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Vitamin D

Vitamin D helps your body absorb calcium.

What is Vitamin D ?

Calcium is one of the main building blocks of bone. A lack of vitamin D can lead to bone diseases such as osteoporosis or rickets. Vitamin D also has a role in your nerve, muscle, and immune systems.

Vitamin D
Vitamin D

Vitamin D serves a dual role in our health—it is both a nutrient that can be obtained from our diet and a hormone synthesized by our bodies. This fat-soluble vitamin is well-known for its role in aiding the absorption and retention of vital minerals like calcium and phosphorus, which are essential for the development and maintenance of strong bones. Furthermore, laboratory research has demonstrated that vitamin D can inhibit the growth of cancer cells, assist in managing infections, and mitigate inflammation. Notably, many organs and tissues in our bodies possess receptors for vitamin D, suggesting that its functions extend beyond bone health. As a result, scientists are actively exploring additional potential roles for this essential nutrient.

While only a limited number of foods naturally contain vitamin D, some are enriched with this nutrient. However, for most individuals, achieving adequate vitamin D intake through diet alone can be challenging. Consequently, the most effective method of ensuring sufficient vitamin D levels is through dietary supplementation. Vitamin D supplements are available in two primary forms: vitamin D2 (known as “ergocalciferol” or pre-vitamin D) and vitamin D3 (referred to as “cholecalciferol”). Both of these forms can also be generated naturally in the presence of ultraviolet-B (UVB) rays from sunlight. This characteristic has earned vitamin D its nickname, “the sunshine vitamin.” However, vitamin D2 is synthesized in plants and fungi, while vitamin D3 is produced in animals, including humans.

The skin’s ability to produce vitamin D upon exposure to sunlight represents the primary natural source of this vital nutrient. Nevertheless, numerous individuals have insufficient vitamin D levels due to factors such as living in regions with limited winter sunlight or having restricted sun exposure. Additionally, people with darker skin tend to exhibit lower blood levels of vitamin D, as the presence of melanin, a skin pigment, acts as a natural sunshade, reducing vitamin D production (while also affording protection against the harmful effects of sunlight, including skin cancer).

Photograph of foods containing Vitamin D

You can get vitamin D in three ways: through your skin, from your diet, and from supplements. Your body forms vitamin D naturally after exposure to sunlight. However, too much sun exposure can lead to skin aging and skin cancer. So many people try to get their vitamin D from other sources.

Vitamin D-rich foods include egg yolks, saltwater fish, and liver. Some other foods, like milk and cereal, often have added vitamin D.

Vitamin D Benefits

Vitamin D, often referred to as the “sunshine vitamin,” plays a crucial role in various aspects of health. Some of the key benefits of vitamin D include:

