December 14, 2015

Choosing a Vitamin D Supplement

By cancerconnect

Long known as an important factor in bone health, a quickly growing body of evidence now also shows that vitamin D may help lower the risk of cancer, heart disease, and even premature death.1,2 If you and your healthcare provider have decided that you’d benefit from vitamin D supplements, the following tips can help you choose the right product.

Q. How can I make sure that I am buying a quality vitamin D supplement?

A. There are several steps you can take to ensure that you’re buying a safe, quality vitamin D product.

  • First, do a little research about the brands you’re considering. Avoid purchasing a supplement from any company that has a history of vitamin D recalls—though you’d hope these wouldn’t still be on the shelf, it’s always better to check (you can search recalls at
  • Second, note the type of vitamin D contained in the supplement. There are two types of vitamin D: vitamin D2 (ergocalciferol) is the form commonly added to foods and is used in many supplements; vitamin D3 (cholecalciferol) is the form of vitamin D manufactured by your body in response to sunlight. Our clinicians prefer D3, the form identical to that produced in the body.
  • Third, pay attention to the dosage. Many experts now recommend up to 2,000 IU per day for most healthy adults.
  • Finally, choose a company that tests all—not just some—raw materials and finished goods for authenticity, potency, and purity (many don’t). One of four dietary supplements tested were sub-potent, contaminated, or both, according to the independent testing company (to learn more, visit

Q. Does it matter which brand of supplement I choose, or are they all pretty much the same?

A. All brands are not the same, and asking the right questions about your supplement is important because while every company will claim to produce quality products, asking specific questions requires them to prove it.  Here are some questions you can ask your supplement company to get the information you need:

  • Have any of your products ever been recalled?
  • Are all raw materials individually tested for arsenic, cadmium, lead, and mercury?
  • Are all raw materials individually tested for identity and potency?

Always select products from manufacturers that provide comprehensive proof and fully guarantee that their products are prepared utilizing the highest standards of manufacturing practice and laboratory quality assurance. Such companies will audit and verify their independent laboratories to insure that validated analytical methods and ethical lab practices for raw material and finished product testing are followed. They will take the time to validate the laboratory test methods as well. They will include testing for microbiologic contamination, authenticity, potency, heavy metals, and stability. Some companies also do additional testing, for such things as chemical solvent residues, aflatoxins, markers of rancidity in oils, pesticide residues, dioxins, PCBs, and other contaminants. Finally, there is the matter of testing the finished products to assure they meet label claims for potency, purity, and stability. Although most supplement companies do not go to these lengths, a few do (including Cancer Nutrition Centers of America), and you should seek them out.

Q. Are tablets or capsules better?

A. Unlike tablets, capsules do not have excipients, lubricants, or other ingredients used to aid the manufacturing process. As a result, capsules are “purer” than tablets. Furthermore, capsules rapidly disintegrate in the stomach, quickly releasing their contents, whereas tablets may incompletely dissolve or not dissolve at all. Generally speaking, capsules are a far better choice than tablets.

Q. Will my vitamin D supplement interfere with my prescriptions?

A. Vitamin D is safe to take with most prescriptions, but it is known to increase calcium and phosphorus absorption. For that reason, you should check first with your doctor if you are taking calcium-channel blockers. For additional information on vitamin D and drug interactions, check out


1.  Heaney RP. Vitamin D in health and disease. Clin J Am Soc Nephrol. Sep 2008;3(5):1535-1541.

2.  Melamed ML, Michos ED, Post W, Astor B. 25-hydroxyvitamin D levels and the risk of mortality in the general population. Arch Intern Med. Aug 11 2008;168(15):1629-1637.

Tags: News Tips and Features, News Tips and Features Other, nutrition