A recent health study has shed new light on how body weight may affect the benefits of vitamin D supplements.
The research was part of a larger project known as the Vitamin D and Omega-3 Trial (VITAL), which examined the health effects of vitamin D and omega-3 supplementation in adults.
The original VITAL trial found that vitamin D supplements appeared to provide health benefits for individuals with a normal body weight but showed little benefit for those who were overweight or obese.
This raised an important question: does body weight influence how vitamin D works in the body?
To explore this issue, researchers examined whether body mass index (BMI)—a common measure used to assess weight relative to height—affects the body’s response to vitamin D supplementation.
The original VITAL study was a large randomized controlled trial in which participants were assigned to receive either vitamin D supplements or a placebo. This design allowed researchers to compare the effects of supplementation with no treatment.
The new study focused on a subgroup of participants who had provided blood samples at the beginning of the trial and again two years later. Researchers analyzed these samples for markers related to vitamin D status, including:
- Total vitamin D (25-OHD)
- Free vitamin D (FVD)
- Bioavailable vitamin D (BioD)
- Vitamin D-binding protein (VDBP)
- Albumin
- Parathyroid hormone (PTH)
- Calcium
Key Findings
The analysis revealed that participants with higher body weight generally had lower levels of several vitamin D–related markers, including total, free, and bioavailable vitamin D, as well as calcium. They also had higher levels of parathyroid hormone, which can increase when vitamin D levels are insufficient.
Among participants who took vitamin D supplements, blood vitamin D levels rose over the two-year period. However, the increase was significantly smaller in individuals with higher body weight. Supplementation did not substantially affect other markers such as albumin, PTH, or calcium.
These findings indicate that body weight may influence how effectively the body absorbs or utilizes vitamin D supplements. This could explain why the original VITAL trial observed greater benefits among people with normal weight compared with those who were heavier.
The results also suggest that healthcare providers may need to consider body weight when recommending vitamin D supplementation strategies.
In simple terms, the study highlights that body weight matters when it comes to vitamin D supplementation. Individuals with higher body weight may not experience the same increase in vitamin D levels from standard supplement doses.
Further research is needed, but these findings represent an important step toward more personalized approaches to vitamin D use and overall health.
The research was published in JAMA Network Open.
