The 1 Surprising Reason You Might Get More UTIs in the Wintertime

The connection between low vitamin D and UTIs

Your immune system needs vitamin D to fight off bad bugs like bacteria that cause health problems, including UTIs. Some studies suggest that vitamin D helps regulate the immune system by boosting the production of antimicrobial peptides, says Jonathan Davila, MD, director of male infertility at Northwell Staten Island University Hospital. Peptides are molecules that have two or more amino acids, which join together to form proteins. These antimicrobial “peptides are important for defending the body against bacterial infections,” Dr. Davila says.

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So, when you don’t get enough vitamin D, your body may not have the proper tools to fight off infections like UTIs. “Low levels of vitamin D may weaken the immune response, making it harder for the body to fend off common UTI pathogens like E. coli,” Dr. Davila says.

Preliminary research on UTIs and vitamin D seems to point to a connection. “Studies have observed that individuals with recurrent UTIs often have lower levels of vitamin D,” Dr. Davila says. A 2019 systematic review and meta-analysis in Annals of Clinical and Laboratory Science found a significant link between vitamin D insufficiency and increased risk of UTI.

Another 2021 systematic review and meta-analysis in The Journal of Urology⁴ had similar findings. Researchers concluded that people with a vitamin D deficiency were twice as likely to have UTI symptoms, and those with UTI infections had significantly lower levels of vitamin D.

Still, it’s a little too early to draw any definitive conclusions from these studies. “More randomized controlled trials would be necessary” to better understand the association between vitamin D and UTIs, Dr. Davila says.

Can vitamin D help prevent UTIs?

Okay, a link between lower vitamin D levels and increased UTI risk is one thing. But can getting enough vitamin D prevent an infection?

“There is some growing evidence that vitamin D supplementation might help reduce the risk of recurrent UTIs by enhancing the body's immune defenses,” Dr. Davila says. Case in point: The same 2021 study in The Journal of Urology also noted that vitamin D intake lowered the risk of developing a lower UTI by 11 percent. “By stimulating the production of antimicrobial peptides, vitamin D could potentially prevent the colonization and proliferation of harmful bacteria in the GU (genitourinary) tract,” he says.

Another January 2020 study in Cell and Tissue Research⁵, which examined mice and took bladder biopsies from postmenopausal women, found that vitamin D supplementation can strengthen the urinary bladder lining and prevent bacteria from infecting the epithelial barrier (aka the cells that cover skin and line hollow organs).

This sounds hopeful. But how much would you need to prevent an infection? Well, that's still unclear. Among the studies included in The Journal of Urology research, there was no standard dose of vitamin D used by the participants. For example, one study reported that taking 5,000 international units (IU) per week was helpful, while another found that more than 1,000 IU per day was the sweet spot for preventing UTIs. In the Cell and Tissue Research study, it was 2,000 IU daily.

What we do know is that the daily recommended amount of vitamin D is much lower: 600 IU for adults under age 70 and 800 IU for those over 70.

All this to say, while the research is promising, take it with a bit of caution. “More comprehensive clinical trials are needed to confirm vitamin D's role in UTI prevention, particularly in people susceptible to recurrent infections,” and how much you need to take for it to be effective, Dr. Davila says.

Other ways to prevent UTIs

As of 2022, the American Urological Association doesn’t recommend vitamin D supplements to prevent recurrent UTIs, Dr. Davila says. But that doesn’t mean vitamin D isn’t helpful—the research is still evolving.

In the meantime, here’s a list of tried-and-true tips to reduce your UTI risk during the dark days of winter (and year-round),  courtesy of Sherry Ross, MD, OB/GYN, women's sexual health expert, and author of She-ology.

• Pee after sex: Sex can introduce bacteria to your urethra, and peeing afterward helps flush it out.
• Reduce frequent antibiotic use: Taking too many antibiotic medications can disrupt the balance of healthy microbes in the body.
• Take d-mannose: This is a monosaccharide naturally found in fruits that’s available as a supplement. It can help prevent bacteria from sticking to the bladder wall, which increases your UTI risk.
• Go to the bathroom when you first feel the urge: Peeing often can help eliminate waste from your body and lower your UTI risk, especially if you get UTIs a lot. So don't wait, even if that means getting out of your warm bed on a chilly night.
• Wash your genitals (and hands) before sex: Practicing good hygiene can help prevent you from introducing bacteria to your urethra.
• Avoid using a diaphragm, vaginal sponge, diva cup, and sex toys if you are prone to UTIs: They can harbor harmful bacteria, especially if they’re not cleaned properly.
• Limit the use of douches and feminine products with perfumes and other irritating chemicals: These products can upset the balance of bacteria in your private parts.
• Steer clear of spermicides and lubricants in the genital area: Again, these products can irritate your genital area, disrupt your pH, and throw off the balance of bacteria.
• Always wipe front to back: This helps you avoid transferring unwanted bacteria from the anus to the vaginal area.
• Wear underwear with a cotton crotch: Breathable fabrics can help prevent moisture from accumulating around your urethra.
• Try Uqora: This is an over-the-counter brand of supplements for urinary tract health. It has vitamin C, B6, magnesium, calcium, potassium, and d-mannose to help flush away UTI-causing bacteria from the bladder.

