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Vitamin D supplements over the winter months can promote health, lessen the effects of COVID-19

Vitamin DPeople need vitamin D to carry out essential biologic functions because it regulates thousands of genes, including those that modulate the immune system, which guards against various types of infection. However, it is estimated that more than 50% of the world’s population have insufficient levels of vitamin D, especially during the winter months due to limited exposure to sunlight – the source of vitamin D production.

According to Joan Lappe, PhD, associate dean for research and a professor in the College of Nursing at Creighton University, there is growing scientific evidence to show that vitamin D can help prevent diseases, including COVID-19.

“Almost all body cells have vitamin D receptors, which indicates they need vitamin D to carry out their work. When there is inadequate vitamin D, body functions can become compromised. A long-term deficiency is likely to negatively affect an individual’s health in some way,” Lappe said.

The cellular function of vitamin D has been well studied and shows mechanisms for promoting health, including recent research that indicates higher vitamin D blood levels are associated with lower rates of COVID-19 infection and lower risk of contracting severe cases that could lead to hospitalization or death. Evidence also suggests that assuring adequate vitamin D levels can be an effective addition to COVID-19 treatment.

Randomized trials have shown that vitamin D supplementation decreases the incidence of osteoporosis, stress fractures and the common cold. Research also suggests that adequate vitamin D levels decrease incidence of cancer, type 2 diabetes, depression and falls.

“Vitamin D is made through skin exposure to sunlight. In our modern world, many people don’t obtain adequate vitamin D from sunlight. When they do have sunlight exposure, they often wear sunscreen which blocks most vitamin D production. In addition, as people age, the ability of their skin to convert vitamin D decreases, which makes the elderly even more vulnerable to vitamin D deficiency,” Lappe said.

Others who could be vulnerable to low vitamin D levels include homebound individuals; those with conditions that limit fat absorption such as liver disease, cystic fibrosis, celiac disease, Crohn’s disease and ulcerative colitis; people who are obese or have undergone gastric bypass surgery; and those with darker skin because of their higher levels of melatonin, Lappe added.

Lappe said vitamin D is not naturally abundant in most foods, but certain types of fish are good sources. Oily fish, such as salmon, mackerel and herring are sources of vitamin D. Ocean-raised fish, however, which feed on vitamin D-rich plankton, have much higher levels than farm-raised varieties. Also, the U.S. fortifies milk with about 100 International Units (IU) of vitamin D per cup, while fortifying other foods, such as yogurt, juices, cereals and soy, with varying amounts, Lappe said.

Vitamin D is also available as a dietary supplement, which Lappe said is safe, inexpensive and widely available. Stand-alone vitamin D supplements can be found in various doses and many multiple-vitamin preparations and calcium supplement pills also contain vitamin D.According to the Dietary Reference Intake (DRI) guidelines, the current recommended intake levels of vitamin D are 400 international units (IU) for children up to age 12 months, 600 IU for ages 1 to 70 years and 800 IU for people over 70 years. However, Lappe said it is widely accepted that these recommendations are too low to maintain adequate blood levels of vitamin D in all adults.

The DRI indicates that 4,000 IU per day of vitamin D is the Tolerable Upper Intake Level, which is the highest level of nutrient intake that is likely to pose no risk of adverse health effects to almost all individuals in the general population. Lappe said the best approach to determining the proper amount of supplementation is to have the blood levels of serum 25-hydroxyvitamin D (25OHD) measured and then base the dose of supplementation on those levels. There is no benefit to taking more vitamin D supplementation than is needed to maintain healthy blood levels.

Other benefits of vitamin D include facilitation of calcium absorption in the stomach, and promotion of bone growth and maintenance.


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