Most of us think of 'Prescription Strength' pills to be somehow better or stronger than a similar 'Over the Counter' variety. But in the case of prescription vitamin D pills, they are FAR inferior to the vitamin D that you can buy in any health food store. In fact, they are less potent, less 'biologically active', more toxic and have a shorter shelf life. How is THAT for prescription strength!
Vitamin D has become something of a superstar recently, with study after study showing that HUGE numbers of people have vitamin D deficiency and that the consequences are many of the 'diseases of civilization' that so plague the western world today. So, as doctors become aware of the health benefits of vitamin D, more are testing for and treating vitamin D deficiency. But while more awareness about vitamin D deficiency is beneficial, it will also bring more usage of prescription vitamin D pills which may NOT be so beneficial.
The most common form of prescription vitamin D is in the form of Vitamin D2, also called Ergocalciferol. This is also the same type of vitamin D that is used for the 'fortification' of most milk and cereal products. But the 'over the counter' formulation of vitamin D in the form of Vitamin D3, also called Cholecalciferol, is far superior to the prescription formula that is routinely prescribed. First of all, prescription vitamin D is at least one-half as effective as vitamin D3 and possibly even up to one-tenth as effective. In 'The case against ergocalciferol (vitamin D2) as a vitamin supplement', the authors state, "50 000 IU vitamin D2 should be considered equivalent to 15000 IU vitamin D3, and likely closer to 5000 IU vitamin D3". That's One-Tenth as effective as vitamin d that you can buy in stores. When these differences were discovered in the 1950's, Germany reformulated their prescription vitamin D to vitamin D3, but almost 60 years later, the United States is still using prescription vitamin D that doesn't work.
And it really doesn't work. One consequence of vitamin D deficiency is an increase in parathyroid hormone levels which alters calcium metabolism for the worse. In many studies, the effectiveness of the vitamin D therapy was measured not just by vitamin D levels increasing, but by parathyroid hormone levels decreasing into the normal range. In studies that directly compare the two, vitamin D3 effectively decreased parathyroid hormone while vitamin D2 did not. Another extremely important function of vitamin D, one that can't be understated, is vitamin D's ability to bind to 'Vitamin D Receptors' in the body. These receptors, also called VDR, are present in almost every tissue in the body and are one possible explanation for the extremely diverse health effects of the vitamin. When VDR's are bound with an active form of vitamin D, it can help to prevent the expression of a mind boggling array of disease causing genes. Yet, vitamin D2 produces an active hormone that has 40% less binding ability to VDR's than does the hormone produced from vitamin D3. This makes vitamin D2 much less 'Biologically Active' than vitamin D3 and leads to the possibility that prescription vitamin D doesn't even prevent the diseases and problems that treatment of vitamin D deficiency is supposed to alleviate!
Another disadvantage of prescription vitamin D2 is that it has a shorter half life in the body. Water soluble vitamins need to be replenished continually; for instance, B vitamins and vitamin C are best metabolized in small doses throughout the day. But fat soluble vitamins like vitamin D do NOT need to be taken every day. In fact the half life of vitamin D3 is 3 weeks. This means that 3 weeks after you take one dose, one half of that dose is still left in your body. This is true whether you get it from the sun, food or supplements. But vitamin D2 has a much shorter half life, which means that you not only need more of the vitamin to prevent or treat deficiency, but you also need to take that higher dose more OFTEN.
"...the vitamin D of irradiated ergosterol vitamin D2,
exerts greater toxic effects at lower levels than do the vitamins D
of fish liver oil vitamin D3.
' A Comparison of the Hypervitamoses Induced by Irradiated Erogsterol and Fish Liver Oil Concentrates'
But taking these higher doses more often could have consequences. Researchers since the 1930's have found higher potential for toxicity, more impurities and less consistent formulations in vitamin D2 preparations than in D3 preparations. In fact, researchers interpreting studies on vitamin D find that the studies done using vitamin D2 have inconsistent results and recommend that all researchers use vitamin D3 for its more predictable results, better biologic action, fewer toxic effects, more consistent formulations and longer shelf life.
So while progress is being made in the awareness of the widespread problem of vitamin d deficiency, doctors who actually test for and treat vitamin D deficiency most often choose to ignore the advice of vitamin D researchers Dr's Houghton and Vieth who state, "... vitamin D2, or ergocalciferol, should not be regarded as a nutrient suitable for supplementation...". It seems that patients would be better served if their doctors, instead, recommend their patients go to the local health food store to treat their vitamin D deficiency.