Even low doses of this key vitamin boost cognition in older women

I’m always impressed by studies on vitamin D that showcase its many health benefits—especially its effect on cognitive health. So, I was particularly interested in a new study that looked at vitamin D’s effect on cognition in older women.

But once I got into the details, I noticed a few design flaws and shortcomings. Nonetheless, researchers still found that supplementing with vitamin D significantly boosted cognitive function in these women.

So, without further ado, let’s take a look…

Even low doses improve cognitive function

The new study, which was published in The Journal of Gerontology, included postmenopausal women with an average age of 58. At the study’s outset, the women had average vitamin D blood levels of 27 nanograms/milliliter (ng/mL). These levels are generally considered to be “sub-optimal.” In addition, all the women were either overweight or obese, which can sequester your body’s storage of vitamin D.

Researchers randomly assigned the women to receive one of three different doses of vitamin D daily for one year. The first group received 600 IU daily. The second group received 2,000 IU daily. And the third group received 4,000 IU daily.

After one year of supplementation, the researchers re-measured the participants’ levels of vitamin D. They also administered cognitive function tests.

All groups had improved vitamin D blood levels. In fact, after one year:

  • The 600 IU group increased their vitamin D blood levels to 30 ng/mL
  • The 2,000 IU group increased their vitamin D blood levels to 36 ng/mL
  • The 4,000 IU group increased their vitamin D blood levels to 41 ng/mL

Unfortunately, none of the women in the study achieved optimal blood levels of vitamin D—between 50 to 60 ng/mL—which other studies show can help reduce chronic disease risk.

But it’s not at all surprising that they didn’t achieve optimal levels, considering the pitifully low doses of vitamin D taken daily by all three groups.

As I always report, you need to take much higher doses daily to reach optimal vitamin D levels and to reduce disease risk. (I’ll tell you exactly how much you need to take daily in a moment.)

Now, let’s look at how the women performed on the cognitive tests…

Vitamin D linked to stronger cognitive performance

The women who took 2,000 IU of vitamin D daily performed significantly better on cognitive tests than the 600 IU group. (Note: the study lacked a placebo group. But the 600 IU group had such a small, insignificant increase in D levels, it essentially performed like a placebo group.)

The cognitive improvements in this 2,000 IU group were especially impressive since they only experienced a slight improvement in vitamin D blood levels, compared to the 600 IU group. So, clearly, even small improvements in blood levels of vitamin D leads to significant gains in cognitive function.

Granted, researchers noted that the 4,000 IU group had a “slower reaction” time compared to the 600 IU group. But that finding doesn’t quite add up…

Remember, the 4,000 IU group had vitamin D blood levels that were 5 ng/mL higher than the 2,000 IU group. Yet, only the 2,000 IU group had significant brain benefits.

Something seems a little off to me here.

Plus, there was another flaw in the study, which makes me even more suspicious of this finding…

The researchers took blood measurements of vitamin D before and after the treatment period (like a real clinical trial study). But they only administered cognitive function tests at the one-year mark, after the participants had been taking vitamin D for a year.

Omitting this important step prevented the researchers from comparing cognitive function on a scientific, “before-and-after” basis—which is the whole reason for conducting this kind of clinical trial research in the first place!

This flawed design gives us very limited information. And it only allows researchers to compare cognitive function among the three groups after treatments.

Significant cognitive gains, despite flawed design and low doses

Despite these significant flaws and the inadequate doses of vitamin D used, there were still two clear findings we can take away from this limited study:

  1. In just a year’s time, older women who took even modest doses of vitamin D experienced meaningful improvements in blood levels of this important nutrient.
  2. Women who achieved higher vitamin D blood levels—while still not optimal or even adequate—performed better on cognitive tests.

Unfortunately, most physicians or journalists don’t take the time to unpack all of the small details of a study like this, leading to irresponsible reports. In fact, in preparing for this Dispatch, I even came across a completely irresponsible article about this study on a mainstream news website.

The headline read, “Why too much vitamin D can be a bad thing.”


I can only assume the headline refers to the questionable finding about slower “reaction times” in the women who took 4,000 IU daily. The reporter even went so far as to suggest these slower “reactions times” could increase the risk of falling among older women.

Well, first of all, falls weren’t even investigated in this study. So, the reporter is completely jumping to conclusions about an outcome that wasn’t even studied.

Plus, the truth of the matter is that women with suboptimal levels of vitamin D are much more likely to break a bone when they fall!

Not to mention, when older women do fall, the fall is often a result of a broken bone. In fact, the weakened bone simply breaks—due to low vitamin D—causing a fall.

Therefore, the real story should be that higher, optimal D levels prevent breaks and falls.

But the headline got it all twisted around. And the reporter buried the important finding about vitamin D improving cognitive function in one sentence, in the middle of a four-page story.

So, in the end, my recommendations remain the same…

1.) To achieve optimal blood levels of vitamin D and to protect against almost every chronic disease, continue to supplement year-round with 10,000 IU of vitamin D3 daily. You can now find vitamin D in a convenient liquid form, together with the potent marine carotenoid astaxanthin. (For my own personal recommendations, visit my website and search the “Shop” tab.)

2.) Between April and October, aim to spend 10 to 15 minutes in the sun each day— without sunscreen—to trigger your skin’s natural production of vitamin D. (I’ll give you all the details in the upcoming August 2019 issue of my Insiders’ Cures newsletter. So, if you’re not yet a subscriber, now is the perfect time to get started.)

3.) Ask your doctor to measure your blood levels of D levels twice a year—ideally, once at the end of the summer and again at the end of winter. Remember, you’re looking to achieve blood levels between 50 and 60 ng/mL.

You can also learn more about vitamin D’s key role in cognitive function—including how it helps prevent and reverse Alzheimer’s disease and dementia—in my online learning protocol, Dr. Micozzi’s Complete Alzheimer’s Cure. People who are following my protocol are already making tremendous strides against this devastating condition! Click here to learn more or enroll today.

P.S. Tune back in tomorrow for a full report on looking at whether or not excessive vitamin D can cause kidney failure.


“Three Doses of Vitamin D and Cognitive Outcomes in Older Women: A Double-Blind Randomized Controlled Trial.” The Journals of Gerontology: Series A 2019;  glz041. doi.org/10.1093/gerona/glz041

“Why too much vitamin D can be a bad thing.” Medical News Today, 3/25/19. (medicalnewstoday.com/articles/324772.php)