Vitamin D 101: Everything You Need to Know to Get Started

📌 Updated: This personal post has been expanded into a full protocol.
For the science-backed guide to optimizing Vitamin D for brain health and aging:

Read the new article here »

Here’s a quick guide for you to get an overview on your Vitamin D intake, including its sources from the sun, food, recommended daily allowance (RDA), optimal intake, maximum safe dose, and considerations for supplementation.

1. Sun Exposure:

When your skin is exposed to the sun’s UVB rays, it synthesizes Vitamin D.
The amount of vitamin D produced varies based on factors such as skin color, geographic location, time of day, season, and sunscreen use.
Spending about 10 to 30 minutes in the sun (without sunscreen) a few times a week can be sufficient for many individuals to meet their Vitamin D needs.
However, caution should be exercised to avoid excessive sun exposure. It can be a good idea to wear a cap and avoid direct sun exposure.

Here’s a guide for you to get your daily vitamin D intake, including its sources from the sun, food, recommended daily allowance (RDA), optimal intake, maximum safe dose, and considerations for supplementation. **1. Sun Exposure:** When your skin is exposed to the sun's UVB rays, it synthesizes vitamin D. The amount of vitamin D produced varies based on factors such as skin color, geographic location, time of day, season, and sunscreen use. Spending about **10 to 30** minutes in the sun (without sunscreen) **a few times a week** can be sufficient for many individuals to meet their vitamin D needs. However, caution should be exercised to avoid excessive sun exposure. **It can be a good idea to wear a cap and avoid direct sun exposure**. **2. Dietary Sources:** To help you better understand the vitamin D content in various foods, here is a list of estimated amounts of vitamin D found in some commonly consumed sources: 1. Fatty fish: Fatty fish are sources of vitamin D. A 3.5-ounce (100-gram) serving of cooked salmon can provide around 570 IU of vitamin D. Mackerel and sardines, in the same serving size, offer approximately 450 IU and 250 IU of vitamin D, respectively. 2. Fortified dairy products: Certain dairy products are fortified with vitamin D to enhance their nutritional value. A typical 8-ounce (240 ml) glass of fortified milk can contain around 100 IU of vitamin D. Similarly, an 8-ounce serving of fortified yogurt or some cheeses can provide roughly 80 IU of vitamin D. 3. Fortified plant-based milk: For those following a plant-based diet, fortified plant-based milk alternatives like almond milk, soy milk, or oat milk can be good sources of vitamin D. On average, an 8-ounce serving of fortified plant-based milk may contain approximately 100 IU of vitamin D. 4. Egg yolks: Eggs are a natural source of vitamin D, with the majority of it concentrated in the yolk. A large egg yolk typically provides about 40 IU of vitamin D. 5. UV-exposed mushrooms: Some varieties of mushrooms, such as shiitake and maitake, can synthesize vitamin D when exposed to ultraviolet (UV) light. Approximately 3.5 ounces (100 grams) of UV-exposed mushrooms may offer around 100-200 IU of vitamin D. **3. Recommended Daily Allowance (RDA):** The RDA for most individuals is currently as follows: - Infants (0-12 months): 400-1,000 IU (International Units) per day. - Children and Adults (1-70 years): 600-800 IU per day. - Adults over 70 years: 800-1,000 IU per day **4. Optimal Intake:** The optimal intake of vitamin D may exceed the RDA, especially for certain groups with increased needs or limited sun exposure. Some experts suggest that an optimal daily intake of vitamin D for adults might range from 1,000 to 4,000 IU per day. However, one must individualize the dose based on age, health status, skin darkness, and geographic location. **5. Maximum Safe Daily Dose:** Vitamin D is a fat-soluble vitamin, meaning it can accumulate in the body over time. **The upper limit of safe daily vitamin D intake for most adults is considered to be around 4,000 IU.** Taking excessively high doses of vitamin D can lead to toxicity, which may result in hypercalcemia (elevated blood calcium levels) and related health issues. **6. Supplementation:** Supplements can be helpful for those who have limited sun exposure or difficulty obtaining enough from dietary sources. Vitamin D supplements are available in various forms, including vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D3 is generally preferred for supplementation as it is similar to the form produced in the skin. **7. Recommended Supplement Dosage:** Generally, daily supplementation in the range of 1,000 to 2,000 IU is safe for most adults. Prescription forms exist in very high doses. **8. Monitoring Vitamin D Levels:** Is is important for you to do this 2x a year, once at the end of summer, and once at end of winter.

