Over half (57%) of UK adults are not getting their optimal amounts of vitamin D (1)
Vitamin D is crucial for many aspects of a healthy life, yet many of us have no idea if we’re getting enough, writes Navita Doshi (qualifying as a Nutritional Therapist), and team member at Reflex Spinal Health. Read on to find out what vitamin D is, how to get it, why it’s so important, the potential signs of low Vit D, and how much you need.
What is Vitamin D?
Vitamin D – Bottled Sunshine
Vit D is a fat-soluble vitamin that comes in different forms.
The 2 main forms are D3 and D2 – both are inactive.
Vitamin D needs to be in its active form called calcitriol for our bodies to use it.(2)
Where to find Vitamin D?
- Sunlight:
Exposing your skin to the sun is the easiest and most natural way to top up your Vit D. When our skin absorbs ultraviolet-B (UVB) radiation from the sun, cholesterol in the skin is converted to the inactive pre-vitamin D which requires further changes within the body to become active (Figure 1).(3)
The British Skin Foundation, recommends limited skin exposure without sun protection to minimise the risk of sunburn and skin cancer: (4)
- Lighter skin – 10-15 minutes between April and September
- Darker skin – 25-40 minutes is recommended.
Figure 1: How we get Vitamin D from the sun
- Food and supplements:(5)
- Foods sourced from animals e.g. salmon, sardines, mackerel, egg yolks, contain the most in the form of inactive vitamin D3.
- Plant-based foods such as mushrooms contain the inactive vitamin D2.
- Inactive vitamin D can also be found in fortified foods such as milk, cereals, and shop-bought supplements.
Vitamin D supplementation
Supplementation is important, especially for those at increased risk of deficiency e.g.: (6)
- The elderly
- Infants
- Pregnant women
- Overweight
- Darker skin
- Those with reduced exposure to sunlight (indoor living, clothing)
- Those that cannot absorb nutrients properly e.g. coeliacs, Crohn disease
- Those with certain genetics. (7)
1 large egg contains approx. 44 IU (International Units) vitamin D3. NHS recommends taking 400 IU vitamin D per day. (8)
You therefore would need to eat about 9 eggs/day to get your daily dose of vitamin D, which is why supplementation is recommended
Always consult your healthcare practitioner before taking vitamin D supplements as too much can be toxic.
You cannot overdose on natural sources of vitamin D from the sun or foods.
Other nutrients are needed to make active Vitamin D
Inactive D3 or D2 is converted to its active form by undergoing a 2-step conversion process, first within our livers and then our kidneys using various enzymes and other nutrients such as magnesium and vitamin B5.(9) Finally, the active (usable) Vit D is now called calcitriol and is released from our kidneys into our blood, ready to be transported throughout our body (Figure 1). (3)
Signs/symptoms of Vitamin D deficiency include:(10)
- Rickets in the developing bones of children
- Osteomalacia (‘soft bones’) in adults
- Osteoporosis (‘brittle bones’)
- Bone pain
- Muscle pain (myalgia)
- Joint pain (arthralgia)
- Fatigue
- Muscle twitching (fasciculations)
Health benefits of Vitamin D (2)
Well-established health benefits of vitamin D:
- Bone health – Vitamin D is well known for its positive effects on bone and muscle health. It is essential in regulating calcium and phosphorous absorption in the gut and the resorption of calcium filtered through the kidneys – 2 key elements in forming strong bones.(2)
- Muscle health – Vitamin D deficiency is also associated with reduced muscle strength and size, known as dynapenia.(11)
Lesser-known health benefits of vitamin D:
- Blood pressure(12, 13)
- Cardiovascular events(14)
- Support blood glucose regulation (15)
- Inflammation
- Immune function -Allergic diseases (16, 17)
- COVID-19 (18)
- Type 2 diabetes (15)
- Brain Health (19)
It is essential to note that the health benefits ranging from blood pressure to brain health were demonstrated in individuals who were deficient and then brought their levels to an optimal range.
Get yourself tested to understand your own vitamin D levels.
Our Practice Manager Louisa – topping up on Vitamin D
How does Vitamin D affect so many different areas of health?
