Who is at risk of suboptimal Vitamin D levels?

Factors such as age, diet, and lifestyle can play a part in increasing the risk for suboptimal Vitamin D.1 Common risk factors include premature birth, old age, obesity, and darker skin.2 Since our skin produces most of the Vitamin D we need when exposed to sunlight, the main factor leading to inadequate Vitamin D levels is low sun exposure.

Groups with a heightened risk for suboptimal Vitamin D levels include3:
Breastfed infants
 oBreastmilk is a poor source of Vitamin D, so infants who are solely breastfed are often at risk for low Vitamin D levels.
Individuals with low sun exposure
 oIndividuals who stay home or indoors: the UVB rays that trigger Vitamin D production in our skin cannot penetrate glass, so the sunlight we’re exposed to indoors (or in the car!) does not contribute to our Vitamin D levels.4
 oThose who cover most of their skin because of their preferred dress codes.
 oRegular sunscreen users, as sunscreen blocks the sun’s Vitamin D-producing UVB rays from reaching our skin, reducing the ability of the skin to produce Vitamin D by up to 99%.5
 oAs we age, our skin’s ability to produce Vitamin D decreases.
 oOlder adults may stay home or indoors more, reducing sunlight exposure.
 oReduced appetite can lead to inadequate dietary consumption of Vitamin D.
Individuals with dark skin tones
 oThe increased levels of melanin in darker skin tones provide natural protection against UV rays and, as a result, individuals with darker skin tones make 90% less Vitamin D from sunlight exposure than lighter-skinned individuals.5
Individuals with obesity
 oWhy obesity is linked to suboptimal Vitamin D is still unclear. Excess fat might be ‘trapping’ the Vitamin D since it is a fat-soluble vitamin, Vitamin D levels might be ‘diluted’ by the increased body mass and volume, or individuals with obesity may adopt lifestyle habits (e.g. staying indoors more) that limit their exposure to sunlight.6
Individuals who cannot fully absorb dietary fats
 oVitamin D is fat-soluble and is absorbed best with fat; hence, any medical issue that impairs fat absorption from the gut may increase the risk of suboptimal Vitamin D levels.
 oIndividuals who have had gastric bypass surgery often have a reduced ability to absorb Vitamin D from dietary sources.7

If you belong to any of these groups, you may wish to speak to your doctor to find out more about Vitamin D supplementation or testing of your Vitamin D levels, where necessary.

1) National Institute for Health and Care Excellence. COVID-19 rapid guideline: vitamin D. NICE Guideline no. NG187, December 2020.
2) Lips P. Prog Biophys Mol Bio 2006;92:4-8.
3) National Institute of Health. Vitamin D Fact Sheet for Health Professionals. Available at: Accessed 30 June 2021.
4) National Health Service UK. How to get vitamin D from sunlight. Available at: Accessed 6 Sep 2021.
5) Hossein-nezhad A, Holick MF. Mayo Clin Proc 2013;88:720-755.
6) Man REK, et al. Nutrients 2017;9:313.
7) Pramyothin P, Holick MF. Curr Opin Gastroenterol 2012;28:139-150.