There’s been a lot of information about the health benefits of vitamin D, and experts say that the current recommended intake of this essential nutrient in the United States is too low to achieve optimal vitamin D levels for people with certain cardiac problems.

According to Medical News Today, researchers at Intermountain Health are conducting an ongoing clinical trial looking into this topic and their first analysis is already complete. These results show that current recommended dietary allowances are inadequate for achieving optimal serum vitamin D levels in people with heart conditions.

While Vitamin D contributes to bone health, experts say that there is not enough evidence to support its role in reducing the risk of cardiovascular disease. However, past observations have shown that there is an association between cardiovascular disease and low vitamin D levels.

The recommended dietary allowance for vitamin D is 600 international units (IU), or approximately 15 micrograms (mcg), for adults younger than 70 years of age, and 800 IU, or around 20 mcg, for adults over 70. However, the researchers noted that in their clinical trial, this might not be enough to reach appropriate levels of vitamin D in the blood for certain populations.

The clinical trial, called TARGET-D, recruited 632 men and women, all of whom had experienced acute coronary syndrome, which refers to decreased blood flow to the heart. A person who suffered a heart attack, for example, would have acute coronary syndrome.

Surprisingly, the researchers found that more than 51% of the participants needed between 5,000 and 8,000 IU of vitamin D supplementation to reach the desired blood levels of 40 nanograms per milliliter (ng/mL). This is much higher than the current dietary guidelines. Additionally, 14.6% of participants needed 10,000 IU or more to reach optimal vitamin D levels.

It also took quite a bit of time, as long as six months for some, for the study participants to achieve these levels. The results indicate that this cohort requires higher doses of vitamin D compared to people without acute coronary syndrome.

“We were not surprised that so many patients had levels lower than or equal to 40 ng/mL, but how much vitamin D supplementation was needed to achieve this level,” said Dr. Heidi May, a cardiovascular epidemiologist with Intermountain Health. The next step is to evaluate if vitamin D blood levels greater than 40 ng/mL in this group improves cardiovascular disease outcomes.

Our bodies produce vitamin D when exposed to sunlight, but research shows about 35% of adults in the U.S. are vitamin D deficient, says Healthline. That’s why getting vitamin D from food or supplements is best. The top food sources include:

• Fatty fish like wild salmon.

• Herring and sardines.

• Cod liver oil.

• Canned tuna.

• Egg yolks.

• Mushrooms.

• Vitamin D-fortified foods like cow’s milk, soy milk, orange juice, cereal, and oatmeal.