Which Is Better for You, Vitamin D3 or Vitamin D?

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When it comes to raising levels of vitamin D in the body, studies have shown that vitamin D3 is better for you than vitamin D2

When it comes to raising levels of vitamin D in the body, studies have shown that vitamin D3 is better for you than vitamin D2. Reasons why vitamin D3 is superior to vitamin D2 include the following:

• Vitamin D3 is naturally produced in the human body, whereas vitamin D2 cannot be manufactured by the body.
• Vitamin D3 supplementation has shown to provide higher levels of the active form of vitamin D (called 25-hydroxyvitamin D or calcifediol) in the blood.
• Vitamin D3 helps sustain elevated levels of the active form of vitamin D (25-hydroxy vitamin D) longer than vitamin D2.

What to know about vitamin D supplements

Vitamin D is a family of fat-soluble vitamins that the body obtains from fortified foods, sun exposure, and over-the-counter and prescribed supplements. Though most people do not get enough vitamin D through diet alone, you should not take vitamin D supplements without first talking to your doctor.

Vitamin D consumed in any form is biologically inert and undergoes two chemical changes (hydroxylation) in the body before activation:

• The first change occurs in the liver, which converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also called “calcifediol.” 
• The second change occurs in the kidneys and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], also called “calcitriol.”
• Whether you consume vitamin D2 or D3 supplements, both are ultimately converted in the body into 25-hydroxyvitamin D [25(OH)D].

Vitamin D supplements may contain either vitamin D2 (called ergocalciferol), D3 (called cholecalciferol), or both. D3 is mainly obtained from animal sources, such as fish oils, liverm and egg yolk, whereas D2 is of plant origin (mushrooms and fortified foods). The FDA has suggested using vitamin D3 for food fortification (milk, cheeses, butter) over D2.

How much vitamin D should you have daily?

Table 1. Vitamin D requirements (National Institutes of Health) Age Male Female Pregnancy Lactation

0 to 12 months
10 mcg (400 international units or IU)
10 mcg (400 IU)

1 to 13 years
15 mcg (600 IU)
15 mcg (600 IU)

14 to 18 years
15 mcg (600 IU)
15 mcg (600 IU)
15 mcg (600 IU)
15 mcg (600 IU)

19 to 50 years
15 mcg (600 IU)
15 mcg (600 IU)
15 mcg (600 IU)
15 mcg (600 IU)

51 to 70 years
15 mcg (600 IU)
15 mcg (600 IU)

Older than 70 years
20 mcg (800 IU)
20 mcg (800 IU)

Whether you take D2 or D3 supplements, the serum concentration of 25(OH)D is currently the main indicator of vitamin D levels. The circulating 1,25(OH)2D is generally not a good indicator of vitamin D level because:

• It has a short half-life measured in hours.
• Its serum levels are variable and dependent on blood parathyroid hormone as well as calcium and phosphate levels.
• Levels of 1,25(OH)2D do not typically decrease unless there is a severe vitamin D deficiency.

Table 2. Serum 25-Hydroxyvitamin D [25(OH)D] concentrations (National Institutes of Health) nmol/L ng/mL Health indications

Less than 30
Less than 12
Associated with severe vitamin D deficiency

30 to less than 50
12 to less than 20
Vitamin D insufficiency

Less than or equal to 50
Less than or equal to 20
Adequate levels

Greater than 125
Greater than 50
Toxic levels

Can taking too much vitamin D be harmful?

The safe upper intake level of vitamin D is 100 mcg per day (4000 IU per day).

Taking too much vitamin D carries risks such as:

• Nausea and vomiting
• Increased blood calcium levels
• Calcinosis (deposit of calcium crystals in soft tissues, such as the kidneys, heart, or lungs)
• Organ dysfunction
• Toxicity (risk is higher with vitamin D supplementation rather than dietary intake)

Excessive sun exposure does not cause vitamin D toxicity. However, too much sun exposure can cause skin damage and raise the risk of skin cancer.

Does vitamin D have cancer fighting properties?

Emerging research suggests that vitamin D may have a role in combating colorectal, breast, prostate, and pancreatic cancers

The effect of vitamin D supplements on cancer may be due to the physicochemical effect of vitamin D on immune cell function and its hormone-like effect on the cells. However, the following factors are unknown:

• Appropriate dose of vitamin D for cancer prevention
• From what age the supplementation should begin for cancer prevention
• How long to ingest the vitamin to potentially see benefits
• Whether there are any potential drug-vitamin D interactions

Many epidemiologic studies have shown that higher intake or blood levels of vitamin D are associated with a reduced risk of colorectal and breast cancers. Other studies, however, have shown that these findings are inconclusive. Research on large-scale populations is needed to confirm these findings.