May explained that other observational studies have reported similar findings, so the research team wanted to evaluate the association in a randomized clinical trial.

The current daily recommendation for vitamin D is 600 International Units (IU) for adults aged 19–70, and 800 IU for adults 71 and older.

Here’s why the current vitamin D dosage recommendation may not be enough, how too little vitamin D can negatively impact your cardiovascular health, and how to ensure you’re getting enough vitamin D.

Vitamin D Impacts Multiple Areas of Health, Including the Cardiovascular System

There are a few ways someone can take in vitamin D.

Enough vitamin D can provide multiple health benefits, including:

• Reduced inflammation
• Protection against osteoporosis
• Neuromuscular function
• Immune function
  

One of the lesser-known effects of vitamin D is its positive impact on the cardiovascular system. This is likely due to its anti-inflammatory action.

According to May, multiple previous studies have established these benefits.

Knowing that vitamin D could impact heart health, the research team set out to determine whether current dosing recommendations are helping people achieve optimal levels.

In the first of the two studies, 632 patients were enrolled in a randomized clinical trial and divided into two groups. One group received targeted, personalized vitamin D treatment, while the other simply received a general recommendation to talk to their doctor about vitamin D supplementation.

Those in the doctor discussion group received no specific amount of supplementation.

Remarkably, 86.5% of subjects in the as-needed dosing group required more than 2,000 IU of daily vitamin D to achieve a 40 ng/ml blood level, and 14.6% required over 10,000 IU daily.

Reaching these levels wasn’t a quick process. Less than 65% of subjects got to the 40 ng/ml mark in three months, and 25% needed at least six months to get there.

To measure the impact of these findings on heart health, the research team conducted an additional analysis.

This time, they identified subjects who had a cardiovascular event within 30 days of enrollment in the study. In these people, baseline vitamin D levels were a median of 25 ng/ml, significantly below the optimal 40 ng/ml level.

May explained that her main takeaway from these studies is that ideal vitamin D intake (especially for heart health) may need to be targeted to individuals, rather than based on a blanket daily recommendation.

“Prior vitamin D supplementation studies gave everyone the same dose of vitamin D, regardless of their blood level,” she said. “This study will be the first to show whether it is important for a patient to obtain a certain blood level of vitamin D to reduce their risk of having an adverse cardiovascular event.”

How Much Vitamin D Do You Really Need?

Since people’s vitamin D needs can vary, it might be tricky to understand how much you personally need, and whether or not you’re getting that amount from food and sunshine alone.

Having your levels tested regularly can give you a sense of whether your intake is sufficient.

“Testing vitamin D levels in the blood and speaking with a healthcare provider will be the best way to determine how much vitamin D you should take, especially when considering higher doses,” Rouse said.

Certain health conditions may also increase your needs.

If you’d like to add a supplement, talk to your doctor about how many IUs are too many. Higher doses than the recommended 600-800 IU per day can be safe—but only up to a point.

According to the National Institutes of Health, ingesting too much vitamin D could result in adverse side effects like nausea, vomiting, poor appetite, dehydration, and kidney stones.

Increasing Your Vitamin D Intake

Besides adding a supplement to your routine, you can always boost your vitamin D levels with dietary choices.

“To achieve optimal Vitamin D levels, dietary sources like fatty fish, egg yolks, and fortified foods are key,” Rouse said.

Spending time in the sun is another simple way to increase your body’s natural production of this vitamin.

Try an outdoor walk around midday when the sun’s UVB rays are the most intense. Expose more of your skin to allow for greater absorption. With the right combination of time in the sun, high-vitamin D foods, and supplementation, you’ll optimize your levels for heart health and other benefits.