Salt deficiency or excess in the diet of a pregnant woman has a negative impact on the development of the fetal kidneys and may lead to hypertension in the offspring in the future, according to a study on rats published by the American Journal of Physiology – Renal Physiology.
Such conclusions were reached by scientists from the University of Heidelberg in Germany and the University of Aarhus in Denmark, who reared pregnant and then lactating female rats on a diet containing low, medium or high amounts of sodium (in the form of table salt, i.e. sodium chloride).
In the fourth week after birth, the baby rats were weaned from their mother’s breasts and switched to a moderate salt diet.
The structure of the kidneys was checked when the small rodents were one week old, then 12 weeks old. Shortly after birth and a week later, they also had their levels of compounds known for their role in kidney development measured. Then, between the ages of two and nine months, the male offspring had their arterial blood pressure monitored using a telemetry device that could measure it from a distance.
It turned out that the number of the so-called Glomeruli, which are part of the basic structural units of the kidney – nephrons, were much smaller in the offspring of females who were on a low or too high salt diet. In nephrons, excess water and mineral salts as well as other unnecessary or toxic substances are filtered out of the blood, which are products of metabolism or enter the body with food. The function of the nephron also regulates blood pressure, regulates the level of mineral salts in the body, and is generally essential for supporting human and animal life.
As the authors of the study recall, in humans, a low number of glomeruli (and hence – nephrons) in the kidneys of a newborn is associated with the risk of hypertension, heart disease and kidney disease in adulthood.
The researchers also found that after 5 months of age, males offspring from mothers who consumed very little or very much salt had higher mean arterial pressure than male offspring of females on a moderate sodium diet.
Too little or too much salt intake during pregnancy also caused changes in the production of proteins responsible for kidney development in the offspring. For example, children of female females who were on a low-salt (low-sodium) diet produced less FGF-10 protein, which promotes kidney development, and children of mothers whose diets were high in salt produced less of the two other proteins necessary for kidney formation. – i.e. the Pax-2 and FGF-2 proteins.
High salt intake during pregnancy has also been associated with high levels of a compound in the amniotic fluid called marinobufagenin, which contributes to high blood pressure in the offspring.
According to the researchers, their results indicate that maternal consumption of both too much and too little salt during pregnancy and lactation delays the development of the glomeruli in the fetus, causing deficiencies in the basic structural units of the kidney and increasing the risk of hypertension. If future research confirms that the latest results also apply to humans, a high sodium diet and a very low sodium diet during pregnancy can be considered a risk factor for renal development disorders and hypertension in the offspring.
It is now important that pregnant and nursing women obey the advice of their treating physician regarding salt intake.
According to the recommendations of the World Health Organization (WHO), both sick and healthy people should not consume more than 6 grams of salt a day. (PAP)