Gene in focus - Part 9: VDR (Vitamin D)

The next gene in our series is VDR; the vitamin D receptor gene. This gene plays a role in how well our bodies can utilise vitamin D, which in turn can affect various different processes. Currently, VDR appears in three different sections of our report - power/endurance, vitamin D needs, and caffeine sensitivity.

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The VDR gene is responsible for the production of a protein called vitamin D receptor, which allows you to respond to vitamin D. Vitamin D is a fat-soluble micronutrient which can be acquired in small amounts from certain foods and direct sun exposure.


The best sources of vitamin D 

Food sources of vitamin D are very limited, these include:

  • Fish (which is the best dietary source of vitamin D)
  • Fortified foods (cereals, grains and occasionally milk)
  • Eggs

However, vitamin D is mostly produced by your skin with the help of direct sun exposure (specifically ultraviolet B rays). So if you’re not a big fan of fish, you should be spending a few minutes per day exposing your skin to direct sunlight. 

Your skin tone will determine how much time you need to spend in the sun to produce sufficient vitamin D. The darker your skin tone, the less likely you are to convert that vitamin D efficiently - so you would need to spend a bit longer in the sun than a fair skinned person. A fair skinned individual needs to spend between four and ten minutes in the sun, while a darker skinned individual would need between 40 and 60 minutes in the sun. 

study found that around 41.% of the population in the USA suffer from a vitamin D deficiency.

There are seven common risk factors leading to a vitamin D deficiency 

  1. Having darker skin
  2. Old age
  3. Obesity
  4. Not eating fish, eggs or dairy
  5. Living far from the equator (e.g. the UK)
  6. Wearing suncream all the time
  7. Spending a lot of time indoors


The importance of vitamin D for your health 

Vitamin D is responsible for maintaining the balance of various minerals such as calcium and phosphate (which help maintain healthy bones and teeth), in your body. When we report on vitamin D requirements, we are doing so from the perspective of bone health. 

VDR and bone health

Changes in the VDR gene, known as polymorphisms, have been shown to have an impact on how strong and healthy our bones are. For example, a 2005 study found that the VDR CC genotype was associated with an increased risk of hip fractures in a group of elderly postmenopausal women. If we know that someone is at an increased risk of developing a fracture of any type, then we can be proactive in preventing that.

From a nutritional standpoint, both vitamin D and calcium work together to improve bone strength. If we find that you have at least one C allele of VDR, we would recommend slightly higher intakes of these nutrients above the recommended daily allowance in order to maintain strong, healthy bones.


VDR and caffeine sensitivity

VDR genotype can also play a role in caffeine sensitivity. We have previously discussed CYP1A2 in this series, a gene that plays a very large role in determining how well you can tolerate caffeine, but we also need to pay attention to which version of the VDR gene we have. 

That’s because there is evidence that those with the CC genotype are more likely to see a loss of bone mineral density with high caffeine intakes. A loss of bone mineral density has also been linked to an increased risk of fractures, which we want to avoid. Due to this, if you have the VDR CC genotype, we would recommend that you limit your caffeine intake to less than 200mg per day, about as much found in two to three cups of coffee, depending on how strong you like your coffee.

Finally, VDR genotype can have an effect on whether you respond well to power-based training or not. Polymorphisms in this gene have been linked to differences in muscle strength and muscle. In this case, CC genotypes may achieve more favourable muscle growth and bone density improvements with strength training, as opposed to endurance training.

From a health perspective, we can see that carrying a C allele means we need to be a little bit more prudent in ensuring we get enough vitamin D while reducing our caffeine intake. Vitamin D can be found primarily in oily fish, but also in eggs and some fortified dairy products. The sun is also a really great source of vitamin D. From a training perspective, C allele carriers are perhaps a bit more likely to have a better response to strength training.

Take the DNAFit test to find out which variation of the VDR genotype you carry. This will help you establish whether you should be increasing your vitamin D intake and decreasing your caffeine intake.

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