  1. Bone Health: Vitamin D is essential for the absorption of calcium and phosphorus in the intestines, which is vital for maintaining strong and healthy bones. It helps prevent conditions like rickets in children and osteoporosis in adults.
  2. Immune System Support: Vitamin D is thought to modulate the immune system, helping to protect against infections and reduce the risk of autoimmune diseases.
  3. Cancer Prevention: Some studies suggest that adequate vitamin D levels may reduce the risk of certain types of cancer, including breast, prostate, and colorectal cancer. It may also play a role in controlling cancer cell growth.Several experiments have suggested a potential link between Vitamin D and the onset of cancer. Vitamin D plays a role in cellular repair and regeneration, potentially inhibiting the proliferation of cancerous tumors, promoting the apoptosis (death) of cancer-damaged cells, and reducing the formation of blood vessels within tumors.
  4. Heart Health: Vitamin D may have a positive impact on cardiovascular health by helping to regulate blood pressure, reducing inflammation, and improving overall heart function.
  5. Mood and Mental Health: There is evidence to suggest that vitamin D may play a role in mood regulation and may help alleviate symptoms of depression and seasonal affective disorder (SAD).Vitamin D receptors are distributed throughout the brain and spinal cord, contributing to various benefits. Vitamin D plays a crucial role in modulating the synthesis of neurotransmitters, as well as promoting nerve growth and repair. Vitamin D can have a positive impact on your daily mood, particularly during the colder and darker months of the year. Numerous studies have suggested a potential connection between low levels of Vitamin D3, often associated with reduced sunlight exposure, and the symptoms of Seasonal Affective Disorder (SAD).
  6. Weight Management: Research has shown that individuals who have a Vitamin D deficiency are at a higher risk of obesity and related complications. However, it’s important to emphasize that addressing Vitamin D deficiency is just one aspect of maintaining a healthy weight and overall well-being. To achieve and maintain a healthy weight, it’s crucial to adopt a balanced and nutritious diet while engaging in regular physical activity. Simply taking a Vitamin D supplement, consuming Vitamin D-rich foods, and increasing sun exposure should be part of a broader approach to health and wellness. Some research has indicated that adequate vitamin D levels may be associated with a healthier body weight and a reduced risk of obesity.
  7. Autoimmune Disease: Vitamin D may be involved in reducing the risk of autoimmune diseases like multiple sclerosis, type 1 diabetes, and rheumatoid arthritis.
  8. Skin Health: Vitamin D can help promote skin health and may be beneficial in managing skin conditions like psoriasis.
  9. Muscle Function: Adequate vitamin D levels are important for proper muscle function, and a deficiency can contribute to muscle weakness and pain.
  10. Respiratory Health: There is some evidence that vitamin D may help reduce the risk of respiratory infections, including the common cold and flu.
  11. Rheumatoid Arthritis: Research has uncovered that individuals who suffer from rheumatoid arthritis, a chronic inflammatory joint disease, often exhibit low levels of Vitamin D. Rheumatoid arthritis is categorized as an autoimmune disease in which the immune system mistakenly targets the linings of the joints, resulting in joint inflammation, stiffness, pain, and decreased mobility. Given that one of the primary benefits of Vitamin D is its role in supporting the immune system’s proper function, it stands to reason that a deficiency in this vitamin may contribute to the development of rheumatoid arthritis. By elevating Vitamin D levels, there is a possibility of mitigating the severity and onset of this disease, as well as other autoimmune conditions.
  12. Type 2 Diabetes: If you have a family history of diabetes or have been diagnosed with hyperglycemia (pre-diabetes), it may be advisable to consider increasing your Vitamin D intake. Recent studies have provided evidence of a connection between Vitamin D deficiency, insulin resistance, and the development of type 2 diabetes. By addressing insulin resistance, it is possible to potentially reduce the risk of developing type 2 diabetes.
    • The pancreatic cells responsible for insulin secretion contain both the alpha-hydroxylase enzyme and vitamin D receptors (VDRs), both of which influence the body’s glucose tolerance and insulin resistance. Inadequate sunlight exposure can lead to reduced insulin secretion by the pancreas, potentially contributing to insulin resistance and affecting the body’s response to glucose.
    • Given these research findings, consulting with your healthcare provider to assess whether increasing your Vitamin D intake could benefit your overall health is a prudent step, especially if you have risk factors for diabetes.
  13. Lower Blood Pressure: Numerous long-term studies have established a connection between low Vitamin D levels and hypertension (high blood pressure). Until recently, it remained unclear whether Vitamin D deficiency directly contributes to the development of hypertension. However, a significant genetic study involving over 150,000 individuals has provided compelling evidence that low levels of Vitamin D can indeed lead to hypertension. In this study, individuals with the highest Vitamin D levels exhibited lower blood pressure, and it was observed that a 10 percent increase in Vitamin D levels corresponded to a 10 percent reduction in the risk of hypertension. If you are dealing with high blood pressure or wish to prevent its onset, increasing your Vitamin D levels may offer potential benefits.

What Are Vitamin D Deficiency Symptoms ?

