Vitamin D is not just one vitamin, but rather a family of nutrients that have similar chemical structures. Vitamin D2 and vitamin D3 are the most commonly found members of this family. 

Both vitamins will help you achieve required daily levels of vitamin D, and will help to support calcium absorption and bone health as well as support immune function. Both are also fat-soluble. However, there are important differences between these two forms.

Vitamin D2 and Vitamin D3

Vitamin D is commonly known as the sunshine vitamin, as sun exposure triggers vitamin D production in the skin. It is vitamin D3 that is produced when your skin is exposed to the sun.

Vitamin D2 comes from plant sources and fortified foods, and vitamin D3 is found in animal sources such as oily fish, liver, and egg yolks. Vitamin D2 is cheaper to produce, so it is found in fortified foods more often than you would find vitamin D3.

a fish with lemons on it

Both vitamin D2 and vitamin D3 are able to increase your overall vitamin D levels, but vitamin D3 is more effective in this role. Each is effectively absorbed into the blood, but once in the liver, the vitamins are processed differently. 

Vitamin D2 is metabolized into 25-hydroxyvitamin D2 and vitamin D3 into 25-hydroxyvitamin D3. Collectively these two compounds are called calcifediol, and this is the circulating form of vitamin D measured in your blood levels. Vitamin D3 yields more calcifediol than its relative, making it more effective at increasing your total calcifediol levels in the blood

When taking supplements, a single dose of vitamin D3 was found to be twice as effective at raising calcifediol levels. If blood tests reveal that you are vitamin D-deficient, then taking a dose of vitamin D3 will help you to get your levels back within a healthy range. 

In addition to this, vitamin D2 supplements have been shown to be lower quality in general. Vitamin D2 is more sensitive to changes in humidity and temperature, so over time, they are more likely to degrade in quality. You can avoid this by keeping your supplements stored at room temperature and in a tightly closed container away from direct sunlight.  

Vitamin D3 and Your Health

Vitamin D3 could be called the bone-supporting vitamin, as well as the sunshine vitamin. It is one of the most vital minerals required for optimal bone health. 

By promoting the absorption of calcium and phosphorus, vitamin D3 is essential for bone mineralization and bone density support. 

Vitamin D3 ensures that your body absorbs enough calcium and phosphorus from your food to support bone strength. This is especially important as you get older, as the breakdown of bone occurs faster than new bone generation. 

a close-up of a white lamp

In addition to bone health, vitamin D3 also provides benefits to other parts of the body.

Heart health: Vitamin D3 works with vitamin K to help promote normal cholesterol levels which supports optimal blood flow for proper heart health.

♦ Weight management: Vitamin D3 possesses appetite-suppressing effects and supports healthy cholesterol levels, which can promote healthy weight management.

♦ Immune health: Vitamin D3 encourages peptide activity in the immune system to support defenses and protect against environmental threats.

♦ Mood health: Vitamin D3 supports cognitive function and can help the body manage stress to promote a sense of calm and focus

Co-Dependency of Vitamin K2

Vitamin D3 works to promote calcium absorption. When you do not get enough calcium from your diet, your body takes it from your bones which can impact bone density. 

Optimal bone health depends on maintaining adequate levels of calcium in the body. Vitamin D3 can keep calcium levels high, but it cannot control where the calcium goes. Vitamin K2 is the partner that gets the calcium to the bones where it is most needed. 

Vitamin K2 helps support bone health in two ways. It activates osteocalcin, which is the protein responsible for activating the accumulation of calcium in your bones. It also activates matrix GLA protein, which prevents calcium from accumulating in soft tissues such as blood vessels and the kidneys.

Dosage and Warnings

Vitamin D3 supplements are best taken with a meal, and you should always follow the dosing instructions provided by your doctor. You should not take vitamin D3 if you have ever had an allergic reaction to the vitamin or if you have any of the following:

♦ High levels of calcium in your blood
♦ High levels of vitamin D in your blood
♦ Any conditions causing malabsorption
♦ Heart disease
♦ Kidney disease
♦ Electrolyte imbalance

a person in a blue lab coat holding a syringe

While vitamin D3 supplements are generally considered safe for use, there are potential reactions that need immediate attention, including hives, chest pain, vomiting, and difficulty breathing.

Symptoms of a vitamin D3 overdose include nausea, urinating more or less than usual, stiffness, body aches, irregular heartbeats, and confusion. 

The Bottom Line

It is important to get supplemental support for vitamin D, as naturally rich sources are rare. 

Vitamin D3 provides numerous benefits, supporting bone health, cognitive health, immune system function, and healthy aging. 

Your body can generate vitamin D3 from the cholesterol in your body with sunlight exposure, but this may not always be a sustainable way to get the levels you need. To get optimal bone health, choose vitamin D3 supplements, and pair it with vitamin K2 for the best outcomes.