Vitamin D: Why is it essential?

What is vitamin D?

Vitamin D differs from other vitamins. In fact, it is a steroid hormone produced from cholesterol when our skin is exposed to sunlight, which is why it’s known as the “sunshine vitamin”. [1]

It belongs to the group of vitamins A, D, E, K, and it is fat-soluble, meaning that requires the presence of fat to be absorbed by the body.

However, sun exposure doesn’t always ensure sufficient vitamin D, especially during the winter months, making it necessary to obtain it through both dietary sources and dietary supplements.

What’s the difference between vitamin D and D3?

Vitamin D is a term that includes two main forms: [2]

• D3 (cholecalciferol)
• D2 (ergocalciferol)

Vitamin D3 is produced when our skin is exposed to sunlight and is found in certain animal-based foods, such as fatty fish, egg yolks, liver, and more. Studies show that D3 is nearly twice as effective at raising blood levels compared to D2.

Vitamin D2 is found in some plant sources, such as mushrooms and yeasts. Additionally, many foods, like plant-based milk, orange juice, and cereals, are fortified with it.

Both forms are metabolized in the body to the active form of vitamin D called calcitriol.

Which foods are rich in Vitamin D?

Unfortunately, very few foods contain significant amounts of vitamin D, which makes deficiency quite common, even in Western countries. Specifically, it can be found in foods like: [3]

• Fatty fish (salmon, mackerel, tuna, cod, herring, sardines)
• Cod liver oil
• Egg yolks
• Shrimp
• Margarine
• Fortified cereals
• Fortified dairy products

The most significant dietary source of vitamin D is cod liver oil, with 1 tablespoon (15 ml) containing over twice the Recommended Dietary Allowance, which is 1,360 IU. Cooked salmon (3.5 ounces or 85 grams) contains 447 IU of vitamin D, while beef liver (3.5 ounces or 85 grams) and a large egg yolk each contain approximately 42 IU.

However, because vitamin D deficiency cannot always be corrected through diet alone, food supplements are commonly recommended.

Properties and Benefits

Vitamin D is crucial for bone and teeth health. Recent studies have highlighted its role in overall health, supporting the immune system, and preventing various serious conditions such as hypertension and psoriasis.

Specifically: [4][5]

1. Immune System

Studies suggest that individuals with low vitamin D levels often have a more vulnerable immune system and are prone to seasonal flu, colds, and some autoimmune diseases. Vitamin D helps strengthen the immune system, prevent infections, and manage certain autoimmune conditions.

Overall, many studies have shown that vitamin D enhances the immune system’s ability to resist viruses and bacteria.

2. Osteoporosis

Vitamin D is traditionally known as the “bone vitamin” because it primarily works to increase calcium absorption in the intestines.

It’s used for:

• Preventing and treating rickets in children
• Treating osteoporosis
• Managing bone pain (osteomalacia)
• Reducing bone loss in individuals with hyperparathyroidism
• Treating a genetic condition called familial hypophosphatemia
• Preventing fractures in people at risk for osteoporosis

In individuals with kidney disease, vitamin D helps enhance calcium absorption and decrease bone loss.

3. Cardiovascular System

Many researchers agree that vitamin D may help prevent heart and vascular diseases, such as high blood pressure and high cholesterol. Several studies have shown a connection between low vitamin D levels and cardiovascular problems, including an increased risk of heart attack, metabolic syndrome, hypertension, and sudden cardiac death.

4.Diabetes

Numerous studies suggest a link between low vitamin D levels in the body and an increased risk of type 2 diabetes. In fact, some researchers believe that vitamin D may act as a protective factor against insulin resistance, as it reduces inflammation.

Moreover, regarding type 1 diabetes, studies conducted in different countries have shown that infants who received vitamin D supplements during infancy had a much lower risk of developing the disease.

5. Psoriasis

Those with psoriasis know that sunlight does them good! This isn’t a coincidence. Vitamin D, produced following sun exposure, is involved in maintaining the skin barrier’s integrity.