Vit D can influence how your genes work, by binding to a vit D receptor inside cells which then binds directly to different gene locations.(20) This vit D receptor is found in every organ of the body (including the brain) and in more than 30 different tissues.
What are optimal levels of Vitamin D?
The reference ranges below are used by the NHS: (21)
- <25 nmol/L – DEFICIENT
- 25-50 nmol/L – INSUFFICIENT
- 50-75 nmol/L – ADEQUATE
- >75 nmol/L – OPTIMUM
Everyone should be aiming for optimal levels of vitamin D (>75 nmol/L) rather than just adequate.
Vitamin D supplementation guidelines
The NHS recommends children from the age of 1 year and adults (Including pregnant and breastfeeding women and people at risk of vit D deficiency) take –
10 micrograms (mcg/μg) of vitamin D a day
= 400 IU (International units) (22)
Those with very low vit D levels should consult their healthcare practitioner for the right level of supplementation as they may prescribe higher doses for a limited time. Taking too much over an extended period can become toxic, resulting in excess calcium in the blood. (23)
Why take Vitamin D and Vitamin K together?
Higher dose vit D supplements should also be taken with vitamin K.
Vitamin K helps to direct calcium to the bones.(24) Without it, the increased calcium can be deposited in arteries and soft tissues causing them to stiffen. It is best to discuss with your health practitioner how much vitamin K to take. Vitamin D and vitamin K2 are often sold in a combined form.
Why might I still have low Vitamin D levels even though I am taking a supplement / I get a lot of sun?
You could be lacking nutrients needed to make active vitamin D such as magnesium or B-vitamins.(9) Equally, you could be genetically predisposed to not making sufficient vitamin D.(20)
In summary, Vit D is crucial to your health having positive benefits from your bones, your brain and imposing your overall health, wellness and wellbeing. If in the UK, try and get some sun on your skin between April to September. Consider supplementation if you think you may be low in vitamin D. It is difficult to get sufficient vit D with food alone. If you’re concerned about your vit D levels, please consult your healthcare practitioner who would know how best to optimise your levels
References
- Braithwaite J. UK Vitamin D Statistics 2024: 57% of Brits Have Low Vit D Levels: Forth; 2024 [Available from: https://www.forthwithlife.co.uk/blog/uk-vitamin-d-statistics/.
- Rebelos E, Tentolouris N, Jude E. The Role of Vitamin D in Health and Disease: A Narrative Review on the Mechanisms Linking Vitamin D with Disease and the Effects of Supplementation. Drugs [Internet]. 2023; 83(8):[665-85 pp.]. Available from: https://dx.doi.org/10.1007/s40265-023-01875-8.
- Bikle DD. Vitamin D: Production, Metabolism and Mechanisms of Action. In: Feingold KR, Anawalt B, Blackman MR, Boyce A, Chrousos G, Corpas E, et al., editors. Endotext.2000.
- The British Health Foundation. 2024 [Available from: https://www.britishskinfoundation.org.uk/sunlight-and-vitamin-d#:~:text=In%20simple%20terms%2C%20they%20have,25%2D40%20minutes%20is%20recommended
- National Institutes of Health supplements -Office of Dietary Supplements. Vitamin D-Fact Sheet for Health Professionals 2024 [Available from: https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/.
- Holick MF. The vitamin D deficiency pandemic: Approaches for diagnosis, treatment and prevention. Reviews in Endocrine and Metabolic Disorders [Internet]. 2017; 18(2):[153-65 pp.]. Available from: https://dx.doi.org/10.1007/s11154-017-9424-1.
- Jiang X, Kiel DP, Kraft P. The genetics of vitamin D. Bone [Internet]. 2019 2019/09/01/; 126:[59-77 pp.]. Available from: https://www.sciencedirect.com/science/article/pii/S8756328218303703.
- Vitamin D-Vitamins and minerals 2024 [Available from: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/.
- Uwitonze AM, Razzaque MS. Role of Magnesium in Vitamin D Activation and Function. J Am Osteopath Assoc. 2018;118(3):181-9.
