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Vitamin D: 10 Little Known Facts

Vitamin D: 10 Little Known Facts

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To commemorate this day, I thought I’d share some interesting vitamin D facts that are not so commonly known…

  • It is not technically a vitamin. Vitamins have to be consumed as they cannot be created in the body. It is better classified as a hormone. Or more accurately, a pre-hormone which has to be converted to its active, hormonal component.
  • It regulates the activity of over 200 different genes.
  • You don’t get much of it from dairy. The main reason is because animals, just like people, need sunlight to make vitamin D. So if you eat mainly intensely farmed animals and their milk products, it won’t be high in vitamin D. Look out for free range, grass fed animals. One good example is Kerrygold butter which claims to be from grass fed animals.
  • Lower fat foods fortified with vitamin D won’t be as good as full fat products. It’s fat soluble and as such, being delivered in a fattier format aids absorption.
  • Obesity is associated with lower vit D levels. The hypothesis here is that the vitamin hides out in the fat cells. It would be interesting to see more research here.
  • Most vitamin D rich foods are from an animal source. Hence, vegetarians and vegans need to pay extra attention to supplementing.
  • Tanning beds can help raise vitamin D levels – but we are not advocating it!
  • Darker skin tones or skin that tans easily make less this vitamin compared to paler skin. This is probably a necessary adaptation due to migration of our ancestors into colder regions with less sunshine. In fact, darker skin tones may require 3-6 times more time in the sun to make the same amount compared to paler skin tones.
  • Older people produce less of it. There may be a few reasons for this. It’s believed that absorption may be poorer in older skin. The body also is less efficient in converting it to its active form. Another reason could also be that older people don’t go outdoors as much.
  • Sunscreen with SPF of 30 effectively blocks out UVB rays, hence indirectly reducing vitamin D production by up to 95%. This piece of info was gleaned from the Journal of Clinical Endocrinology and Metabolism 2011.

I hope this has given you some food for thought. I personally recommend a vitamin D shot into the muscle 4-6 times/year for paler skins and 6-8/year for darker skin tones; spaced out more during the summer months. Some people prefer taking higher dose orally. I personally prefer injections as they are easy to administer and receive. Plus I don’t have the hassle of having to remember to consume them. For me, I always know when I’m running low on vitamin D when my temperature regulation goes out the door. Cold feels too cold and hot feels too hot.

This reminds me, I think I’m due for my winter shot now….

Book yours by calling us on 020 7096 5475, or emailing us at help@harpalclinic.co.uk.


  1. Ghorbani, Zeinab, et al. “Vitamin D in Migraine Headache: a Comprehensive Review on Literature.” Neurological Sciences, 2019, doi:10.1007/s10072-019-04021-z.
  2. Guo, Jing et al. “A Narrative Review of The Role of Foods as Dietary Sources of Vitamin D of Ethnic Minority Populations with Darker Skin: The Underestimated Challenge.” Nutrients vol. 11,1 81. 3 Jan. 2019, doi:10.3390/nu11010081
  3. Hanel, Andrea, and Carsten Carlberg. “Vitamin D and Evolution: Pharmacologic Implications.” Biochemical Pharmacology, 2019, doi:10.1016/j.bcp.2019.07.024.
  4. Krysiak, Robert, et al. “The Effect of Vitamin D on Thyroid Autoimmunity in Euthyroid Men with Autoimmune Thyroiditis and Testosterone Deficiency.” Pharmacological Reports, vol. 71, no. 5, 2019, pp. 798–803., doi:10.1016/j.pharep.2019.04.010.
  5. Libon, Florence, et al. “Sunscreens Block Cutaneous Vitamin D Production with Only a Minimal Effect on Circulating 25-Hydroxyvitamin D.” Archives of Osteoporosis, vol. 12, no. 1, 2017, doi:10.1007/s11657-017-0361-0.
  6. Piccolo, Brian D et al. “Circulating 25-Hydroxyvitamin D Concentrations in Overweight and Obese Adults Are Explained by Sun Exposure, Skin Reflectance, and Body Composition.” Current developments in nutrition vol. 3,7 nzz065. 27 May. 2019, doi:10.1093/cdn/nzz065
  7. Webb, Ann R et al. “Colour Counts: Sunlight and Skin Type as Drivers of Vitamin D Deficiency at UK Latitudes.” Nutrients vol. 10,4 457. 7 Apr. 2018, doi:10.3390/nu10040457

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