Published on July 28, 2021

Study reports on an association between dietary patterns and severity of COVID-19 illness

Several factors have been associated with the severity of COVID-19 disease, including age, ethnicity, and preexisting conditions. Nutrient deficiencies, especially of vitamin D, have also been shown to affect COVID-19 severity and outcome. It is also known that specific nutrients play important roles in immune health, and that certain diets lack several of these essential nutrients, leading to widespread deficiencies.

Could a Certain Type of Diet Affect COVID-19 Severity?

A study by Kim et al. evaluated the association between self-reported dietary patterns and COVID-19 infection, severity, and duration of symptoms among 2884 health care workers, all of whom had a high frequency of exposure to patients with COVID-19. Participants completed a detailed web-based questionnaire, including information about demographics, medical history, medications, lifestyle, and COVID-19, along with a food frequency questionnaire.

The analysis included 568 cases of COVID-19 and 2316 controls. COVID-19 cases were grouped as either being moderate-to-severe or very mild to mild. Diet types were combined into groups as well, with 254 participants in the plant-based diets group (those who indicated eating a whole food, plant-based diet or who indicated eating a vegetarian diet), 294 participants in the plant-based or pescatarian diet group (those in the plant based diet group plus those indicating a pescatarian diet), and 483 participants in the low carbohydrate, high protein diet group.

Did COVID-19 Disease Severity Vary Based on Diet?

Among the COVID-19 cases, 430 reported very mild to mild symptoms and 138 reported moderate-to-severe symptoms. Those with moderate-to-severe cases were less likely to report following a plant-based diet (8.6% for very mild to mild vs 2.9% for moderate-to-severe; p=0.02) and were more likely to report following a low carbohydrate, high protein diet (14.2% for very mild to mild vs 21.7% for moderate-to-severe; p=0.04).

Click to Enlarge & Print

In other words, those who reported following a plant based diet had a 72% lower risk of moderate-to-severe COVID-19 illness compared to all other diets (p=0.02). Those in the plant based or pescatarian diet group had a 59% lower risk of moderate-to-severe COVID-19 illness (p=0.05). Following a low carbohydrate, high protein diet was associated with a 48% higher risk of moderate-to-severe COVID-19 illness, however, this finding was not statistically significant.

Overall, the researchers found that those eating a low carbohydrate, high protein diet had a greater than 3-fold increased risk of moderate-to-severe COVID-19 illness compared to those eating a plant-based diet (p<0.05).

What was the Difference in the Types of Food Eaten?

The following foods were more likely to be reported for each of the groups compared:

  • Plant-based diet – more vegetables, fruit, plant proteins (legumes and nuts); less poultry, red meat, processed meats, sugary beverages and alcohol
  • Plant-based diet or Pescatarian diet – more vegetables, fruit, legumes, nuts, fish and seafood; less poultry, red meat, processed meats
  • Low carbohydrate, High protein diet – more legumes, nuts, soups, and animal products (eg, eggs, poultry); less refined grains, sweets and desserts, vegetable oil, croquettes, dumplings, and pizza

How Could the Foods You Eat Affect COVID-19 Disease Outcomes?

Plant based diets are often higher in nutrients such as vitamins A, C and E, folate, iron, potassium, and magnesium – all of which have been shown to support a healthy immune system. Fruits, vegetables, nuts and legumes, fish and seafood, and other foods found in diets such as the Mediterranean diet, have also been shown to have anti-inflammatory properties whereas processed meats and red meats may be more pro-inflammatory.

The AA:EPA ratio is a test that one can use to measure the amounts of unhealthy fats to healthy fats in their blood. It is also used as an indicator of inflammation within the body, and can be added to any GrassrootsHealth test kit that includes both vitamin D and the Omega-3 Index. At the time of testing, participants complete a health and lifestyle questionnaire that includes questions about their type of diet and fish intake over the previous 6 months along with specific health outcomes, including whether they experienced any COVID-19 symptoms. Create your custom participant test kit here, and add more insights to how diet and resulting nutrient levels might affect everyone’s health by participating in the GrassrootsHealth projects today!

Measure Your Level of Vitamin D and Other Important Nutrients

Having and maintaining healthy vitamin D levels and other nutrient levels can help improve your health now and for your future. Choose which to measure, such as your vitamin D, 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. You can also track your own intakes, symptoms and results to see what works best for YOU.

Enroll and test your levels today, learn what steps to take to improve your status of vitamin D (see below) and other nutrients and blood markers, and take action! By enrolling in the GrassrootsHealth projects, you are not only contributing valuable information to everyone, you are also gaining knowledge about how you could improve your own health through measuring and tracking your nutrient status, and educating yourself on how to improve it.

Help everyone Move Research into Practice with vitamin D and other nutrients! As a special birthday gift to everyone, in honor of the science, we have created a special scholarship fund for anyone to donate to that will go towards helping others participate. Your donation will allow anyone to get help with funding their participation when they need it.

Text-to-give: Text Daction to 44321 to add to our Scholarship Fund.

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!