- Sizar O, Khare S, Goyal A, Givler A. Vitamin D deficiency. 2023. In: StatPearls. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532266/.
- Delinocente MLB, Luiz MM, De Oliveira DC, De Souza AF, Ramírez PC, De Oliveira Máximo R, et al. Are Serum 25-Hydroxyvitamin D Deficiency and Insufficiency Risk Factors for the Incidence of Dynapenia? Calcified Tissue International [Internet]. 2022; 111(6):[571-9 pp.]. Available from: https://dx.doi.org/10.1007/s00223-022-01021-8.
- Chen S, Gemelga G, Yeghiazarians Y. Is Vitamin D Supplementation an Effective Treatment for Hypertension? Curr Hypertens Rep [Internet]. 2022 Oct; 24(10):[445-53 pp.]. Available from: https://pubmed.ncbi.nlm.nih.gov/35737199/.
- Chen S, Sun Y, Agrawal DK. Vitamin D deficiency and essential hypertension. J Am Soc Hypertens [Internet]. 2015; 9(11):[885-901 pp]. Available from: https://pubmed.ncbi.nlm.nih.gov/26419755/.
- Cosentino N, Campodonico J, Milazzo V, De Metrio M, Brambilla M, Camera M, et al. Vitamin D and Cardiovascular Disease: Current Evidence and Future Perspectives. Nutrients [Internet]. 2021; 13(10):[3603 p.]. Available from: https://dx.doi.org/10.3390/nu13103603.
- Mitri J, Muraru MD, Pittas AG. Vitamin D and type 2 diabetes: a systematic review. European Journal of Clinical Nutrition [Internet]. 2011; 65(9):[1005-15 pp.]. Available from: https://dx.doi.org/10.1038/ejcn.2011.118.
- Martens PJ, Gysemans C, Verstuyf A, Mathieu AC. Vitamin D’s Effect on Immune Function. Nutrients [Internet]. 2020 Apr 28: 12(5). Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7281985/.
- Zhang P, Xu Q, Zhu R. Vitamin D and allergic diseases. Frontiers in Immunology. 2024;15.
- L Bishop E, Ismailova A, Dimeloe S, Hewison M, White JH. Vitamin D and Immune Regulation: Antibacterial, Antiviral, Anti‐ JBMR Plus [Internet]. 2021; 5(1). Available from: https://dx.doi.org/10.1002/jbm4.10405.
- Anjum I, Jaffery SS, Fayyaz M, Samoo Z, Anjum S. The Role of Vitamin D in Brain Health: A Mini Literature Review. Cureus [Internet]. 2018. Available from: https://dx.doi.org/10.7759/cureus.2960.
- Voltan G, Cannito M, Ferrarese M, Ceccato F, Camozzi V. Vitamin D: An Overview of Gene Regulation, Ranging from Metabolism to Genomic Effects. Genes (Basel) [Internet]. 2023 Aug 25 [cited; 14(9). Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10531002/#:~:text=Vitamin%20D%20is%20able%20to,%2Dtype%20lymphocytes%20%5B103%5D.
- Vitamin D – Reference ranges 2024 [Available from: https://www.southtees.nhs.uk/services/pathology/tests/vitamin-d/.
- Vitamin D-Vitamins and minerals 2020 [Available from: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/#:~:text=Do%20not%20take%20more%20than,(2%2C000%20IU)%20a%20day.
- Marcinowska-Suchowierska E, Kupisz-Urbańska M, Łukaszkiewicz J, Płudowski P, Jones G. Vitamin D Toxicity–A Clinical Perspective. Frontiers in Endocrinology [Internet]. 2018; 9. Available from: https://dx.doi.org/10.3389/fendo.2018.00550.
- van Ballegooijen AJ, Pilz S, Tomaschitz A, Grübler MR, Verheyen N. The Synergistic Interplay between Vitamins D and K for Bone and Cardiovascular Health: A Narrative Review. Int J Endocrinol [Internet]. 2017; 2017:[7454376 p.]. Available from: https://pubmed.ncbi.nlm.nih.gov/29138634/.
