According to the World Health OrganizationTrusted Source (WHO), almost 1.3 billion adults aged 30-79 worldwide have hypertension (high blood pressure). And since 1990, the number of people globally with hypertension has doubled.
There are several well-known factors that increase the risk of hypertension. These include:
- Age: Hypertension is more common over the age of 65
- Ethnicity: Some ethnic groups are more prone to hypertension than others
- Weight: Obesity is a primary risk factor for hypertension
- Regular alcohol and tobacco use
- Sex: males have a higher risk of developing hypertension than females. However, this is only until females reach menopause
- Existing health conditions: Cardiovascular disease, diabetes, chronic kidney disease and high cholesterol levels can lead to hypertension, especially as people age
A less recognized factor that can drive up blood pressure is salt sensitivity — the tendency of the body to hold onto salt rather than excrete it through the kidneys.
A review of epidemiological data published in Hypertension suggests that women of all ages and ethnicities are more salt sensitive than men. And this tendency to hold onto more salt increases after menopause.
“The most important fact highlighted in this review article is that women, whether pre or postmenopausal, are more salt sensitive than men.”
— Dr. Eric Belin de Chantemèle, study author and physiologist at the Vascular Biology Center at the Medical College of Georgia at Augusta University.
What is salt sensitivity?
Salt comprises around 40% sodium ions and 60% chloride ions. We need a small amount of sodium, around 500mg (or a quarter teaspoon of salt) per day, to conduct nerve impulses, contract and relax muscles, and maintain the proper balance of water and minerals.
However, most people take in more sodium than they need. In higher-income countries, some 75% of salt intake comes from processed foods and meals eaten outside the home.
The Centers for Disease Control and Prevention (CDC) advises increasing the fresh food in your diet to reduce salt intake, and if eating processed foods, look for those that have less than 600mg per serving.
According to the CDC, research shows a strong relationship between the amount of salt consumed and raised pressure (BP) levels. And for most people, reducing salt intake results in reduced BP.
Globally, people consume an average of 9 to 12 grams of salt daily — around double the WHO recommendation of 5 grams daily for cardiovascular health.
Some people can effectively excrete higher salt intake, so it does not increase their BP. However, for many, changes in dietary salt intake can cause noticeable increases or decreases in BP. These people are said to be salt sensitive.
The American Heart Association estimates that salt sensitivity is present in approximately 51% of people with hypertension and 26% of people who do not have high blood pressure.
And this review suggests that salt sensitivity is a factor in about half of the cases where the cause of hypertension is not apparent and that it also often contributes to treatment-resistant hypertension.
How salt intake affects women vs. men
It has long been recognized that men under 65 have a higher risk of hypertension than women, but the risk increases for women following menopause.
This review, however, suggests that because females are predisposed to salt sensitivity, which may raise BP, the reality is not as straightforward as that.
The explanation they suggest is, perhaps, surprising. According to Dr. Belin de Chantemèle, human and laboratory animal evidence indicates that female kidneys are better at excreting salt. The problem, it appears, is with the vasculatue, because salt should also relax the blood vessels, but it does not in those who are salt-sensitive.
“Although sex steroid hormones are important in the regulation of the cardiovascular system, new research suggests that sex chromosomes may also be involved. […] Increased vascular resistance from salt sensitivity leads to endothelial dysfunction, which may be more of a factor in females than in males.”
— Sebnem Unluisler, M.Sc., genetic engineer at the London Regenerative Institute.
When the blood vessels relax and expand, BP reduces. However, if the blood vessels do not relax, BP increases.
Dr. Belin de Chantemèle said that the blood vessels do not relax in many women, making them prone to salt-sensitive BP changes.
The role of hormones in BP
The role of estrogen in BP control has been long debated. This review found that salt-sensitive BP increased after menopause when estrogen levels were lower.
Dr. Meagan Williams, internist and Director of Women’s Health at Harbor Health, told Medical News Today why this might happen:
“SSBP [salt-sensitive blood pressure] increases after menopause — which could suggest that female sex hormones (like estradiol) are actually protective against SSBP, rather than the factor that makes women more salt sensitive.”
But it may not be just estrogen that is having an effect. Dr. Belin de Chantemèle highlighted the role of another hormone in SSBP:
“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 appears to reduce the ability of blood vessels to relax.“