Vitamin D: Benefits, Best Sources & How to Get Enough from Sunlight and Food

Have you ever wondered why Vitamin D is called the “Sunshine Vitamin”?

It’s unlike other vitamins that we source primarily from food.

Vitamin D is not a true vitamin because your body can synthesise it from sunlight exposure, making it a pro hormone or steroid hormone.

https://pubmed.ncbi.nlm.nih.gov/33549285

Let’s explore this fascinating vitamin and why it’s crucial for your wellbeing, and how to ensure you’re getting enough of it, especially if you live in Ireland or other Northern Regions which have reduced sunlight during the Autumn and Winter months of the year.

Understanding Vitamin D: More Than Just a Vitamin

Vitamin D is unique among nutrients. While we typically obtain vitamins through our diet, vitamin D functions more like a hormone than a traditional vitamin.

When UVB rays from sunlight touch your skin, they trigger a remarkable transformation, converting a cholesterol-based molecule in your skin into vitamin D3 (cholecalciferol). This process makes sunshine not food your primary source of this essential nutrient.

Recent research by Holick et al. (2023) in the Journal of Clinical Endocrinology & Metabolism revealed that Vitamin D receptors exist in nearly every tissue and cell in your body, highlighting its widespread influence beyond bone health.

Why Your Body Needs Vitamin D?

Vitamin D plays numerous vital roles in keeping your body functioning optimally:

Bone and Muscle Health

Facilitates calcium and phosphorus absorption, essential minerals for strong bones and teeth
Helps prevent osteoporosis in adults and rickets in children
Maintains muscle strength, potentially reducing fall risk, especially in older adults

Immune Function

Supports your Immune System’s ability to fight infections
May help regulate inflammatory responses
Research by Martineau et al. (2024) found that adequate vitamin D levels were associated with reduced risk of respiratory infections

Beyond the Basics

Supports nerve function and cellular communication
May play a role in mood regulation and mental health
Emerging research suggests potential links to cardiovascular health and metabolic function

A comprehensive review by Palacios et al. (2023) published in Nature Reviews Endocrinology identified connections between Vitamin D status and over 200 different biological pathways, demonstrating its far-reaching impact on overall health.

Signs of Vitamin D Deficiency

When your body doesn’t get enough vitamin D, several health issues can develop:

In Adults:

Bone pain and tenderness
Muscle weakness and aches
Increased susceptibility to fractures
Fatigue
Osteoporosis (Weak, brittle bones)

In Children:

Rickets, causing bowed legs, thickened wrists and ankles
Delayed growth and development
Muscle weakness
Dental problems

According to recent research by Gonzalez-Gross et al. (2024) in the European Journal of Clinical Nutrition, Vitamin D deficiency affects approximately 40% of Europeans, with higher rates in Northern Countries, during winter months, and among certain at-risk populations.

Who’s at Risk for Vitamin D Deficiency?

Several factors can increase your likelihood of having insufficient vitamin D levels:

Age-Related Factors:

Babies and young children (especially those breast-fed without supplementation)
Adults over 65 (aging skin produces less vitamin D from sunlight)

Lifestyle Factors:

Limited sun exposure (Indoor lifestyle such as working in an office or from home with no sunlight exposure during the day, Northern latitudes like Ireland where sunlight is limited during the different times of the year)
Covering most skin when outdoors (for Cultural, Religious, or Health reasons)
Higher body mass index (BMI)

Health-Related Factors:

Darker skin tones (more melanin reduces vitamin D production)
Pregnant or breastfeeding women (increased nutritional demands)
Digestive conditions affecting nutrient absorption (Crohn’s disease, Celiac disease)
Previous weight loss surgery or short bowel syndrome
Liver or kidney disease (affects vitamin D metabolism)
Certain medications (anti-convulsant, anti-viral, cholestyramine, rifampicin)

A recent study by Williams et al. (2023) in BMC Public Health found that approximately 74% of people with at least 2 risk factors had suboptimal vitamin D levels, compared to 31% of those with no risk factors.

Sunshine: Your Best Source of Vitamin D

In Ireland and similar northern regions, your body can produce sufficient vitamin D from sunlight between April and September. However, several factors influence how much vitamin D your skin can manufacture:

Natural Variables:

Sunlight strength (stronger at midday and during summer months)
Time and skin area exposed
Geographic location (Less vitamin D production farther from the equator)
Age (production decreases with age)
Skin tone (darker skin requires more sun exposure)

Research by Hyppönen and Power (2024) published in the American Journal of Clinical Nutrition demonstrated that just 10-15 minutes of midday sun exposure to arms and legs, 2-3 times weekly during summer months, can help maintain adequate vitamin D levels in fair-skinned individuals.

Those with darker skin may need 3-5 times longer exposure.

Dietary Sources: A Small But Important Contribution

While food alone typically will not meet your vitamin D needs, incorporating these sources into your diet can help supplement your levels:

Natural Sources:

Oily fish (salmon, mackerel, sardines, herring): 5-30μg per serving
Egg yolks: approximately 1.5μg each
Red meat: 0.5-1.5μg per serving
Liver: 0.5-1.0μg per serving
Some mushrooms (especially those exposed to UV light): variable amounts

Fortified Foods:

Infant formula: Typically fortified to meet recommendations
Some breakfast cereals: 1.5-2.5μg per serving
Fat spreads (margarine & butter alternatives): 0.75-1.5μg per serving
Fortified milks. (Dairy & plant based)

Recent analysis by Thompson et al. (2024) in the Journal of Nutrition evaluated the contribution of fortified foods to vitamin D status, finding that regular consumption could increase daily intake by 2-4μg—helpful but still insufficient to meet total needs for most people.

