Vitamin D3 (Cholecalciferol)

What is Vitamin D3?

Vitamin D is a fat-soluble vitamin and hormone precursor that plays a major role in bone health, immune function, muscle repair, and inflammation regulation (1). Vitamin D is unique among nutrients because in addition to dietary sources, it’s also synthesised in the skin through exposure to UVB radiation. However, due to sunscreen use, clothing coverage, and spending extended time indoors, many of us don’t produce sufficient amounts (2).

Vitamin D3 (cholecalciferol) is the most bioactive form of the vitamin, and is the same type your skin synthesises when exposed to sunlight (3). It’s more effective at raising and maintaining vitamin D levels than D2 (ergocalciferol), making it the gold standard for supplementation (4).

Why Do Outdoor Adventurers Need Vitamin D3?

It’s easy to think that if you spend a lot of time outdoors, then your vitamin D needs are covered. However, if we follow sun safety recommendations, then we’re most likely wearing a combination of sunscreen, hats, long sleeves, and avoiding activity during peak UV periods of the day, all of which can lead to deficiency (5). 

Vitamin D is a key player in musculoskeletal health, helping you absorb calcium, maintain strong bones, and repair muscle tissue after long days on the trail (6,14). It’s also involved in modulating immune responses, reducing your risk of respiratory infections (7), and potentially improving mental resilience, although research is ongoing (8).

Dietary Sources of Vitamin D3?

Vitamin D is naturally found in fatty fish (like salmon, sardines, and mackerel), cod liver oil, liver, and egg yolks. Some countries also fortify foods like milk and cereal, but in Australia and USA fortification is limited, and intakes are generally low (9).

Vegan or low-fat trail diets tend to lack natural sources, and unless you're carrying a side of salmon in your pack (please don't), supplementation is often necessary to maintain adequate levels, especially in winter or on long-distance treks.

What’s the Best Form of D3 For Hikers?

Vitamin D3 (cholecalciferol) is the form your body prefers. The 100,000 IU/g format used in Optiventure is a high-potency microencapsulated powder, meaning you get a tiny, accurate dose that’s shelf-stable and travel-friendly (10). It also avoids the bulky oil-filled capsules typical of vitamin D supplements.

The form used here is bioavailable, easy to blend with other micronutrients, and designed for optimal uptake even in powdered formulations.

Key Information About Vitamin D3

Deficiency Stats

Despite the Aussie sun, vitamin D deficiency is widespread. Around 1 in 4 Australian adults have inadequate levels during winter and spring, with even higher rates in southern states like Victoria and Tasmania (13).

Outdoor adventurers may think they're in the clear, but even athletes and frequent hikers show low vitamin D status in multiple studies, especially during colder months, at high altitudes (14), and with older age (6). 

Why Optiventure Has 3,000IU of Vitamin D3

The 0.03mg dose of Vitamin D3 delivers 3,000 IU – a therapeutic-level dose that’s still well within the safe daily upper limit (10,000 IU) for short-term use (15). Here's why that matters:

• It replenishes low stores quickly, especially when you're not getting consistent sun exposure
• It supports bone density, muscle recovery, and immune regulation during demanding hikes
• It's a realistic, compact alternative to chasing sunlight or oily fish on the trail
• It stays stable and effective even in a rugged, lightweight supplement format

A 3,000 IU dose has been shown in studies to be safe and effective for improving vitamin D status, particularly when taken for short to moderate periods like a hiking trip or seasonal boost (14,16). It’s not a megadose – it’s a performance dose.

