Low Vitamin D Levels Linked to Prediabetes and Prehypertension

A recently published study showed that adults with low vitamin D levels had more than double the risk of prehypertension and prediabetes than adults with higher vitamin D levels.

Prediabetes and prehypertension have been associated with low vitamin D levels. In a recent issue of the journal Diabetes Care, scientists report a correlation between reduced vitamin D levels and prediabetes and prehypertension in adults. Both prediabetes and prehypertension are estimated to exist in at least one-fourth of disease-free adults. 

Researchers analyzed data from 898 men and 813 women who participated in the National Health and Nutrition Examination Survey (NHANES), 2001-2006. Blood pressure measurements were obtained during examinations conducted upon enrollment, and blood samples were evaluated for glucose, serum 25-hydroxyvitamin D and other factors.


Prediabetes was defined as having a fasting serum glucose of between 100 and 125 milligrams per deciliter, and prehypertension was defined as systolic blood pressure of 120 to 139 mmHg and/or diastolic blood pressure between 80 and 89 mmHg. Prediabetes was 33 percent higher among those with vitamin D levels of 76.3 nmol/l (30.5 ng/ml) or less compared to those with higher levels. Prehypertension was evident in 61 percent of those with the lower vitamin D levels. Participants with undiagnosed diabetes and untreated hypertension had even lower vitamin D levels on average. Serum vitamin D levels tended to decline with increasing age and body mass.

When the risk of having both conditions was considered, those with low vitamin D levels had 2.4 times the risk of that experienced by subjects with higher vitamin D levels.  

It is reasonable that among those with prediabetes or prehypertension, vitamin D supplementation resulting in increased serum vitamin D levels may help reverse subtle changes in fasting serum glucose and resting blood pressure that may lead to more advanced disease states. 

Alok K. Gupta, MD, Meghan M. Brashear, MPH and William D. Johnson, PHD. Prediabetes and Prehypertension in Healthy Adults Are Associated With Low Vitamin D Levels. Diabetes Care March 2011 vol. 34 no. 3 658-660.

Higher Level of Vitamin D Necessary

Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis. Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol.

Vitamin D is essential for promoting calcium absorption in the gut and maintaining adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and prevent hypocalcemic tetany. It is also needed for bone growth and bone remodeling by osteoblasts and osteoclast. Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults. Together with calcium, vitamin D also helps protect older adults from osteoporosis.

Vitamin D has other roles in human health, including modulation of neuromuscular and immune function and reduction of inflammation. Many genes encoding proteins that regulate cell proliferation, differentiation, and apoptosis are modulated in part by vitamin D. Many laboratory-cultured human cells have vitamin D receptors and some convert 25(OH)D to 1,25(OH)2D. It remains to be determined whether cells with vitamin D receptors in the intact human carry out this conversion.

Vitamin D deficiency is now recognized as a worldwide problem. Poor dietary intake and lack of moderate sun exposure have resulted in widespread vitamin D deficiencies throughout much of the world. Additionally, very few foods contain vitamin D naturally, and foods fortified with vitamin D are typically inadequate to satisfy adult vitamin D requirements.

Numerous recent scientific research papers and our own in-house clinical research suggests that higher vitamin D levels - much higher than previously thought - are needed for most people to attain optimal blood levels of vitamin D. USANA's recent change to the Mega AO formulation is a reflection of this recent research and an ongoing commitment to provide USANA customers with the most effective, scientifically valid, and up-to-date products possible.

Pregnancy Complications may be Related to Low Vitamin D Levels

Early-onset severe preeclampsia occurs in roughly 2 to 3 percent of pregnancies, and it contributes to about 15 percent of preterm births in the U.S. each year. New research shows that pregnant women with low vitamin D levels are at higher risk for this condition.

Studies have linked low vitamin D levels to an increased risk of many diseases, including type 1 diabetes, asthma, heart disease, certain cancers and depression. A new study has found that women who develop a severe form of pregnancy-related high blood pressure tend to have lower blood levels of vitamin D than healthy pregnant women.

Preeclampsia is a syndrome marked by a sudden increase in blood pressure and kidney dysfunction. Early-onset severe preeclampsia is a particularly serious form that arises before the 34th week of pregnancy.

