Researchers at the Medical College of Georgia, Augusta University, found that hypertension caused by salt sensitivity was higher among females than among males in a new study. The researchers suggest imposing a lower threshold for hypertension in women, allowing quicker notification of changes and actions of intervention.
“The realities are that women and men regulate our blood pressure differently and our blood pressures are different at baseline,” says Dr. Eric Belin de Chantemele, physiologist in the Vascular Biology Center at the Medical College of Georgia, Augusta University.
Likely reasons for the observed difference between sexes are chromosomes, sex hormones such as estrogen and genetics such as estrogen receptors, the authors note.
“Evidence also indicates that females tend to like salt more than males. Like many sex-related differences, the proclivity for salt likely relates to the physiological need to retain sodium and the fluid following sodium, sufficient to sustain another life in pregnancy. There is also evidence that the male hormone testosterone suppresses the appetite for salt,” Belin de Chantemele states.
Fighting a common belief
Published in Hypertension, the study stresses the common belief that women are more protected against cardiovascular diseases than men. While confirmed in several rat studies, human studies have found contradicting results.
Before menopause, women are more salt sensitive, and when entering menopause, it exacerbates the prevalence and severity, explain the authors.
“That supports yet another emerging concept that the sex chromosome XX predisposes females to salt sensitivity, presumably because females need to nearly double their fluid volume during pregnancy, and estrogen does help mitigate some of the related increased risk, at least until its levels drop after menopause,” says Belin de Chantemele.
Being salt-sensitive means the body naturally tends to “hold onto salt rather than disposing of excess in the urine.” This might also affect blood pressure, as if an increase or decrease of 10% in response to salt consumption, it’s considered salt sensitivity of blood pressure.
“Salt sensitivity is one of the leading factors for hypertension. And, if you look at people with treatment-resistant hypertension – which is most people – most are salt sensitive,” Belin de Chantemele says. “It’s crucial to know the cause of that.” Salt sensitivity is a usual factor in cases where hypertension is “not obvious,” such as kidney problems or treatment-resistant hypertension.
The Centers for Disease Control and Prevention says that only one in four adults controls their hypertension. Belin de Chantemele maintains that reducing one’s salt intake reduces salt sensitivity, especially for women.
The World of Action on Salt, Sugar and Health recently stressed that improving the nutritional content of food and drinks by reformulating recipes with less salt, sugar and saturated fat is “by far the most important strategy that any company should make to improve public health.”
“We think it’s mostly the vasculature not relaxing in response to an intake of sodium that is leading to an elevation in pressure,” Belin de Chantemele underscores.
“Animal studies of salt sensitivity generally indicate that the kidneys, which should excrete more sodium when we consume too much, work fine in females. In fact, human and lab animal evidence indicates that female kidneys are better at salt excretion,” he says. “The problem, it appears, is with the vasculature because salt should also make the blood vessels relax.”
What happens in the body?
According to Belin de Chantemele, “if you expand your blood vessels more, then you will be able to keep your blood pressure stable, but if your vessels do not relax, that is how pressure goes up. Later on, you also excrete sodium to reduce your blood volume, but the first response should be relaxation of your blood vessels.”
While adding that, it’s how it works for salt-resistant people, but it doesn’t work so well in many females. Another major factor that explains the difference between genders is that the female body is prepared to reproduce, and a higher level of the hormone aldosterone is present in the body.
The adrenal gland produces aldosterone and directly affects blood pressure by regulating salt-water balance in the body. “Females tend to have way more receptors for aldosterone, called mineralocorticoid receptors,” the authors note. Additionally, aldosterone of high levels might increase inflammation, enlargement of the heart and scarred and stiff blood vessels.
By Beatrice Wihlander