2. Dietary Sources:

To help you better understand the Vitamin D content in various foods, here is a list of estimated amounts of Vitamin D found in some commonly consumed sources:

Fatty fish: Fatty fish are sources of vitamin D. A 3.5-ounce (100-gram) serving of cooked salmon can provide around 400-500IU of vitamin D. Mackerel and sardines, in the same serving size, offer approximately 450 IU and 200 IU of vitamin D, respectively.
Fortified dairy products: Certain dairy products are fortified with vitamin D to enhance their nutritional value. An 8-ounce (240 ml) glass of fortified milk can contain around 100 IU of vitamin D. Similarly, an 8-ounce serving of fortified yogurt or some cheeses can provide roughly 80 IU of vitamin D.
Fortified plant-based milk: For those following a plant-based diet, fortified plant-based milk alternatives like almond milk, soy milk, or oat milk can be good sources of vitamin D. On average, an 8-ounce serving of fortified plant-based milk may contain approximately 100 IU of vitamin D.
Egg yolks: Eggs are a natural source of vitamin D, with the majority of it concentrated in the yolk. A large egg yolk typically provides 20-40 IU of vitamin D.
UV-exposed mushrooms: Some varieties of mushrooms, such as shiitake and maitake, can synthesize vitamin D when exposed to ultraviolet (UV) light. Approximately 3.5 ounces (100 grams) of UV-exposed mushrooms may offer around 100-200 IU of vitamin D.

3. Recommended Daily Allowance (RDA): The RDA for most individuals is currently as follows:

Infants (0-12 months): 400-1,000 IU (International Units) per day.
Children and Adults (1-70 years): 600-800 IU per day.
Adults over 70 years: 800-1,000 IU per day

4. Optimal Intake: The optimal intake of vitamin D may exceed the RDA, especially for certain groups with increased needs or limited sun exposure. Some experts suggest that an optimal daily intake of vitamin D for adults might range from 1,000 to 4,000 IU per day. However, one must individualize the dose based on age, health status, skin darkness, and geographic location.

5. Maximum Safe Daily Dose: Vitamin D is a fat-soluble vitamin, meaning it can accumulate in the body over time. The upper limit of safe daily vitamin D intake for most adults is considered to be around 4,000 IU. Taking excessively high doses of vitamin D can lead to toxicity, which may result in hypercalcemia (elevated blood calcium levels) and related health issues.

6. Supplementation: Supplements can be helpful for those who have limited sun exposure or difficulty obtaining enough from dietary sources. Vitamin D supplements are available in various forms, including vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D3 is generally preferred for supplementation as it is similar to the form produced in the skin.

7. Recommended Supplement Dosage: Generally, daily supplementation in the range of 1,000 to 2,000 IU is safe for most adults. Prescription forms exist in very high doses.

8. Monitoring Vitamin D Levels: It is important for you to do this at least 2x a year, once at the end of summer, and once at end of winter.

I recently wrote in detail about my own Vitamin D deficiency issues usually in early Spring, and how I have formulated a new strategy to prevent that better in the future. You can read that here.

Disclaimer

This information is not medical advice. This content and other content on this website is for informational and educational purposes only and is not intended to be a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

References

Lu Z, Chen TC, Zhang A, Persons KS, Kohn N, Berkowitz R, Martinello S, Holick MF. An evaluation of the vitamin D3 content in fish: Is the vitamin D content adequate to satisfy the dietary requirement for vitamin D? J Steroid Biochem Mol Biol. 2007 Mar;103(3-5):642-4. doi: 10.1016/j.jsbmb.2006.12.010. Epub 2007 Jan 30. PMID: 17267210; PMCID: PMC2698592.
Keegan RJ, Lu Z, Bogusz JM, Williams JE, Holick MF. Photobiology of vitamin D in mushrooms and its bioavailability in humans. Dermatoendocrinol. 2013 Jan 1;5(1):165-76. doi: 10.4161/derm.23321. PMID: 24494050; PMCID: PMC3897585.