In a recent study, researchers compared vitamin D levels in 50 women with early severe preeclampsia to vitamin D levels of 100 healthy pregnant women. The average vitamin D level in the preeclampsia group was 18 ng/mL compared to an average of 32 ng/mL in the healthy group. A 10 ng/mL increase in vitamin D levels was linked to a 63 percent reduction in risk of the complication.

Since total Vitamin D levels in the blood seem to be linked to an increase in this pregnancy complication, further study is needed to understand the impact of vitamin D deficiency on pregnancy outcomes.

Robinson CJ, Alanis MC, Wagner CL, et al. Plasma 25-hydroxyvitamin D levels in early-onset severe preeclampsia. 2010. Am J Obstet Gynecol 203:ePub ahead of print.

Vitamin D3 May Reduce the Risk of Colorectal Cancer

According to a new research study published in the American Journal of Epidemiology, increased blood levels of vitamin D may reduce the risk of colorectal cancer by up to 40 percent.

In a new study, researchers examined the association between circulating 25-hydroxyvitamin D(3), the best indicator of total vitamin D exposure, and incident, sporadic colorectal cancer risk. Data was obtained from a pooled analysis of three colonoscopy-based case-control studies conducted in Minnesota, North Carolina, and South Carolina between 1991 and 2002. In total, 616 people individuals with colorectal cancer were compared to 770 polyp-free control subjects.

Analysis showed that higher circulating vitamin D3 concentrations were associated with a decrease in colorectal cancer risk of 40%. In participants that were also using NSAIDs (anti-inflammatory medications), the potential risk reduction of higher vitamin D levels increased to 66%.

These findings support the idea that higher vitamin D levels may reduce the risk of colorectal cancer, especially when combined with anti-inflammatory agents. The human body manufactures vitamin D upon exposure to sunshine, but in some northern regions sunlight levels during the winter are inadequate for synthesizing vitamin D. Therefore, dietary supplements and fortified foods are generally an efficient way to boost circulating levels of vitamin D.

Fedirko RM, et al. Blood 25-Hydroxyvitamin D3 Concentrations and Incident Sporadic Colorectal Adenoma Risk: A Pooled Case-Control Study V. 2010. American Journal of Epidemiology

Vitamin D Levels Linked to Healthy Lung Function

Vitamin D may play a role in keeping our lungs healthy, with higher concentrations of vitamin D resulting in positive effects on lung function and health.

Low concentrations of vitamin D have been associated with a number of diseases. Research out of New Zealand indicates that serum concentrations of vitamin D may also influence pulmonary (lung) function.

In a study published in the journal Chest, original analysis was performed on data from 14,091 adult subjects (all participants in the U.S. National Health and Nutrition Examination Survey conducted between 1988 and 1994). Lung function was measured in two ways: by the volume of air that could be forcibly blown out in total (forced vital capacity, or FVC), and the volume blown out in one second (forced expiratory volume, or FEV1). Vitamin D was measured using serum 25-hydroxyvitamin D, a standard indicator of vitamin D levels.

After adjusting for age, gender, height, body mass index, ethnicity, and smoking history, the difference in lung function between the groups with the highest and lowest vitamin D intake was substantial in both the FVC and FEV1 tests (172 mL and 126 mL respectively, p <0.0001). Further adjustment for physical activity, vitamin D supplementation, milk intake, and serum antioxidant status revealed additional strong correlation between the highest and lowest intake groups (142 mL (FVC) and 106 mL (FEV1), p < 0.0001).

Although further studies are necessary to determine whether vitamin D supplementation may be beneficial in cases of chronic respiratory disease, this study has shown that vitamin D may have a positive influence on pulmonary health, with greater levels of vitamin D associated with more positive benefits.

Chest 2005 Dec;128(6):3792-8

Vitamin D Deficiency Associated with Cardiovascular Disease Prevalence

In a large sample of U.S. adults, new research indicates that vitamin D deficiency is associated with an increased prevalence of cardiovascular disease.

Inadequate vitamin D levels are known to be associated with certain cardiovascular disease (CVD) risk factors, but until recently the association between vitamin D levels and the prevalence of CVD had not been comprehensively examined in the general U.S. population.

In a recent study published in Atherosclerosis, researchers examined data from the Third National Health and Nutrition Examination Survey (NHANES), a population-based sample of more than 16,000 U.S. adults.

