What is vitamin D?
Vitamin D is an important element to building strong and healthy bones as well as good overall health. It is also a vital nutrient that makes sure that the brain, lungs, heart, and muscles function well.
Vitamin D is a fat-soluble vitamin. The body can make its own vitamin D when the skin is exposed to sunlight. Vitamin D can also be acquired from supplements and foods. The vitamin D acquired from sunlight and from supplements are changed by the body several times before it can be utilized. When it is ready, the body uses vitamin D to control the quantity of calcium in the blood, gut, and bones, and to help the cells throughout the body to properly communicate.
Vitamin D is the only vitamin that the body can make. Another unique characteristic of vitamin D is that it turns into a hormone called as calcitriol or activated vitamin D after metabolism.
Having the exact amount of vitamin D does not depend on the amount of your food intake. For the body to have enough levels of vitamin D, the skin must be exposed to sunlight on a regular basis. Vitamin D supplements must also be taken.
Once the skin is exposed to sunlight, it creates vitamin D and then sends it to the liver. Meanwhile, vitamin D from foods and supplements is sent to the liver by the gut. From here, the liver changes vitamin D to a substance referred to as 25-hydroxyvitamin D or 25(OH)D. This chemical is then sent throughout the body and turns into activated vitamin D, which is now ready to do its duties.
Since the vitamin D obtained from food, supplements and sun exposure is in the biologically inert state, it needs to undergo two hydroxylations to get activated. The first hydroxylation occurs in the liver, wherein vitamin D is converted to 25-hydroxyvitamin D [25(OH)D]. This is also known as calcidiol. The other hydroxylation occurs in the kidney, where it is converted to physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], which is also known as calcitriol.
Vitamin D is essential to have strong bones. Phosphorus and calcium are also important for developing the strength and structure of the bones. Moreover, vitamin D is needed to be able to take up these minerals. Even if the body has high levels of calcium and phosphorus, not having enough vitamin D means no absorption of the nutrients.
Vitamin D also carries other roles in the body such as cell growth modulation, neuromuscular function, immune function and inflammation reduction. Many genes are modulated in part by vitamin D. These genes encode proteins which regulate cell proliferation, differentiation, and apoptosis.
The best indicator of vitamin D status is the serum concentration of 25(OH)D. It reflects the vitamin D obtained from food and supplements and produced by the skin. It has a long circulating half-life of 15 days. However, this serum concentration does not indicate the quantity of vitamin D stored in the tissues of our body. Calcitriol or 1,25(OH)2D is not a good indicator of vitamin D status since it has a short half-life of 15 hours. Serum concentrations are also regulated by the parathyroid hormones, calcium, and phosphate. Until vitamin D deficiency is severe, the levels of 1,25(OH)2D typically do not decrease.
Vitamin D can help in the following body functions:
- Immune system by fighting off infections
- Brain development
- Muscle function
- Anticancer effects
- Respiratory system (for healthy airways and lungs)
- Cardiovascular system (for a healthy heart and normal blood circulation)
Why is vitamin D so important?
Vitamin D has a wide range of importance in the body. It does not only help fight infections but has other benefits as well.
Our muscles need vitamin D for them to move, as the nerves need vitamin D to deliver messages from the brain to the different parts of the body and vice versa. Vitamin D, with the help of calcium, protects older adults from developing osteoporosis.
Vitamin D is vital for decreasing the risk of hypertension, heart attack, stroke, and atherosclerotic heart disease. Studies have shown that a lack of vitamin D increases an individual's risk of heart attack by 50 percent. Vitamin D is also a strong immune modulator as it helps prevent autoimmune diseases such as inflammatory bowel disease and multiple sclerosis.
Vitamin D can be found in every single cell in the body.
Are there any natural sources of vitamin D?
Yes, there are natural sources of vitamin D aside from exposing your skin to the sun. Among the best sources of vitamin D are fatty fish such as tuna, salmon, and mackerel. Fish liver oils are also a great source of vitamin D. The vitamin D found in these foods is mainly in the form of vitamin D3. Certain mushrooms also provide vitamin D, particularly vitamin D2.
Is vitamin D naturally found in some foods?
