Vitamin D, D2, and D3: The Differences and the Best Choice

Vitamin D is an essential fat-soluble vitamin that plays a vital role in multiple bodily functions. Vitamin D2 comes from plant sources while vitamin D3 comes from animals, and the latter is considered superior.

Vitamin D is crucial for absorbing other nutrients, such as calcium and phosphorus, which improve bone health. It is obtained through both diet and the body’s natural production. Receptors for vitamin D are present in various organs and tissues, indicating its critical role in our system. Ongoing research is uncovering its other physiological functions.

Normally, your skin produces vitamin D when exposed to sunlight, which is why it is often referred to as "the sunshine vitamin." However, individuals with limited sun exposure or seasonal sunshine, as well as those who spend long periods indoors, may need to rely on their diet to meet their vitamin D requirements.

People with darker skin tones, who have higher melanin content, often have lower levels of vitamin D in their blood. Melanin acts as a screen, shielding the skin from the sun, which inhibits vitamin D production. This shielding property of melanin also helps protect against the harmful effects of ultraviolet rays.

Vitamin D is available in two commonly found forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D2 is derived from plants and fungi, while D3 is produced by animals and humans.

Vitamin D deficiency is a significant health concern, with approximately 50% of the world’s population experiencing insufficiency. It is essential to distinguish between insufficiency and deficiency, as the latter indicates significantly lower levels of the vitamin. In the United States, more than 35% of adults are deficient in vitamin D.

Deficiency of vitamin D in children can lead to a condition called rickets, which weakens growing bones and may cause deformities. In teenagers and adults, vitamin D deficiency can result in conditions such as osteomalacia and osteoporosis. The former causes bone pain and muscle weakness, while the latter leads to brittle bones prone to fractures.

While vitamin D can be found in some plants and animals, natural food sources are generally limited. For most people, taking supplements is the most effective way to ensure adequate vitamin D intake.

Best Sources of Vitamin D2 and D3

Vitamin D2 is relatively scarce in natural food sources, so many manufacturers artificially add it to their products. Common sources of D2 include dairy and plant milk like soy, almond, and oat milk, breakfast cereals, orange juice, and yogurt. Mushrooms are another good source of D2, with a half-cup providing 46% of the daily vitamin D requirement.

Vitamin D3 primarily comes from animals. Rich sources of D3 include trout, salmon, cod liver oil, tuna, beef liver, eggs, sardines, and cheese. The exact amount of vitamin D varies depending on the source, so it is advisable to check the nutrition label for accurate information.

Dietary supplements for vitamin D2 and D3 are widely available. Vitamin D2 supplements are usually derived from ergosterol in yeasts and treated with UV radiation. Vitamin D3 supplements are produced from cholesterol-like molecules extracted from lanolin, a substance found in sheep’s wool, which are then exposed to UV rays. Some non-animal sources of D3, such as lichen, also exist, but it is important to verify the preparation method with the supplement manufacturer.

Both D2 and D3 supplements effectively raise vitamin D levels in the blood and share similar metabolic pathways. However, numerous studies suggest that D3 increases blood vitamin levels to a greater extent and maintains them for a longer duration compared to D2.

Vitamin D3: The Superior Choice

Vitamin D2 and D3 have overall similar functions once they enter the body, but they differ slightly in their molecular structures.

While both forms raise serum vitamin levels, D3 is generally considered the superior source. Research indicates that D3 supplements result in a 31% greater increase in blood vitamin levels compared to D2 supplements. D3 from both oral and intramuscular methods has significantly higher bioavailability, with roughly 87% more blood vitamin levels compared to D2.

It is important to note that these studies focus on supplement sources of D2 and D3, rather than natural sources. Additionally, further research is needed to understand how D2 and D3 supplements affect individuals of diverse backgrounds, including factors such as age, gender, and ethnicity.

A separate study supported the notion that D3 supplements may be more effective than D2 supplements. The study involved 38 participants who were given either D2 or D3 supplements. After five weeks, D3 supplements were found to be more effective in increasing blood vitamin levels compared to an equivalent quantity of D2.

Your diet and any supplements you may take should provide sufficient vitamin D to meet the daily recommended value. According to the National Institutes of Health, the recommended daily vitamin D intake varies based on age:

• 0-12 months: 10 micrograms
• 1-70 years: 15 micrograms
• Over 70 years: 20 micrograms

Potential Inferiority of Vitamin D2 Supplements

D2 supplements may be of inferior quality compared to D3 supplements. Recent studies have shown that D2 is more susceptible to environmental factors like humidity and temperature, resulting in a shorter shelf life.

It is worth mentioning that vitamin D2 and D3 provide similar functions and benefits to the body. Both can be obtained through fortified food products or supplements. For more information, refer to reputable sources such as the Harvard T. H. Chan School of Public Health, the National Institutes of Health, and scientific journals dedicated to nutrition and endocrinology.