References

1. Holick, M. F. (2007). Vitamin D deficiency. New England Journal of Medicine, 357(3), 266–281. https://doi.org/10.1056/NEJMra070553
2. Webb, A. R., & Engelsen, O. (2006). Calculated ultraviolet exposure levels for a healthy vitamin D status. Photochemistry and Photobiology, 82(6), 1697–1703. https://doi.org/10.1562/2006-03-17-RA-869
3. Armas, L. A., Hollis, B. W., & Heaney, R. P. (2004). Vitamin D2 is much less effective than vitamin D3 in humans. The Journal of Clinical Endocrinology & Metabolism, 89(11), 5387–5391. https://doi.org/10.1210/jc.2004-0360
4. Tripkovic, L., Lambert, H., Hart, K., Smith, C. P., Bucca, G., Penson, S., Chope, G., Hyppönen, E., Berry, J., Vieth, R., & Lanham-New, S. A. (2012). Comparison of vitamin D2 and D3 supplementation in raising serum 25-hydroxyvitamin D status: A systematic review and meta-analysis. The American Journal of Clinical Nutrition, 95(6), 1357–1364. https://doi.org/10.3945/ajcn.111.031070
5. Nowson, C. A., & Margerison, C. (2002). Vitamin D intake and vitamin D status of Australians. Medical Journal of Australia, 177(3), 149–152. https://doi.org/10.5694/j.1326-5377.2002.tb04765.x
6. Bischoff-Ferrari, H. A., Borchers, M., Gudat, F., Dürmüller, U., Stähelin, H. B., & Dick, W. (2004). Vitamin D receptor expression in human muscle tissue decreases with age. The Journal of Clinical Endocrinology & Metabolism, 89(12), 5383–5388. https://doi.org/10.1210/jc.2004-0979
7. Martineau, A. R., Jolliffe, D. A., Hooper, R. L., Greenberg, L., Aloia, J. F., Bergman, P., … Griffiths, C. J. (2017). Vitamin D supplementation to prevent acute respiratory tract infections: Systematic review and meta-analysis of individual participant data. BMJ, 356, i6583. https://doi.org/10.1136/bmj.i6583
8. Jorde, R., & Kubiak, J. (2018). Depression and vitamin D. Current Opinion in Psychiatry, 31(6), 464–471. https://doi.org/10.1097/YCO.0000000000000450
9. Food Standards Australia New Zealand (FSANZ). (2023). NUTTAB 2023 – Australian Food Composition Database. https://www.foodstandards.gov.au/science/monitoringnutrients/nuttab/pages/default.aspx
10. DSM Nutritional Products. (n.d.). Vitamin D3 100,000 IU/g Product Specification Sheet. Retrieved [date you accessed it], from [insert direct URL if available]
11. National Health and Medical Research Council. (2006). Nutrient Reference Values for Australia and New Zealand: Vitamin D.https://www .nrv.gov.au/nutrients/vitamin-d
12. Calvo, M. S., Whiting, S. J., & Barton, C. N. (2005). Vitamin D intake: A global perspective of current status. The Journal of Nutrition, 135(2), 310–316. https://doi.org/10.1093/jn/135.2.310
13. Australian Bureau of Statistics. (2014). Australian Health Survey: Biomedical Results for Nutrients, 2011–12. https://www.abs.gov.au/statistics/health/health-conditions-and-risks/australian-health-survey-biomedical-results-nutrients/latest-release
14. Close, G. L., Russell, J., Cobley, J. N., Owens, D. J., Wilson, G., Gregson, W., … Morton, J. P. (2013). Assessment of vitamin D concentration in non-supplemented professional athletes and healthy adults during the winter months in the UK. International Journal of Sport Nutrition and Exercise Metabolism, 23(2), 96–104. https://doi.org/10.1123/ijsnem.23.2.96
15. Vieth, R. (1999). Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. The American Journal of Clinical Nutrition, 69(5), 842–856. https://doi.org/10.1093/ajcn/69.5.842
16. Holick, M. F., & Chen, T. C. (2008). Vitamin D deficiency: A worldwide problem with health consequences. The American Journal of Clinical Nutrition, 87(4), 1080S–1086S. https://doi.org/10.1093/ajcn/87.4.1080S
17. National Institutes of Health, Office of Dietary Supplements. (2024, July 12). Vitamin D: Fact sheet for health professionals [Fact sheet]. U.S. Department of Health and Human Services. https://ods.od.nih.gov/factsheets/VitaminD‑HealthProfessional