Certain kinds of foods naturally contain vitamin D. That is why some foods are fortified, which means that vitamin D has been added. Salmon, mackerel, tuna, cheese, beef liver, egg yolk, sardines, and shrimp are some of the foods that have vitamin D, while milk, margarine, cereal, yogurt, soy beverages, and orange juice are some of the foods, which vitamin D has been added.
Vitamin D supplements can help boost the level of vitamin D in the body as it can be hard to have enough vitamin D every day just by sun exposure and eating foods that contain vitamin D.
Vitamin D Deficiency
Vitamin D deficiency is a condition where the body does not get an adequate amount of vitamin D. When there is severe vitamin D deficiency, it can lead to a medical condition known as "osteomalacia" in adults and "rickets" in children. Rickets and osteomalacia can cause thin, soft, and brittle bones. Other conditions such as cancer, type 2 diabetes, depression, asthma, high blood pressure, Alzheimer’s disease, and autoimmune diseases including type 1 diabetes, multiple sclerosis, and Crohn’s disease, are also linked to a lack of vitamin D.
Symptoms of Vitamin D Deficiency
People may not be aware that they have a vitamin D deficiency, as sometimes, the symptoms of vitamin D deficiency are ignored or could be mistaken as another condition. Bone pain and muscle weakness may indicate that you have vitamin D deficiency. Blood testing is the only way that can help determine if a person is vitamin D deficient. The following are symptoms of vitamin D deficiency:
- Difficulty thinking clearly
- General tiredness
- General sense of not feeling well
- Aches and pains
- Cognitive impairment in older adults
- Severe asthma in children
- Waddling gait
- Slipped epiphyses (rickets)
- Symptoms of hypocalcemia
- Muscle pain
- Severe muscle or bone pain and weakness that can lead to a difficulty in ascending and descending stairs, waddling gait, and a difficulty in getting up off the floor
- Stress fractures, particularly in the pelvis, hips, and legs
Vitamin D is needed for calcium absorption. It also maintains blood calcium levels and enables the normal mineralization of bones. Low calcium levels can lead to tetany. Vitamin D deficiency can cause secondary hypertension, which causes increased bone loss, osteopenia, osteoporosis, osteomalacia, and increased fracture risk.
Chronic vitamin D deficiency due to bone softening can cause numerous bone malformations. The possible signs and symptoms include:
- Pain in the legs and lower back due to vertebral collapse
- Knock knees
- Rachitic rosary
- Pigeon breast
- Enlarged wrists and ankles
- Delayed fontanel closing
- Softening of the skull
- Poorly developed muscles
- Bulging forehead
- Difficulty walking and climbing stairs
- Kyphoscoliosis (spine curvature disorder)
It is a disease characterized by low bone mass and the deterioration of bone tissues. This increases the fragility of the bones and increases the risk of bone fractures. Mostly, osteoporosis is associated with insufficient calcium intake but inadequate vitamin D reduces calcium absorption, which causes osteoporosis. It is caused due to the long-term effect of calcium and vitamin D insufficiency. Rickets and osteomalacia are also caused due to the effects of vitamin D deficiency. Sufficient storage levels of vitamin D help maintain bone strength, thereby preventing osteoporosis in older adults, postmenopausal women, and individuals on chronic steroid therapy.
Evidence and epidemiologic data have suggested that vitamin D status could affect an individual's risk of cancer. It has been indicated that vitamin D plays an important role in the prevention of colon, breast and prostate cancers. Emerging data has suggested that vitamin D has a strong protective effect against colon cancer, but there is no such strong data for its protective effect against breast and prostate cancer.
Vitamin D is associated with hypertension, peripheral vascular disease, coronary artery disease, myocardial infarction, hyperlipidemia, heart failure, and stroke. These conditions might be due to the anti-inflammatory effects of vitamin D.
Studies have shown a connection between low vitamin D levels and an increased risk of both upper and lower respiratory tract infections.
Studies have shown a possible link between vitamin D and depression. The reason is that vitamin D plays a vital role in regulating adrenaline, noradrenaline, dopamine production in the brain through vitamin D receptors in the adrenal cortex, and protection against serotonin and dopamine depletion.
Research is still ongoing in this area. There has been evidence of the role of vitamin D in preventing and treating multiple sclerosis.
Individuals who have tuberculosis have shown to have low vitamin D levels.
