Vitamin D from dietary intake or sun exposure requires two activation steps in the body. The first activation occurs in the liver, while the second activation occurs in the kidneys, allowing for regulation of calcium metabolism. However, vitamin D receptors are present throughout the body, in tissue such as the skin, cartilage, heart, prostate, bones and intestines. Thus, the second activation step also takes place in local tissues. Recent discoveries have highlighted the important modulatory effects of vitamin D on various cells of the immune system.

Enhances and regulates immune function*

Studies show that vitamin D has important immunomodulatory effects. It is known that various cells of the immune system, such as T lymphocytes and antigen presenting cells, express the vitamin D receptor on their surface when activated. Recently, it has been found that treatment of these immune cells with vitamin D influences their expression of cytokines, w
ich are chemical messengers of the immune system. The immune modulating effects of vitamin D extend to monocytes and dendritic cells of the immune system as well. Dendritic cells are important antigen-processing cells of the immune system that function to initiate the immune response. By altering the cytokine expression of dendritic cells, vitamin D may support a balanced immune response and keep the immune system in a normal healthy state of vigilance.

Supports optimal cardiovascular function*

Research has uncovered the role vitamin D plays in supporting cardiac function. Heart myocytes (cells) express the vitamin D receptor, as do smooth muscle cells of blood vessels. The benefits of vitamin D on the heart are potentially far-reaching. Studies on mice heart cells have shown that vitamin D administration impacts their growth and proliferation. It has also been shown that vitamin D has a modulatory effect on heart rhythm. In mouse heart cells, knocking out the effects of the vitamin D receptors led to an increased rate of contraction and relaxation. Further studies in mice have led researchers to conclude that vitamin D supports the overall structure and function of the heart in terms of shape, size, and performance.

Studies in humans have confirmed the importance of vitamin D for heart function. In a study consisting of 1,739 participants from the Framingham Offspring Study, those individuals with the highest levels of vitamin D had superior cardiac function in relation to those with low vitamin D levels. These results make sense when taken in context of the overall effects of low vitamin D. Restoration of optimal vitamin D status supports a healthy, balanced immune response, and may thus restore the optimal health of the heart and cardiovascular system.

Furthermore, recent research highlights the profound benefits of vitamin D sufficiency in the realm of markers of cardiovascular wellness. Studies have previously shown that vitamin D supplementation has no effect on weight loss. However a recent study conducted in 200 healthy overweight individuals has shown that vitamin D supplementation can enhance the cardiovascular benefits associated with weight loss. The individuals participating in a 12-month weight reduction program were divided into two groups – one received placebo while the other group received supplemental vitamin D on a daily basis. At the end of the study, it was found that neither placebo nor vitamin D had a measurable effect on weight loss, as both groups lost similar amounts of weight. However, significantly enhanced cardiovascular support with vitamin D supplementation was indicated by favorable cardiovascular markers and blood lipid markers in the vitamin D group.

A further way in which vitamin D may influence the health of the cardiovascular system is through its potential to help maintain blood pressure levels already in the normal range. While the mechanism of vitamin D's effect on blood pressure regulation is unclear, it is known that vitamin D regulates calcium balance, supports endothelial function, activates gene transcription, and influences the sodium-potassium balance and aldosterone system in the kidneys. It is likely that vitamin D exerts its influence on blood pressure maintenance in one or more of these ways. A study was conducted to assess the effects of vitamin D status on blood pressure. In this study, data from the Third US National Health and Nutrition Examination Survey was used to determine the association of blood pressure levels with vitamin D status in healthy individuals. The results of this study, which included data from 12,644 people, showed that those individuals with the highest vitamin D status had an increased ability to maintain their blood pressure levels in the normal range. By supporting blood pressure levels within a range that is already normal, vitamin D promotes the health and wellness of the cardiovascular system.

Supports healthy bone density and structure*

The role of vitamin D for bone health (alongside that of calcium) has been well characterized in published literature. Vitamin D is obviously required for optimal calcium absorption, yet studies report many women with low levels of vitamin D. One such study found that out of a total of 2,606 postmenopausal women assessed, more than 64% had levels of vitamin D of less than 30 ng/mL (measured as serum levels of 25(OH)D, a common blood measure of vitamin D sufficiency). These authors state that, according to a recent review article, the optimal vitamin D levels as measured by 25(OH)D are between 50 and 80 ng/mL. Thus, levels near 30 ng/mL are significantly below those considered optimal.

An interesting study was performed recently in Finland in which 212 adolescent females were divided into three groups – a placebo group receiving no vitamin D, a low-dose vitamin D group (5mcg/200 IU per day) and a higher dose vitamin D group (10mcg/400 IU per day). The study aimed to measure the effects of vitamin D intake on bone mineral density in these young healthy females who also had adequate calcium status. At the end of the one year study, both vitamin D groups had significantly enhanced bone density measured at the femur bone, whereas the 10mcg (400 IU) group also had significantly higher mineral density at the lumbar spine. These findings indicate the importance of vitamin D in bone structure and formation and also indicate the role of vitamin D in bone health independent of calcium intake.

Promotes healthy aging by enhancing cellular function*

Given its role as a promoter of gene expression, vitamin D affects numerous systems throughout the body. Research unmistakably shows that vitamin D is also a regulator of cellular health and wellness. Aged, unhealthy cells tend to lose their ability to perform their original intended function due to the cumulative effects of oxidative damage. Vitamin D, acting as a pro-hormone, promotes the ability of cells to maintain their normal life cycle of birth, functional performance, and death.10 By promoting the normal cell cycle, vitamin D ensures the progression of cells through their functionality and their healthy renewal.

SAFETY

Vitamin D toxicity is extremely rare. In order to reach toxic levels, most adults would have to consume 250mcg (10,000 IU) or more per day for many months or years. Vitamin D3 (cholecalciferol, the form found naturally in animals and humans) toxicity has rarely been reported in the literature. Most reports of vitamin D toxicity have been attributed to faulty production, labeling and dosing errors or to the use of vitamin D2 (ergocalciferol). When used in the amounts recommended, vitamin D3 is very safe.