What You Need To Know About Vitamin D

According to the Mayo Clinic, the major role of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D helps the body absorb calcium, which forms and maintains strong bones to prevent osteoporosis. Research over the past few decades has uncovered that vitamin D also protects against certain cancers, depression, diabetes, and heart disease. Although, some scientists say that vitamin D deficiency is linked to hypertension, multiple sclerosis, autism and Alzheimer’s diseases, more research is needed to support these claims.

According to the Vitamin D Council (a nonprofit organization, working to educate the public on vitamin D, sun exposure and health), the following people are more likely to be lacking in vitamin D:

  • People with darker skin. The darker your skin the more sun you need to get the same amount of vitamin D as a fair-skinned person. For this reason, if you’re Black, you’re much more likely to have vitamin D deficiency that someone who is White.
  • People who spend a lot of time indoors during the day. For example, if you’re housebound, work nights or are in hospital for a long time.
  • People who cover their skin all of the time. For example, if you wear sunscreen or if your skin is covered with clothes.
  • People that live in the North of the United States or Canada. This is because there are fewer hours of overhead sunlight the further away you are from the equator.
  • Older people have thinner skin than younger people and this may mean that they can’t produce as much vitamin D.
  • Infants that are breastfed and aren’t given a vitamin D supplement. If you’re feeding your baby on breast milk alone, and you don’t give your baby a vitamin D supplement or take a supplement yourself, your baby is more likely to be deficient in vitamin D.
  • Pregnant women.
  • People who are very overweight (obese).

Supplemental vitamin D comes in two forms:

Ergocalciferol (vitamin D2), derived from plants

Cholecalciferol (vitamin D3), derived from animals

D3 is the form naturally produced by our bodies in response to sun exposure.

After careful analysis of randomized controlled trials involving vitamin D supplementation, the Vitamin D Council recommends that doctors and health professionals use D3 supplements over D2.

Vitamin D works if other nutrients are present in the diet. These include:

  • Magnesium
  • Vitamin K
  • Zinc
  • Boron
  • Vitamin A

That’s why it’s essential to eat a well-balanced, wholesome diet.

To find out if your vitamin D levels are low, ask your physician to order a vitamin D blood test.

Upper limits of recommended Vitamin D supplementation set by various organizations:

                 Vitamin D Council                         Endocrine Society          *Food and Nutrition Board
Infants:    2000 IU/day                                            2000 IU/day                     1000-1500 IU/day
Children: 2000 IU/day / 25 lb body wt           4000 IU/day                      2500-3000 IU/day           Adults:    10,000 IU/day                                        10,000 IU/day                   4000 IU/day

The *Food and Nutrition Board upper limits are the official U.S. government recommendations.

If you are already taking a multiple vitamin and/or other dietary supplements, check the labels to see how much vitamin D is present. 


Certain foods provide small amounts of vitamin D. Plant sources provide only the D2 form while the more beneficial D3 comes only from animal-based foods like:

  • Fish, such as salmon, mackerel, tuna and sardines
  • Egg yolk
  • Fortified milk*
  • Cod liver oil

*Pasteurized milk has been fortified milk with vitamin D since the early 1900s. Today, about 98 percent of the milk supply in the U.S. is fortified with about 400 International Units (IU) of vitamin D per quart. Traditionally, dairies fortified milk with vitamin D2, yet recently many have switched over to D3. Check the label to see which form of vitamin D is added to your brand. Other dairy products like cheese, yogurt and ice cream are typically not fortified with vitamin D. Plant-based fortified beverages like soy milk and almond milk use D2 because it’s a plant-derived form of vitamin D, which was produced in the early 1920s through ultraviolet exposure of foods like mushrooms and yeast.

A new study published in the February 2015 Journal of the Academy of Nutrition and Dietetics concludes that vitamin D supplements are absorbed 32 percent more when taken with a meal containing a commonly consumed amount of fat compared to a meal without fat.

According to the Vitamin D Council, if you have a parathyroid or granulomatous disorder or kidney disease, you should avoid vitamin D supplementation unless you have approval from your physician.

Always seek the advice of your physician and registered dietitian before starting a supplement regimen.

For healthy recipes and a diet geared towards optimal health, pick up a copy of Layne’s book: Beyond The Mediterranean Diet: European Secrets Of The Super-Healthy.