From the Guidelines
Taking vitamin D supplements in the summertime when you've been exposed to the sun is generally unnecessary for most healthy adults. Your body naturally produces vitamin D when your skin is exposed to sunlight, with just 10-30 minutes of midday sun exposure several times a week typically providing sufficient vitamin D for many people 1. However, certain factors may warrant continued supplementation even during summer months. These include having darker skin (which reduces vitamin D production), living in northern latitudes, regularly using sunscreen (SPF 15 or higher blocks vitamin D production), staying indoors most of the time, or having medical conditions that affect vitamin D absorption.
Key Considerations
- The Institute of Medicine recommends a daily intake of 600 IU for individuals from 1 to 70 years of age, and 800 IU for individuals 71 and older, but emphasizes that this can be achieved through a combination of sun exposure and dietary intake 1.
- The concept of a "daily" dose can be misleading, as vitamin D has a half-life of 2 weeks to 3 months and is stored in adipose tissue and the liver, allowing for less frequent replenishment 1.
- Summer sun exposure may provide enough vitamin D for the winter, and major institutions have used dosing schedules as infrequent as once every 1–4 months 1.
Important Notes
- Excessive vitamin D supplementation can lead to toxicity over time, causing symptoms like nausea, weakness, and kidney problems.
- If you're uncertain about your specific needs, it's best to consult with your healthcare provider who may recommend a blood test to check your vitamin D levels before making a decision about summer supplementation.
From the Research
Vitamin D Supplementation in Summer
- The decision to take vitamin D supplements in the summer when exposed to the sun depends on various factors, including the individual's vitamin D status and overall health 2.
- Sensible sun exposure is an inexpensive and enjoyable way to maintain vitamin D stores, especially for young, otherwise healthy adults 2.
- However, some individuals, such as those with inflammatory bowel disease or prior gastric bypass, may require more vitamin D to sustain their vitamin D status, even with sun exposure 3.
Recommended Dosage
- The recommended dosage of vitamin D supplements varies among different organizations and studies, ranging from 400-2000 IU/day for adults 3, 4.
- A daily dose of 2000 IU (50 µg) of vitamin D3 may be considered a simple, effective, and safe dosage to prevent and treat vitamin D deficiency in the adult general population 4.
- It is essential to note that high doses of vitamin D may cause increased fall risk, and individual responses to vitamin D supplementation can vary depending on factors such as baseline 25(OH)D, body mass index, ethnicity, and genetics 5, 6.
Health Outcomes
- Vitamin D supplementation has been linked to various health outcomes, including reduced risk of falls, improved pain management in fibromyalgia, and reduced risk of progression to type 2 diabetes mellitus 5.
- However, the evidence for vitamin D supplementation in preventing or treating other conditions, such as cardiovascular disease, cancer, and cognitive decline, is less clear 5.
- Further research is needed to determine the optimal dosing standards and timing of vitamin D supplementation for different health outcomes and populations 5, 6.