10 facts about vitamin D from research. Why it’s important to know your level.
GrassrootsHealth found an inverse association between vitamin D serum levels and all non-skin cancer incidence. The analysis included pooled data from two study cohorts of women aged 55 years and older. Those with vitamin D serum levels ≥ 40 ng/ml, had a 67% lower risk of cancer when compared with those <20 ng/ml.
This analysis found that women with vitamin D levels of 40-60 ng/ml have a 46% lower preterm birth rate than the general population (the findings were more robust in Hispanic and Black women). The analysis also showed a 59% lower risk for premature birth by pregnant women who had blood levels of vitamin D (25(OH)D) at or over 40 ng/ml by their third trimester than women who had levels below 20 ng/ml.
For this study on diabetes, the GrassrootsHealth data was compared to data from the National Health and Nutrition Examination Survey (NHANES). The GrassrootsHealth cohort has a median 25(OH)D level of 41 ng/ml vs. NHANES with a median of 22 ng/ml. When comparing the number of cases seen in each population group in the study period, the GrassrootsHealth cohort has a full 60% lower incidence rate of diabetes.
The recommended intake of vitamin D specified by the IOM is 600 IU/day through age 70 years, and 800 IU/day for older ages. Calculations by GrassrootsHealth scientists and other researchers have shown that these doses are only about one-tenth those needed to cut incidence of diseases related to vitamin D deficiency. The authors propose a new RDA with a value of approximately 7,000 IU/day from all sources.
In a prospective study of 844 female participants aged 60+ years, GrassrootsHealth examined the relationship between serum 25(OH)D and the incidence of breast cancer. Those with concentrations ≥50 ng/ml had an 80% lower risk of breast cancer than those with concentrations <50 ng/ml, adjusting for age and BMI. These findings suggest that 25(OH)D concentrations above 50 ng/ml may provide additional benefit in the prevention of breast cancer.
From 780 non-supplement taking, adult, D*action participants who completed a limited questionnaire on dietary intake along with a lifestyle questionnaire, some food sources were found to be associated with vitamin D serum levels: eggs, whole milk cottage cheese, red meat and total protein. 25(OH) D3 rose by about 1 ng/ml for each weekly serving of whole milk cottage cheese (3 oz) and each daily serving of one of the following: eggs (1 egg), red meat (3 oz) and total protein (3 oz).
Based on this analysis of data provided by D*action participants, non-food factors associated with vitamin D serum levels were indoor tanning use, sun exposure, body mass index (BMI), and percent of work performed outdoors.
The research team used data collected from 2,012 participants enrolled in GRH’s D*action study. Thirteen individuals reported having kidney stones during the study time; occurrences were confirmed by medical records or interview. The study found no statistically significant association between 25(OH)D serum levels and kidney stone risk. In fact, the researchers found a non-significant trend towards lower incidence of kidney stones for those with higher 25(OH)D serum levels.
In this re-analysis, the total basal input (food plus sun) was calculated to range from a low of 778 IU/d in patients with end-stage renal disease to a high of 2667 IU/d in healthy Caucasian adults. The authors conclude that: 1) all-source, basal vitamin D inputs are approximately an order of magnitude higher than can be explained by traditional food sources; 2) cutaneous input accounts for only 10–25% of un-supplemented input at the summer peak; and 3) the remainder must come from undocumented food sources, possibly in part as preformed 25(OH)D.
In an analysis of vitamin D serum levels and daily supplemental vitamin D intake amounts for 7,324 D*action participants, we found that while average serum level rises with increased intake, there is a wide range of individual serum levels at any given intake amount. For example, with a supplemental intake of 4000 IU/day, serum levels were observed from 20 ng/ml (50 nmol/L) to 120 ng/ml (300 nmol/L).