Vitamin D, D2, and D3: What Are the Differences and Which Is the Best?

Vitamin D is a fat-soluble vitamin that plays a vital role in several bodily functions. Vitamin D2 is from plant sources and vitamin D3 is from animal sources and it is considered superior.

Vitamin D is a fat-soluble vitamin that plays a vital role in several bodily functions. The most commonly available types of vitamin D in your diet are vitamin D2 and D3. Although both help you meet your vitamin D needs, they have some differences. This article provides information about the different types of vitamin D and their benefits.

Vitamin D is a type of vitamin that your body needs to absorb other nutrients such as calcium and phosphorus, which improves bone health. Vitamin D is a nutrient you get from food and a hormone your body produces. Several organs and tissues in the body have receptors for vitamin D, indicating the critical role this nutrient plays in our system. There is increasing research being done on its other physiological functions.

Your body gets vitamin D from the sun; your skin cells produce it when you’re out in the sun. This is how the vitamin got its nickname – “the sunshine vitamin.” That’s why vitamin D deficiency is common in people with limited or seasonal sunshine and those who stay indoors for a long time. In such cases, you’ll need to depend on your diet to meet your vitamin D needs.

People with a high melanin content (those with darker skin tones) also usually have lower levels of vitamin D in their blood. This is because melanin (a pigment) acts like a screen that shades the sun and inhibits the production of the vitamin by the skin. The shielding property of melanin is also responsible for reducing the damaging effects of the sun's harmful ultraviolet rays that could lead to skin cancer.

Vitamin D is usually available in two forms. The first is vitamin D2 (also called ergocalciferol); the other is vitamin D3 (also called cholecalciferol). Vitamin D2 is sometimes referred to as pre-vitamin D. Vitamin D2 is usually found in plants and fungi, whereas animals and humans produce D3.

Vitamin D deficiency may cause severe health issues. Research indicates that roughly 50% of the world’s population has vitamin D insufficiency. Keep in mind that this is different from deficiency, which refers to considerably lower levels of the vitamin. Studies in the U.S. have shown that more than 35% of the country’s adults are deficient in vitamin D.

Vitamin D deficiency in children could lead to a serious condition called rickets that makes growing bones soft and weak; in some cases can also cause deformities. Vitamin D deficiency in teens and adults could cause conditions such as osteomalacia and osteoporosis. While the former condition can cause pain in your bones and muscle weakness, the latter makes them brittle and vulnerable to breaking.

While some plants and animals contain D2 and D3, very few natural foods contain vitamin D. For most people, taking supplements is the best way to get this nutrient.

As there are few natural food sources of vitamin D2, many manufacturers artificially add it to their products. These manufacturers typically rely on plant sources to add D2 to their products, such as:

• Dairy and plant milk products like soy, almond, and oat milk
• Breakfast cereals
• Orange juice
• Yogurt

The vitamin D content depends on who makes it. You can check the nutrition label to know the vitamin D content of the product. Mushrooms are another good source of D2. Half a cup of mushrooms gives you 46% of your daily vitamin D needs.

Animals are the primary source of vitamin D3. These include:

• Trout: 16.2 micrograms per serving contains 81% of the daily value
• Salmon: 14.2 micrograms per serving contains 71% of the daily value
• Cod liver oil: 34 micrograms per serving contains 170% of the daily value 
• Tuna: 1 microgram per serving contains 5% of the daily value
• Beef liver: 1 microgram per serving contains 5% of the daily value
• Eggs: 1.1 micrograms per serving contains 6% of the daily value
• Sardines: 1.2 micrograms per serving contains 6% of the daily value
• Cheese: 0.4 micrograms per serving contains 2% of the daily value

Dietary supplements for vitamin D2 and D3 are widely available. The preparation of vitamin D2 supplements usually involves treating ergosterol in yeasts with UV radiation. Ergosterol is the animal equivalent of cholesterol.

UV radiation is used to make vitamin D3 supplements as well. Molecules similar to cholesterol are first extracted from a waxy substance called lanolin, obtained from sheep's wool. These cholesterol molecules are then treated with UV rays to get vitamin D3.

There are also some non-animal sources of vitamin D3, such as lichen. Lichens are microorganisms that are a symbiotic partnership between two distinct organisms, a fungus and an alga. If you want to avoid animal vitamin sources, contact the supplement manufacturer to know their preparation method.

D2 and D3 supplements help raise the vitamin levels in the blood and have similar metabolic pathways. Research indicates that both these supplements can cure conditions like rickets equally well.

But most studies reveal that vitamin D3 increases blood vitamin levels to a greater extent and maintains these levels for a longer time than vitamin D2.

While both vitamin D2 and D3 play the same role once they enter your body, they have minor differences in their molecular structures.

D2 and D3 raise the serum vitamin levels, but D3 is widely considered the better vitamin source. A 2012 study found that D3 is considerably more effective than D2 at raising serum vitamin D levels when taken every day. The study also indicated that eating D3 supplements led to a 31% increase in blood vitamin levels compared to D2 supplements.

It also found that the bioavailability of vitamin D from the D3 supplementation was considerably higher (roughly 87% more) than from D2. The study further revealed that the blood vitamin levels were much higher from D3 supplementation for both oral and intramuscular methods.

Keep in mind that this study only tested supplement sources of vitamin D2 and D3, not natural ones. The study also recommended that more research is needed to understand how D2 and D3 supplements affect people from varied backgrounds, such as their age, gender, and ethnicity.

A separate 2016 study also indicated that D3 supplements could indeed be more effective than D2 supplements. The study involved 38 participants divided into two equal groups. One group was given D2 supplements, while the other was given D3 supplements. All the participants in the same group were matched for age, body mass index, and ethnicity.

After being given supplements for five weeks, the participants were given a five-week resting period. Their vitamin levels were calculated at the start of the study and the end of 10 weeks.

According to the study, D3 supplements, when taken twice a week for five weeks, were more effective in increasing blood vitamin levels as compared to the same quantity of vitamin D2.

Your diet and any supplements you may take should give you enough vitamin D to meet the daily recommended value. The National Institutes of Health (NIH) recommends eating an adequate amount of vitamin D depending on age.

• Zero to 12 months: 10 micrograms (for men and women)
• One to 70 years: 15 micrograms (for men and women)
• Over 70 years: 20 micrograms (for men and women)

The quality of D2 supplements may not be as good as the D3 supplements. Recent progress in measuring vitamin levels has helped medical experts identify that vitamin D2 is more vulnerable to environmental factors such as humidity and temperature.

One such study found that vitamin D2 supplements have a shorter shelf life due to these vulnerabilities.

Vitamin D is an essential nutrient for your body and is critical for healthy bones and a robust immune system.

Vitamin D is available from the sun and other food sources in the form of vitamin D2 and D3, and both carry out almost the same functions in your body. Plants and fungi are good sources of vitamin D2 (ergocalciferol), while animals and humans produce D3 (cholecalciferol). Vitamin D3 is produced by your skin when you’re out in the sun.

Vitamin D3, irrespective of whether it’s produced by animals or humans, is generally considered the better source of vitamin D as compared to D2. Research has shown that the vitamin from D3 sources stays in your body for longer compared to D2 sources.

Few foods naturally contain vitamin D. That’s why manufacturers may fortify foods like milk, juices, and cereals with vitamin D. Mushrooms are a good natural source of vitamin D2, while fish is a good source of vitamin D3.

You can get your daily vitamin D fix from food products typically fortified with it or from animal sources. You can also take vitamin D supplements to meet your daily needs.