You may know vitamin D as an essential nutrient that helps you absorb calcium and keep bones strong, but vitamin D is actually a category that includes several different chemical compounds.

Doctors generally prescribe vitamin D2 supplements if you have a vitamin D deficiency, but some experts say that vitamin D3 is easier for your body to absorb and may work better to boost your health.

Helps absorb calcium: Your kidneys convert vitamin D to its active form, which plays an important role in regulating calcium levels in your blood.

"It is more effective in raising vitamin D levels in the blood," Lanham-New says.

A small 2011 study published in the Journal of Clinical Endocrinology & Metabolism found that vitamin D3 was 87% more potent in raising vitamin D levels in the blood of 33 healthy adults,  compared with D2.

Another small study in 2015 published in the European Journal of Clinical Nutrition found that while vitamin D2 and D3 were both effective in boosting vitamin D levels, people who took vitamin D3 kept up higher blood levels of vitamin D 77 days after stopping the supplements

This is particularly important for people "who are most at risk of vitamin D deficiency such as the elderly, ethnic groups with darker skin, pregnant and lactating women."