The World Health Organization recommends we consume no more than 2,000 mg of sodium a day - less than a teaspoon of salt - supposedly because of studies showing it impacts heart disease and stroke. And they recommend at least 3,510 mg of potassium daily, again to lower our odds of heart disease and stroke.
Leaving aside the credibility of the epidemiology papers that led to these recommendations, that potassium target means drinking 9 cups of milk every day. Or eating 2.5 cups of beet greens. Or 6 potatoes. Very few people can do that, or want to do that. And they aren't, according to national surveys conducted by the governments of France, Mexico, the United Kingdom and the United States.
"The data confirm that we eat too much sodium and not enough potassium," said Dr. Adam Drewnowski, professor of epidemiology who directs the Center for Public Health Nutrition at the School of Public Health at the University of Washington. "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."
In fact, the targets are so out of reach that Drewnowski said he would be "shocked" if in any nation in the world a majority of the population is achieving the WHO's dietary goals.
Part of the problem is that sodium and potassium are found in many of the same foods. If you drink milk to get potassium, for example, you are edging closer to your salt quota. With a normal diet, it is very difficult to double one and cut the other by two-thirds.
WHO targets are basically a diet for wealthy elites. For a family of four to reach their potassium targets by eating potassium-rich foods would mean an extra $42 each week. Potassium supplementation is not really feasible because of its bitter taste.
Most of the sodium in the American diet comes from processed foods, including breads, pizza, processed meats and cheese. Reformulating foods to lower their sodium content is one strategy to reduce sodium intake that won't require expensive government campaigns to change behavior. But that only works in some countries.
WHO is make global health guidelines based on a few western countries. Even for the United Nations, that lacks an evidence basis.
"Pizza is a major source of sodium in the U.S. I doubt that this is also the case in Asia," Drewnowski said. "We get too much data from Boston and not enough from Bangladesh."
The bottom line, said Drewnowski, is that dietary guidelines, especially global health guidelines, need to set targets that are reasonable and are backed by 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."
Citation: Adam Drewnowski, Colin D Rehm, Matthieu Maillot, Alfonso Mendoza, Pablo Monsivais, 'The feasibility of meeting the WHO guidelines for sodium and potassium: a cross-national comparison study', BMJ Open 2015;5:3 e006625 doi:10.1136/bmjopen-2014-006625. The study was supported by NIH grants R01 DK 077068-04 and R21 DK085406; University of Cambridge Centre for Diet and Activity Research, UKCRC Public Health Research Centre of Excellence; British Heart Foundation, Cancer Research UK, Economic and Social Research Council, Medical Research Council, National Institute for Health Research, and Wellcome Trust, under the auspices of the UK Clinical Research Collaboration.
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