Vitamin D deficiency can manifest with a range of symptoms, although in some cases, it may be asymptomatic (showing no noticeable signs). When symptoms do occur, they can vary in severity. Common symptoms and signs of vitamin D deficiency include:

  1. Fatigue: Persistent fatigue and tiredness are often early signs of vitamin D deficiency.
  2. Bone Pain: Aches and pains in the bones, particularly in the back, hips, and legs, can be indicative of vitamin D deficiency. This pain may be associated with a condition called osteomalacia in adults or rickets in children.
  3. Muscle Weakness: Muscle weakness, particularly in the proximal muscles (those closer to the body’s core), can occur.
  4. Joint Pain: Some individuals with vitamin D deficiency may experience joint pain or discomfort.
  5. Mood Changes: Low vitamin D levels have been associated with mood disorders such as depression and Seasonal Affective Disorder (SAD). Symptoms may include mood swings, irritability, and low mood.
  6. Frequent Infections: Vitamin D plays a role in immune function, and deficiency may lead to an increased susceptibility to infections.
  7. Impaired Wound Healing: Slow or impaired wound healing is another potential symptom.
  8. Hair Loss: Some individuals may experience hair loss as a result of vitamin D deficiency.
  9. Cognitive Changes: In severe cases, cognitive impairments may occur, although this is less common.
  10. Unexplained Weight Loss: Unintentional weight loss may be observed in individuals with severe vitamin D deficiency, although it is not a specific symptom.
  11. Not Sleeping Well: You can not sleep well if you have vitamin D deficiency
  12. Loss of Appetite:   You will be lose appetite if you have vitamin D deficiency
  13. Getting Sick Easily: You will get sick more easily
  14. Pale Skin : Paleness is related to blood flow in the skin rather than deposit of melanin in the skin.

Which Foods Contain More Vitamin D ?

vitamin D
vitamin D

Several foods naturally contain vitamin D, while others are fortified with this nutrient. Here are some foods that are good sources of vitamin D:

  1. Fatty Fish: Fatty fish are among the best natural sources of vitamin D. Examples include salmon, mackerel, trout, and sardines.
  2. Cod Liver Oil: Cod liver oil is a concentrated source of vitamin D and is available as a supplement.
  3. Mushrooms: Some types of mushrooms, such as shiitake and maitake mushrooms, naturally contain vitamin D when exposed to UV light during growth.
  4. Egg Yolks: Egg yolks contain small amounts of vitamin D. However, the vitamin D content in eggs can vary depending on the diet of the hens.
  5. Fortified Dairy Products: Many dairy products, including milk, yogurt, and some cheeses, are fortified with vitamin D. Check the labels to ensure they contain added vitamin D.
  6. Fortified Plant-Based Milk: Plant-based milk alternatives like soy milk, almond milk, and oat milk are often fortified with vitamin D, especially the commercial varieties.
  7. Fortified Orange Juice: Some brands of orange juice are fortified with vitamin D.
  8. Fortified Cereals: Certain breakfast cereals are fortified with vitamin D.
  9. Beef Liver: Beef liver contains small amounts of vitamin D.

While you’ll primarily find vitamin D in fatty fish (a terrific source of omega 3 fatty acids), you’ll also find it in vitamin D-fortified foods (such as milk, breakfast cereal, and orange juice). Here’s a breakdown of specific foods that contain the two forms of vitamin D (vitamin D2 and vitamin D3).[8,9]

