A recent study has proven that Vitamin D is necessary for good health and taking the supplement in the proper dosage can help offset early mortality. The study employed meta-analysis methodology to assess the level of vitamin D that was associated with a cut-off threshold for higher all-cause mortality rates.
A meta-analysis is a type of study in which previously published data are reanalyzed together. Since individual studies report data usually from studies with smaller sample sizes, doing a meta-analysis allows all the data from all the subjects in chosen studies to be analyzed all together. This increases the statistical power of the study and therefore a meta-analysis result is considered to be possibly more valid.
The recently reported meta-analysis study was published in the American Journal of Public Health. The lead author was Dr. Cedric Garland. Dr. Garland is in the Department of Family and Preventive Medicine at the University of California San Diego at La Jolla.
Thirty-two previously published studies were included in the meta-analysis and the dates of these articles ranged from January 1, 1966 to January 15, 2013. The pooled data from these studies included serum (blood) concentrations of vitamin D (i.e., serum 25[OH]D) and all-cause mortality rates, meaning death from all types of causes. Researchers calculated a “hazard ratio” comparing the lowest concentration of vitamin D (0-9 nanograms per milliliter) to the highest concentration of vitamin D (>30 nanograms per milliliter). The results from the study suggested that vitamin D concentrations less than or equal to 30 nanograms per milliliter were associated with a higher rate of all-cause mortality.
The interpretation of this result is that people who have serum concentrations of vitamin D less than 30 nanograms per milliliter have a greater likelihood of earlier death, at least statistically. Accordingly, those who have higher serum concentrations than the 30 nanograms per milliliter cut-off have less likelihood of earlier death.
A result from the study that some might find alarming is people who had less than 10 nanograms per milliliter of serum vitamin D had a much greater chance of early mortality. They were twice as likely to die in a span of 9 years than those who had greater than 30 nanograms per milliliter of vitamin D.
The study included data from 566,583 participants and subjects from 14 countries. The study population average age was 55 years at the time of participation in a research report that was included in the meta-analysis.
The authors of the meta-analysis study said that their results were in general agreement with a previously published report of the National Academy of Sciences except that the cut-off point varied. The study recently published in the American Journal of Public Health reported a cut-off value of 30 nanograms per microliter but the previously reported study reported a cut-off value of 20 nanograms per microliter.
The best amount of vitamin D was suggested to be at least 30 nanograms per milliliter by this recent meta-analysis study. It should be kept in mind, however, that this was a statistical study. It provided information that can be used in the assessment of health, lifespan expectations and levels of vitamin D. Other types of studies are needed, however, that actually look at vitamin D levels in individuals over the course of their lifetime to see how they relate to the development of health problems or maintenance of health.
By Margaret Lutze