New Research Links Taking Vitamin D to Better Cardiometabolic Health, but Doctors Have Some Notes

The meta-analysis, which was published in the journal Engineering, analyzed data from 99 randomized controlled trials that involved nearly 18,000 people. After crunching the data, the researchers found that taking a dose of about 3,320 international units (IU) of vitamin D a day was linked with reductions in blood pressure, overall cholesterol, hemoglobin A1C (a marker of type 2 diabetes), fasting blood glucose, and insulin.

“The findings of this study underscore the need for personalized vitamin D intervention strategies,” the researchers wrote in the conclusion.

This isn’t the first study to look at the potential effect of taking vitamin D supplements on cardiometabolic health. Here’s what we know about the link—and what doctors think.

How much vitamin D do you need?

Vitamin D is a fat-soluble vitamin that’s found naturally in some foods, like trout, salmon, and mushrooms, and added to certain products like cereal and milk. It’s available as a dietary supplement, too. The two main types of vitamin D found in supplements are vitamin D2 (also known as ergocalciferol) and vitamin D3 (cholecalciferol).

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You can also get vitamin D through something called vitamin D synthesis, which is what happens when your skin is exposed to UV rays from sunlight, according to the National Institutes of Health (NIH).

Vitamin D needs vary by a person’s gender and age, but most adults need 15 to 20 micrograms (or 600 to 800 IU) of the vitamin a day. But research has found that about 94 percent of people ages 1 and older get less than 400 IU of vitamin D from food and drinks per day. Meaning, the majority of people aren’t getting nearly enough vitamin D.

How could vitamin D help with cardiometabolic issues?

This is slightly tricky, given that previous research hasn’t found vitamin D supplements to be helpful for a range of cardiometabolic issues. In fact, one May 2015 study in JAMA Internal Medicine specifically says that vitamin D supplements are “ineffective” for lowering blood pressure, while a June 2014 article in Hypertension says it has “no effect” on blood pressure. One meta-analysis ⁴found that vitamin D helped to lower LDL (“bad”) cholesterol, but did not impact HDL (“good”) cholesterol levels.

Some research has found that vitamin D may help with insulin resistance and A1C levels—but more studies are needed to confirm this.

David Bleich, MD, chief of the division of Endocrinology, Diabetes & Metabolism and professor of medicine at Rutgers New Jersey Medical School, stresses that the latest study (and several others) don’t prove that taking vitamin D can help with these health conditions. Instead, it finds a link between people who take vitamin D and a lowered risk of developing these health issues.

“This has been bantered about for two decades,” Dr. Bleich says. “People have tried to make this association between inflammation, vitamin D, and immune response, and leap over to cardiometabolic endpoints, but, while it looks pretty good in animal and rodent models, it becomes murkier when you get to human beings.”

Cheng-Han Chen, MD, interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, California, agrees: “The underlying mechanisms behind how vitamin D may influence blood pressure, cholesterol, and blood sugar control are not well understood, and should be the subject of further research,” he says.

What do doctors recommend?

If you’re concerned about your risk of developing any of these health conditions, Dr. Bleich recommends talking to a doctor. “We have good medications that are specifically focused on these types of problems,” he says. “I don’t think you need to use alternative medications, although I understand that many people will.”

"There is still not enough evidence to date to recommend vitamin D supplementation to help prevent heart disease," says Dr. Chen. But he stresses the importance of leaning into lifestyle factors that are proven to help heart health, like eating a balanced diet, engaging in regular physical activity, getting seven or more hours of sleep a night, maintaining a healthy weight for your body size, avoiding alcohol and tobacco, and trying to reduce your stress levels.

"If you still have trouble with blood pressure, cholesterol, or blood sugar control, then you might benefit from medications prescribed by your physician," Dr. Chen says.

Still, Dr. Bleich says that vitamin D is a relatively safe supplement to take, provided you keep your intake under FDA-approved limits of 100 micrograms or 4,000 IU per day. (Levels beyond that are considered toxic and could lead to symptoms like nausea, vomiting, bone pain and weakness, and kidney problems, per the Mayo Clinic.)

Ultimately, if you’re having health concerns, it’s best to talk to a medical professional. They should be able to offer up personalized guidance from there.