In the total survey population, 1,308 subjects had some form of CVD. Using the standard definition of vitamin D deficiency (a serum level below 20 ng/mL), participants with CVD had a higher incidence of vitamin D deficiency (29.3%) than those without CVD (21.4%). After adjusting for age, gender, race/ethnicity, season of measurement, physical activity, body mass index, smoking status, hypertension, diabetes, elevated cholesterol, chronic kidney disease, and vitamin D use, the researchers showed that subjects deficient in vitamin D had a 20% increased risk of CVD.

The results of this analysis indicate a significant relationship between vitamin D deficiency and CVD prevalence in a large, highly representative sample of the U.S. adult population.

Atherosclerosis 2009 Jul; 205(1):255-60.

Low Vitamin D Levels May Increase Heart Disease Risk

A study published in the journal Circulation showed that low levels of vitamin D may increase the risk of cardiovascular events, including heart attack, heart failure, or stroke. Individuals with both hypertension and low vitamin D levels had nearly double the risk of cardiovascular problems.

Interest in vitamin D has been increasing in recent months with a growing number of studies linking the vitamin to protection against osteoporosis and certain cancers. There is also evidence that a higher intake of vitamin D may be helpful with regard to high blood pressure, fibromyalgia, diabetes mellitus, multiple sclerosis, and rheumatoid arthritis

In a population-based study, researchers used data from 1739 participants in the Framingham Offspring Study to study the relationship between vitamin D levels and cardiovascular health risk. Although vitamin D levels above 30 ng/mL are considered optimal for bone metabolism, only 10 percent of the participants had levels in this range. In fact, 28 percent had blood levels lower than 15 ng/mL. Participants with levels below 15 ng/mL had a 62 percent greater chance to develop cardiovascular events than those with higher levels. People with low vitamin D levels and high blood pressure (> 140/90 mmHg), were found to have double the risk of cardiovascular problems compared to people with normal blood pressure and vitamin D levels.

Vitamin D is produced in the skin on exposure to UVB radiation (sunlight) and obtained in the diet from foods like oily fish, egg yolk, and liver. Recent studies have shown, however, that sunshine levels in some northern countries are so weak during the winter months that the human body makes little to no vitamin D, leading to widespread deficiencies. In addition, increased skin pigmentation also reduces the effect of UVB radiation, meaning darker skinned people are at greater risk.

The results from this study raise the possibility that treating vitamin D deficiency, by supplementation and/or lifestyle measures, could reduce the risk of cardiovascular events.

Wang TJ, et al. Vitamin D Deficiency and Risk of Cardiovascular Disease. 2008. Circulation 117(4):503-11

Serum 25-Hydroxyvitamin D Concentrations

Serum concentration of 25(OH)D is the best indicator of vitamin D status. It reflects vitamin D produced cutaneously and that obtained from food and supplements and has a fairly long circulating half-life of 15 days. However, serum 25(OH)D levels do not indicate the amount of vitamin D stored in other body tissues. Circulating 1,25(OH)₂D is generally not a good indicator of vitamin D status because it has a short half-life of 15 hours and serum concentrations are closely regulated by parathyroid hormone, calcium, and phosphate. Levels of 1,25(OH)₂D do not typically decrease until vitamin D deficiency is severe.

There is considerable discussion of the serum concentrations of 25(OH)D associated with deficiency (e.g., rickets), adequacy for bone health, and optimal overall health (Table 1). A concentration of <15 nanograms per milliliter (ng/mL) (or <37.5 nanomoles per liter [nmol/L]) is generally considered inadequate; concentrations >15 ng/ml (>37.5 nmol/L) are recommended. Higher levels are proposed by some (>30 ng/ml or >75 nmol/L) as desirable for overall health and disease prevention, but insufficient data are available to support them. Serum concentrations of 25(OH)D consistently >200 ng/ml (>500 nmol/L) are potentially toxic.

Table 1: Serum 25-Hydroxyvitamin D [25(OH)D] Concentrations and Health*

ng/mL**	nmol/L**	Health status
<10-11	<25-27.5	Associated with vitamin D deficiency, leading to rickets in infants and children and osteomalacia in adults
<10-15	<25-37.5	Generally considered inadequate for bone and overall health in healthy individuals
≥15	≥37.5	Generally considered adequate for bone and overall health in healthy individuals
Consistently >200	Consistently >500	Considered potentially toxic, leading to hypercalcemia and hyperphosphatemia, although human data are limited. In an animal model, concentrations ≤400 ng/mL (≤1,000 nmol/L) demonstrated no toxicity.

