Plenty of Sunshine, Yet Low Vitamin D? Understanding the Sunshine Paradox
Being born and raised in one of the sunniest countries in the world might make vitamin D deficiency seem unlikely. However, study after study and countless research papers have found that vitamin D deficiency is common in Saudi Arabia.
Several factors can reduce vitamin D production in the skin, including covering most of the skin, spending time indoors during the hottest hours of the day, and using sunscreen.
This article discusses what the research reveals, who should consider testing their vitamin D levels, and how to supplement safely.
Key Takeaways
· The overall prevalence of vitamin D (VD) deficiency across 16 studies conducted in Saudi Arabia in 2018 was estimated using a meta-analysis. The overall effect size was 63.5%, with a wide range of effect sizes across the individual studies.
· Vitamin D supports bone and muscle health, and supplements can be beneficial for people who are deficient.
· The recommended daily amount for adults is 600 IU (15 mcg) up to age 70 and 800 IU (20 mcg) daily thereafter. The upper limit is 4,000 IU (100 mcg) per day.
· Higher doses may be used to correct a deficiency, but they should be taken under medical supervision with follow-up blood testing.
· Taking more than the recommended upper limit does not provide additional benefits and may lead to imbalances, such as elevated blood calcium levels.
Why Is Vitamin D Deficiency Common in a Sunny Country?
The skin produces vitamin D when exposed to ultraviolet B (UVB) rays. However, several common factors may restrict this process:
· Avoiding high temperatures during the day by spending most of the time in air-conditioned buildings.
· The common and valued practice in the Kingdom of covering most of the body with clothing.
· Regular use of sunscreen for skin cancer protection.
· Increased melanin levels, which can reduce vitamin D production.
· Obesity, which may be associated with reduced vitamin D levels in the blood.
· Few foods naturally contain vitamin D. The main dietary sources include fatty fish and egg yolks, while the amount of vitamin D in fortified foods varies.
Exact prevalence rates should be interpreted with caution because diagnostic methods differed across the studies. Further research is also needed, as recommended by the authors of the 2018 meta-analysis.
The overall message, however, is that low vitamin D levels are frequently observed, highlighting the importance of increasing awareness.
Understanding Your Blood Test
The level of 25-hydroxyvitamin D [25(OH)D] in the blood is used to determine vitamin D status. The following categories are used by the National Institutes of Health Office of Dietary Supplements (NIH ODS):
|
Category |
25(OH)D (nmol/L) |
25(OH)D (ng/mL) |
What It Means |
|
Deficiency |
< 30 |
< 12 |
Associated with rickets and osteomalacia |
|
Inadequacy |
30–50 |
12–20 |
May be suboptimal for bone health |
|
Sufficient |
> 50 |
> 20 |
Adequate for most healthy people |
|
Possible Concern |
> 125 |
> 50 |
Potential adverse effects at high levels |
Some other professional organizations may use slightly different thresholds, so talk with your doctor about your individual results.
Potential Benefits
Bone Health
Vitamin D helps the body absorb calcium. According to the NIH ODS, vitamin D supplements provide modest benefits for measures of bone mineral density in some small groups of postmenopausal women and older men. However, results regarding fracture reduction in generally healthy older adults have been inconsistent.
Prevention of Rickets and Osteomalacia
Rickets and osteomalacia are conditions associated with weakened or softened bones. Correcting a vitamin D deficiency can help prevent these conditions.
Other Health Conditions
For cancer prevention, heart disease, depression, and weight loss, the NIH ODS reports that studies and clinical trials have produced mixed results. Supplements should not be promoted as treatments for these conditions.
Who May Need Testing or Supplements?
Some people may need to discuss vitamin D testing or supplementation with their doctor, including:
· Individuals who get little sun exposure or protect most of their skin when outdoors.
· Older adults and people with dark skin.
· People with obesity or those who have undergone bariatric surgery.
· People with fat malabsorption, such as those with coeliac disease or Crohn's disease.
· Breastfed babies, who require 400 IU of vitamin D daily, according to pediatric guidance.
· Anyone experiencing bone pain, bone weakness, or repeated fractures should not treat with supplements and should instead consult a healthcare professional.
Side Effects and Precautions
· Excessive vitamin D intake can lead to hypercalcaemia, or high levels of calcium in the blood. Symptoms may include nausea, vomiting, weakness, and confusion. In severe cases, it can lead to kidney damage and heart rhythm disturbances. The NIH ODS notes that toxicity is generally associated with very high blood concentrations, above 375 nmol/L (150 ng/mL).
· Review all the products you take, as vitamin D may be found in fortified foods, calcium supplements, and multivitamins.
· Orlistat can reduce the absorption of vitamin D. Thiazide diuretics and steroids may also interact with vitamin D. If you take regular medications, consult your pharmacist or doctor.
· Vitamin D is fat-soluble, so taking it with a meal that contains some fat can help with absorption.
· High-dose vitamin D regimens are established and used in clinical practice, including weekly or monthly dosing. These doses should only be taken according to your doctor's instructions and should not be copied from recommendations shared on social media.
Practical Tips
1. Discuss with your doctor whether you should consider getting a 25(OH)D blood test.
2. Take the recommended supplement dose for the recommended period, and have your levels retested when advised.
3. Include vitamin D-containing foods in your diet, such as oily fish, eggs, and fortified foods.
4. Brief but safe sun exposure may help support vitamin D production. However, consider the risks of skin cancer and heat-related illness, particularly during the summer.
Frequently Asked Questions
Vitamin D2 or D3: Which Is Better?
Both vitamin D2 and D3 can increase vitamin D levels, with D3 being the more commonly used form. Use the product recommended by your doctor.
Is It Okay to Take Vitamin D Daily Rather Than Weekly?
Many people take vitamin D daily. Healthy adults should generally stay within the upper limit of 4,000 IU per day unless a higher treatment dose has been specifically recommended and supervised by a healthcare professional.
Does Vitamin D Make Me Feel Better or Healthier?
Clinical trials have produced inconsistent results regarding vitamin D supplementation and depression or other health conditions in people who are not vitamin D deficient.
Can I Get Too Much Vitamin D From the Sun?
The skin regulates its own vitamin D production, so vitamin D toxicity from sunlight is not a concern. However, excessive sun exposure can cause sunburn and skin damage.
Conclusion
Vitamin D deficiency is common in Saudi Arabia and should be taken seriously. However, the most appropriate approach is to have your vitamin D levels tested if you are at risk, use supplements when a deficiency is identified, and retest your levels when recommended to ensure they have reached an appropriate range.
Avoid self-dosing with high amounts of vitamin D and be cautious of claims that vitamin D can cure a wide range of unrelated health conditions.
This article is intended for general educational purposes only and does not replace advice from a doctor or pharmacist.
References
- Al-Alyani H, Al-Turki HA, Al-Essa ON, Alani FM, Sadat-Ali M. Vitamin D Deficiency in Saudi Arabians: A Reality or Simply Hype: A Meta-Analysis (2008–2015). Journal of Family and Community Medicine. 2018. DOAJ – Article
- National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. NIH ODS – Vitamin D Fact Sheet