The association of vitamin D with hepatitis B virus replication: Bystander rather than offender

Low vitamin D is frequent in hepatitis B virus (HBV)-infected patients and several studies show an inverse association of serum vitamin D level with HBV viral load. However, the causal relationship remains unclear.

HBV carriers receiving regular 6-month surveillance without current antiviral treatment or cirrhosis were invited to participate into this trial. The markers of HBV replication included serum HBV DNA and quantitative HBsAg (qHBsAg) levels. Those with undetectable HBV DNA or sufficient vitamin D levels, cancer or electrolyte imbalance were excluded. The eligible subjects were randomized to receive either vitamin D supplement 2000 IU per day for 2 months (vitamin D group) or none (control group).

A total of 196 HBV carriers (93 males and 103 females; mean age 51.9 ± 10.0 years) were screened. Of them, 28 patients had undetectable serum HBV DNA levels, which is defined as spontaneous viral clearance. The vitamin D levels were not different between patients with detectable HBV DNA and those without (p = 0.18). After exclusion, 149 patients were randomized to two groups: 75 in vitamin D group and 74 in control group. After 2 months vitamin D supplement, the serum vitamin D levels were significantly higher in the vitamin D group than the control group (p < 0.001). However, the serum qHBsAg and HBV DNA levels were comparable between these two groups.

There is no causal relationship between vitamin D and HBV replication. The role of liver reserve on serum vitamin D levels in patients with chronic HBV infection needs further investigation.