development.

"The developing brain is the most sensitive organ. Iodine deficiency doesn't make people idiots, but it does make them less smart," says Maberly.

In the U.S., iodine deficiency is more common in women than men. It's also common in pregnant women and adolescents, he tells WebMD.

Iodine deficiency is thought to be rare in the U.S. It's considered a problem of third-world countries, but Maberly disagrees. "Iodine nutrition in the U.S. is borderline," he tells WebMD. "A pregnant woman may not be protected. Even if she eats a normal diet, her intake is probably inadequate. Only 70% of table salt is iodine-fortified."

Until nearly five years ago, Americans who got dairy, bread, and meat in their diets got plenty of iodine, he explains. Machines used in production were cleaned with an iodine disinfecting solution, so some iodine ended up in dairy, bread, meat products. That ended when companies quit using iodine disinfectant.

Iodized salt is rarely found in canned, frozen, or boxed food, says Maberly. French fries and other snack foods mostly contain regular salt -- not iodized salt.

In fact, Americans now get one-third less iodine than they once did, he notes.

Both newborns and toddlers are affected by iodine deficiency. A recent study showed lower IQ scores among children with mild iodine deficiency -- proof that the problem exists in developed countries, writes researcher Piedad Santiago-Fernandez, MD, an endocrinologist at the Complejo Hospitalario Carlos Haya in Malaga, Spain.


"Whether a person is salt-sensitive is at the heart of this issue."

It's true, says Michael Karl, MD, an endocrinologist with the University of Miami School of Medicine. "You can certainly see even subtle changes in iodine can affect IQ," Karl tells WebMD. "Iodine is critical in the first years of life, extraordinarily important up to 3 or 5 years of age."

Children in financially stressed families are likely at highest risk. They rarely take multivitamins, he tells WebMD. "Iodine deficiency is not an epidemic yet, but it's serious enough that it should be watched."

Sea salt and most salt substitutes are not iodized. Unless fruits and vegetables are grown in iodine-rich soil, they will not contain iodine. Restaurants usually order salt in bulk, and often it's not iodized salt.

However, anything from the sea - such as seaweed (kelp) or fish -- can be a good source of iodine, says Maberly. A cup of cow's milk contains nearly 100 micrograms of iodine. Some breads contain iodine, but not all.

The normal requirement for iodine, according to World Health Organization standards: Adults need 150 micrograms a day. Women trying to get pregnant should increase their intake to 200 to 300 micrograms a day.

"We certainly should make pregnant and lactating women aware of this deficiency," says Karl. "I don't think most primary care doctors are aware of it."



STAY INFORMED

Get the Latest health and medical information delivered direct to your inbox!