A Practical Guide to Vitamin D: Food, Sunlight, and Supplements

Now that we have covered the science, let us get practical. If you have determined that improving your vitamin D status makes sense, you have three sources available: sunlight, food, and supplements. Understanding how each works helps you make informed choices.

Sunlight: The Original Source

Your skin produces vitamin D when exposed to ultraviolet B (UVB) radiation from sunlight. This is how humans have maintained vitamin D status throughout most of our evolutionary history.

How Much Sun Do You Need?

The classic recommendation is 15 to 20 minutes of direct sun exposure to arms and legs, without sunscreen, several times per week. However, this varies enormously based on:

Skin tone: People with darker skin have more melanin, which reduces vitamin D synthesis. Those with very dark skin may need 3 to 6 times more sun exposure than those with light skin to produce the same amount of vitamin D.

Latitude and season: At latitudes above about 35 degrees (north of Los Angeles in the US), UVB rays are insufficient for vitamin D synthesis during winter months, regardless of how much time you spend outside. The sun’s angle is simply too low.

Time of day: Midday sun (10 AM to 2 PM) provides the most efficient vitamin D synthesis.

Cloud cover and pollution: Both reduce UVB reaching your skin.

Age: Older adults produce vitamin D less efficiently from sun exposure.

The Sunscreen Dilemma

Sunscreen blocks UVB and therefore reduces vitamin D synthesis. However, skin cancer is a real concern. A reasonable approach for most people: get brief, regular sun exposure for vitamin D (15 to 20 minutes on arms and legs), then apply sunscreen for longer sun exposure. Alternatively, rely on food and supplements for vitamin D and use sunscreen consistently if you are at high risk for skin cancer.

Food Sources

Very few foods naturally contain significant vitamin D. This is why deficiency is so common, particularly in populations with limited sun exposure.

Best Natural Sources

Fatty fish: Salmon (600 to 1000 IU per 3.5 oz serving), mackerel, sardines, and trout are the best food sources. Wild-caught salmon contains more vitamin D than farmed.

Cod liver oil: Very high in vitamin D (around 1300 IU per tablespoon) but also high in vitamin A, so moderation is important.

Egg yolks: About 40 IU per yolk. Eggs from pasture-raised chickens may contain more.

UV-exposed mushrooms: Mushrooms exposed to UV light can produce vitamin D2. Check labels, as most commercial mushrooms are grown in the dark and contain little vitamin D.

Fortified Foods

Many foods in the US are fortified with vitamin D:

Milk: About 100 IU per cup

Fortified orange juice: About 100 IU per cup

Fortified cereals: Varies, check labels

Some yogurts and plant milks: Check labels, fortification varies

Why Food Alone Is Often Insufficient

Even with conscious effort, it is difficult to get enough vitamin D from food alone to correct deficiency. You would need to eat fatty fish daily and consume multiple servings of fortified foods to reach 2000 IU, the minimum dose associated with mental health benefits. For most people, achieving adequate vitamin D through diet alone is impractical.

Supplements

For many people, especially those at risk of deficiency, supplementation is the most reliable way to achieve and maintain adequate vitamin D levels.

D3 vs D2

Vitamin D3 (cholecalciferol) is the form your skin produces and is more effective at raising blood levels than D2 (ergocalciferol). Most experts recommend D3 for supplementation.

Forms Available

Softgels and capsules: The most common form. Softgels are often suspended in oil for better absorption.

Liquid drops: Allow flexible dosing and may be easier for those who have difficulty swallowing pills.

Gummies: Palatable but often contain added sugars. Fine if you prefer them, but check the actual vitamin D content.

Tablets: Work fine but may be absorbed slightly less efficiently than oil-based forms.

What to Look for in Quality

Third-party testing: Look for products verified by USP, NSF, or ConsumerLab, which test for accuracy and purity.

Appropriate dose: Most people need 1000 to 4000 IU, so choose a product that makes your target dose convenient.

Minimal additives: Simple formulations are generally preferable.

When and How to Take It

With a fat-containing meal: Vitamin D is fat-soluble and absorbed better when taken with dietary fat. Taking it with breakfast that includes eggs, or with dinner, typically works well.

Consistency matters more than timing: Whether you take it morning or evening is less important than taking it regularly.

My Practical Recommendations

If you have not tested and want to supplement anyway: 1000 to 2000 IU of D3 daily is a reasonable starting point that is unlikely to cause harm.

If you are deficient (under 20 ng/mL or 50 nmol/L): Start with 4000 IU daily for 8 to 12 weeks, then retest. Once adequate, transition to 1000 to 2000 IU daily for maintenance.

If you are insufficient (20 to 30 ng/mL or 50 to 75 nmol/L): 2000 to 3000 IU daily for 8 weeks, then retest.

Consider magnesium: Magnesium is required for vitamin D metabolism. Many people are low in magnesium, so ensuring adequate intake (through diet or a supplement like magnesium glycinate) may help optimize vitamin D’s effects.

When to Involve Your Doctor

Consult your healthcare provider before starting vitamin D supplementation if you have:

Kidney disease or a history of kidney stones

Sarcoidosis or other granulomatous diseases

Primary hyperparathyroidism

A history of high calcium levels

If you are taking medications that interact with vitamin D (certain anticonvulsants, steroids, cholestyramine)

For most people without these conditions, vitamin D supplementation at the doses discussed here is safe and does not require a prescription.

The Bottom Line

Getting enough vitamin D requires deliberate attention for most people, particularly those with risk factors for deficiency. Some combination of sensible sun exposure, vitamin D-rich foods, and supplementation is usually necessary. Testing helps you understand where you are starting and whether your approach is working.

This concludes our series on vitamin D and mental health. I hope it has given you a clearer, more nuanced understanding of this topic than the typical oversimplified coverage provides. As with most health interventions, the key is understanding who is likely to benefit, setting realistic expectations, and integrating vitamin D optimization into a comprehensive approach to mental wellness.

References

1. Holick MF. Vitamin D deficiency. New England Journal of Medicine. 2007;357(3):266-281.
2. Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academies Press; 2011.
3. Wacker M, Holick MF. Sunlight and vitamin D: A global perspective for health. Dermatoendocrinology. 2013;5(1):51-108.
4. Tripkovic L, Lambert H, Hart K, et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: A systematic review and meta-analysis. American Journal of Clinical Nutrition. 2012;95(6):1357-1364.
5. Uwitonze AM, Razzaque MS. Role of magnesium in vitamin D activation and function. Journal of the American Osteopathic Association. 2018;118(3):181-189.