URGENT SUMMER WARNING: Getting your vitamin D the “old fashioned” way might not be enough

Summer is back and with it comes longer days, and of course, more sunlight. And I’m here to remind you how important it is to keep taking your vitamin D, no matter how many tropical vacations you have on the books.

Because even if you manage to fit 20 minutes of unfiltered sunshine into your day, every day (as I’ve recommended for years), it’s just not going to be enough—unless of course, you’re catching all of those rays in your swimsuit in South Florida. (I wish!)

And recent research shows, once again, exactly what you stand to lose by not taking this recommendation seriously.

The British Medical Journal recently published an analysis of data from nearly 34,000 Japanese adults. (One of the first of its kind to focus on an Asian population—which is important, since ethnicity does influence vitamin D metabolism.)

Blood samples showed that vitamin D levels varied by season—and not surprisingly, summer and autumn levels tended to be higher. But even after accounting for these fluctuations—as well as other factors, like age, weight, exercise habits, smoking status, alcohol intake, and diet—a notable pattern emerged.

After 16 years of follow-up, just over 3,300 of the participants received a cancer diagnosis. But those subjects with the highest levels of vitamin D were 20 percent less likely to fall into this group.1

In particular, higher levels of vitamin D cut the risk of liver cancer by nearly half. And considering the fact that this form of cancer has been rising at an alarming rate, I’d say that’s a pretty big deal.

So if you want to prevent cancer—and a plethora of health conditions and chronic disease—it’s this simple: Take at least 5,000 IU of vitamin D3 daily, year-round. I personally supplement with 10,000 IU.

And if you’re not getting outside much—especially if you’re deficient or borderline deficient already—you may need to be taking 10,000 IU too. Which is perfectly safe, provided your doctor is monitoring your levels regularly.

The next time you go to the doctor, ask for a 25(OH)D blood test, which measures your vitamin D levels. I always shoot for around 80 ng/mL in my patients. That’s obviously a lot higher than the 29 ng/mL that most mainstream doctors go by. But if you’re going to get the most out of this critical nutrient and truly protect your body, you really can’t afford to aim any lower.


  1. Budhathoki S, et al. BMJ. 2018 Mar 7;360:k671.