When vitamin D levels are low, various symptoms can arise, including fatigue, depression, reduced concentration, and frequent infections. Since most people do not meet the recommended daily vitamin D intake through food alone, they often turn to supplements. However, vitamin D deficiency symptoms do not appear immediately, making it difficult to determine whether one is truly deficient.
Feeling tired for no apparent reason?
Fatigue and lethargy are common symptoms, but if you’ve been feeling unusually tired for several months without a clear cause, a deficiency in essential nutrients like vitamin D may be to blame. Vitamin D aids the absorption of calcium and phosphorus in the body and plays a vital role in forming and maintaining healthy bones. It also strengthens the immune system and suppresses inflammation, helping to reduce the risk of chronic diseases.
More than 40% of adults are deficient
More than 40% of adults are known to be deficient in vitamin D. To produce vitamin D naturally, your skin needs at least 20 minutes of sun exposure. However, this can be difficult for modern individuals who spend most of their time studying, working, or doing housework indoors. The problem is even more pronounced in winter, when reduced sunlight and less outdoor activity create conditions that increase the likelihood of vitamin D deficiency.
Most people are unaware of their deficiency
Many people do not check their vitamin D levels during regular health exams and are unaware of whether they are deficient. A simple blood test at a hospital can determine your level, with results available in two to three days. Testing once or twice a year is sufficient, ideally in September and March. September typically shows the highest levels after the sun-rich summer, while March reflects the lowest. Comparing the two can help you adjust your intake accordingly.
Deficiency criteria and recommended intake
Vitamin D deficiency is a blood concentration below 20–30 ng/mL. The recommended daily intake is about 15–20 mcg. According to the U.S. National Institutes of Health, the average person consumes only about 4.2 to 5.1 mcg through their daily diet. A dose containing around 600 IU per day is considered appropriate for supplements. High-dose supplements should be taken only under medical advice.
Exact dosage, different results
Even if two people take the same dose of vitamin D, their blood levels may vary significantly due to differences in absorption. Individual factors such as genetic traits can create a sixfold difference in absorption rates. In one study, people who took 4,000 IU per day showed a wide range of blood concentrations—from as low as 10 ng/mL to as high as 150 ng/mL. Because of this variability, blood testing is essential to determine the proper dosage for each individual.
Get some sun
To reduce fatigue, you must improve your diet, get sunlight, exercise regularly, and get quality sleep. Just 30 minutes of sun exposure can help the body produce vitamin D. Rather than forcing yourself to go outside just for sunlight, try building a habit of light walking to increase outdoor activity naturally. During winter, it’s especially important to be mindful of sun exposure.
Better absorbed with fat
Vitamin D is a fat-soluble vitamin that is better absorbed with dietary fat. To improve absorption, avoid taking supplements on an empty stomach. Instead, consume vitamin D with a breakfast with healthy fats like avocado, nuts, or olive oil.
A perfect match with calcium
Vitamin D is essential for calcium absorption and is often paired with calcium supplements. If vitamin D levels increase while calcium intake remains low, the active form of vitamin D will draw calcium from the bones to maintain blood calcium levels. This can actually worsen bone health over time. For vitamin D to work effectively in the body, it’s important to consume calcium-rich foods.
Foods rich in vitamin D
Salmon is one of the richest natural sources of fat-soluble vitamin D. A 100g serving contains an average of 570–600 IU, meeting the recommended daily intake. It also contains omega-3 fatty acids, which help with vitamin D absorption. Egg yolks contain about 40 IU per yolk. Other good sources include canned tuna and ricotta cheese.
Higher risk of benign paroxysmal positional vertigo (BPPV)
Recent studies have shown a link between vitamin D deficiency and benign paroxysmal positional vertigo (BPPV). This condition often appears in middle-aged individuals in their 40s and 50s due to degenerative changes in the ear’s balance organs, causing calcium crystals (otoliths) to dislodge more easily. While vitamin D deficiency is not a direct cause, experts point out that reduced outdoor activity and lower vitamin D production may increase the risk of BPPV.
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