Vitamin D is a crucial nutrient for overall health. It supports calcium absorption, promotes bone health, prevents osteoporosis, facilitates muscle movement, aids neurotransmission in the nervous system, and strengthens the immune system to combat infections, viruses, and autoimmune diseases.
Where does the body get vitamin D from?
The body acquires vitamin D, an essential nutrient for bone health, immune function, and overall well-being, from several sources. Naturally occurring in two forms—ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3)—this vitamin can be obtained through a combination of diet, sunlight, and supplementation. Foods rich in natural vitamin D, such as fatty fish, egg yolks, and liver, are excellent dietary sources. Additionally, many countries fortify products like milk, cereals, and orange juice with vitamin D to enhance public health. Sunlight also plays a significant role, as the skin produces vitamin D3 when exposed to UV rays, though factors like skin tone, age, and geographic location can influence this process. For individuals who may have limited dietary intake or sun exposure, vitamin D supplements provide a reliable alternative to maintain optimal levels and support overall health.
Foods containing natural vitamin D
Foods containing natural vitamin D are an essential part of maintaining healthy levels of this crucial nutrient. Fatty fish such as salmon, tuna, mackerel, and trout are among the best natural sources, as they are rich in vitamin D3, which is highly effective in supporting bone health and immune function. Fish liver oils, like cod liver oil, are also excellent sources. In addition to fish, some other foods contain smaller amounts of natural vitamin D, including mushrooms, egg yolks, butter, cheese, and beef liver or offal. Interestingly, the amount of vitamin D in these foods is not significantly altered by common cooking methods, as neither heat nor technological processes impact its content. This makes them reliable sources of vitamin D when included in a balanced diet. For those who have dietary restrictions or preferences that limit their intake of these foods, fortified options or supplements may be necessary to ensure adequate vitamin D levels.
Vitamin D-fortified foods
Vitamin D-fortified foods are an important source of this essential nutrient, especially for individuals who may not get enough from natural food sources or sunlight. Both forms of vitamin D—D2 (ergocalciferol) and D3 (cholecalciferol)—are commonly used by the food industry to fortify various products. This fortification process ensures that people can easily incorporate vitamin D into their diet through everyday foods. In many countries, common products such as milk, breakfast cereals, yogurt, margarine, and orange juice are enriched with vitamin D to help prevent deficiencies and support public health. The amount of added vitamin D varies by product and region, as regulations and practices differ between countries. To help consumers make informed choices, the vitamin D content is typically listed on product labels, allowing individuals to monitor their intake and ensure they are meeting their nutritional needs. Fortified foods are particularly beneficial in areas with limited sunlight or during months when natural sun exposure is insufficient.
Sunlight
In humans, part of the vitamin comes from the process of skin transformation of 7-dehydrocholesterol into cholecalciferol when exposed to sunlight. It should be taken into account that certain factors reduce the amount of vitamin D produced by the skin, such as natural barriers like clouds and pollution, or artificial barriers like windows, as well as having dark skin or advanced age. Another important point is that excess ultraviolet radiation from the sun can cause skin cancer, so exposure to the sun should be done by taking measures such as using sunscreen and limiting exposure to a few minutes a day at times when radiation is lower.
Dietary supplements
Dietary supplements provide a convenient way to ensure adequate vitamin D intake, particularly for individuals who may struggle to obtain sufficient amounts from food or sunlight. Available in various forms, vitamin D supplements come as standalone options or as part of multivitamin and multimineral formulas. These supplements typically contain either vitamin D2 (ergocalciferol) or D3 (cholecalciferol), with D3 being the more effective form for raising blood levels of vitamin D. Regular use of these supplements can help increase the concentration of vitamin D in the blood, supporting bone health, immune function, and overall well-being. It’s important to note that vitamin D is a fat-soluble vitamin, meaning it is best absorbed when taken with a meal that contains some fat. This enhances the body’s ability to utilize the nutrient, making it more effective in supporting health. For those considering supplementation, it’s advisable to consult a healthcare provider to determine the appropriate dosage and avoid excessive intake, which can lead to health complications.
How do you know if you are getting enough vitamin D?
One way to know if you are getting enough vitamin D is through a blood test that indicates the concentration levels of 25-hydroxyvitamin D, which is measured in nanomoles per litre (nmol/L) or nanograms per millilitre (ng/mL).
The following table shows an interpretation of 25-hydroxyvitamin D values in the blood.
| 25-hydroxyvitamin D levels |
Interpretation |
| ≥ 50 nmol/L (20 ng/mL) |
Value sufficient for good general and bone health |
| < 30 nmol/L (12 ng/mL) |
Value considered too low representing a health risk and weak bones |
| > 125 nmol/L (50 ng/mL) |
Very high value could represent a health risk |
Importance of maintaining adequate vitamin D levels
Vitamin D deficiency has significant health effects. In children, prolonged vitamin D deficiency can cause rickets, which is the softening and weakening of bones that manifests as stunted growth, bowleggedness, tenderness and pain in the legs, arms and spine. In adults it can cause osteomalacia (softening of the bones in adults), it can also influence the development of osteoporosis and weakening of muscles, which increases the risk of falls and possible fractures. Vitamin D also plays an important role in neurotransmission in the nervous system and brain health, and some studies have found a link between vitamin D deficiency and depression, as well as the risk of multiple sclerosis.
On the other hand, excessive vitamin D intake can be detrimental to health, causing kidney failure, cardiac arrhythmia and even death. Blood levels above 375 nmol/L or 150 ng/mL) can cause muscle weakness, nausea, vomiting, loss of appetite, dehydration, excessive urination and thirst, kidney stones, and confusion. It is important to note that elevated vitamin D levels are usually caused by excessive consumption of dietary supplements, they are never caused by sun exposure because the amount of vitamin D produced by the skin is limited.
Conclusion and disclaimer
A person’s vitamin D levels are affected by their dietary habits (not all people have access to or are tolerant to foods that contain natural or fortified vitamin D), sun exposure (depending on their lifestyle and geographical location) and vitamin D supplementation (you should follow your doctor’s instructions). The information presented in this article is in no way a substitute for the advice of a health professional. We recommend that you always consult with a qualified professional, physician, nutritionist, etc. before taking any vitamin D supplement.
Just as Vitamin D is important for the health of humans, it is also important for the health of dogs and cats. Take a look at the Vitamin D test for dogs and take care of your furry friend’s health.
