During the pandemic, many dietary tips are given. But are there foods that can help prevent severe COVID-19 infections?
Our food choices have a direct impact on the health and function of our bodies and immune systems.
As the coronavirus continues to circulate, people want to know what they can do at home to protect themselves from severe COVID infections. Eating nutritious foods that support a healthy immune system is a good start.
Scientists are beginning to study the link between diet and COVID-19 infections. They make an important point. Maintaining a healthy body and immune system requires a variety of nutrients.
“There is no single nutrient that can act as a panacea to protect people [from COVID-19],” says Philip Calder, a nutritional immunologist at the University of Southampton, England.
Diet is not the most important thing
A study of 2,884 participants from France, Germany, Italy, Spain, the UK and the US, published in May in the BMJ Medical Journal, found that those who reported eating a plant- and fish-based diet (mostly plant-based with some seafood) were less likely to develop moderate-to-severe COVID infection compared to those who ate meat.
The odds of developing moderate-to-severe COVID were 73% lower among those who ate a plant-based diet and 59% lower among those who reported eating a plant-based or fish-based diet compared to those who did not eat a plant-based or fish-based diet. People who ate a low-carbohydrate, high-protein diet were three times more likely to develop moderate to severe COVID infection than people who ate a plant-based diet.
Although the researchers controlled for age, gender, race, medical specialty, body mass index, medical conditions and lifestyle factors such as smoking and physical activity, the study had some limitations. More than 70% of the participants were men and 95% were medical professionals.
Other influencing factors, such as stress and sleep, were not included in the study.
“There are a lot of things,” Calder said, “that affect people’s immune systems, and diet is just one of them. It’s not the most important thing.”
Of the 568 COVID cases in the study, only 298 had positive PCR or antibody tests. The remaining cases had only reported symptoms of COVID. When the study was limited to those who tested positive, it was not significant because of the small sample size, although the association was consistent with the primary outcome.
The researchers screened participants for increased COVID-19 exposure, but were unable to control exactly how high the exposure was for each health worker.
The food we need
This study has its limitations, but its conclusions are somewhat consistent with the World Health Organization’s (WHO) recommendations for our diet.
Humans need micronutrients and a large number of nutrients, most of which are found in plant foods.
Micronutrients include vitamins and minerals, which are essential for our bodies to function well and for a strong immune system.
Macronutrients provide us with the energy our bodies need to function and get through the day. They can be broadly divided into three categories: Carbohydrates, Proteins and Fats.
The WHO recommends a diet that includes a variety of fruits and vegetables, legumes (e.g. lentils, chickpeas, beans, peas), nuts, whole grains (e.g. brown rice, oats, millet, corn) and foods of animal origin. People should eat at least five servings (or a total of 400 grams) of fruits and vegetables per day. Although starchy root vegetables such as potatoes, sweet potatoes and cassava are healthy, they do not count as one of the five daily servings.
It’s also about what not to eat. Sugar consumption should not exceed 12 teaspoons per day, but ideally only 6 teaspoons for added health benefits. This includes all sugars added to foods and drinks, as well as sugars that occur naturally in foods, such as honey, fruit juices and syrups. Sugars in fruits and vegetables are not included. Salt intake should be limited to one teaspoon per day.
Feed your gut
When you feed yourself, you also feed your microbiome, a collection of bacteria, as well as fungi, parasites and viruses that co-exist in your body. The largest number of these microbes are found in the gut.
“The microbiome does a lot of work, such as helping us digest food, making important vitamins, protecting us from infections and building our immune system,” explains Sheena Cruickshank, an immunologist at the University of Manchester (UK).
Cruickshank says the microbiome helps maintain the barrier that protects us by strengthening the cells in our gut and actively protecting us from invading germs.
Your diet also plays an important role in determining what kind of microbes live in your colon.
Fiber such as resistant starch – like cooked potatoes, beans or lentils – helps feed the good bacteria. Probiotic foods that contain live, beneficial bacteria can also help. These include fermented foods such as yoghurt, kefir with live, active bacteria, kimchi, miso, sauerkraut, pickled vegetables, tempeh and kombucha.
These foods help keep the gut healthy, which in turn helps the immune system in its fight against COVID-19.