Food Portion Size Vitamin D (IU)
Cod liver oil 1 tbsp. 1360
Halibut, Greenland, raw 3 oz. 932
Rainbow trout, freshwater 3 oz. 645
Salmon (various) 3 oz. 383-570
Canned tuna (light) 3 oz. 231
Herring 3 oz. 182
Egg yolk (dried) 1 oz. 178
Canned sardine 3 oz. 164
Tilapia 3 oz. 127
Flounder 3 oz. 118
Soy beverage (soy milk), unsweetened 1 cup 119
Yogurt, plain (nonfat or low fat) 8 oz. 116
Mushrooms, raw (various) 1 cup 114-1110
Fortified milk (non-fat) 1 cup 108
Almond beverage (almond milk), unsweetened 1 cup 107
Fortified milk (low fat) 1 cup 104
Rice beverage (rice milk), unsweetened 1 cup 101
Kefir, plain (low fat) 1 cup 100
Fortified orange juice, 100% 1 cup 100
American Cheese, fortified (low fat or fat free) 1.5 oz. 85
Beef, variety meats and by-products, liver, cooked, braised 3 oz. 41
Fortified cereal (various brands) 1 cup 40-100
Cheddar Cheese 1 cup 32
Pork, fresh, loin, sirloin (roasts), bone-in, separable lean and fat, cooked, roasted 3 oz. 25

Getting Vitamin D From Sunlight

Getting vitamin D from sunlight is indeed an effective way for your body to produce this essential nutrient. Here are some important points to consider when using sunlight as a source of vitamin D:

  1. Exposure Time: Spending a short amount of time outdoors, even just a few minutes, with your skin exposed to sunlight can trigger the production of vitamin D. The exact time needed can vary based on factors such as your skin type, the time of day, and the strength of the sunlight.
  2. Sunscreen: While it’s important to protect your skin from the harmful effects of excessive sun exposure, using sunscreen with a high sun protection factor (SPF) can reduce the skin’s ability to produce vitamin D. To balance skin protection and vitamin D synthesis, consider spending some time in the sun without sunscreen for a portion of your sun exposure time.
  3. Timing and Location: The body’s ability to produce vitamin D from sunlight is influenced by the angle of the sun and the UVB rays it emits. Vitamin D synthesis is generally more efficient when the sun is higher in the sky, which is typically the case around midday. The effectiveness of sunlight for vitamin D synthesis also depends on your geographical location and the time of year. In regions with limited winter sunlight, supplementation may be necessary during the colder months.
  4. Skin Type: Individuals with darker skin may require more sun exposure to produce the same amount of vitamin D as those with lighter skin, as melanin, a skin pigment, can reduce the skin’s ability to produce the vitamin.
  5. Supplementation: If you have limited sun exposure due to factors like climate, work schedule, or skin sensitivity, or if you have specific health conditions that increase your risk of vitamin D deficiency, a healthcare provider may recommend vitamin D supplements or dietary changes to meet your nutritional needs.

Who is More at Risk for Vitamin D Deficiency?

Several factors can increase the risk of vitamin D deficiency. Individuals who are more at risk for vitamin D deficiency include:

  1. Limited Sun Exposure: People who spend most of their time indoors, work night shifts, or live in regions with long, overcast winters may have reduced sun exposure, making it more challenging to synthesize vitamin D from sunlight.
  2. Dark Skin: Individuals with darker skin have more melanin, which can reduce the skin’s ability to produce vitamin D from sunlight. Consequently, they may require more sun exposure to maintain adequate vitamin D levels.
  3. Older Age: The skin’s ability to synthesize vitamin D decreases with age, and older adults may spend less time outdoors. Additionally, they may have reduced absorption of dietary vitamin D.
  4. Obesity: Vitamin D is a fat-soluble vitamin, and it can become sequestered in fat tissue. This means that individuals with obesity may have lower bioavailable vitamin D, even if they have sufficient overall levels.
  5. Limited Dietary Intake: People with diets low in vitamin D-rich foods, such as fatty fish, fortified dairy products, and eggs, may be at greater risk of deficiency.
  6. Digestive Disorders: Certain medical conditions, such as celiac disease, Crohn’s disease, and inflammatory bowel disease, can impair the absorption of dietary vitamin D in the intestines.
  7. Medications: Some medications, including certain anticonvulsants, glucocorticoids, and weight-loss drugs, can interfere with vitamin D metabolism and absorption.
  8. Liver or Kidney Conditions: Conditions that affect the liver or kidneys can impair the conversion of vitamin D into its active form or its transport through the body.
  9. Pregnancy and Breastfeeding: Pregnant and breastfeeding women may require additional vitamin D to meet their own needs and those of their developing baby.
  10. Geographical Location: Individuals living at higher latitudes, where there is limited sunlight during certain seasons, may be at greater risk, especially in winter months.
  11. Ethnic Background: People of certain ethnic backgrounds, including those with South Asian, African, or Middle Eastern ancestry, may have a higher prevalence of vitamin D deficiency due to genetic and cultural factors.
  12. Chronic Illness: Individuals with chronic medical conditions, such as chronic kidney disease or multiple sclerosis, may be more susceptible to vitamin D deficiency.
  13. Malabsorption Disorders: Conditions that affect nutrient absorption in the intestines, such as celiac disease or cystic fibrosis, can hinder the absorption of dietary vitamin D.

