Vitamin D2 (Ergocalciferol)

At a glance

Also calledErgocalciferol, the plant and fungal form of vitamin D
Ergocalciferol; vitamin D2; the plant and fungal form of vitamin D, produced when ultraviolet light hits ergosterol in yeast or mushrooms. It is the form used in most high-dose prescription vitamin D in the United States and the form in vegan supplements and ultraviolet-treated mushrooms. Distinct from vitamin D3 (cholecalciferol), which is covered separately.
Typical dose600 IU a day to age 70, 800 IU from 71
The Institute of Medicine's reference intakes cover vitamin D as a whole and do not set separate figures for D2, so the 600 IU per day figure for ages 1 to 70 and 800 IU per day from 71 applies here too (Ross et al., 2011). Whether a D2 international unit does the same work as a D3 international unit is exactly the point at issue: given the same weekly dose for 12 weeks, D2 raised steady-state blood levels by 24 ng/mL against 45 ng/mL for D3 (Heaney et al., 2011).
Upper limit4,000 IU a day from age 9, set by the Institute of Medicine
The Institute of Medicine's Tolerable Upper Intake Level of 4000 IU per day for ages 9 and over is set for vitamin D as a whole and is not stated separately for D2 (Ross et al., 2011).

Myth check

"D2 and D3 are the same thing, so it does not matter which one the bottle says."

They are not interchangeable unit for unit. Pooling trials that gave people both forms head to head, D3 raised blood 25-hydroxyvitamin D significantly more than D2 (Tripkovic et al., 2012). In a direct 12 week comparison at 50000 IU weekly, D3 produced a 45 ng/mL rise against 24 ng/mL for D2, which the authors put at D3 being roughly 87 percent more potent, and it left two to three times more stored in body fat (Heaney et al., 2011). The size of the gap depends on how the vitamin is taken: it was clear with occasional large doses and disappeared with daily dosing.

The difference is real but it is a difference in blood levels, not in anything a person feels. Whether the extra rise from D3 produces better health has not been shown, so the practical question is whether a given regimen reaches the level intended, not which letter is on the bottle.

The findingsStrongest first

1↑

OtherD3 raises blood levels more than D2, but not when taken daily

At the same weekly dose for 12 weeks, vitamin D3 raised blood levels 45 nanograms per millilitre against 24 for vitamin D2. Taken daily, the gap vanished.

★★★Protect bones and joints

Sources2 behind this page

Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysisTripkovic L et al., 2012DOI 10.3945/ajcn.111.031070
Vitamin D3 is more potent than vitamin D2 in humansHeaney RP et al., 2011DOI 10.1210/jc.2010-2230

Vitamin D2 (Ergocalciferol)

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