Labdoor analyzed 20 best-selling vitamin D supplements in the United States for vitamin D3 content, heavy metal contamination, and presence/absence of GMO events.
All 20 products exceeded their claimed vitamin D3 content, averaging 23% over their stated label claims. 6 of the 20 products exceeded their label claims by greater than 40%.
Additionally, all products recorded at least 1000 IU vitamin D per serving, significantly above vitamin D’s 400 IU Daily Value (DV) and its 600 IU Recommended Dietary Allowance (RDA).
All supplements passed their heavy metals and GMO assays.
All 20 vitamin D supplements met or exceeded their claimed vitamin D3 content, ranging from +0 to +900.0 IU versus their stated label claims.
The average label variance in this testing batch was 23%.
All products in this report were screened by Inductively Coupled Plasma (ICP)-based techniques for the presence of heavy metals. Samples of each product passed all six heavy metals assays, indicating that samples contained under 1 PPM (part per million) each of arsenic, lead, cadmium, bismuth, antimony, and silver compounds.
Most vitamin D supplements tested in this batch recorded similar Nutrition Facts panels, with only minimal variation in calorie, fat, carbohydrate, and sugar content.
All products recorded vitamin D3 levels in excess of the Institute of Medicine’s (IOM) 600 IU Recommended Dietary Allowance (RDA) in a single serving, ranging from Nature Made Vitamin D3, which exceeded the vitamin D RDA by 66.7%, to Natrol Vitamin D3, which exceeded the vitamin D RDA by 383.3%.
Three products – Vitafusion Vitamin D3 Gummy Vitamins, Source Naturals Vitamin D3, and Natrol Vitamin D3 – significantly exceeded their stated label claims, reaching vitamin D3 quantities at which two servings would exceed the 4000 IU per day Upper Limit (UL).
Even at these high doses; however, clinical studies indicate that toxicity is unlikely to occur. According to the National Institutes of Health (NIH), most clinical reports set a toxicity threshold of 10,000 IU - 40,000 IU vitamin D per day. The Mayo Clinic has noted toxic reactions after several months of consumption of 50,000 IU vitamin D daily.
Three products – Nature Made Adult Chewable Vitamin D, Trisorb Vitamin D, and Natrol Vitamin D3 – utilized sucralose (Splenda), an artificial sweetener, in their formulations. Sucralose has been suggested as a trigger of migraines in those who have previously suffered from migraines, but has shown no conclusive carcinogenic, reproductive, or neurological adverse effects in existing clinical research.
FD&C Blue No. 2 and FD&C Red No. 40 – both found in Nature Made Adult Chewable Vitamin D3 – have been linked to DNA damage and increased incidence of cancer in animal models. FD&C Red No. 40 has also been suggested as a cause of hyperactivity in humans.
All products recorded at least 1000 IU vitamin D per serving, significantly above vitamin D’s 400 IU Daily Value (DV), set by the U.S. FDA, and its 600 IU Recommended Dietary Allowance (RDA), set by the U.S. Institute of Medicine.
Additionally, every supplement utilized vitamin D3 (cholecalciferol) instead of vitamin D2 (ergocalciferol). Vitamin D3 is expected to work more effectively in the body since it is the form of vitamin D that is already synthetized by humans.
Vitamin D’s most established function is that of promoting calcium absorption in the gut – which maintains adequate serum calcium and phosphate concentrations – promoting neuromuscular health and normal mineralization of bone.
In a clinical setting, vitamin D (in combination with calcium) is most often used to treat and reverse conditions resulting in thin, brittle, and fragile bones: rickets in children, ostemalacia in adults, and osteoporosis in older adults.
Research has suggested a variety of other biological roles for vitamin D, including modulation of cellular growth, immune function, and reduction of inflammation. Vitamin D is also thought to regulate – at least, partially - genes encoding proteins involved in cellular proliferation, differentiation, and apoptosis (programmed cell death).