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How vitamin D may help reduce the symptoms of seasonal affective disorder and depression
The shortest (and darkest) days of the year are upon us — this common supplement may help reduce symptoms of SAD.
Winter is hard no matter how you look at it. After all, freezing temperatures and long spans of darkness can make anyone want to curl up on the couch and stay there indefinitely. And with the shortest, coldest days of the year upon us, it's understandable if you're struggling right now. What you might not have considered is that if you're managing symptoms of depression or seasonal affective disorder (SAD), it might be worth having your doctor check your levels of vitamin D to determine whether you're deficient.
The sun is a big source of vitamin D, and during the winter months when the days are short and dark, getting enough sun exposure to bolster your levels becomes more challenging. "It's harder for most people to get enough vitamin D naturally during the winter because the sun's rays are weaker, and we tend to spend more time indoors," Samantha Cassetty, MS, RD, founder of Sam's Plate and co-author of Sugar Shock, tells Yahoo Life.
Lower levels of vitamin D have been linked to a slew of serious health issues, including depression, SAD and anxiety — and there's some evidence that taking vitamin D may help with those conditions. But vitamin D does a lot more than that, making this a crucial nutrient to make sure you're getting enough of.
If you're not familiar with vitamin D, it's fair to have questions. Here's what you need to know about the nutrient, plus what to look for if you're interested in taking a supplement to increase your levels.
A note on supplements
The products included in this article are dietary supplements. Such supplements are regulated far less stringently by the FDA than medications, with little oversight on safety or effectiveness before they go to market. Supplements may also interact with other medications and aren't appropriate for all populations or health conditions. While our health writers personally select and test products that are evidence-based, it's important to talk to your health care provider before adding a dietary supplement to your routine.
What does vitamin D do?
"Vitamin D is essential for many processes in the body, most notably in bone formation and health, and others such as immune support," Diane Rigassio Radler, PhD, RD, director of the Institute for Nutrition Interventions at Rutgers, tells Yahoo Life.
Vitamin D is also involved in cognitive function, Jessica Cording, RD, nutritionist and author of The Little Book of Game-Changers, tells Yahoo Life. "It can play a role in mood and mental performance," she says.
Research on the effect of vitamin D supplementation on mood disorders has been mixed, but there is data to suggest taking the vitamin could help with certain mental health conditions. A scientific analysis published in the Journal of Affective Disorders in 2024 found that vitamin D supplements had a "significant effect" on reducing depression symptom scores in people with the condition. Another study, published in the journal Depression and Anxiety, analyzed data from more than 7,500 people and found that vitamin D supplements can boost mood in those with low levels of the nutrient in their blood, as well as people who are diagnosed with major depressive disorder.
Research has also found that people with SAD typically have low levels of vitamin D, although studies are ongoing to see if taking vitamin D supplements can help.
Vitamin D status may impact blood pressure too. A study published in the Journal of the Endocrine Society in November 2024 followed 221 older people with hypertension and had them take either 600 or 3,750 international units (IU) of vitamin D daily for a year. The researchers discovered that taking the supplement at any dose was associated with a decrease in the participants' blood pressure.
Vitamin D may even help you live longer. "In elderly people, reversing low vitamin D levels with supplements has been shown to reduce mortality," Christy Brissette, MS, RD, owner of 80 Twenty Nutrition, tells Yahoo Life. However, it's important to note these benefits were seen when supplementation was done by those with a documented vitamin D deficiency, not those whose serum levels were considered normal.
Can you get vitamin D from food?
Yes, you can get vitamin D from food, although it's not as easy to get this way as some other nutrients. And data suggests that most Americans don't get enough of the recommended amounts of vitamin D in their diets. Exact recommendations vary by life stage and health conditions, but most adult men and women need between 15 and 20 micrograms (mcg) of vitamin D each day, but on average consume only 5.1 mcg and 4.2 mcg per day, respectively.
If you'd like to work on increasing your vitamin D intake through food, these are the biggest breakdowns of vitamin D in foods, according to the National Institutes of Health (NIH).
Cod liver oil: 1 tablespoon contains 34 mcg.
Trout: 3 ounces contains 16.2 mcg.
Sockeye salmon: 3 ounces contains 14.2 mcg.
Mushrooms: 1/2 cup contains 9.2 mcg.
Fortified 2% milk: 1 cup contains 2.9 mcg.
Fortified cereal: 1 serving contains 2 mcg.
Why is vitamin D supplementation beneficial for many people?
Diet and sun exposure are the two ways people can naturally increase their vitamin D levels, but unfortunately, most people aren't getting enough of either. If you're not consuming vitamin D in your food, you need to get out in the sun ... something that's admittedly hard to do in the winter. "The largest source of vitamin D is how we manufacture it with the help of the sun," Radler says. "In the winter months, we usually do not have sunlight exposure that is sufficient to meet our needs."
Specific populations are more likely to experience a deficiency: Radler points to older adults (who may not manufacture vitamin D as efficiently as younger individuals), breastfed infants whose mothers aren't supplementing with vitamin D, individuals with darker skin, those with a family history of osteoporosis, and those who live in more northern locales with less direct sun exposure. And if you don't eat fatty fish or drink fortified milk? You'll definitely want to consider taking a supplement, Cording says. "[Those] who follow a vegan diet" are more likely to be deficient.
