Researchers in Italy discovered that parents with more than one child are less likely to give their babies vitamin D supplements regularly. In a survey of 241 families with infants, 91% of parents with one child gave vitamin D at least four times per week, but only 78% of parents with two or more children did. This is important because vitamin D helps babies develop strong bones and a healthy immune system. The study suggests that having multiple children at home makes it harder for parents to remember and stick to vitamin D routines, even though other factors like parent education level or how much time babies spend outside didn’t seem to matter.

The Quick Take

  • What they studied: Whether the number of children in a family affects how consistently parents give their babies vitamin D supplements
  • Who participated: 241 caregivers of babies aged 4 weeks to 12 months visiting a hospital in Milan, Italy between March and April 2023
  • Key finding: Parents with two or more children were about 2.7 times more likely to miss vitamin D doses compared to parents with just one child (78% good adherence vs. 91%)
  • What it means for you: If you have multiple young children, you may need extra reminders or simpler systems to remember vitamin D supplements. This doesn’t mean you’re doing anything wrong—it just shows that busy households need different support strategies.

The Research Details

Researchers asked parents at a hospital in Milan, Italy to fill out a survey about their families and vitamin D routines. The survey happened over about 40 days in spring 2023 and included questions about how many children were in the home, parent education, whether babies had any health problems, and how often they gave vitamin D supplements. The researchers then used statistical tools to figure out which family factors were connected to parents missing vitamin D doses.

This type of study is called a ‘snapshot’ study because it looks at families at one point in time rather than following them over months or years. The researchers weren’t trying to prove that having more children causes poor adherence—just to identify a connection that might exist.

Understanding why some families struggle with vitamin D supplements helps doctors and health workers give better advice. Instead of just telling all parents to give vitamin D, they can recognize that families with multiple children might need extra support, reminders, or easier systems to stay on track.

This study has some strengths: it included a decent number of families (241) and used proper statistical methods. However, it only looked at families in one hospital in Italy, so results might be different in other countries or communities. The study also couldn’t prove that having siblings directly causes lower adherence—just that the two things happen together. Additionally, the study relied on parents reporting their own behavior, which might not always be completely accurate.

What the Results Show

Out of 241 families surveyed, 85% of all infants received vitamin D supplements at least four times per week, which is considered good adherence. However, when researchers looked more closely, they found a big difference based on family size: 91% of families with one child gave vitamin D regularly, compared to only 78% of families with two or more children.

When researchers used advanced statistics to look at many factors at once (like parent education, baby’s age, health problems, and outdoor time), having siblings in the home was the only factor that clearly stood out as connected to poor adherence. Families with multiple children were about 2.7 times more likely to miss vitamin D doses regularly.

Interestingly, other things researchers expected to matter didn’t seem to make much difference. Whether parents had higher education, whether the baby was younger or older, whether the baby had health problems, or even how much time the baby spent outside—none of these things significantly affected vitamin D adherence.

The study found that 15% of all infants weren’t getting vitamin D four times per week or more. This means that even in a developed country with good healthcare access, a significant number of babies might not be getting enough vitamin D protection. The research also showed that the challenge of managing supplements increases noticeably once families have more than one young child, suggesting that the ‘busy household’ effect is real and measurable.

Previous research has shown that vitamin D supplements are important for babies’ bone development and immune health. This study adds new information by identifying that family size is a specific barrier to following through with vitamin D routines. While other studies have looked at why parents don’t follow medical advice, this is one of the first to specifically highlight that having multiple children creates a unique challenge for vitamin D adherence.

The study only included families from one hospital in Milan, Italy, so the results might be different in other places with different healthcare systems or cultures. The study asked parents to report how often they gave vitamin D, which might not be completely accurate—parents might remember giving it more often than they actually did. The study was also done in spring (March-April), so results might be different in other seasons when outdoor sun exposure varies. Finally, the study couldn’t explain why having multiple children makes adherence harder—it just showed that the connection exists.

The Bottom Line

Healthcare providers should recognize that families with multiple children need extra support for vitamin D routines. This might include: simpler dosing schedules, written reminders, phone or app notifications, or pre-filled vitamin D dispensers. Parents of multiple young children should ask their doctor about the easiest way to remember vitamin D supplements and consider setting phone reminders or linking the routine to another daily habit (like breakfast time).

This research is most relevant to: parents with multiple young children, pediatricians and family doctors, public health workers designing vitamin D programs, and anyone involved in infant health. If you have one child, this doesn’t mean you should ignore vitamin D—it’s still important. But if you have multiple children, this research validates that you might need extra systems in place to stay on track.

Vitamin D benefits develop gradually over weeks and months. You won’t see immediate changes, but consistent supplementation over several months helps build strong bones and supports immune function. If you improve your adherence starting today, you should see better vitamin D levels in your baby’s blood work within 2-3 months.

Want to Apply This Research?

  • Set up a daily vitamin D tracking log in your app that records: date, time given, which child received it, and any missed doses. This creates accountability and helps identify patterns in when doses are most likely to be forgotten.
  • Link vitamin D administration to an existing daily routine (breakfast, lunch, or bedtime) for each child. Use the app to send notifications at that specific time each day. For families with multiple children, consider a checklist format where you check off each child as they receive their dose.
  • Track adherence weekly by recording the percentage of doses given (e.g., ‘gave 6 out of 7 doses this week = 86% adherence’). Set a goal of 80-90% adherence and review monthly. If adherence drops below 70%, adjust your system—try different times, reminders, or involve older siblings in helping younger ones.

This research shows an association between family size and vitamin D adherence but does not prove that having multiple children causes poor adherence. Vitamin D supplementation for infants is recommended by major health organizations and should not be stopped without consulting your pediatrician. If you have concerns about your child’s vitamin D levels or supplementation routine, speak with your healthcare provider. This summary is for educational purposes and should not replace professional medical advice.