Other Actions

Vitamin D has been found to be beneficial in situations such as:

• Obesity
• Rheumatoid arthritis
• Chronic obstructive pulmonary disease
• Prevention of dementia
• Asthma
• Endothelial healing
• Enhancement of gut microbiota

Since it is involved in regulating the levels of inorganic components like phosphorus and calcium, it is often used for conditions caused by low levels of these minerals, such as:

• Familial hypophosphatemia
• Fanconi syndrome
• Hypoparathyroidism
• Pseudohypoparathyroidism

Normal Levels

Vitamin D levels in the body are monitored through a blood test called 25-hydroxyvitamin D or 25 (OH) D3. [6]

Specifically:

• Values > 20 ng/ml are considered normal.
• Values between 12-20 ng/ml are indicative of insufficiency.
• Values < 12 ng/ml indicate severe deficiency with bone metabolism disturbances.
• Values >50 ng/ml are considered too high and might be dangerous.

Low values can indicate a deficiency or potential bone issues. These values may slightly vary depending on the laboratory and method used.

Symptoms of vitamin D deficiency

Vitamin D deficiency can lead to: [7]

• Rickets in children
• Bone pain
• Muscle weakness
• Increased susceptibility to infections

Even without symptoms, a deficiency can put your health at risk. Low blood levels are associated with an increased risk of:

• Cardiovascular diseases
• Cognitive decline in the elderly
• Preeclampsia and cesarean section in pregnant women

Who is at risk of deficiency?

Groups of the population at higher risk of developing vitamin D deficiency include: [7]

• Individuals with dark skin, as melanin acts as a filter for the absorption of UVB radiation (Ultraviolet B radiation)
• People with limited or no sun exposure, such as elderly individuals who remain indoors or are homebound
• Individuals who cover their skin entirely with clothing
• People who avoid sun exposure
• Individuals who excessively use sunscreen products
• People with medical conditions like obesity, chronic kidney disease, liver failure, celiac disease, Crohn’s disease, cystic fibrosis.

Dosage

According to the National Institutes of Health in the USA, the amount of vitamin D needed to achieve normal levels is: [6]

• For infants up to 1 year old: 10 micrograms (mcg) or 400 International Units (IU) per day.
• For children from 1 year of age to adults up to 70 years: 15 mcg or 600 IU per day.
• For older individuals, breastfeeding women, or people at risk of vitamin D deficiency: 20 mcg or 800 IU.

When to Take Vitamin D?

As a fat-soluble vitamin, vitamin D needs a fatty meal to be properly absorbed. [8]

For this reason, it is recommended to take it after breakfast or lunch, as these meals usually contain some form of fat (e.g., butter, eggs, olive oil, etc.).

How Quickly Does Vitamin D Increase?

The half-life of vitamin D in the body is 14-21 days. This means that about every two to three weeks, half of the amount you had previously remains in your body. [9]

More precisely, for every 1,000 IU of vitamin D3 you take daily, the levels of 25(OH)D3 in the blood increase by 10 ng/ml after a few weeks.

Possible Side Effects

While it is challenging to have excessive amounts of vitamin D from food or excessive sun exposure, taking many vitamin D supplements for an extended period can lead to vitamin D toxicity.

This occurs because it is fat-soluble, meaning it can be stored in the body, especially in fat, for a long time.

Some side effects of excessive vitamin D intake include: [10]

• Fatigue
• Weakness
• Sleepiness
• Headache
• Loss of appetite
• Dry mouth
• Metallic taste
• Nausea
• Vomiting

Excessive vitamin D can increase calcium concentration in the body (hypercalcemia) and weaken bones or harm the kidneys and heart.

The main symptoms of vitamin D toxicity include:

• Confusion
• Lack of concentration
• Sleepiness
• Depression
• Nausea
• Abdominal pain
• Constipation
• High blood pressure

Vitamin D is safe when taken in recommended amounts. Most people do not experience side effects unless they exceed the dosage. 

At Vita4you.gr, you will find a variety of vitamin D supplements!