When does vitamin A help? The circumstances are specific.

Sign up for the Slatest to get the most insightful analysis, criticism, and advice out there, delivered to your inbox daily.
Measles is back. After the disease was declared eliminated in the United States in 2000, it was easy to feel like it was gone for good. But “eliminated” means there was no ongoing local spread. It’s not the same as “eradicated.” With a few dozen cases popping up here and there each year, as soon as vaccination rates dip, the illness rears can rear its ugly head once more—just as it is right now.
People have mostly forgotten how bad measles can be. In a world where vaccination rates are typically above 95 percent, it’s incredibly rare to see even a single hospitalization for the condition. But, now, as outbreaks spread, parents across the country are desperately looking for a way to protect their children from an infection with a fatality rate of around 1 in 1,000. That might sound low, but compare it to COVID-19 in 2020 in children age 5: It’s around 100 times more deadly. And for kids who survive measles, there can be other nasty complications. For example, there is evidence that for some kids measles permanently damages the immune system, leaving them more vulnerable to other diseases.
The obvious way to protect your family is simple: vaccination. The measles, mumps, and rubella (MMR) vaccine is one of the safest medical interventions we have and provides extremely good protection against the disease. But Robert F. Kennedy Jr., the new head of the Department of Health and Human Services, has suggested that vitamin A supplements are just as useful as vaccines. “Studies have found that vitamin A can dramatically reduce measles mortality,” he wrote in an op-ed for Fox News. “Good nutrition remains a best defense against most chronic and infectious illnesses.”
Unfortunately, the idea that good nutrition is a “best defense” simply isn’t true. You can eat a remarkably healthy diet and still become very ill. Vitamin A supplements do have some benefits—but they won’t protect your children from measles.
Advertisement
Advertisement
Advertisement
First, there is a grain of truth to the idea that vitamin A can be a useful tool when it comes to measles. The vitamin is a molecule that your body uses for a wide range of purposes. One of the main things that it does is help you mount an effective immune defense. We have known for decades that people with very low vitamin A levels are at much higher risk of suffering and dying from many infectious diseases.
Advertisement
To put it simply (in fact, perhaps too simply!): Vitamin A deficiency causes you to be particularly vulnerable to infectious disease, including measles. Correcting that deficiency solves this problem.
There are a number of studies from the ’80s and ’90s to back up this idea. A famous study found that a vitamin A supplement for children who were admitted to the hospital with measles reduced the risk of those kids dying by nearly 80 percent. A 2017 review that aggregated a range of trials together did not show a benefit for mortality, but did find that the vitamin reduced the risk of children having a diagnosed case of the disease.
These studies are why vitamin A supplementation is still recommended as a treatment for children who are hospitalized with measles. But the problem is that they don’t really have all that much relevance to children in the United States today. The famous study I mentioned above was conducted in 1987 in Cape Town in a mostly Black population at a time when the apartheid regime still held sway. The studies aggregated together in the 2017 review were mostly conducted in China, India, and Africa in the ’80s.
In most of these settings, vitamin A deficiency was not just common—it was ubiquitous. Some of these countries had deficiency rates above 20 percent. Meanwhile, the most recent and robust data we’ve got, from the ’90s, suggests that fewer than 1 in 100 children in the U.S. have a vitamin A deficiency. Some even more recent data puts the rates even lower, although that study was mostly looking at pregnant women. This is perhaps not surprising in a world where you can get enough vitamin A dining exclusively on the McDonald’s menu.
Advertisement
Advertisement
We also know that vitamin A supplements are unlikely to help kids who have enough vitamin A. For example, a massive 1990 study conducted in India showed that vitamin A supplements reduced the risk of kids dying from measles and other infectious diseases by more than half. However, all of this benefit was in children who showed very obvious signs of malnourishment, like stunted growth or skin clinging to their bones. Those kids had an 89 percent reduction in their risk of death. Children who were not malnourished had no reduction in risk at all.
Also, things are actually little more complicated than “If you have a vitamin A deficiency, a supplement can protect against measles.” One of the largest trials ever conducted—in over 1 million children—took place in northern India in the ’00s and calls that straightforward idea into question. In this region, vitamin A deficiency was very common. The study randomly allocated kids to either get a very high-dose vitamin A supplement or a placebo medication once every six months. At the end of the trial, death rates from measles and a variety of other diseases were the same, although the rate of vitamin A deficiency had dropped drastically in the supplement group. There was also no difference in the rate of diagnosed measles between vitamin A and a placebo in this massive trial.
Advertisement
Advertisement
Advertisement
This seems to conflict with the evidence from the ’80s and ’90s that was summarized in the 2017 review I discussed above, but if you look closer, it makes sense. While vitamin A deficiency was still quite common in India in the ’00s—the study found rates of 10–15 percent without supplementation—the situation was still much better than it was two decades earlier. (For example, a study in 1993 showed that rates of eye disease caused by vitamin A deficiency were 22 percent in Uttar Pradesh, where this large randomized trial was later conducted.) The point is that the more modern evidence does not seem to show as much benefit for vitamin A supplementation for measles (though there are benefits for other things). This could be because the rate of severe malnutrition has dropped globally since the first of these studies were conducted.
Advertisement
It’s also worth noting that none of these studies have tested the sort of supplement that you can buy in a supermarket or pharmacy. Most store-bought vitamin A supplements have somewhere between 300 and 1,500 micrograms of the substance in them. The average amount used in these studies—which, remember, are of kids with severe deficiency—is about 30,000 micrograms. That’s between 20 and 100 times higher than your average multivitamin.
Advertisement
Advertisement
If you live in an area with severe malnutrition, where kids are literally starving on the streets, then a vitamin A supplement is probably a good way to reduce your child’s risk of extremely nasty disease. But if you live in the U.S., where fewer than 1 in 100 kids have low vitamin A levels and even fewer have a true deficiency, the supplements probably aren’t going to do very much.
Yes, your immune system can function better when you are not malnourished, but the best way to protect against measles is vaccination. Really, it’s not even an either/or proposition—feed your kids and also get them vaccinated. We got rid of the disease for 25 years. There’s no need to bring it back.