* Serum concentrations of 25(OH)D are reported in both nanograms per milliliter (ng/mL) and nanomoles per liter (nmol/L).
** 1 ng/mL = 2.5 nmol/L

An additional complication in assessing vitamin D status is in the actual measurement of serum concentrations of 25(OH)D. Considerable variability exists among the various assays available and among laboratories that conduct the analyses. This means that compared to the actual concentration of 25(OH)D in a sample of blood serum, a falsely low or falsely high value may be obtained depending on the assay or laboratory used. A standard reference material for 25(OH)D became available in July 2009 that will now permit standardization of values across laboratories.

What Are Possible Results of a Vitamin D Deficiency?

What is Cholecalciferol (Vitamin D3)? Vitamin D is a fat-soluble nutrient essential for bone growth and general health. It is acquired through diet and exposure to sunlight. Light-induced synthesis occurs in the skin when ultraviolet light reacts with a form of cholesterol, converting it to vitamin D. This molecule is then altered by the liver and kidneys to form the physiologically active vitamin.

Several compounds have vitamin D or potential vitamin D activity. The most important forms are vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol). The latter is the form normally found in humans, and it is also the form used in most nutritional supplements and clinical research.

A unique property of vitamin D is that it functions very much like a hormone. Its target tissues include the kidneys, intestines, and bones, where it helps regulate calcium and phosphorus homeostasis. Its specific activity in the intestines involves stimulating the synthesis of active transport proteins that mediate absorption of calcium. In bone tissue, vitamin D plays a role in regulating calcium deposition (bone mineralization) and mobilization. A role for vitamin D in immune system modulation is now under investigation.

Vitamin D is an essential component of bone health in both children and adults. Without vitamin D, bones do not calcify properly, leading to the condition known as "rickets." Vitamin D also plays an important role in tooth development. It is necessary for proper tooth eruption, growth, and strength. Through its role in regulating calcium and phosphorus metabolism, vitamin D plays a continuing role in maintaining a stable nervous system, normal heart activity, and normal blood clotting.

Exposure to the sun is the most important source of vitamin D for most humans. Limited amounts of vitamin D are available from food, including fortified milk, certain types of fish, and fortified breakfast cereals. Vitamin D deficiency is most directly related to poor bone health, including rickets and osteomalacia. However, vitamin D deficiency is also associated with an increased risk of other disorders, including certain cancers, type I diabetes, multiple sclerosis, tuberculosis, rheumatoid arthritis, muscle weakness and pain, depression, hypertension, and pregnancy complications. While many of these associations are actively being researched to determine the extent of their connection with vitamin D deficiency, we currently know that vitamin D unquestionably exerts a significant influence on many body systems.

Calcium and Vitamin D Enhance Heart Health Benefits of Weight Loss

Weight Loss & Heart Health

Weight loss and reduced waist circumference are related to an improvement in heart health and factors related to metabolic syndrome. According to recent research, supplementing with calcium and vitamin D during weight loss enhances heart health benefits in women with typically low calcium intakes.

Recent research has shown that overweight individuals with low calcium and dairy consumption are at increased risk of developing metabolic syndrome. These findings suggest that adequate calcium intake could create a healthier metabolic profile.

Canadian researchers investigated this issue by testing cardiovascular benefits of long-term calcium supplementation in women with low calcium intake. Healthy, overweight or obese women with a daily calcium intake of less than 800 mg/day were randomly assigned to one of two groups: a group consuming two tablets/day of a calcium + vitamin D supplement (600 mg elemental calcium and 200 IU vitamin D/tablet), or a group consuming placebo. Both groups completed a 15-week reduced calorie weight-loss program.

Significant decreases in LDL cholesterol levels, as well as the ratios of total to LDL and LDL to HDL were seen the calcium + vitamin D group. These changes were independent of changes due to fat loss and reduced waist circumference. A tendency for more beneficial changes in HDL cholesterol, triglycerides, and total cholesterol was also observed in the calcium+D group.

This was the first study to show that calcium and vitamin D enhance the beneficial effects of weight loss on cardiovascular risk factors in overweight women with typically low calcium intakes.

Major GC, et al. Supplementation with calcium + vitamin D enhances the beneficial effect of weight loss on plasma lipid and lipoprotein concentrations. 2007. American Journal of Clinical Nutrition 85(1): 54-9.