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Getting enough vitamin D is crucial for our health. Although our bodies produce vitamin D with exposure to the sun, reports indicate that at least 25% of the U.S. population is vitamin D deficient. Photo: Getty Images.<\/p>\n \tGetting enough vitamin D is crucial for our health. Although our bodies produce vitamin D with exposure to the sun, reports indicate that at least 25% of the U.S. population is vitamin D deficient. Photo: Getty Images.<\/p>\n
Some supplements you can take or leave<\/a>. Vitamin D is one you should consider taking.<\/p>\n Unlike, say, vitamin C, it\u2019s hard to get enough of through diet alone. And while our bodies can make vitamin D with exposure to the sun\u2019s ultraviolet-B light (hence the \u201csunshine vitamin\u201d nickname), our indoor lifestyles and our wise use of sunscreen conspire to limit our personal vitamin D production. So, by at least one measure<\/a>, about 25% of the U.S. population is vitamin D deficient, and another 41% don\u2019t get quite enough. Older people, women, African Americans, and those ages 20-29 are particularly prone to vitamin D deficiency.<\/p>\n At the same time, the evolving science around vitamin D continues to describe the ways getting enough vitamin D helps us stay healthy. What\u2019s increasingly clear is that getting too little vitamin D in childhood \u2013 and perhaps well beyond \u2013 may boost risk of autoimmune diseases such as multiple sclerosis and even cardiovascular disease in adulthood.<\/p>\n Vitamin D may limit multiple sclerosis damage<\/p>\n Vitamin D is best known for preventing rickets<\/a>, the childhood bone disorder. That connection led to vitamin D fortified milk and other foods. But more recently, vitamin D\u2019s broader impact on the immune system has been a research focus.<\/p>\n One example is a recent study<\/a> of patients who had had a single episode of what, if repeated, becomes multiple sclerosis<\/a> (MS), an autoimmune condition in which the body attacks the protective sheaths surrounding nerve cells. It found that 60.3% of patients given vitamin D supplements for two years had brain and spinal-cord lesions \u2013 less than the 74.1% of patients with lesions who had been given a placebo rather than vitamin D.<\/p>\n Dr. Enrique Alvarez<\/a>, a University of Colorado School of Medicine Neurologist who specializes in MS patients at UCHealth Neurosciences Center \u2013 Anschutz Medical Campus<\/a>, said the study was well designed and that it \u201chighlights the effect that vitamin D may be helpful.\u201d But he added that there was a high degree of disease in both the vitamin D and placebo groups, and that today\u2019s MS drugs have a bigger impact.<\/p>\n \u201cSo, vitamin D may reduce disease activity, but I would consider it an add-on to our current therapies,\u201d Alvarez said.<\/p>\n The study corroborated what\u2019s known as the long-recognized \u201clatitude effect<\/a>\u201d in MS prevalence, Alvarez noted. In northern and southern latitudes where the sun shines less, there\u2019s more MS in a given population.<\/p>\n Vitamin D is most important in childhood<\/p>\n Vitamin D\u2019s impact on immune-system development may be why<\/a>. In particular, vitamin D is central to the health of the thymus<\/a>, an immune system organ that\u2019s central to teaching T-cells<\/a> what\u2019s friend or foe early in life. (The thymus actually shrinks after puberty). A recent study<\/a> of mice genetically engineered to produce no vitamin D found that their thymuses aged prematurely. That led their immune systems to be more likely to attack the body\u2019s own tissues, which is what happens in autoimmune diseases.<\/p>\n The link between vitamin D deficiency and MS is also why Alvarez and colleagues recommend vitamin D supplements when patients ask what they can do to lower their kids\u2019 risk of getting the disease. (MS is not considered<\/a> a hereditary disease, but the risk of MS are higher if a parent or sibling has it).<\/p>\n Low vitamin D levels in childhood may also have cardiovascular impacts, another recent study found. The Finnish study<\/a> had stored blood samples taken from 3,516 kids ages 5 to 15 years old in 1980 and, adjusting for factors such as diet, physical activity, and socioeconomic status, looked at their risk of early-onset atherosclerotic cardiovascular disease in 2018. They found those with low childhood vitamin D levels to have had between 1.5 times and twice the likelihood of cardiovascular disease by the time they were in their mid-fifties.<\/p>\n Addressing vitamin D deficiency is key<\/p>\n Not all research has pointed to vitamin D as a potential benefactor. Dr. Adit Ginde<\/a>, a University of Colorado School of Medicine Emergency Medicine physician and the school\u2019s vice chair for research, was part of a team that studied<\/a> vitamin D\u2019s potential to reduce acute respiratory infections. They found a slight benefit, but it didn\u2019t reach the threshold of statistical significance. Similarly, a major trial<\/a> considering whether vitamin D brought lower incidence of cancer or cardiovascular events found no benefit.<\/p>\n Those results don\u2019t necessarily contradict those of the Finnish study, though, because the vitamin D was given to adults rather than children whose thymuses are busy training T cells. So there\u2019s still much work to be done, Ginde says. For one thing, the Finnish study was observational and would need to be confirmed with clinical trials involving vitamin D supplementation \u2013 no easy task given the decades between cause and effect.<\/p>\n \u201cThere have been a number of studies that showed an association between vitamin D deficiency, but very few clinical trials that showed that vitamin D supplementation can improve health outcomes,\u201d Ginde said.<\/p>\n Boosting the immune system: How much vitamin D should you take?<\/p>\n The MS study stands out as one of the few that have demonstrated such a link, it\u2019s compelling, he added. It backs a growing sense among researchers that vitamin D\u2019s biggest impacts may have to do with immune function, be it in tamping down autoimmune and inflammatory diseases or preventing infections.<\/p>\n \u201cThere are still many unanswered questions that are being tackled,\u201d Ginde said.<\/p>\n