Researchers studied 88 adults to understand how vitamin D supplements might affect inflammation in people with heart disease. They found that the length of time someone takes vitamin D supplements may change how inflammation markers appear in the blood, but this effect was different depending on whether someone was overweight or had obesity. The study suggests that vitamin D’s effect on heart-related inflammation isn’t one-size-fits-all—it depends on both body weight and how long you’ve been taking supplements. However, because this was a small study, scientists say larger studies are needed to confirm these findings before making strong recommendations.

The Quick Take

  • What they studied: Whether vitamin D supplements change how inflammation appears in people with heart disease, and whether this effect depends on someone’s weight
  • Who participated: 88 adults divided into three groups: 20 with normal weight, 34 who were overweight, and 34 with obesity. All were healthy enough to participate and didn’t have active infections
  • Key finding: For one inflammation marker called hs-CRP, the effect of vitamin D supplementation on heart disease-related inflammation changed based on how long people took supplements and their weight category. The pattern was different for people at normal weight versus those with obesity
  • What it means for you: Vitamin D supplements may affect inflammation differently depending on your weight and how long you take them, but this is early research. Don’t change your vitamin D routine based on this study alone—talk to your doctor about what’s right for you

The Research Details

This was a cross-sectional study, which means researchers looked at a group of people at one point in time rather than following them over months or years. They measured inflammation markers in blood samples and asked participants about their vitamin D supplement use, including how long they’d been taking them. The researchers looked at four different inflammation markers to see if vitamin D affected them differently. They organized people into three weight categories and tested whether vitamin D’s effect on inflammation changed depending on which weight group someone was in.

This research approach helps scientists spot patterns and connections between vitamin D use and inflammation. By looking at people in different weight categories, the researchers could see whether vitamin D works the same way for everyone or whether body weight matters. This type of study is good for generating new ideas that can be tested in larger, longer studies

This study has some important limitations to consider: it’s quite small (only 88 people), which means the findings might not apply to larger populations. It’s a snapshot in time rather than following people over years, so we can’t be sure about cause-and-effect. The researchers did test their main finding multiple ways to make sure it was real, which is a good sign. However, the small size means results should be viewed as preliminary and needing confirmation in bigger studies

What the Results Show

The main finding involved a specific inflammation marker called hs-CRP (high-sensitivity C-reactive protein). The researchers found a three-way interaction, meaning the relationship between heart disease, vitamin D supplementation duration, and inflammation changed depending on body weight category. For people in the moderate-weight category (overweight), longer vitamin D supplementation made the difference in inflammation between those with and without heart disease larger. For people with obesity, the opposite happened—longer supplementation made the difference smaller. This suggests vitamin D’s effect on heart-related inflammation isn’t straightforward and depends on both supplement duration and body weight.

The researchers also measured three other inflammation markers: presepsin, ferritin, and β-defensin-2. None of these showed the same three-way interaction pattern that hs-CRP did. This suggests that vitamin D supplementation duration may specifically affect hs-CRP rather than inflammation more broadly. The researchers found no simple interaction between body weight and heart disease for any of the markers, meaning weight alone didn’t change how heart disease affected inflammation

Previous research has shown that both heart disease and higher body weight are linked to chronic low-grade inflammation. This study adds a new piece: the duration of vitamin D supplementation may matter for how inflammation appears in people with heart disease. However, because this is a small preliminary study, it doesn’t overturn existing knowledge—it suggests a new pattern that needs confirmation

The biggest limitation is sample size: 88 people is relatively small, which means findings might not apply to larger populations. This is a snapshot study (cross-sectional), so researchers can’t prove that vitamin D supplements caused the inflammation changes—only that they’re associated. The study didn’t randomly assign people to take vitamin D or not; it just looked at who was already taking it. People’s supplement use wasn’t controlled or verified carefully. The study was done at one point in time, so we don’t know if these patterns hold over months or years

The Bottom Line

Based on this preliminary research, there’s no strong recommendation to change your vitamin D supplementation. If you have heart disease or are concerned about inflammation, talk with your doctor about whether vitamin D supplements are appropriate for you. This study suggests that how long you take vitamin D might matter, but much larger studies are needed before doctors can make specific recommendations about duration. Continue following your doctor’s guidance on vitamin D supplementation

This research is most relevant to people with heart disease who are considering or currently taking vitamin D supplements, and to healthcare providers treating these patients. People without heart disease probably shouldn’t change their vitamin D habits based on this study. Anyone overweight or with obesity who has heart disease might want to discuss these findings with their doctor, though the evidence is still preliminary

This is early-stage research, so there’s no clear timeline for seeing benefits. The study was done at one point in time, so we don’t know how quickly any effects might appear. If you start or change vitamin D supplementation based on your doctor’s advice, it typically takes several weeks to months to see changes in inflammation markers

Want to Apply This Research?

  • Track vitamin D supplement intake with dates started and stopped, noting the duration of continuous use. Record this monthly alongside any inflammation-related symptoms (fatigue, joint pain, general inflammation markers if available from doctor visits)
  • If your doctor recommends vitamin D supplementation, use the app to set a daily reminder and track consistency. Note the start date clearly so you can monitor how long you’ve been supplementing. If you have heart disease, discuss with your doctor whether tracking inflammation markers (like hs-CRP from blood tests) alongside supplement duration would be helpful
  • Over 3-6 months, track vitamin D supplement adherence and any changes in how you feel. If your doctor orders inflammation blood tests, note the dates and results in the app alongside your supplement duration at that time. This personal tracking can help you and your doctor identify patterns specific to your situation

This research is preliminary and based on a small study of 88 people. It should not be used to make decisions about starting, stopping, or changing vitamin D supplementation. If you have heart disease, are overweight, or are considering vitamin D supplements, consult with your healthcare provider before making any changes. This study shows associations only and cannot prove that vitamin D supplements cause changes in inflammation. Always follow your doctor’s personalized recommendations for vitamin D supplementation and heart disease management.