Babies born prematurely often develop with fewer filtering units in their kidneys than full-term babies. A new study in mice shows that people with this condition may be extra sensitive to salt in their diet, causing their blood pressure to rise more than others when they eat salty foods. The research suggests that while having fewer kidney filters doesn’t automatically cause high blood pressure, eating too much salt could trigger problems later in life. This finding is important because it shows that premature babies might benefit from watching their salt intake as they grow up.

The Quick Take

  • What they studied: Whether people born with fewer kidney filtering units are more likely to develop high blood pressure when they eat a lot of salt
  • Who participated: Laboratory mice bred to have low nephron endowment (fewer kidney filters) compared to normal mice, including both males and females
  • Key finding: Mice with fewer kidney filters showed a bigger increase in blood pressure when fed a high-salt diet compared to normal mice, especially females. Interestingly, males and females responded slightly differently to the salt challenge.
  • What it means for you: If you were born prematurely, reducing salt intake may be especially important for protecting your heart and kidneys as you age. However, this is early research in mice, so talk to your doctor about personalized recommendations.

The Research Details

Researchers created a special type of mouse that was born with fewer kidney filtering units (called nephrons), similar to what happens in premature human babies. They measured the blood pressure of these mice and normal mice using continuous monitoring equipment that tracked pressure 24/7. First, they measured baseline blood pressure when the mice ate normal food. Then, they switched the mice to a high-salt diet and measured how much their blood pressure changed. This allowed researchers to see if having fewer kidney filters made mice more sensitive to salt’s effects on blood pressure.

The study included both male and female mice to see if sex made a difference in how salt affected blood pressure. The researchers also measured kidney function markers to understand what was happening inside the kidneys during the salt challenge.

This research design is important because it isolates one specific factor—low nephron endowment—without other complications that premature babies often experience. This helps researchers understand whether having fewer kidney filters alone is enough to cause salt sensitivity, or if other factors are needed. By studying this in a controlled way, scientists can better understand what happens in human premature babies.

This is original research published in a respected journal focused on high blood pressure. The study used continuous blood pressure monitoring, which is more accurate than single measurements. The researchers tested both sexes to look for differences. However, this is animal research in mice, so results may not directly apply to humans. The study size and specific statistical details were not provided in the abstract, which limits our ability to assess the strength of the findings.

What the Results Show

At baseline, mice with low nephron endowment had normal blood pressure just like regular mice—there was no difference. This is an important finding because it shows that having fewer kidney filters doesn’t automatically cause high blood pressure.

When researchers switched the mice to a high-salt diet, the results changed dramatically. Both male and female mice with low nephron endowment showed a larger increase in systolic blood pressure (the top number) compared to normal mice. This suggests that salt intake triggers blood pressure problems in mice with fewer kidney filters.

Female mice with low nephron endowment also showed a bigger increase in diastolic blood pressure (the bottom number) than normal females. Interestingly, male mice with low nephron endowment showed less of an increase in diastolic pressure than normal males, suggesting that males and females may respond differently to salt when they have fewer kidney filters.

The researchers measured kidney hormones and salt excretion to understand the mechanism. Female mice with low nephron endowment showed less suppression of a hormone called renin and had difficulty excreting extra salt in their urine. This suggests their kidneys couldn’t handle salt normally. Male mice with low nephron endowment showed more signs of chronic kidney disease, but this didn’t explain their salt sensitivity, indicating that kidney disease alone wasn’t responsible for the blood pressure changes.

Previous research showed that premature babies have higher rates of high blood pressure and kidney disease later in life. This study supports that observation by showing a biological mechanism—salt sensitivity—that could explain why. The finding that salt intake modifies the risk adds an important piece to the puzzle, suggesting that diet is a modifiable factor that could help prevent problems in people born prematurely.

This research was conducted in mice, not humans, so results may not directly apply to people. The study didn’t specify the exact number of mice used, making it harder to judge how reliable the findings are. The researchers noted that when they divided the data by sex, the sample size became smaller, which reduced their ability to detect some differences between males and females. Additionally, this is a single study, so results need to be confirmed by other researchers before drawing firm conclusions.

The Bottom Line

People born prematurely should consider monitoring their salt intake as they age, particularly if they have family history of high blood pressure or kidney disease. This recommendation is based on emerging evidence and should be discussed with a healthcare provider. Current general guidelines suggest limiting salt to less than 2,300 mg per day for most adults, but premature birth survivors may benefit from even lower intake. Regular blood pressure monitoring is advisable.

This research is most relevant to people born prematurely, their parents, and their healthcare providers. It’s also important for people with a family history of high blood pressure or kidney disease who were born early. General population members can benefit from the reminder that salt intake affects blood pressure, but the findings are specifically about premature birth. People with normal kidney development may not need to be as restrictive with salt, though current health guidelines recommend moderation for everyone.

Blood pressure changes from salt intake can happen within days to weeks, but the long-term kidney damage that researchers are concerned about develops over years or decades. People born prematurely may not notice problems until their 20s, 30s, or later in life. Starting good habits early—like limiting salt—may help prevent problems from developing.

Want to Apply This Research?

  • Track daily sodium intake in milligrams and correlate with blood pressure readings taken at the same time each day. Set a goal of under 2,000 mg sodium daily and monitor how blood pressure responds over 4-week periods.
  • For users born prematurely: Use the app to identify high-sodium foods in your diet (processed foods, canned soups, deli meats, sauces) and replace them with fresh alternatives. Set reminders to check nutrition labels for sodium content before eating packaged foods.
  • Establish a baseline blood pressure over 2 weeks, then reduce sodium intake and track blood pressure weekly for 8 weeks. Use the app to create a personal sodium-to-blood-pressure response chart. Share results with your healthcare provider to determine if your individual response matches the research findings.

This research is preliminary animal study data and should not replace professional medical advice. If you were born prematurely or have concerns about your blood pressure or kidney health, consult with your healthcare provider before making dietary changes. This study was conducted in mice, and results may not directly apply to humans. Always discuss personalized nutrition and health recommendations with a qualified healthcare professional who understands your complete medical history.