It’s one of the greatest public health achievements of our time. In 1996, the Food and Drug Administration added folic acid to the list of B vitamins (and iron) that companies have to add to “enriched” bread, pasta, rice, grits, flour, and more.

Why? In the early 1990s, randomized trials found that folic acid supplements drastically cut the risk of birth defects that occur when the neural tube fails to close properly in the first few weeks of pregnancy.

Those neural tube defects include anencephaly, which is fatal, and spina bifida, which can cause walking disabilities, paralysis, pressure sores, incontinence, and other lifelong health problems.

Fortifying grains with folic acid worked: Since 1996, neural tube defects in the U.S. have dropped by 28 percent. That means roughly 1,300 fewer babies are born with one each year.

But the FDA’s rule didn’t include corn masa, the flour in corn tortillas and tamales, two staples of many Latin American cuisines. That’s because the agency had no “standard of identity” for “enriched” corn masa. (A “standard of identity” is essentially a list of required ingredients.)

Sadly, although rates of neural tube defects have fallen in all U.S. racial and ethnic groups since the late 1990s, they’re still more common among Hispanic people.

So in 2012, a coalition of advocates and Gruma, which owns brands like Maseca and Mission tortillas—with support from Walmart—asked the FDA to allow manufacturers to voluntarily add folic acid to corn masa flour. In 2016, the FDA agreed.

Problem solved? Not quite.

Six years after the FDA gave companies the green light to add folic acid, the Center for Science in the Public Interest (Nutrition Action’s publisher) examined 59 corn masa flour and 476 corn tortilla products.

Only 14 percent of corn masa flours and not a single corn tortilla product—even those made by Walmart or Gruma—were fortified with folic acid. Gruma told us that it plans to fortify many of its corn tortillas by the end of 2024. We’ll hold the company to that...and keep pressing other companies to fortify.

In the meantime, keep in mind that all major health authorities—including the National Academy of Medicine, the Centers for Disease Control and Prevention, and the American College of Obstetricians and Gynecologists—recommend that anyone who could become pregnant take a daily multivitamin or other supplement with 400 micrograms of folic acid.

That’s because neural tube defects occur before many people know they’re pregnant, and nearly half of all pregnancies are unplanned.

One more note: Health authorities recommend supplements with “folic acid,” not “folate” or “5-MTHF.” Folic acid is better absorbed than folate, which occurs naturally in some foods. And although 5-MTHF­—which the body metabolizes folic acid into—may also prevent neural tube defects, it has never been tested in clinical trials.