A growing body of research spotlights vitamin D, the sunshine vitamin, as essential to overall health.  But how much you need remains a topic of hot debate.  Here, the lowdown on the latest information.


Every so often, something comes along that promises to relieve us of a serious ailment, whether cancer or heart disease.  The latest hope under the sun is actually something we get from the sun: vitamin D.  Turns out, this modest nutrient may be instrumental in preventing (and perhaps even treating) not just one condition but an array of them, strong bones being just the beginning.


Just by sitting outside in the sun, a fair-skinned person in a swimsuit without sunscreen will get thousands of international units, or IU, of vitamin D within 10 minutes at high noon on a bright summer day.  But given concerns about skin cancer, doctors often advise getting the vitamin mostly from food and supplements.  Regardless of its source, vitamin D is modified and activated in the liver and kidneys, and then it travels in the blood to perform its many functions.  Vitamin D influences 229 genes and therefore can have wide-ranging effects throughout the body.    Several well-documented studies have found an association between higher vitamin D levels and a significant reduction (50%) in breast-cancer risk.  While correlation is not causation, it may in part offer an explanation.    Other research looks at the reasons the flu virus is so much more virulent in the winter months.   Seasonality also means differences in sun exposure, and many immune cells have vitamin D receptors.  When the vitamin latches onto cells, the cells destroy unfriendly microbes.  It’s likely that cells also prevent the immune system from ramming into overdrive and causing inflammation.  This suggests that vitamin D deficiency may also promote risk for a range of inflammatory diseases, including rheumatoid arthritis, irritable bowel syndrome, asthma, and cardiovascular conditions.


While experts disagree on the level of vitamin D necessary for bone health and disease prevention, current research (the VITAL study) is directed at the preventive effects of 2,000 IU per day.    The first set of data from this study is slated for release in late 2017.  This dose may offer the best balance of efficacy and safety.  If you think you may be deficient, discuss the issue with your physician.  Based on your lifestyle and health conditions, your doctor can discuss a protocol that incorporates a daily dose of sun, supplements, and vitamin D-rich foods so you can feel your best today, and perhaps well into the future.

Joanne Chen



  • With any given dose of sunlight, different people end up with different amounts of vitamin D in the blood, depending on their geography, genes, skin color and age.
  • Vitamin D is unlike any other vitamin in that it’s found in relatively few foods, so supplementation is essential for most individuals.  Most over-the-counter supplements are D3, the same form that your skin makes in sunlight.
  • Since vitamin D is a fat-soluble substance, it’s more bioavailable when you take it with foods containing some fat, such as almond butter or 2% milk.
  • Focus on high-vitamin D foods, including salmon, canned tuna and egg yolks.
  • The fat-soluble nature of vitamin D means it can get trapped in excess body fat.  If you’re obese, talk with your doctor about the possibility of increasing your daily vitamin D intake.
  • Don’t forget to consume adequate calcium from dark leafy greens and cold water fish!