Published on March 9, 2022

Study concludes “Vitamin C supplementation effectively increased work motivation and attentional focus and contributed to better performance on cognitive tasks requiring sustained attention”

Key Points

  • The brain has the highest concentrations of vitamin C than any other tissue in the body, and vitamin C is involved in multiple critical brain functions
  • Supplementation with vitamin C resulted in significant improvements in attention, work absorption, and shorter reaction times when solving mathematical problems, as well as a distinct improvements in fatigue and work engagement
  • Supplemental vitamin C intake has also been shown to affect how a person’s vitamin D level responds to vitamin D supplementation, such that those taking 1000 mg/day of vitamin C or more had a higher vitamin D level for any given vitamin D intake amount than those taking less supplemental vitamin C

Vitamin C has many health benefits, and from its immune-boosting properties to its anti-cancer actions, vitamin C can be a true life-saver.

Did you know that the brain has the highest concentrations of vitamin C than any other tissue in the body, and that vitamin C is involved in multiple critical brain functions?

Study Investigates Vitamin C’s Role in Mental Health and Vitality

In a two part study, Sim et al. looked at the relationship between vitamin C intake, vitamin C serum levels, and different aspects of mental vitality. The first part of the study, which included data from 214 healthy, young adults between the ages of 20 and 39 years, analyzed the association between vitamin C serum levels, vitality (as fatigue and attention), and mood status (as stress, depression, and positive and negative affect). The second part of the study was a double-blind randomized controlled trial (RCT) that included 24 healthy adults who were given 1000 mg/day of vitamin C (as two doses of 500 mg) for 4 weeks, compared to 22 healthy adults who were given a placebo. All participants had low vitamin C levels at enrollment, defined as less than 50 umol/L. Vitality measures for the trial included fatigue, attention, work engagement and absorption, self-control resources, and mood status, as well as attention capacity and processing speed.

Vitamin C Significantly Benefited Attention Levels

In all aspects of this study, vitamin C intake and levels were significantly associated with measured levels of attention. In the first study, while vitamin C serum level was not significantly related to fatigue or mood, attention levels significantly increased as vitamin C levels increased. The RCT found that, when compared to the placebo group, the vitamin C supplementation group experienced increased vitamin C levels along with significant improvements in attention and work absorption, and a distinct but non-significant improvement in fatigue (p=0.06) and work engagement (p=0.07). The vitamin C group also had significantly shorter reaction times when solving mathematical problems.

Those Taking Vitamin C Experienced Overall Improvements in Vitality

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When looking at changes in mental vitality only among the vitamin C supplementation group, compared to baseline, 4 weeks of supplementation resulted in significantly

  • decreased levels of fatigue
  • increased attention span
  • increased level of work engagement and absorption (suggestive of motivation)
  • increase in vigor
  • increased self-control resources

In conclusion, “vitamin C supplementation significantly increased subjective feelings of concentration and promoted better cognitive performance requiring sustained attention.”

The Brain Needs Vitamin D, Too

Vitamin D is also essential to healthy brain function, and has been biologically linked to emotional well-being, mood, cognition, and better mental health overall. One study on vitamin D and mental health in particular found that self-perceived measurements of mental and emotional wellness were positively associated with higher vitamin D levels. Interestingly, supplemental vitamin C intake has been shown to affect how a person’s vitamin D level responds to vitamin D supplementation (called the dose-response), such that those taking 1000 mg/day of vitamin C or more had a higher vitamin D level for any given vitamin D intake amount than those taking less supplemental vitamin C. Specifically, 94% more supplemental vitamin D was needed for 50% of the population to reach a vitamin D level of 40 ng/ml (100 nmol/L).

Could Your Vitamin D Level (and Your Mental Vitality) Benefit from Vitamin C?

Not taking vitamin C? Try a self-experiment to see if adding vitamin C to your daily routine could improve your mental vitality and your vitamin D level! Measure your vitamin D level before and a few months after adding vitamin C to see if it makes a difference for you, all while improving your overall health.

Having and maintaining healthy vitamin D levels and other nutrient levels can help improve your health now and for your future. Choose which additional nutrients to measure, such as your omega-3s and essential minerals including magnesium and zinc, by creating your custom home test kit today. Take steps to improve the status of each of these measurements to benefit your overall health. With measurement you can then determine how much is needed and steps to achieve your goals.  You can also track your own intakes, symptoms and results to see what works best for YOU.

Enroll in D*action and Test Your Levels Today!

What Does it Take YOU to Get Your D to 40 ng/ml (100 nmol/L)?

Did you know your health could be greatly affected by making sure you have a vitamin D level of at least 40 ng/ml (100 nmol/L)? Help us help you.

STEP 1 - Do you know what your vitamin D level is? If not, be sure to test today to find out.

STEP 2 – Determine your target level. Are you at your target level? Experts recommend a level of at least 40-60 ng/ml (100-150 nmol/L).

STEP 3 – Need to boost your level? Use the D*calculator to see how much vitamin D it may take to reach your target. Opt for the Loading Dose for a quicker boost.

STEP 4 – Optimize how your body absorbs and utilizes vitamin D with co-nutrients and these simple steps.

STEP 5 – Re-Test! This is an important step to make sure you have reached your target level, and to ensure you are not taking too much! Re-testing after 3-4 months is recommended.

STEP 6 – Adjust, Repeat…

Give your immune system the nutrients it needs to support a healthy you and protect yourself from unnecessary diseases, especially COVID-19.


The first Randomized Controlled Trial on vitamin D and COVID-19 has shown a 96% lower risk of ICU admission for those receiving vitamin D (as 25(OH)D to quickly boost vitamin D blood levels) along with the standard treatment, compared to those receiving standard treatment alone.

These results support many previous observational studies showing a relationship between vitamin D levels and intake and COVID-19 severity.

Review the Latest Nutrient Research for COVID-19

GrassrootsHealth Nutrient Research Institute has launched the new Immune Boost project with the use of our myData-myAnswers nutrient health system that nearly 15,000 people are already using for their health. Specific markers that influence immune health are suggested for testing as part of this project including:

  • Vitamin D
  • Omega-3 Index
  • Essential elements magnesium, selenium, and zinc
  • hsCRP

Our goal is to demonstrate how one can use the Nutrient Research Model established by Dr. Robert Heaney to show the effect of vitamin D serum levels of at least 40 ng/ml (100 nmol/L) on risk reduction for all ethnicities in the population. Status and intake of other nutrients will also be analyzed for any type of relationship to immune status and symptom severity. Join the project today!

Please let us know if you're interested in helping sponsor this project.

CLICK HERE for updates and new information about the project.

Through GrassrootsHealth Nutrient Research Institute, you can also test your essential elements magnesium, copper, zinc and selenium, toxins such as lead, mercury and cadmium, as well as your omega-3 levels, inflammation levels and thyroid stimulating hormone (TSH) level. Find out your levels today! Log on to the test selection page (click the link below) to get your tests and see for yourself if your levels can be improved.

Make sure you track your results before and after, about every 6 months!

Click Here to Access the Test Page

How can I track my nutrient intake and levels over time?

To help you track your supplement use and nutrient levels, GrassrootsHealth has created the Personal Health Nutrient Decision System called

For each specific supplement, you can track what days you take it, how much, and many other details.  This will help you know your true supplemental intake and what patterns of use work for you to reach and maintain optimum nutrient levels. Check it out today!