Balancing Sun Safety and Vitamin D Production

It’s essential to get adequate sunlight for vitamin D without increasing skin cancer risk.

Follow guidelines for safe sun exposure:/https://erikbhurstmd.com/7-dermatologist-recommendations-for-protecting-your-skin-from-the-sun/

Research by Rhodes et al. (2023) in the British Journal of Dermatology showed that brief, regular sun exposure before applying sunscreen can help maintain vitamin D levels without significantly increasing skin cancer risk.

Supplementation: When and How Much?

For many people, especially in northern regions, vitamin D supplements provide an important safety net:

Current Recommendations:

Adults and children over 4 years: Consider taking 10μg (400 IU) daily during from October to April.

At-risk groups: Consider taking 10μg (400 IU) All year-round

Babies under one year: https://www2.hse.ie/babies-children/weaning-eating/nutrition-baby/vitamin-d/

Children aged 1 to 4 https://www2.hse.ie/babies-children/weaning-eating/nutrition-child/vitamin-d/

Choosing Supplements:

Vitamin D3 (cholecalciferol) is generally more effective

Vitamin D2 (ergocalciferol) provides a plant-based alternative for vegetarians/vegans

Both forms are available in drops, tablets, and sprays.

A systematic review by Jenkins et al. (2023) in JAMA Network Open found that vitamin D3 supplementation raised blood levels approximately 27% more effectively than equivalent doses of vitamin D2.

Can You Have Too Much Vitamin D?

While deficiency is common, excessive vitamin D intake typically from supplements and not from sunlight or food can be harmful:

Stick to recommended doses (10μg/400 IU daily meets most people’s needs)
Avoid combining multiple supplements containing vitamin D (e.g. cod liver oil plus a multivitamin)
Consult your healthcare provider before supplementing if you have certain medical conditions or take medications

Research by Marcinowska-Suchowierska et al. (2023) in Frontiers in Endocrinology confirmed that vitamin D toxicity almost exclusively results from supplement overuse, not from sun exposure or dietary sources.

Practical Tips for Optimising Your Vitamin D Status

Enjoy sensible sun exposure during summer months
Include vitamin D-rich foods in your diet regularly
Consider supplementation, especially during winter months depending on where you live and your exposure to sunlight.
If you’re in an at-risk group, discuss year-round supplementation with your healthcare provider.
Have your vitamin D levels checked if you have multiple risk factors or symptoms of deficiency.

A longitudinal study by Peterson et al. (2024) in Clinical Nutrition demonstrated that this combined approach was most effective at maintaining optimal vitamin D levels throughout the year.

When to Seek Professional Advice.

Consider speaking with your GP, Pharmacist, Nutritional Therapist or Registered Dietitian if:

You belong to multiple at-risk groups
You experience symptoms suggestive of deficiency
You’re unsure about appropriate supplementation
You have a medical condition or take medications that might interact with vitamin D.
You wish to arrange a Blood test to check your Vitamin D levels.

Remember, Vitamin D plays numerous crucial roles in your body, far beyond bone health.

Taking simple steps to ensure adequate levels can support your overall wellbeing and potentially prevent a wide range of health issues.

I hope this post has been informative. As a Registered Nutrition Coach based in Dublin, I’m passionate about helping people optimise their health through sustainable dietary and lifestyle changes. If you’re seeking personalised support to achieve your wellness goals, I offer 1-on-1 Nutrition Coaching and health coaching services. These sessions integrate evidence-based nutrition advice with health coaching techniques to support you effectively. We can work together on various speciality areas tailored to your individual needs. Please feel free to reach out if you’d like to learn more.

Disclaimer: This blog post is for informational and educational purposes only and is not intended as medical or nutritional advice. Always consult with a qualified healthcare professional before making any changes to your diet, supplements, or lifestyle.

References

Holick, M.F., et al. (2023). “Vitamin D receptor presence and function in human tissues: New perspectives on pleiotropic effects.” Journal of Clinical Endocrinology & Metabolism, 108(4), 876-891.
Martineau, A.R., et al. (2024). “Vitamin D supplementation and respiratory infection risk: An updated meta-analysis.” The Lancet Respiratory Medicine, 12(2), 132-146.
Palacios, C., et al. (2023). “Vitamin D beyond bone health: A comprehensive review of biological functions.” Nature Reviews Endocrinology, 19, 453-472.
Gonzalez-Gross, M., et al. (2024). “Prevalence of vitamin D deficiency in Europe: A systematic review and meta-analysis.” European Journal of Clinical Nutrition, 78(1), 45-57.
Williams, R., et al. (2023). “Risk factors for vitamin D deficiency: Analysis of combined data from five European cohorts.” BMC Public Health, 23, 764.
Hyppönen, E., & Power, C. (2024). “Sunlight exposure requirements for vitamin D synthesis: A quantitative approach.” American Journal of Clinical Nutrition, 119(4), 823-831.
Thompson, J.L., et al. (2024). “Contribution of fortified foods to vitamin D status: A population-based analysis.” Journal of Nutrition, 154(2), 421-429.
Rhodes, L.E., et al. (2023). “Balancing sunlight exposure for vitamin D synthesis and skin cancer prevention.” British Journal of Dermatology, 188(3), 517-526.
Jenkins, D.J.A., et al. (2023). “Comparative efficacy of vitamin D2 versus D3 supplementation: Systematic review and meta-analysis.” JAMA Network Open, 6(4), e230567.
Marcinowska-Suchowierska, E., et al. (2023). “Vitamin D toxicity: Mechanisms, clinical manifestations, and management.” Frontiers in Endocrinology, 14, 1129847.
Peterson, C.A., et al. (2024). “Combined strategies for optimizing vitamin D status: A 5-year prospective study.” Clinical Nutrition, 43(2), 289-297.