Insufficient Vitamin D Recommendations May Not Safeguard Heart Health Effectively

New research suggests that current recommendations for vitamin D dosage might not be sufficient.

The American Heart Association’s 2023 Scientific Sessions showcased two studies from Intermountain Health, which investigated the effects of vitamin D on heart disease and stroke. They discovered that the current dosage guidelines for this micronutrient could be too low.

Severe health consequences can result due to insufficient vitamin D intake.

Lead study author Heidi May, Ph.D., noted that previous observational studies indicated low levels of vitamin D were associated with poor cardiovascular outcomes.

As similar observations were reported by other studies, the research team decided to inspect the relationship in a randomized clinical trial.

Currently, adults between the ages of 19-70 are recommended 600 International Units (IU) of vitamin D per day, while adults over 71 years are advised to take 800 IU daily.

This article explains why the current vitamin D dosage recommendation might not be enough, the potential negative effects of vitamin D deficiency on cardiovascular health, and how to ensure your intake is adequate.

Vitamin D intake can be ensured in a few ways.

Also known as “the sunshine vitamin,” the sun’s rays are a primary source of vitamin D. This nutrient can also be found in fortified milk, orange juice, fatty fish, and beef liver.

Getting enough vitamin D can trigger various health benefits, consisting of:

One underappreciated benefit of vitamin D is its positive effect on the cardiovascular system, potentially due to its anti-inflammatory properties.

Veronica Rouse, RD, CDE, of The Heart Dietitian, explained to Health that “Vitamin D contributes to heart health by managing blood pressure, reducing inflammation, and improving blood vessels' functions, which promotes better blood flow.” According to May, several past studies have confirmed these benefits.

May stated, “Many heart disease risk factors have been shown to be affected by vitamin D, such as high blood pressure, diabetes, and being overweight.”

Knowing the impact of vitamin D on heart health, the researchers deliberated whether current dosage recommendations were resulting in individuals reaching optimal levels.

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

Those in the targeted treatment group were given vitamin D supplements to reach blood levels over 40 nanograms per milliliter (ng/ml), which is considered an optimal level for cardiovascular disease prevention.

The other group did not receive any specific amount of supplementation.

Interestingly, 86.5% of subjects in the tailor-made dosage group needed over 2,000 IU of daily vitamin D to achieve 40 ng/ml blood level, and 14.6% required over 10,000 IU daily.

Reaching these levels was not instantaneous. Less than 65% accomplished the 40 ng/ml mark in three months, and 25% took at least six months to get there.

To gauge the consequences of these findings on heart health, the research team conducted another analysis.

They identified subjects who had a cardiovascular event within 30 days of joining the study. Their baseline vitamin D levels averaged 25 ng/ml, significantly below the preferred 40 ng/ml level.

May concluded that her studies suggest that ideal intake of vitamin D, particularly for heart health, may need to be individualized rather than relying on a generic daily recommendation.

“Previous vitamin D supplementation studies administered everyone the same dose of vitamin D, irrespective of their blood level,” she said. “This study will be the first to show whether it is essential for a patient to reach a specific blood level of vitamin D to lower their risk of having an adverse cardiovascular event.”

Given that people's vitamin D needs can differ, understanding how much you personally need, and whether you’re receiving adequate amounts from food and sunshine alone, can be difficult.

Regular testing of your levels can indicate whether your intake is sufficient.

“The best way to determine how much vitamin D you should take, particularly at higher doses, is by testing your blood levels and consulting with a healthcare provider,” Rouse advised.

Certain health conditions might also necessitate an increased dosage.

People with absorption issues related to inflammatory bowel disease, celiac disease, cystic fibrosis, or bariatric surgery might need additional vitamin D supplementation.

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.

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.

Both vitamin D-fortified milk and orange juice, for example, contain just under 100 IU per cup. Or, for an even greater boost, try cod liver oil; it contains 1,360 IU of vitamin D per tablespoon. 

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.