For the first time, researchers have documented a link between lower birth weight and salt sensitivity in humans. Previous research has uncovered salt sensitivity in animal models. Dr Giacomo Simonetti (Bern University Hospital, Switzerland) conducted the study, published in Hypertension, which concluded that it might be important for children with lower birth weights and smaller kidneys to take extra care throughout life.
Senior author, Dr. Markus Mohaupt, (Bern University Hospital, Switzerland says, "I think we can now make a strong recommendation that care needs to be taken with the salt intake of low-birth-weight infants, and this is something that needs to be continued lifelong. These children need to avoid excessive salt intake. It is likely that fast food will be more harmful to them than to children who had normal birth weights. Infants with low birth weights frequently come from complicated pregnancies, with the mother suffering from preeclampsia, and these mothers also have an increased cardiovascular risk, so the mother can be counseled about dietary issues for both herself and her child. If the mother instigates a healthy lifestyle, both mother and child will benefit."
Past studies have proven that infants with low birth rates are more prone to hypertension and cardiovascular disease.”We have shown that children aged between 7 and 15 who had low birth weights are more likely to be salt sensitive — have increased blood pressure with higher intakes of salt — than children of the same age who did not have low birth weights. Also, children who low birth weights had had smaller kidneys than those with normal birth weights, which may explain why they are salt sensitive”, says Dr. Mohaupt.
The researchers studied fifty children. Of those, thirty-five had low weights from either premature births or growth restrictions. Kidney function (glomerular filtration rate) was normal, but lower in the smaller children, which lead the researchers to the above opinion that smaller kidney size is a contributing factor.
Ambulatory blood pressure readings were obtained after the children were given sodium controlled then high sodium diets. Blood pressure, at baseline was normal in all of the infants, though the group with low birth weight had higher readings. Forty-seven percent of the smaller children and thirty-seven percent of the low birth rate children were found to have salt sensitivity. Since the problem increases with age, the researchers expect salt sensitivity to correlate with 18% to 20% of the population – a statistically significant finding.
Dr. Mohaupt concluded, "There's nearly a 50% chance of favorably affecting blood pressure by simply reducing salt intake in children born small for their gestational age and nearly a 40% chance for those born with low birth weight. These individuals can be determined very easily if their family physician just gets data on their births."
Simonetti GD, Raio L, Surbek D, et al. Salt sensitivity of children with low birth weight. Hypertension. 2008;DOI:10.1161/HYPERTENSIONAHA.108.114983. Available at: http://hyper.ahajournals.org.