Are you nearing or past 50, and anxious about loss of mental acuity? 

Join the club. Brain decline beginning in or after middle age is a frequent fear.

The evidence that fishy diets help is clear: see Fish Affirmed as Brain Food and related reports in the Omega-3s & Brain Health section of our news archive. 

Likewise, colorful, antioxidant-rich fruits and vegetables may be allies: see Colorful Antioxidants May Curb Alzheimer'sAlzheimer's Risk Curbed by Antioxidants in Juice, Aging Brains Appear to Benefit from Foodborne Antioxidants, and more in the Foods & Brain Health section of our news archive. 

A new study finds that dark leafy greens like spinach, kale, and collards may offer special brain benefits.

And, for the first time, it suggests that the abundant vitamin K they provide may be a powerful ally against cognitive decline … in other words, "brain fog”.

Dark, leafy greens linked to mental protection
The new epidemiological study comes from Chicago's Rush University Medical Center.

A team led by Martha Clare Morris, Sc.D., tracked the diets and cognitive abilities of 954 older adults for an average of five years.

The participants – whose age averaged 81 – reported their daily food and beverage intake by answering a detailed 144-item questionnaire at the beginning of the study.

The researchers estimated the volunteers' total daily nutrient intakes, and followed the participants for two to 10 years, assessing their cognitive abilities annually with a comprehensive battery of 19 tests. 

After adjusting the results to account for the known brain-health effects of various factors, they found that those who ate the most green leafy vegetables enjoyed a significantly slower rate of cognitive decline

Specifically, people who ate one to two servings of green leafy vegetables per day had the cognitive ability of a person 11 years younger than those who ate none. 

Note: Epidemiological studies cannot prove a cause-effect relationship ... but they matter when there are enough such studies, the results of most align, and any links found between a food or nutrient and health outcomes enjoy supportive lab evidence.

In this case, more studies are needed, but the results align so far, and the links found between these foods and nutrients and brain health do enjoy supportive lab evidence

Brain benefits linked to specific nutrients
The researchers also estimated the participants' intakes of individual nutrients found in dark, leafy greens.

They found that vitamin K, lutein, folate and beta-carotene appeared to do the most to keep brains healthy. 

In addition to dark green leafy vegetables, many other colorful fruits and vegetables are good sources of these nutrients.

And as the reports linked to above found, the polyphenol-type antioxidants in colorful fruits and vegetables appear to confer brain benefits.

Prior studies have linked folate and beta-carotene intake to slower cognitive decline, but, as Professor Morris said, "No other studies have looked at vitamin K in relation to change in cognitive abilities over time, and only a limited number of studies have found some association with lutein.”(FASEB 2015)

"With baby boomers approaching old age, there is huge public demand for lifestyle behaviors that can ward off loss of memory and other cognitive abilities with age,” said Morris. "Our study provides evidence that eating green leafy vegetables and other foods rich in vitamin K, lutein and beta-carotene can help to keep the brain healthy to preserve functioning.” 

She made an obvious point: "Since declining cognitive ability is central to Alzheimer's disease and dementias, increasing consumption of green leafy vegetables could offer a very simple, affordable and non-invasive way of potentially protecting your brain from Alzheimer's disease and dementia.” (FASEB 2015)

Next, the researchers want to discover exactly how these nutrients in leafy green vegetables support brain health.

What is vitamin K, and what does it do?
Vitamin K is a fat-soluble vitamin, mostly known for helping blood to clot and bones to stay strong.

Research in recent years has linked vitamin K to reduced risks for cardiovascular disease, osteoporosis, and certain kinds of cancer.

And evidence that vitamin K plays important roles in the brain keeps accumulating, albeit slowly.

Interestingly the most common form of vitamin K found in animal foods (menaquinone-4) exerts anti-inflammatory effects and protects against oxidative stress ... two important factors in brain protection (Tsaioun KI 1999; Allison AC 2001; Ferland G 2012).

One of the few human studies conducted to date found that Alzheimer's patients consumed considerably less vitamin K than a control group, suggesting that inadequate intake of vitamin K may promote the disorder (Presse N et al. 2008).

It's not yet clear whether both forms of the vitamin – K1 (plant foods) and K2 (mostly animal foods) – help brain health equally:
  • Vitamin K1 (phylloquinone) abounds in colorful vegetables (especially dark, leafy greens), avocado, kiwifruit, grapes, and certain vegetable oils (especially olive and canola oils). Absorption of vitamin K1 is greater when it's accompanied by fats.
  • Vitamin K2 (several menaquinone compounds) abounds in butter, animal fats and organs, egg yolk, certain cheeses (e.g., Gouda and Brie), and fermented plant or dairy foods (e.g., sauerkraut, natto, and kefir).
We'll keep our eye on vitamin K research relative to brain health, and alert you to any significant developments.

In the meantime, you can help protect your brain by enjoying seafood and (colorful) vegetables in abundance!

  • Allison AC. The possible role of vitamin K deficiency in the pathogenesis of Alzheimer's disease and in augmenting brain damage associated with cardiovascular disease. Med Hypotheses. 2001 Aug;57(2):151-5.
  • Booth SL, Pennington JA, Sadowski JA. Food sources and dietary intakes of vitamin K-1 (phylloquinone) in the American diet: data from the FDA Total Diet Study. J Am Diet Assoc. 1996 Feb;96(2):149-54.
  • Federation of American Societies for Experimental Biology (FASEB). Eating Green Leafy Vegetables Keeps Mental Abilities Sharp. March 25, 2015. Accessed at
  • Ferland G. Vitamin K, an emerging nutrient in brain function. Biofactors. 2012 Mar-Apr;38(2):151-7. doi: 10.1002/biof.1004. Epub 2012 Mar 15. Review.
  • Presse N, Shatenstein B, Kergoat MJ, Ferland G. Low vitamin K intakes in community-dwelling elders at an early stage of Alzheimer's disease. J Am Diet Assoc. 2008 Dec;108(12):2095-9. doi: 10.1016/j.jada.2008.09.013.
  • Tsaioun KI. Vitamin K-dependent proteins in the developing and aging nervous system. Nutr Rev. 1999 Aug;57(8):231-40. Review.