What are the Signs of Vitamin D Toxicity ?

Vitamin D toxicity, also known as hypervitaminosis D, can occur when there is an excessive accumulation of vitamin D in the body. It’s important to note that vitamin D toxicity is rare and typically only occurs with extremely high doses of vitamin D supplements. Signs and symptoms of vitamin D toxicity can include:

  1. Hypercalcemia: Elevated levels of calcium in the blood (hypercalcemia) are a hallmark sign of vitamin D toxicity. Symptoms of hypercalcemia can include:
    • Nausea and vomiting
    • Frequent urination
    • Dehydration
    • Loss of appetite
    • Abdominal pain or discomfort
    • Constipation
    • Confusion and cognitive changes
    • Muscle weakness
    • Fatigue
    • Kidney stones
  2. Kidney Issues: Excessive vitamin D can lead to the calcification of soft tissues, including the kidneys. This can impair kidney function and lead to kidney damage.
  3. Bone Pain and Weakness: Ironically, high levels of vitamin D can lead to bone pain and weakness. This may seem counterintuitive since vitamin D is essential for bone health, but excessive levels can disrupt calcium balance and lead to bone mineralization issues.
  4. Digestive Symptoms: Some individuals may experience gastrointestinal symptoms such as diarrhea and stomach cramps.
  5. Excessive Thirst: Increased thirst and excessive drinking of fluids can be a symptom of hypercalcemia associated with vitamin D toxicity.
  6. Cardiovascular Issues: In severe cases, vitamin D toxicity can affect the cardiovascular system, leading to irregular heart rhythms or even heart attack.

It’s important to remember that vitamin D toxicity is rare and is primarily associated with the excessive intake of vitamin D supplements. The body can regulate the production of vitamin D from sunlight and dietary sources to some extent, which helps prevent toxicity in most cases.

How Much Vitamin D do I Need?

The recommended daily intake of vitamin D can vary based on factors such as age, sex, life stage, individual health status, and geographical location. Here are general guidelines for daily vitamin D intake:

  1. Infants:
    • 0-12 months: 400-1,000 IU (10-25 micrograms) per day, depending on age and feeding method. Breastfed infants may require a supplement because breast milk is generally low in vitamin D.
  2. Children and Adolescents:
    • 1-18 years: 600-1,000 IU (15-25 micrograms) per day. The exact amount may vary based on individual needs, so it’s advisable to consult with a pediatrician.
  3. Adults:
    • 19-70 years: 600-800 IU (15-20 micrograms) per day.
    • Over 70 years: 800-1,000 IU (20-25 micrograms) per day.
  4. Pregnant and Breastfeeding Women:
    • Pregnant and lactating women may require higher levels of vitamin D. Recommendations typically range from 600-4,000 IU (15-100 micrograms) per day, depending on individual circumstances. It’s important to consult with a healthcare provider for personalized guidance.
  5. Individuals at Risk of Deficiency:
    • Some individuals, such as those with limited sun exposure, dark skin, obesity, certain medical conditions, or specific dietary restrictions, may require higher vitamin D intake. In such cases, a healthcare provider may recommend supplementation and monitor blood levels to determine the appropriate dosage.
  6. Geographical Location and Season:
    • People living at higher latitudes with limited sunlight during certain seasons may be at greater risk of vitamin D deficiency, especially in winter months. In such cases, supplementation during the winter may be beneficial.

