Salty diet linked to eczema flares

Eating a diet high in sodium may increase the risk of developing atopic dermatitis, commonly known as eczema, according to a study in JAMA Dermatology. “We found that in a large study of adults in the United Kingdom, estimated sodium intake based on a urine sample was associated with an 11 per cent increase in the risk of eczema, and that more sodium was associated with more severe eczema,” says corresponding author, Katrina Abuabara, MD, an associate professor of dermatology at the University of California in San Francisco, and dermatologist at UCSF Health in San Francisco.

In a study used to confirm the findings in a US population, researchers also found that eating just one extra gram of sodium per day — less than the amount found in your average fast food sandwich or burger — increases the likelihood of atopic dermatitis flares by 22 per cent. Atopic dermatitis is a chronic disease that causes dry, itchy skin. The condition usually starts in childhood, but some people get it later as adults. Eczema affects more than 31 million people in the United States (about 1 in 10 people), making it one of the most common skin conditions. The number of people with atopic dermatitis has risen over the years, especially in industrialized countries, which may be related to environmental and lifestyle factors like diet.

For the latest study, investigators started with data from over 215,000 people between the ages of 30 to 70 years (the average age was 56) who had enrolled in the UK Biobank. A review of medical records and prescription codes revealed that almost 11,000 (5 per cent) had eczema. By analyzing urine samples of all the participants in the study, researchers found that the average person excreted about three grams of sodium in a 24-hour period. Then they analyzed all the data to see if there was a relationship between sodium levels and atopic dermatitis.

The researchers discovered that each additional gram of sodium excreted over the average was associated with the following: 11 per cent higher risk of having an atopic dermatitis diagnosis; 16 per cent higher risk of having atopic dermatitis currently; 11 per cent higher odds of increased severity of atopic dermatitis.

To confirm their results, investigators looked at 13,000 US adults in the National Health and Nutrition Examination Survey and found that eating just one additional gram a day of sodium per day — about half a teaspoon of table salt — was associated with 22 per cent higher risk that a person would have an active case of atopic dermatitis. These findings suggest that what has been seen in laboratory studies is actually happening in the population: Sodium might promote the emergence of atopic dermatitis and exacerbate it, says Christina Zielinski, PhD, professor at the German Center for Infection Research at the Technical University of Munich.

Dr Zielinski found in an earlier study that people with atopic dermatitis have increased salt concentrations — 30 times higher — in their inflamed skin compared with people without the conditions.