Dietary sodium and potassium guidelines "completely unfeasible": researcher

Current dietary guidelines for potassium and sodium are “completely unfeasible”, according to a US researcher.

The World Health Organization (WHO) recommends consuming no more than 2000 mg of sodium a day - less than a teaspoon of salt - and at least 3510 mg of potassium a day. This is quite a lot of potassium: we’d need to eat six potatoes, drink nine cups of milk or eat 2.5 cups of beet greens daily to meet this recommendation.

Examining national dietary surveys from France, Mexico, the United Kingdom and the United States to see how many people meet the WHO recommendations, Dr Adam Drewnowski, who directs the Center for Public Health Nutrition at the School of Public Health at the University of Washington, along with five international colleagues found that only:

• 0.3% of Americans,
• 0.5% of French people,
• 0.15% of Mexicans, and
• 0.1% of British people

meet the recommended dietary targets.

“The data confirm that we eat too much sodium and not enough potassium. But they also suggest that the numbers being proposed by WHO and other health agencies are completely unfeasible. The chances that a majority of a population would achieve these goals is near zero,” said Dr Drewnowski.

He said he would be “shocked” if, in any country in the world, a majority of the population is meeting these goals.

“The problem is that sodium and potassium are found in many of the same foods,” Dr Drewnowski explained.

“Milk has sodium in it, so if you want to reduce your sodium intake you can drink less milk. But milk also has potassium, so if you want to increase your potassium intake, you have to drink more milk. So you cannot have a recommendation that tells you to reduce the amount of sodium you eat by two-thirds and to double the amount of potassium you take in.”

Boosting potassium intake can be expensive, too, with potassium-rich foods like greens, citrus and fish tending to cost more. Estimates suggest that meeting potassium guidelines would add about $42 per week to the food budget of a family of four.

While reformulating foods to reduce their sodium content may help, Dr Drewnowski says global guidelines need to take global food patterns into account. “Pizza is a major source of sodium in the US. I doubt that this is also the case in Asia. We get too much data from Boston and not enough from Bangladesh,” he said.

Dietary guidelines need to set targets that are reasonable and are backed by more data from low- and middle-income countries. “The current WHO targets do not appear to be feasible. These targets cannot be met,” Dr Drewnowski said.

The research appears in the journal BMJ Open