Unlike some nutrition queries that are somewhat gray and equivocal in nature, when vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) go head-to-head, the winner is clear. Allow me to use an analogy to explain. To wrap my Olympics nutrition visual: Vitamin D3 is on the middle podium with its anthem playing loud and clear, whereas vitamin D2 didn’t medal at all. Harsh but true. Before I get granular on why D3 triumphs over D2, let’s recap why vitamin D should be top of mind in the first place. Despite its importance, there is clear data demonstrating how widespread the vitamin D gap is in our country. For instance, we know that the large majority (93%) of American adults are not even consuming 400 IU of vitamin D1 from their daily diet. Extrapolating from that nationally representative stat, I guesstimate 99% of us are failing to eat at least 3,000 I.U. of vitamin D (the minimum intake level to achieve vitamin D sufficiency, i.e., serum 25(OH)D level > 30 ng/ml) from food alone. This is where supplementation can help—but only if you choose the right form. Vitamin D3 and D2 have historically been differentiated by their origin: animal versus plant. Vitamin D3 is almost always animal-derived, from lanolin from sheep’s wool. This is a fine source of D3 and the most common in the market. In contrast, vitamin D2 is plant-derived from irradiated yeast and mushrooms mostly. But that’s old news. Innovative technologies in the past several years have developed vitamin D3 options from plant origins (I see you, vegans), specifically from lichen and algae, the latter algal source being significantly more sustainable and pure. Albeit rare, there are even certified organic plant-origin varieties of D3. Why does this ultimately matter? Well, aside from 25(OH)D being the primary indicator of whole-body vitamin D status, this compound is converted into 1,25(OH)2D (the activated form of vitamin D) for its many essential actions in cells, tissues, and organs throughout the body—like our bones, muscles, immune cells, brain, etc.* The fact that vitamin D3 is way better than D2 at helping us achieve and maintain vitamin D sufficiency has been demonstrated by loads of robust research in humans. I’m talking about numerous randomized, placebo-controlled, and double-blind clinical trials; so many, in fact, that a landmark systematic review and meta-analysis2 in the American Journal of Clinical Nutrition concluded that “vitamin D3 is more efficacious at raising serum 25(OH)D concentrations than is vitamin D2.”* How much better is vitamin D3 at increasing 25(OH)D levels? Some studies estimate that the potency of D3 is a whopping 87% higher than D23. This effect of vitamin D3 supplementation superiority has been proved over and over:* Let me share a few prime examples: Next, vitamin D2 metabolites have weaker binding9 to the vitamin D binding protein, which binds the nutrient and carries it throughout the body to do its job. And finally, vitamin D2 demonstrates reduced hydroxylation of vitamin D37 (a necessary activation step in normal vitamin D metabolism) while also increasing the catabolism (aka breakdown) of 25(OH)D3 for excretion. These competitive mechanisms have been demonstrated with vitamin D2 supplementation at multiple doses (1,000 I.U./day5, 2,000 I.U./day6, 100,000 I.U./month7), and the ultimate effect is reduced 25(OH)D3 levels. Talk about counterproductive. I concur and wish nutritionists and health media reporters would stop talking about D3 and D2 as equally suitable options. They’re not. D3 equals gold. Spread the word. In addition to her mindbodygreen contributions, Ferira is published in Health, Metagenics Institute, American Family Physician, The Journal of Clinical Endocrinology & Metabolism, and Osteoporosis International. She has a passion for the translation of evidence-based science into innovative and high-quality products and information that help people lead healthier lives. She is a believer in compassionate, informed, and personalized approaches to nutrition, health care, and wellness. Ashley lives in beautiful Charleston, South Carolina, where she was born and raised. Whether savoring an orchestral performance or delectable meal at a local restaurant, you will find her enjoying Charleston’s cultural and culinary arts with family and friends.