Common symptoms of low vitamin D levels include fatigue, brain fog, feeling down and getting sick frequently, Cording says. But it's possible to have a deficiency without any corresponding symptoms. For that reason, the best way to know if you could benefit from a supplement is to ask your doctor for a simple blood test, Radler says. Just know that not all insurance companies will cover routine testing and you may have to specifically ask your doctor for a screening.
What to look for in a vitamin D supplement
Dietitians suggest looking at a few different factors when choosing a vitamin D supplement:
Type. Most suggest looking for a supplement with vitamin D3. "It's the most effective form for raising and maintaining vitamin D levels in the body," Cassetty says.
Dosage. If blood testing confirms that you have a deficiency, your doctor will likely suggest a specific dosage. "The recommended daily allowance for most adults is 600 IUs, but many people benefit from 1,000 to 2,000 IUs per day, and people with low levels might need more," Cassetty says. Make sure you ask your doctor for a dosage suggestion before choosing a high-dose supplement, as it is possible to take too much.
Testing. Third-party testing (meaning an outside company checks the product) is considered the gold standard for purity and potency, Cording says. However, she points out that some brands are known for doing their own rigorous testing as well.
No fillers. "Check the label to make sure it's free of unnecessary fillers, allergens and colors," Cassetty says. "You'd be surprised how often these things come up when you look at supplement labels."
The best vitamin D supplements, tested by a dietitian
Yahoo Life recently tested and reviewed 17 vitamin D supplements to determine which ones were worth purchasing. Testing was performed by a registered dietitian in conjunction with input from a panel of three additional dietitians. We also asked the dietitians interviewed for this article whether they have specific brands or supplements they trust and recommend. These were the three products that made the cut, and each of the products featured here is third-party tested. To find more, check out our full review on the best vitamin D supplements here.
Double Wood
Double Wood Supplements D3 + K2 Liquid Drops won out as our testing panel's favorite vitamin D thanks to its powerful, well-balanced formulation and exceptional convenience. It offers a high dose of vitamin D to support bone health, immune function and overall wellness, and goes a step further by including 200 mcg of vitamin K2 — a critical nutrient for promoting bone growth and proper calcium utilization.
What truly sets this one apart, though, is its simplicity and quality. It contains only three ingredients: vitamin D3, vitamin K2 and medium-chain triglyceride (MCT) oil, which boosts the absorption of these fat-soluble vitamins. The formula eliminates unnecessary additives, making it a reliable choice for those seeking transparency in their supplements. The product is also third-party tested, with reports readily available on the company's website for customer review.
The dropper design makes this supplement easy to use, with clear dosage markings for precision. You can dispense it directly into your mouth or mix it into a drink, and the tasteless formula ensures no unpleasant aftertaste.
However, one important consideration is its inclusion of vitamin K. Yes, it enhances the product's health benefits, but if you're on blood thinners, consult a health care provider before use.
Pure Synergy
This organic supplement uses sources that are certified by the United States Department of Agriculture. It also pairs vitamins D3 and K2 to help strengthen bones and support calcium absorption. The brand conducts both in-house and third-party lab testing for peace of mind. This particular supplement has 2,000 IU per serving, which is a little lower than others. That can make it a good choice for people looking for a slight boost in their vitamin D levels without having a lot.
Nature Made
If swallowing a pill isn't for you, Nature Made's D3 gummies are a good solution. These gummies are sugar-free and sweetened with maltitol, which has little impact on blood sugar levels. Our tester found it tastes like cherry candy and is pleasant to chew. The gummies contain 2,000 IU of vitamin D per serving and are made with palm oil, a source of fat to support vitamin D absorption, so you don't have to take these with food. They're third-party tested as well.
FAQs
Can you have too much vitamin D?
Yes, it’s possible to have too much vitamin D. In rare and extreme cases, vitamin D toxicity has caused renal failure, hardening of soft tissues in the body, cardiac arrhythmias and even death, per the NIH. That’s why it’s often a good idea to consult with a dietitian or doctor to see where your levels are at baseline to know what is a good dose for your needs.
How can you know if you're deficient in vitamin D?
It’s possible to be deficient in vitamin D and have no symptoms. However, people with a vitamin D deficiency or low levels may have fatigue, brain fog, a lot of illnesses, tingling in the hands or feet, or muscle pain or weakness, Brissette says.
Should you take vitamin D with food?
It depends. Vitamin D is best absorbed when it’s taken with fat, Brissette says. However, some supplements will include the fat in the form of MCT oil or palm oil, so you can simply take it as is. Read the label carefully to see if your supplement contains this or not.
Can I take vitamin D with my medication?
It depends on what else you're taking. "Vitamin D supplements can interact with medications such as statins and thiazide diuretics,” Brissette says. So if you're taking a medication regularly, talk to your doctor before taking a new supplement.
Meet our experts
Diane Rigassio Radler, PhD, RD, director of the Institute for Nutrition Interventions at Rutgers
Jessica Cording, RD, nutritionist and author of The Little Book of Game-Changers
Samantha Cassetty, MS, RD, nutrition and wellness expert, founder of Sam's Plate and co-author of Sugar Shock
Christy Brissette, MS, RD, owner of 80 Twenty Nutrition
Our health content is for informational purposes only and is not intended as professional medical advice. Consult a medical professional on questions about your health.
