Shorter days mean less sunlight — and for many people, that can also mean less vitamin D.
As summer fades and daylight hours get shorter, vitamin D is once again becoming part of the seasonal health conversation. The body produces vitamin D when skin is exposed to sunlight, but during fall and winter, weaker UVB rays can make that process less effective in many parts of the world.
Vitamin D plays an important role in helping the body absorb calcium and supporting healthy bones, muscles and immune function. While some vitamin D comes from foods such as fatty fish, egg yolks and fortified products, getting enough through diet alone can be difficult.
When Should You Start Taking Vitamin D?
For people who choose seasonal supplementation, early fall is a common time to start. In regions where winter sunlight is limited, health authorities often advise paying closer attention to vitamin D intake throughout the colder months.
In the United States, the recommended daily intake for most adults ages 19 to 70 is 600 IU, or 15 micrograms, while adults over 70 are advised to get 800 IU, or 20 micrograms, per day.
Certain people may be more likely to have low vitamin D levels, including those who spend little time outdoors, have limited sun exposure or have conditions that affect nutrient absorption. Individual needs can vary, so higher-dose supplements should not automatically be considered better.
More Isn’t Always Better
Vitamin D is essential, but excessive supplementation can be harmful. For generally healthy adults, experts recommend meeting established daily intake guidelines rather than routinely taking large doses without a medical reason.
If you are concerned about vitamin D deficiency, take medications that may affect vitamin D levels or are considering a high-dose supplement, speaking with a healthcare professional can help determine what makes sense for you.