Can vitamin D help once you already have a UTI?

“While vitamin D supports the immune system, there is currently no strong evidence to suggest that taking vitamin D during an active UTI will speed up recovery,” Dr. Davila says. That means if you have a UTI, don’t try to treat it at home with a vitamin D supplement. Left unchecked, a UTI can move to your kidneys and cause complications like kidney damage or sepsis (a life-threatening infection).

Instead, stick to the standard treatments that are proven to work. “The best way to treat an uncomplicated UTI is with antibiotics,” says Dr. Ross. “If the infection is severe (causing more advanced symptoms such as fever and low-back pain), intravenous antibiotics along with hospitalization may be necessary,” she adds.

That said, taking vitamin D, along with antibiotics, can be useful. “Maintaining optimal vitamin D levels may help boost overall immune function, potentially reducing the severity of symptoms or the likelihood of recurrent infections after the initial treatment,” Dr. Davila says.

How to test for low vitamin D

A quick blood test can tell you whether you’re dealing with low vitamin D. “Vitamin D levels are typically measured through a blood test that assesses [a form of vitamin D known as] serum 25-hydroxyvitamin D,” Dr. Davila says. In the blood, it’s usually calculated as nanograms per milliliter (ng/mL).

According to both Drs. Davila and Ross:

• A deficiency is below 20 ng/mL
• Low levels (still insufficient for adequate bone and overall health) are between 20 and 29 ng/mL
• A healthy range is typically 30 to 100 ng/mL
• Levels above 100 ng/mL (depending on the person) can have harmful effects and lead to other health problems such as kidney stones.

Possible symptoms of a vitamin D deficiency

Frequent UTIs or other infections could be your body’s way of alerting you to a vitamin D deficiency. But a lack of vitamin D can manifest in a variety of other ways, too. Here are some common signs of low vitamin D levels to look out for:

• Bone pain
• Hair loss
• Fatigue
• Tingling or numbness in the feet
• Muscle weakness or spasms
• Slower wound healing
• Mood changes, including depression

However, it's worth noting that a severe vitamin D deficiency can lead to bone diseases (such as rickets in children and osteomalacia in adults). So it's important to ask your healthcare provider for a vitamin D test if you're experiencing any of the above symptoms.

How to get more vitamin D 

When the days get shorter, and it’s too cold to hang out in the sun, it can be tricky to get enough vitamin D. But don’t worry—there are plenty of easy ways to boost your vitamin D levels during winter without stepping outside.

Eat foods rich in vitamin D

While the best way to get vitamin D is from the sun, your diet can help you reach your daily target. Some foods—like egg yolks, saltwater fish, and liver—naturally have this essential nutrient, but most people get vitamin D from a variety of fortified foods, including milk, cereal, and yogurt, according to the Office of Dietary Supplements at the National Institutes of Health (NIH).

Try supplements

If you’re not getting enough vitamin D through your diet (many of us don’t), a supplement might be a good choice. Before taking a new supplement, though, it’s always a good idea to check in with your healthcare provider. They can recommend a dose that works best for you and ensure whether a supplement is safe for your health needs.

Get fresh air when you can

On less brutally cold days, take a walk. Even 15 minutes of sun on your face (always wear SPF!) can make a difference in your vitamin D levels. Ideally, go outside during peak sun hours (i.e., not at sunrise or sunset) because this is the best time for your body to absorb sunlight.

When to see a healthcare provider

If you’re dealing with frequent UTIs in the winter and suspect a vitamin D deficiency might be to blame, it's a good idea to check in with your healthcare provider. While some infections clear up on their own, a recurring issue could be a sign that your immune system needs a little extra help (especially if low vitamin D is involved).

According to Drs. Davila and Ross, you should consider seeking medical advice if you have:

• More than two UTIs in less than six months or three UTIs in one year
• Other frequent infections
• Bone pain or loss
• Hair loss
• Fatigue
• Muscle weakness
• Mood changes, including symptoms of depression

Your provider will be able to discuss options for vitamin D testing and possible treatments if they find you have a deficiency.

The bottom line

Vitamin D supplements may help support immune health and possibly reduce UTI risk, but they’re no substitute for standard care. Antibiotics are still the go-to treatment for bacterial UTIs. Keeping your vitamin D levels up can be part of a bigger health plan—along with staying hydrated, practicing good hygiene, and addressing underlying health conditions like diabetes or kidney stones that can increase UTI risk, Dr. Davila says.