Vitamin D and Cardiovascular Disease: Jury Is Still Out

JULY 06, 2017
Jeannette Y. Wick, RPh, MBA, FASCP
Fat-soluble vitamin D seems to be the vitamin we talk about most these days. In particular, researchers, clinicians, and pharmacists all have an opinion about whether vitamin D supplementation is necessary or wise.

Researchers from Emory University School of Medicine in Atlanta have published a paper in the Journal of the American College of Cardiology. In it, they discuss the controversy surrounding vitamin D and its potential associations with cardiovascular disease (CVD).

The authors indicated that serum levels of vitamin 25-0H D below 20 ng/mL are inadequate to maintain bone health, and are therefore diagnostic of deficiency. However, they noted that researchers and clinicians have not yet reached a consensus about the optimal level to maintain overall health. Some experts indicate that levels between 20 ng/mL and 29 ng/mL are indicative of insufficiency.

Hepatic mitochondria and their associated microsomal enzymes metabolize vitamin D, whether the patient obtains it from food sources or supplements. When patients consume too much vitamin D2 or vitamin D3, this process is completely unregulated and patients' vitamin D levels will rise proportionally to their intake. On the other hand, cutaneous synthesis from sun exposure allows patients levels to reach a preset point, and after that, additional sun exposure will not increase vitamin D levels.

In terms of cardiovascular disease, there seems to be some association between vitamin D deficiency and hypertension, insulin resistance, type 2 diabetes, and dyslipidemia in patients who are vitamin D-deficient. Vitamin D deficiency is also considered an independent risk factor for CVD development.

According to the study, up to 50% of all adults worldwide are vitamin D-deficient or vitamin D-insufficient. The authors reviewed potential mechanisms by which vitamin D might influence development of CVD and evidence supporting vitamin D deficiency's relationship to comorbid conditions. They proposed that CVD may cause low vitamin D levels rather than being caused by low levels.

Sometime in 2018, the VITamin D and Omega-three triAL (VITAL) will conclude its first part and provide some evidence to indicate whether vitamin D supplementation at a level of 2000 IU/day with or without omega-3 fatty acids has specific CVD effects. This large study has enrolled about 25,000 healthy, middle-aged American adults. It has also been structured to gauge long-term effects. VITAL is expected to augment the wealth of information that we possess concerning vitamin D supplementation for bone health.

Additionally, the authors stressed that patients whose vitamin D levels are lower than 19 ng/mL should be treated with 50,000 IU/week of either vitamin D2 or D3 for 8 weeks followed by a maintenance dose between 1500 and 2000 IU daily.

They also remind readers that patients with end-stage renal and or hepatic diseases often develop hypocalcemia related to vitamin D activation impairment and need supplementation. Patients with secondary hyperparathyroidism or hypoparathyroidism also need vitamin D supplementation.

Healthy individuals will benefit by casual sunlight exposure (10 to 15 minutes every day) and including fatty fish or fish oils in their diets in addition to vitamin D-enhanced food products. Most diets contain an insufficient quantity of vitamin D2 or D3, which means that patients can benefit from vitamin D supplementation.

Reference
Al Mheid I, Quyyumi AA. Vitamin D and cardiovascular disease: controversy unresolved. J Am Coll Cardiol. 2017 Jul 4;70(1):89-100. doi: 10.1016/j.jacc.2017.05.031.
 
 
 

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