Cognitive Decline and Vitamin D


Score another point for vitamin D.

There’s already good evidence that, in addition to its crucial role in maintaining bone health, the so-called “sunshine vitamin” can:

  • Help regulate your immune system
  • Reduce your risk of high blood pressure
  • Lower your blood pressure if it’s high
  • Reduce your risk of depression
  • Reduce your risk of type 2 diabetes and several kinds of cancer

That’s a healthy list of benefits. For those of you who prefer a simple bottom line—a 2014 study found that people with low vitamin D levels were twice as likely to die prematurely—from all causes, not just bone diseases.

New evidence: pushing back against cognitive decline

A recent study showed for the first time that vitamin D deficiency also seems to play a significant role in cognitive decline, generally, and Alzheimer’s, specifically. Over the five years of the study, people with low levels of vitamin D, on average, lost major thinking skills 2.5 times faster than people with adequate vitamin D levels.

One of the cognitive functions that low D-level subjects lost more quickly is what’s known as episodic memory—our own life story, our who, when, where, why, and how. Caregivers and family who witness this loss in a loved one—”Dad didn’t recognize me…”—find it among the most painful of the ravages of cognitive decline.

Also lost—executive function, the management skills that help us get things done minute by minute, day by day: to plan and manage behavior to accomplish a goal,to recognize a need to change that behavior, and our necessary and quite extraordinary ability to imagine cause-and-effect scenarios.

Other cognitive functions were unaffected by the low level of vitamin D. But loss of any function is a tragedy for both the patient and his or her caregivers.

Bring on vitamin D.

How to ensure adequate vitamin D

I’ve written before about the role of exposure to sunlight in vitamin D production in our bodies. It’s necessary. But keep it safe, limited to 20 minutes/day of direct exposure—before sunscreen goes on and you seek the shade or cover up with light, loose-fitting clothes.

But what if it’s winter?

“The sun is not strong enough for the body to make vitamin D from October to May, especially for those living north of Atlanta,” says a spokesperson for the American Dietetic Association. That’s probably why nearly half of people tested at winter’s end were low on vitamin D. Our ability to produce vitamin D also slows as we age. In the new study, most of the older subjects—in their 80s and 90s—fell well below the “adequate” level of vitamin D.

You can make up for this somewhat by eating more vitamin D-rich foods. The list is short, but it will help. At the top, wild-caught fish: salmon, mackerel, tuna, sardines—but once a week only, thanks to pollution. Free-range meats are also a good source, as are egg yolks and canned fish.

A vitamin D3 supplement might also be part of the solution. Make sure you get your doctor’s signoff and recommended dosage before taking a vitamin D3 or any other supplement.

There went the sun: seasonal affective disorder

To underscore the importance of vitamin D, let’s look at its role in seasonal affective disorder (SAD). When the days grow shorter and the sun more distant, SAD, which is far more common in women than in men, kicks in and knocks you out. The cause seems to be the drastic decline in the neurotransmitter serotonin—one of our natural feel-good chemicals.

Symptoms can include:

  • Sadness
  • Low energy or fatigue
  • Increased appetite, with a craving for carbs
  • Weight gain
  • Headaches
  • Listlessness, i.e. lack of interest and motivation
  • Excessive sleep without feeling rested
  • Atypical irritability

Treatment options for SAD include light therapy (phototherapy), psychotherapy, and medications. I strongly recommend you avoid medication—there are better solutions. Talk therapy? Maybe, if you and your doctor think it will help. But first, do give light therapy a try. It’s safe, simple, relaxing, and it’s proven effective for many people, including some of my patients.

As always, what you eat has a tremendous impact on how you feel. So, if you’re feeling SAD:

  • Balance your carb intake with the right amount of protein and fats—get 50 to 60 percent of your daily calories from healthy carbs (fruits, vegetables, whole, organic grains), 20 to 35 percent from healthy saturated fats, and 10 to 15 percent from protein. And avoid refined sugar, which seems to exacerbate the condition.
  • Exercise 20 to 30 minutes a day—walk, dance, or any other activity. It’s incredibly simple and works amazingly well.
  • Get more essential fatty acids (EFAs) from foods rich in omega-3s like wild fish (one serving/week) and organic meat. These will also improve your levels of nutrients like melatonin, 5-HTP, and GABA.

And of course, a vitamin D3 supplement. Start with 1,000 IU daily. If there’s no improvement after a week, up the amount, with your doctor’s approval, to 4,000 IU, which I consider the safe maximum

I recommend starting with a 25(OH)D blood test. Ask your doctor to run it. A level of 20 nanograms/milliliter to 50 ng/mL is fine for healthy people. A level less—than 12 ng/mL—indicates vitamin D deficiency. Your doctor can customize a treatment plan based on your test results.

Don’t let the lack of sun catch you crying. Give vitamin D a chance to help you stave off cognitive decline and make it an enjoyable winter.


Last Updated: August 16, 2018
Originally Published: 
October 9, 2015