Sodium divide: Women more prone to high blood pressure from salt intake

A new study suggests that women across all ages and ethnicities are more salt-sensitive than men, a fact that could significantly impact blood pressure control strategies

Hypertension, or high blood pressure, remains one of the leading causes of premature death globally, according to the World Health Organization (WHO). 

The UN agency’s report estimates that hypertension affects an estimated 1.28 billion adults worldwide, with the highest prevalence seen in low and middle-income countries. Since 1990, this number has doubled, underscoring the magnitude of the global health challenge.

Studies have also revealed a common cause of hypertension – salt sensitivity. A new study suggests that women across all ages and ethnicities are more salt-sensitive than men, a fact that could significantly impact blood pressure control strategies.

What is salt sensitivity?

The condition refers to changes in blood pressure levels parallel to change in salt intake. Some individuals are more sensitive to the blood pressure-raising effects of salt, and their blood pressure may increase more significantly with higher salt consumption. Salt sensitivity is considered a risk factor for developing hypertension. People who are salt-sensitive may benefit from reducing their salt intake to help manage and prevent high blood pressure.

Salt retention relates to the body’s ability to retain or excrete salt. When salt retention is increased, the body holds on to more salt, leading to increased fluid retention and potentially higher blood pressure. Managing salt intake is important for individuals with salt retention issues to help control blood pressure.

Salt is composed of around 40 percent sodium ions and 60 percent chloride ions. The human body requires a small amount of sodium, roughly 500mg (or a quarter teaspoon of salt) per day, for nerve impulse conduction, muscle contraction, relaxation, and for maintaining the right balance of water and minerals.

However, most people consume more sodium than they need, particularly in higher-income countries where 75 percent of salt intake comes from processed foods and meals eaten outside the home. 

Recent epidemiological data published in the journal Hypertension proposes that women, irrespective of age or ethnicity, display greater salt sensitivity than men. This tendency to retain more salt intensifies after menopause.

The research indicates a strong correlation between salt intake and blood pressure levels. For most, lowering salt consumption results in reduced blood pressure. Yet, despite the WHO’s recommendation of 5 grams daily for cardiovascular health, global salt consumption averages between 9 to 12 grams daily.

Some people can efficiently excrete higher amounts of salt without experiencing a rise in blood pressure. However, others show noticeable blood pressure fluctuations with dietary salt intake changes. 

The American Heart Association estimates that approximately 51 percent of people with hypertension and 26 percent of those without it show signs of salt sensitivity. This review suggests that salt sensitivity is present in about half of the cases of unexplained hypertension and often contributes to treatment-resistant hypertension.

Dr Ashwani Mehta, a senior cardiologist from Sir Ganga Ram Hospital, New Delhi, explains: “Salt-sensitive hypertension is defined as an increase in blood pressure associated with increased salt intake. Approximately 50 percent of humans with hypertension have salt sensitivity with this number varies between sexes and is influenced by race.”

Are women more salt-sensitive than men?

Traditionally, men under 65 have been perceived as having a higher risk of hypertension than women, but the risk increases for women following menopause. However, the study points out that due to women’s predisposition to salt sensitivity, the reality might be more nuanced.

Dr. Mehta notes: “Females of all ages, and ethnicities have more salt-sensitive hypertension than males and that this propensity to hold onto more salt, which drives blood pressure up, increases after menopause.”

“Evidence from human and laboratory studies indicates that female kidneys are more efficient at excreting salt than their male counterparts. However, the challenge lies in the vasculature, as salt should ideally relax the blood vessels, which does not happen in those who are salt-sensitive. This lack of relaxation can lead to an increase in blood pressure,” Dr. Mehta adds.

The role of hormones in blood pressure

The role of estrogen in blood pressure control has been the subject of extensive debate. The salt-sensitive blood pressure increases after menopause when estrogen levels are lower. The female sex hormones, like estradiol, have been found to offer some protection against salt-sensitive blood pressure.

“Data from our own studies and the literature point towards an inability of women to decrease the production of the salt-retaining hormone aldosterone, which also controls the ability of blood vessels to relax. Improper levels of aldosterone in response to salt ingestion appear to reduce the ability of blood vessels to relax,” says Dr Mehta. 

While these findings shine a light on the different ways salt intake affects men and women, Dr Mehta stresses the need for further research. 

“It is very difficult in the clinical setting to find out who is salt sensitive. More research is needed to find out the mechanism and treatment,” he says. “However, if any person is thought to have salt sensitivity, they should restrict salt intake, and increase potassium intake in the form of green leafy vegetables and fruits.”