It’s important to note that while it is possible to obtain some vitamin D from dietary sources and sunlight, many individuals may not achieve optimal levels through these means alone, especially during seasons with limited sunlight. Therefore, some people may benefit from vitamin D supplements to ensure adequate intake.

Earlier studies have shown that a shortage of D is associated with menstrual pain and that getting regular amounts of vitamin D — even less than the average recommended daily amount of 1,200 IU — reduces the chances of period pain . For vitamin D without supplements, add plenty of vitamin D-fortified milk, juice, salmon, and tuna to your diet.

Assuming that a person gets virtually no vitamin D from sunshine — and that this person gets adequate amounts of calcium — the IOM committee recommends getting the following amounts of vitamin D from diet or supplements (Note that the IOM’s upper limit is not a recommended intake, but what the IOM considers the highest safe level):

  • Infants age 0 to 6 months: adequate intake, 400 IU/day; maximum safe upper level of intake, 1,000 IU/day
  • Infants age 6 to 12 months: adequate intake, 400 IU/day; maximum safe upper level of intake, 1,500 IU/day
  • Age 1-3 years: adequate intake, 600 IU/day; maximum safe upper level of intake, 2,500 IU/day
  • Age 4-8 years: adequate intake, 600 IU/day; maximum safe upper level of intake, 3,000 IU/day
  • Age 9-70: adequate intake, 600 IU/day; maximum safe upper level of intake, 4,000 IU/day
  • Age 71+ years: adequate intake, 800 IU/day; maximum safe upper level of intake, 4,000 IU/day

That’s not enough, says Boston University vitamin D expert Michael Holick, MD, PhD, professor of medicine, physiology, and biophysics, Boston University Medical Center. Holick recommends a dose of 1,000 IU a day of vitamin D for both infants and adults — unless they’re getting plenty of safe sun exposure.

Is There a Difference Between Vitamin D3 and Vitamin D2 Supplements?

Yes, there is a difference between vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) supplements. Both are forms of vitamin D, but they have distinct sources and characteristics:

  1. Vitamin D3 (Cholecalciferol):
    • Source: Vitamin D3 is primarily derived from animal sources. It is synthesized in the skin when exposed to sunlight (UVB rays) and is also found in small amounts in some animal-based foods such as fatty fish, liver, and egg yolks.
    • Supplement Form: Vitamin D3 supplements are available in various forms, including capsules, tablets, and liquid drops.
    • Effectiveness: Vitamin D3 is considered the more effective form for raising blood levels of vitamin D. It has a longer duration of action in the body, which means it may require less frequent dosing.
    • Recommended Usage: Vitamin D3 supplements are often recommended for individuals who have vitamin D deficiency or are at risk of deficiency, as they tend to increase blood levels of vitamin D more effectively than vitamin D2.
  2. Vitamin D2 (Ergocalciferol):
    • Source: Vitamin D2 is derived from plant-based sources, such as certain types of fungi and yeast. It can also be produced synthetically.
    • Supplement Form: Vitamin D2 supplements are available in various forms, including capsules and tablets.
    • Effectiveness: Vitamin D2 is considered less effective than vitamin D3 in raising blood levels of vitamin D. It has a shorter duration of action and may require higher doses or more frequent dosing to achieve the same effect as vitamin D3.
    • Usage: While vitamin D2 is less commonly recommended compared to vitamin D3, it may still be used in specific situations, such as when an individual has dietary restrictions or preferences that make vitamin D3 less accessible.

In general, vitamin D3 is the preferred form for supplementation, especially when higher doses or long-term use are required to address deficiency or maintain optimal vitamin D levels. However, both vitamin D2 and vitamin D3 can be effective at increasing vitamin D levels when used appropriately.

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