Vitamin D is often called the “sunshine vitamin,” and for good reason—it’s one of the few nutrients your body can make on its own. All it takes is some sunlight on your skin. Unlike most vitamins, which must come entirely from food, vitamin D is unique: part hormone, part nutrient, and completely essential for your overall health.
When sunlight hits your skin, a fascinating process begins. Ultraviolet (UV) rays trigger skin cells to produce vitamin D3, also known as cholecalciferol—the same form found in many supplements and some animal-based foods. But here’s the catch: most people aren’t getting enough. Your skin’s ability to make vitamin D depends on several factors, including your age, skin tone, geographic location, and daily habits. For example, those with darker skin possess more melanin, which diminishes the capability of the skin to generate vitamin D from sun exposure. Northern latitudes, indoor activity, or frequent use of sunscreen can also restrict the amount your body can make.
So why is this vitamin so crucial?
Vitamin D is essential in aiding your body to absorb calcium and phosphorus, two minerals that are used to build and maintain healthy bones and teeth. Your body can’t use the calcium you eat, regardless of how much leafy greens or dairy you take in, without sufficient amounts of vitamin D. That’s why a deficiency can cause severe bone disorders: rickets in kids, and osteomalacia or osteoporosis in adults.
But the perks of vitamin D don’t stop with your bone system. It’s also critical to maintaining an effective immune system, which keeps your body from getting sick and might even reduce your risk for autoimmune diseases such as type 1 diabetes and rheumatoid arthritis. Low levels of vitamin D have even been implicated in higher rates of multiple sclerosis,heart disease, and life-threatening respiratory infections like the flu or COVID-19, according to some studies. There’s also encouraging evidence that vitamin D might help stabilize mood and relieve symptoms of depression and anxiety, particularly in individuals who are already deficient.
Even though it’s a crucial nutrient, vitamin D deficiency is prevalent. You might be at greater risk if you reside in an area with poor sunlight, have dark skin, are older than 65, or have excess body weight. Even everyday habits—such as spending most of the day indoors or applying sunscreen regularly—can make it more difficult to obtain enough vitamin D. Symptoms of deficiency are insidious: tiredness, muscle pain, bone pain, or hip, leg, or pelvis stress fractures. In kids, it may manifest as delayed growth or tooth cavities. If you’re not sure, a quick blood test can check your vitamin D levels.
It may be difficult to get sufficient vitamin D from diet alone since not many foods are rich in vitamin D. Fatty fish—such as salmon, sardines, rainbow trout, and canned tuna—are among the richest sources. Egg yolks, beef liver, and UV-treated mushrooms have small amounts as well. In America, most foods are fortified with vitamin D, such as milk, some yogurts, breakfast cereals, orange juice, and plant milk alternatives such as soy and almond milk. Always read the nutrition label to determine if vitamin D has been fortified.
For individuals who are at risk of a deficiency, supplements are commonly suggested. Vitamin D is available in two primary forms: D2 (plant-derived) and D3 (animal-derived or vegan-friendly lichen). Both will increase your levels, but D3 works better. The daily recommended allowance for most adults is 600 IU (15 micrograms), rising to 800 IU (20 micrograms) for over 70s. Certain health conditions, such as osteoporosis, may necessitate greater requirements, but first, discuss it with your doctor before taking higher doses.
And don’t forget: sometimes more isn’t better. Vitamin D is fat-soluble, so your body accumulates too much. Too high amounts from supplements—NOT from sun or food—will cause toxicity. Symptoms range from nausea, vomiting, and constipation to muscle weakness, and in extreme cases, life-threateningly high levels of calcium that can develop into kidney stones or heart problems. The dietary upper limit for most adults is 4,000 IU (100 micrograms) daily.
Vitamin D is tiny, but its effects on your health are gigantic. Whether it’s a stroll in the sun, a grilled salmon serving, or a well-researched supplement, ensuring that you have adequate vitamin D is one of the easiest, smartest decisions you can make to aid your bones, strengthen your immunity, and add some sunshine to your overall health.
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