Vitamin D: An Introduction 

Vitamin D plays a major role in maintaining bone health. It helps the body effectively utilize calcium from the diet. 

Some food sources of vitamin D include egg yolk, dairy, fatty fish, and grains. Exposure to sunlight is a major source of vitamin D. The UV rays in sunlight induce vitamin D production in the skin. About 15 minutes of exposure to sunlight is recommended to maintain optimal vitamin D levels. 

In today's world, people may not have enough exposure to sunlight.

Sunscreens are commonly used to prevent sunburns and tans, thereby blocking UV rays and the production of vitamin D. A sunscreen of SPF 30 can reduce the amount of vitamin D produced on sunlight exposure by more than 90%. 

Vitamin D Deficiency

The worldwide prevalence of vitamin D deficiency is very high, as high as 50%. Vitamin D deficiency leads to bone loss, pain, risk of fractures, and several disease conditions, like rickets and lupus. 

Certain groups of people are at an increased risk of vitamin D deficiency. These include: 

• Breastfed infants
• Dark-skinned people who have lesser sunlight exposure 
• Individuals suffering from obesity, cystic fibrosis, Crohn's disease, celiac disease, and certain other diseases

Vitamin D Supplements: Are They For You?

Very few foods have enough vitamin D to reach recommended daily intakes, and sunshine can be unreliable in certain climates. 

In these cases, vitamin D supplements can be taken in addition to food sources.

Make sure to talk to your doctor before taking vitamin D supplements.

Overdose can lead to vitamin D toxicity, which is dangerous. 

Melanin and Vitamin D 

Vitamin D production depends on several factors, including the color of your skin, duration of exposure, amount of skin exposed, and genetics. 

People with darker skin have more melanin, the pigment responsible for skin color. This protects skin cells from harmful radiation damage. 

Melanin also blocks the amount of UVB radiation that enters the skin, thereby reducing the amount of vitamin D produced. So people with darker skin tones are at a higher risk for vitamin D deficiency.

Genetics of Vitamin D Deficiency

Studies have found some genetic changes associated with vitamin D deficiency.

Two such genes are GC and VDR.

Let's see how they regulate vitamin D levels.

1. The GC gene contains instructions for producing vitamin D binding protein that binds to the active form of vitamin D.
2. Active vitamin D is then transported to target cells by this protein.

1. Active vitamin D is released at the target cell and can bind to the Vitamin D Receptor produced by the VDR gene.
2. This complex then binds to several other proteins to influence gene expression and calcium homeostasis.

This is especially seen in organs like the kidneys, bones, intestines, parathyroid glands, and the cardiovascular system. 

Mutations or changes in the VDR gene affect vitamin D levels and can increase or decrease the sensitivity of the body to the effects of vitamin D. 

Vitamin D Genetic Test

You can easily find out if you have any genetic variations that affect your vitamin D levels through a genetic test.

Most genetic tests provide your DNA information in the form of a text file, called the raw DNA data.

This data may seem like Greek and Latin to you. Xcode Life, can help you interpret it.

All you have to do is upload your raw data and order a nutrition report. Xcode Life then analyzes your raw data in detail to provide you with comprehensive nutrition analysis, including information on your vitamin D levels.

Video

Vitamin D Receptor (VDR): An Introduction

The Vitamin D receptor (VDR) gene is associated with the synthesis of Vitamin D receptor, a cell membrane receptor that binds to vitamin D.

Specific alleles of this gene are known to either increase or decrease the sensitivity of the body to the effects of Vitamin D. This receptor is involved in the intestinal transport of calcium, iron and other minerals.

Variants of the gene are shown to be associated with changes in the levels of vitamin D levels and power.

Vitamin D plays an important role in stimulating calcium absorption and also in bone mineralization by promoting osteoblast differentiation.

Association with Vitamin D levels:

The taq1 polymorphism (rs731236) of the VDR gene is associated with Vitamin D levels among Indians. People with the T variant of the gene were associated with lower serum vitamin D levels.

Association with Power:

A study conducted on identifying handgrip strength, which is indicative of muscle strength, showed that there was a significant association between taq1 polymorphism and muscle strength.

People with the C variant of the gene are found to be better at power-based activities than endurance.

What is vitamin D deficiency?

Vitamin D is responsible for bone strength in the human body.

It helps the body utilize the calcium absorbed from the diet effectively. 

Some natural sources of vitamin D include sunlight and a variety of foods like fish, egg yolk, fortified dairy and grain products, etc.

Insufficient vitamin D supply causes a serious condition called vitamin D deficiency. 

Approximately, 1 billion individuals worldwide, that is, nearly 15% of the world's population have this deficiency. 

What are the signs of vitamin D deficiency?

Most people tend to oversee the signs and fail to realize that they have this deficiency. Here is what can be looked out for:

• Bone pain and bone loss
• Falling sick frequently
• Fatigue
• Slow healing of wounds
• Muscle pain
• Hair loss
• Depression
• Compromised immune system

What are the risk factors or causes of vitamin D deficiency?

Certain medical conditions can predispose an individual to be deficient in vitamin D levels. These include:

• Individuals suffering from conditions like Crohn’s disease, celiac disease or cystic fibrosis
• Individuals who have had gastric bypass surgery
• Obesity: Fat molecules grab vitamin D and do not release it for use in the body
• Very limited exposure to the sun
• A prolonged period of breastfeeding: Human breast milk contains a low amount of vitamin D
• A diet lacking enough vitamin D supplements (like vegan diets)

You may also be interested in: What do genes tell us about vitamin D requirements?

How does vitamin D deficiency affect your health?

Research suggests that vitamin D deficiency is linked to many serious disorders like:

• Lupus
• Multiple sclerosis
• Pre-menstrual syndrome
• Inflammatory bowel diseases
• Eczema
• Tooth and gum decay
• Alzheimer's
• Dementia
• Schizophrenia
• Depression
• Asthma
• Osteoporosis
• Rickets
• Cancer
• Erectile dysfunction

What are the best food sources of vitamin D?

Very few food items naturally contain vitamin D. Including them in your diet would greatly help alleviate vitamin D deficiency. 

• Fishes like tuna, salmon, swordfish, herring, and sardines
• Milk & dairy products like eggs, yogurt and cheese and vegan alternatives like soy and almond milk 
• Mushrooms 
• Cod Liver Oil

Is vitamin D deficiency genetic?

Research has identified four genetic variants that are associated with vitamin D deficiency.

These genes are involved in metabolization and transportation of vitamin D in the body.

More such genetic variants inherited, the higher the risk for low vitamin D levels in the body.

Does your 23andme, Ancestry DNA, FTDNA raw data have VDR gene variant information?

References

1. https://www.ncbi.nlm.nih.gov/pubmed/16159929
2. https://www.ncbi.nlm.nih.gov/pubmed/11684540
3. https://www.ncbi.nlm.nih.gov/pubmed/15012617
4. https://www.ncbi.nlm.nih.gov/pubmed/22681928
5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5068478/

“Nutrigenetics, fitness genetics, health genetics are all nascent but rapidly growing areas within human genetics. The information provided herein is based on preliminary scientific studies and it is to be read and understood in that context.”