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A new study finds high amounts of dietary sodium are linked to worse eczema symptoms. urbazon/Getty Images
  • A recent study investigates whether sodium intake might influence atopic dermatitis, a type of eczema.
  • Using a large sample of participants, researchers suggest that higher sodium intake may be linked to an increased likelihood of having the condition.
  • Higher sodium intake was also associated with more severe atopic dermatitis.

A new study in JAMA Dermatology published today suggests a link between sodium intake and the risk of developing atopic dermatitis. The study also found that higher levels of sodium were linked to an increase in the severity of symptoms.

In the study, which involved almost 216,000 people, the scientists analyzed sodium levels in urine at a single time point to estimate usual dietary sodium intake.

Their analysis showed that people with higher levels of estimated 24-hour sodium excretion were more likely to have atopic dermatitis. And higher levels were also linked to having more active and severe symptoms.

Atopic dermatitis is a chronic skin condition characterized by dry, inflamed, and itchy skin.

It is a dermatological condition thought to be driven by inflammation. In high-income countries, it affects an estimated 20% of children and 10% of adults.

Despite its high prevalence, experts are still figuring out what influences the risk of developing eczema and what makes it worse.

Although there are likely a wide range of factors, experts believe that diet plays a role.

Scientists have already investigated a number of dietary aspects, including maternal diet, omega-3 intake, and probiotics. However, many questions remain.

The latest study used data from 215,832 people aged 37–73. Of these, 10,839 had an atopic dermatitis diagnosis. They estimated 24-hour urine sodium excretion from spot urine samples and used this to gauge participants’ usual dietary sodium intake.

Their analysis showed that a 1-gram increase in estimated 24-hour sodium excretion was associated with an 11% increase in the odds of having atopic dermatitis.

It was also linked to a 16% increased odds of having active atopic dermatitis and an 11% increased odds of having more severe symptoms.

To validate this finding, the scientists also analyzed data from more than 13,000 participants in the National Health and Nutrition Examination Survey. They showed that a 1-g per day increase in dietary sodium — estimated using diet questionnaires — was associated with a 22% higher chance of having atopic dermatitis.

According to the authors of the new study, a German textbook published more than 100 years ago recommends a low-salt diet for people with atopic dermatitis.

However, this recommendation had little data to back it up. More recently, scientists have started to take more interest in the links between dietary sodium and eczema.

For instance, recent research shows that eating fast food more than three times each week is associated with worse eczema severity in children.

Although fast food certainly is high in added salt and sodium, other components of the food, such as sugar, fat, or additives, may have influenced these outcomes.

However, a small study from 2019 found that people with atopic dermatitis had higher sodium levels in affected parts of their skin compared to healthy skin. The same study showed that elevated sodium levels may influence the immune system, which suggests that sodium could play a part in the condition’s severity.

Katrina Abuabara, MD, associate professor of dermatology at the University of California, San Francisco, and one of the authors of the new study, explained to Healthline how sodium and salt intake can impact atopic dermatitis symptoms and the immune system overall.

“It is hypothesized that sodium is stored in the skin to prevent water loss and may help prevent infection. However, it can also activate cells in the immune system, triggering some inflammatory pathways and removing the ‘brakes’ from others,” Abuabara said.

“One study has examined this process specifically in atopic dermatitis,” she told us, “but more research is needed to understand the impact of sodium on atopic dermatitis and other autoimmune and inflammatory diseases.”

Abuabara said despite the findings, physicians are unlikely to suggest dietary changes just yet.

“This study was the first step in that we were able to show an association between dietary salt and atopic dermatitis in a large population,” she explained. However, she also told us that more research is needed before recommendations change.

“I think it is important to have experimental evidence that dietary salt can improve eczema symptoms before we recommend dietary changes specifically for eczema.”

However, Abuabara said that many American adults may benefit from eating less sodium for other health reasons.

“The average American eats more than the recommended amount of salt, and low-salt diets have been proven to reduce the risk of heart disease, especially among older adults,” Abuabara said.

With this in mind, we spoke with Lucy McCann, MD, a registered associate nutritionist and clinical academic researcher. She provided some tips on ways to reduce sodium intake in your diet.

She recommends the following:

  • When cooking, try to add flavor with herbs and spices rather than salt.
  • Check food labels for their salt content. The Dietary Guidelines for Americans recommends eating no more than 2.3 g of sodium each day (5.75 g of salt).
  • When you do enjoy salty foods, try to limit your portion size.
  • Opt for low-salt versions of foods where possible.
  • When buying tinned goods, choose ones in water rather than brine.
  • As often as possible, choose whole foods like fruit and veg rather than salty snacks.

Overall, McCann, who was not involved in the study, told us that “for most people, home cooking is not the problem, rather, the salt in ultra-processed, prepackaged, or fast foods is the primary reason for high dietary intake. Reducing your intake of these foods could make a real difference to your overall salt consumption.”

A large-scale study suggests that consuming more salt may increase the risk of having active atopic dermatitis and be linked to more severe symptoms.

However, more research is needed, and Abuabara plans to continue the investigation. “We are about to begin enrolment for a National Institutes of Health-funded study to better understand the relationship between dietary sodium, skin sodium, and eczema severity over time,” she told Healthline.