Thanks to the sun, vitamin D is literally everywhere. Yet research has found that almost 40% of peoplemay be dealing with a vitamin D deficiency. There is a fix for this, however, leading those who have lower levels of vitamin D to increase it through supplements. This is important because you need vitamin D for some pretty major functions, such as helping your body absorb calcium to develop strong bones.

For those who take vitamin D supplements, you may wonder if you can put that bottle back in the medicine cabinet during the summer months when your sunlight exposure is greater. Here’s what you need to know about vitamin D intake - including how much you need and the signs that sunshine isn’t giving you quite enough.

Can you ditch vitamin D supplements during summer?

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Here’s how you naturally get vitamin D

First, vitamin D has two main types, vitamin D2, and vitamin D3. There are typically two avenues you can get these natural sources of vitamin D: the sun and your diet. You get vitamin D from sunlight simply by just being in it. (File this under: Really cool things your body just does.) The sun’s ultraviolet B (UVB) rays interact with a protein in the skin called 7-DHC. Once UVB and 7-DHC get together, it turns into vitamin D3 in the body. This happens whether or not you wear sunscreen.

As for your diet, there are certain foods that are rich in vitamin D. These include salmon, sardines, trout, mushrooms, and eggs. Other foods are fortified with vitamin D like milks (dairy and non-dairy such as soy and almond), orange juice, breakfast cereals, and yogurt. This means that vitamin D2 and/or D3 were added to these foods to up the nutritional profile.

What are some signs of having low vitamin D levels?

It may seem like you have a lot of access to vitamin D between the amount you get from sunlight and from the foods you eat and while that’s certainly true you still may not have enough. Most people don’t consume extremely large quantities of vitamin D-filled foods. (For example, it’s recommendedthat adults get a minimum of 600 IU of vitamin D a day. One egg has 44 IU of vitamin D.) Plus, a large population of people live in an area with winter, causing shorter days with less sunlight for a few months out of the year. These factors combined can lead to a vitamin D deficiency.

If you’re not constantly eating fatty fish or spending time outdoors, a vitamin D deficiency may be a problem for you. Some signs include:

  • Fatigue

  • Bone pain

  • Muscle cramps, aches, or weakness

  • Mental health changes, such as mood shifts or depression

Do you really need vitamin D supplements if you’re out in the summer sun a lot?

For those who are vitamin D deficient, taking a daily vitamin D supplement can make up for the lost levels your body requires. If this is you, chances are you found this deficiency through blood work with a healthcare provider or by using an at-home testing service like Base to measure vitamin levels that may be affecting your energy levels and causing fatigue.

However, with summer approaching you may be curious: do you really need to keep taking a vitamin D supplement every day? As you might expect, the answer is nuanced

First, it’s difficult to measure just how much vitamin D you get from the sun for a few reasons. The first is if you’re wearing sunscreen (and if you’re wearing it correctly) as well as what time you’re outdoors in the summer. In some cases properly wearing sunscreen can block UVB and therefore vitamin D production by over 90%. Most experts haven’t changed their stance on sun protection, though, because SPF is needed to minimize the risk for skin cancer.

As for timing, the sun is typically the strongest between 10 a.m. and 4 p.m., which means if you go outside during these hours you’ll need less exposure to sunlight to produce vitamin D than you would later in the day. One study published in Advances in Experimental Medicine and Biolog found that noon is the ideal time to maximize vitamin D production.

Certain people may also be able to absorb and produce more vitamin D than others. Those who are fair-skinned can produce more vitamin D from sunlight than those with darker skin. (Yet it’s worth noting that those with fair skin may also be more likely to regularly apply SPF, limiting vitamin D production.) Skin tone aside, as the skin ages, it’s also less adept at making vitamin D.

Health conditions requiring certain medications as well as inflammatory bowel diseases like ulcerative colitis and Crohn’s disease impact the body’s ability to hold on to vitamin D. That’s because these conditions affect the digestion of fat, and since vitamin D is a fat-soluble vitamin, it requires fat from the body and ingested foods to be properly absorbed. Even obesity may affect vitamin D levels. While it’s stored in fat, having excess fat may prohibit the body from being able to access and utilize vitamin D.

Play it safe and keep a pulse on your vitamin D levels year-round

There are so many factors when it comes to knowing if you’re getting enough vitamin D. While the summer sun can certainly help, those with preexisting conditions, darker skin tones, or those of a certain age may still need to take a vitamin D supplement in addition to soaking up some extra rays.\ That’s why the best course of action is to continually monitor your vitamin D levels, to see just how much the changing seasons impact the amount of vitamin D in your body. You can do this with the help of a healthcare provider and regular blood tests, or with Base’s quarterly at-home tests, which are sent right to your front door. With a quick finger prick, you’ll get personalized recommendations on how frequently you should be taking vitamin D and how much you may need.

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