Risks of Vitamin D Deficiency
In some people, being exposed to sunlight as well as consuming vitamin D-fortified foods are essential for maintaining a healthy vitamin D level in the body. Some people take dietary supplements to meet their daily dose of vitamin D.
By human milk alone, vitamin D cannot be met. Mothers who already have high does of vitamin D will have high levels of this nutrient in their milk. A survey done by Canadian pediatricians found that the incidence of rickets was almost 2.9 per 10,000 infants and the majority of them were breastfed.
If the skin is darker due to greater amounts of melanin in the epidermal layer, then the ability of the skin to produce vitamin D reduces. People who have darker skin like African-Americans have a greater risk of developing a vitamin D deficiency. The reason is that a dark skin needs 10 times more sun exposure compared to a lighter skin to get the sufficient amount of vitamin D. The skin pigment works as a natural sunscreen. Thus, the more skin pigments a person have, the more time is needed to spend under the sun to produce enough amounts of vitamin D.
Limited Sun Exposure
Individuals who are homebound, women wearing long robes, and cover their head for religious reasons, and people having occupations that limit their sun exposure are also at risk of not getting adequate amounts of vitamin D from sunlight.
A hormone in the brain called "serotonin" is linked to mood elevation. The level of serotonin increases when the body is exposed to light and it decreases when sun exposure is reduced.
Fat Malabsorption with Inflammatory Bowel Disease
Since vitamin D is a fat–soluble vitamin, the absorption of vitamin D depends on the gut's ability to absorb dietary fat. Individuals who have fat malabsorption might require vitamin D supplementation. Fat malabsorption may cause some medical conditions such as liver disease, cystic fibrosis, Crohn’s disease, and ulcerative colitis.
Gastric Bypass Surgery
Gastric bypass surgery involves bypassing a part of the small intestine, which absorbs vitamins and minerals. Thus, the patients, who underwent a gastric bypass surgery, might become vitamin D deficient over time due to malabsorption problems.
50 Years and Older
Due to old age and because the skin is not able to synthesize vitamin D efficiently, older adults are at a greater risk of developing a vitamin D deficiency. As people get older, their skin does not produce much vitamin D as a reaction to sun exposure. Simultaneously, their kidneys will become less capable of converting vitamin D, which will be used by the body for other functions. In addition, many older adults prefer to spend their time indoors, which means that their sun exposure is decreased leading to low levels of vitamin D.
Being Overweight or Obese
Vitamin D is fat-soluble, which means that body fat acts as a sink by collecting it. People who are overweight or obese need more vitamin D compared to people with normal weight. This is also the fact for people who have higher body weights because of muscle mass.
A combination of aches and pains with fatigue is often misdiagnosed as chronic fatigue syndrome or fibromyalgia. However, these are classic symptoms of osteomalacia, which is the softening of the bones due to a vitamin D deficiency in adults. When the body is lacking vitamin D, there will be a problem in putting calcium in the collagen matrix and into the skeleton. Therefore, a vitamin D deficient individual may experience throbbing and aching bones.
One of the first symptoms of vitamin D deficiency is a sweaty head. Even infants can experience a sweaty head and may indicate that they are deficient in vitamin D.
Having a gastrointestinal problem that specifically affects the absorption of fats may also lead to a vitamin D deficiency since vitamin D is a fat-soluble nutrient. Gastrointestinal conditions that can affect the absorption of vitamin D are Crohn’s disease, inflammatory bowel disease, and non-celiac gluten sensitivity.
What happens if vitamin D deficiency is left untreated?
Vitamin D deficiency is a treatable condition. If vitamin D deficiency is not managed well or is left untreated, complications may arise.
Studies show that people with a vitamin D deficiency can develop a recurrent major depressive disorder that has seasonal patterns. It means that they will only feel depressed during a particular time of the year like winter. Another study linked to vitamin D deficiency is the fast proliferation of breast cancer cells.
Other complications that could develop if you are vitamin D deficient:
- Impaired functioning of the immune system
- Insulin resistance
- Brittle or thin bones that can increase one's risk of having osteoporosis
Researchers suggests that vitamin D might also play an important role in preventing and treating type 1 and type 2 diabetes, hypertension, multiple sclerosis, and glucose intolerance. However, there have been no definite clinical trials to prove this. Most of the evidence comes from in vitro, animal, and epidemiological studies.