\u201cIt\u2019s not just a vitamin; it actually functions as a hormone \u2026 that not only keeps the bones strong and healthy but also has a role for muscle function,\u201d explained Dr. Kendall F. Moseley<\/a>, medical director of Johns Hopkins Metabolic Bone and Osteoporosis Center. Recent studies have also been looking into how vitamin D may help with \u201ccancer prevention, immune function, cardiovascular disease,\u201d and even dementia<\/a>.<\/p>\n While some people who don\u2019t get enough vitamin D may experience muscle weakness, bone pain and mood changes, others have no symptoms at all, according to Cleveland Clinic<\/a>. So it\u2019s important to be aware of factors that could put you more at risk of a deficiency.<\/p>\n We talked to doctors about unexpected reasons why you may be lacking vitamin D, how to know if you\u2019re deficient, and easy ways to boost your levels.<\/p>\n Reason 1: It\u2019s difficult to get enough vitamin D from your diet.<\/p>\n \u201cA healthy diet in general only generates about 100 to 400 international units (IU) of vitamin D per day, which by most standards is not sufficient,\u201d Moseley told HuffPost. \u201cAnd the types of foods that have vitamin D in them are not always \u2026 at the top of one\u2019s menu.\u201d<\/p>\n Foods high in vitamin D include fatty fish (such as tuna, salmon and mackerel), egg yolks, beef liver and cod liver oil. You can also get vitamin D from fortified foods like milk, yogurt and cereal. But it\u2019s still challenging to get enough from diet alone, she said. <\/p>\n Reason 2: Your skin isn\u2019t in direct sunlight that often \u2014 even during the summer.<\/p>\n When you\u2019re exposed to sunlight and the ultraviolet B rays (or UVB) hit your skin, it causes your body to produce vitamin D. But there are several barriers that can block these UVB rays from reaching your skin, Moseley explained.<\/p>\n During the winter or in cloudier climates, you will be exposed to less sunlight. Yet even in sunny places or during warmer months, most people are not getting a ton of vitamin D from the sun. The time of day you go outside is a major factor, Holick explained.<\/p>\n \u201cEven in the summertime \u2026 if you go outside at 8 or 9 \u2026 in the morning and are exposed to sunlight, you will not make any significant vitamin D,\u201d he said. The same goes for after 3 p.m. \u201cIt really depends on the zenith angle of the sun,\u201d he added.<\/p>\n Holick developed an app called dminder.info<\/a> that can tell you how much vitamin D you\u2019re making when you\u2019re outside, depending on the time of day and other factors, and how to stay safe from burns.<\/p>\n The air quality where you live also matters. \u201cIf you live in a polluted city, like Los Angeles \u2026 the pollutants in the air absorb the vitamin-D- producing-ultraviolet-B-rays, thereby decreasing your ability to make vitamin D,\u201d he said.<\/p>\n Additionally, Moseley added, because of increased awareness of skin cancer, people aren\u2019t sunbathing or exposing themselves to the sun as much as they used to. <\/p>\n Dermatologists recommend protecting your skin from sunburn by seeking shade and wearing sunscreen with at least an SPF 30, as well as sun-protective gear, \u201csuch as long sleeves, pants, a wide-brimmed hat and sunglasses with UV protection,\u201d according to the American Academy of Dermatology Association<\/a>. <\/p>\n It\u2019s important that we use sunscreen for skin cancer prevention, \u201cbut it can definitely reduce the vitamin D absorption,\u201d pointed out Dr. Leila Khan<\/a>, an endocrinologist at Cleveland Clinic who specializes in metabolic bone disease.<\/p>\n Another reason people are exposed to less sunlight: They\u2019re not spending as much time outside as they used to, between working most of the day inside or commuting by car, she added.<\/p>\n Carol Yepes via Getty Images<\/p>\n Direct sunlight helps your skin produce vitamin D, but the time of day is a major factor.<\/p>\n Reason 3: Your body produces less vitamin D as you get older.<\/p>\n As people age, their skin can have a harder time making vitamin D even despite absorbing the sun\u2019s rays, Moseley said. <\/p>\n \u201cIn normal circumstances, when sunlight \u2014 specifically UVB rays \u2014 hits the skin, it triggers a chemical reaction that converts a cholesterol-like compound (called 7-DHC) into vitamin D,\u201d she explained. \u201cAs people age \u2026 the skin gradually loses its stores of 7-DHC. Additionally, aging skin becomes thinner and less efficient at responding to UV light.\u201d<\/p>\n Holick added that a 20-year-old can produce two to three times more vitamin D than a 70-year-old when they\u2019re both exposed to the same amount of sunlight.<\/p>\n Reason 4: You have a darker skin tone.<\/p>\n![\"Direct](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/08\/6a85c80c230000b0847c9da1.jpeg\")
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