A high intake of potassium and other nutrients does not significantly counteract high blood pressure caused by a high salt intake, say researchers writing in Hypertension.
Led by Professor Jeremiah Stamler from the Feinberg School of Medicine at Northwestern University, Chicago, the study looked at data from participants of the INTERMAP study (International Study on Macro/ Micronutrients and Blood Pressure) - and found that the addition of numerous nutrients made no difference to the established link between high sodium intake and raised blood pressure.
While sodium:potassium intake ratio was shown to have an inverse relationship with blood pressure, a higher intakes of potassium (which is abundant in fruits and vegetables) only made a significant beneficial difference to this relationship at lower levels of sodium intake, the multi-centre research team said.
Therefore, they conclude that following an otherwise healthy diet cannot counteract the detrimental effect of salt on BP.
“The adverse association of dietary sodium with BP is minimally attenuated by other dietary constituents; these findings underscore the importance of reducing salt intake for the prevention and control of prehypertension and hypertension,” commented co-lead author .
The study included 4,680 men and women aged 40-59 in Japan, China, the U.K and U.S. Participants attended four clinic visits at which systolic and diastolic BP was measured. Dietary intake was recorded though a 24-hour dietary recall. The scientists also measured urinary sodium and potassium.
The researchers added in 80 dietary variables either one-at-a-time or in four multivariate combinations (macronutrients, vitamins, minerals and amino acids) to their regression models predicting the effect on BP of these nutrients.
The findings add to the large weight of existing evidence of the harmful effects on BP of excessive salt in the diet.
The results are important because they imply that major reductions in BP cannot be achieved by other dietary/ lifestyle measures alone, emphasised the researchers.
Even the DASH (Dietary Approaches to Stop Hypertension) diet, may not be effective if participants still have high intakes of salt. Thus salt intake reduction is critical, the researchers added.
"Regularly consuming excessive amounts of sodium, derived mainly from commercially processed food products, is an important factor in the development of the elevated blood pressure patterns," said Stamler.
The findings have immediate practical implications for public health and food manufacturers, argued the researchers.
"To prevent and control the ongoing epidemic of prehypertension and hypertension, the salt content in the food supply must be reduced significantly," advocated Stamler.
"We're learning more about the role other nutrients play in influencing the blood pressure-raising effects of sodium, and that the focus on sodium remains important," said Professor Cheryl Anderson, vice-chair of the American Heart Association's Nutrition Committee.
"Restaurant and pre-packaged food companies must be part of the solution because Americans desire the ability to choose foods that allow them to meet their sodium reduction goals."
Published online 5 March 2018. DOI: 10.1161/HYPERTENSIONAHA.117.09928
Relation of Dietary Sodium (Salt) to Blood Pressure and Its Possible Modulation by Other Dietary Factors The INTERMAP Study
Authors: Jeremiah Stamler, Queenie Chan et al, for the INTERMAP Research Group