By Katharine Lang on October 18, 2023 — Fact checked by Hannah Flynn
For many people, particularly following vaccination, infection with SARS-CoV-2, the virus that causes COVID-19, resolves within a few days. But for others, it results in long COVID, a variety of often debilitating symptoms that persist for weeks, months or even years. Why this happens in some is unclear, and there are currently no effective treatments. Some experts believe diet could be key to symptom management. What is the evidence for this?
Researchers describe long COVID — also known as post-COVID-19 condition — as “an often debilitating illness,” noting that it “occurs in at least 10%” of people who have had COVID-19.
It can result in a wide range of symptoms, which, according to the Centers for Disease Control and Prevention (CDC), may include:
- tiredness or fatigue that interferes with daily life
- fever
- difficulty breathing, cough or shortness of breath
- chest pain and heart palpitations
- difficulty thinking or concentrating, also referred to as “brain fog”
- headache
- sleep problems
- dizziness when standing up
- pins-and-needles feelings in limbs
- change in smell or taste
- depression or anxiety
- diarrhea
- stomach pain
- joint or muscle pain
- skin rashes
- changes in menstrual cycles.
Why some people develop long COVID is not entirely clear, but factors that increase the likelihood include older age, being female, having other chronic conditions, and having had severe COVID-19.
Studies have shown that vaccination and early treatment with antivirals may decrease the likelihood of developing long COVID. A nonpeer-reviewed preprint has suggested that treatment with convalescent plasma could do the same.
So what might be some of the underlying mechanisms in long COVID, and could achievable interventions, such as following a specific diet, help manage its symptoms. Medical News Today looked at the existing evidence, and spoke to experts to find out more.
Dr. Adupa Rao, a medical director at the Keck Medicine Covid Recovery Clinic, told MNT that “there is no clear signal why certain people develop long COVID.“
However, according to him, a misfiring immune system, triggered by SARS-CoV-2, may prolong the state of illness indefinitely for some people.
“We suspect that the underlying problem is that the immune system gets activated after COVID infection and stays on after the infection has resolved,” said Dr. Rao.
“The continuous activation of the immune system means that the body is very active seeking to fight infection and is in the high-inflammatory state,” he explained.
Prof. Arturo Casadevall, chair of Molecular Microbiology & Immunology at Johns Hopkins Bloomberg School of Public Health, agreed, noting that “the inflammatory nature of long COVID is an increasingly accepted fact although it is important to keep in mind that we have known this disease for only 3 years.”
Treatments similar to those for other post-viral syndromes, such as chronic fatigue/myalgic encephalomyelitis, may be beneficial. These include getting plenty of rest and doing gentle, but not vigorous, exercise.
A 2017 meta-analysis of dietary intervention for post-viral syndromes found that supplements and long-term elimination diets were generally not beneficial.
The study’s conclusion was that a balanced diet and a variety of nutritious foods were most likely to help with symptoms.
Kelsey Costa, a registered dietitian nutritionist with National Coalition on Healthcare (NCHC), agreed, telling MNT that, “in managing post-viral conditions like chronic fatigue syndrome, a nutritious, balanced diet can enhance body functionality, improving well-being.”
“While diet alone is not a cure for post-viral conditions like chronic fatigue syndrome, it can play an essential role in managing symptoms and supporting overall health and well-being,” she added.
Although studies have identified ways to reduce the likelihood of developing long COVID, there are, as yet, according to a wide-ranging review “no broadly effective treatments.”
This review highlighted treatments that are effective for some of the symptoms, such as low-dose naltrexone for pain, fatigue and neurological symptoms, low-dose aripiprazole for fatigue, unrefreshing sleep and brain fog, and probiotics for gastrointestinal symptoms.
It also emphasized that exercise was not advisable, recommending instead pacing “an active self-management strategy whereby individuals learn to balance time spent on activity and rest for the purpose of achieving increased function and participation in meaningful activities”.
No therapy, however, is effective in isolation, and lifestyle changes to treat the symptoms are generally preferable to medication which may have side effects, so experts suggest that a dietary approach could give relief to some.
Several diets have been considered as potential treatments for long COVID, and evidence is building that some may be beneficial while others are less effective.
They include vegetarian and vegan diets, anti-inflammatory diets, and antihistamine use and so far, the evidence appears to suggest that anti-inflammatory diets may have the greatest beneficial effect.
Prof. Casadevall noted that:
“Since long [COVID] is an inflammatory condition, it is reasonable to hypothesize that diets that reduce inflammation would be associated with improved long-COVID outcomes, but rigorously establishing a causal relationship is going to take time and effort given that so many variables are at play, including diet composition, genetics, microbiome, etc.”
Although a small study has suggested that treatment with antihistamines may help alleviate symptoms of long COVID, Costa told MNT that there was little scientific evidence that an antihistamine diet was beneficial.
However, she was more optimistic about the potential of both plant-based and anti-inflammatory diets in mitigating symptoms of long COVID.
“Emerging evidence indicates a potential benefit of a diet rich in fruits, vegetables, and bioactive compounds, in managing long COVID symptoms. These types of diets have been shown to have anti-inflammatory and antioxidant effects, which may help reduce some of the symptoms associated with long COVID,” she commented.
A 2021 study found “evidence from epidemiological, observational, and clinical studies done in the pre-pandemic era that a plant-based dietary pattern may be of general benefit with regard to some clinical conditions that can also be found in individuals with COVID-19.“
“These include fatigue, sleep disorders, headaches, anxiety, and depression as well as musculoskeletal pain,” the author writes.
The study also suggests that a plant-based diet, comprising primarily plants and few, or no, animal products, could help relieve these symptoms that are commonly reported by those with long COVID.
Costa hypothesized it might be the plant-based diet’s anti-inflammatory properties that conferred these benefits:
“While research related explicitly to long COVID is ongoing, existing studies suggest that plant-based diets can beneficially impact conditions commonly associated with long COVID, such as fatigue, headaches, anxiety, depression, and muscle pain.”
“By reducing the intake of pro-inflammatory mediators and increasing the consumption of anti-inflammatory foods, adopting a plant-based diet could be an easily accessible strategy to combat the prolonged systemic inflammation often seen in long COVID patients,” she told us.
One diet proven to have health benefits is the Mediterranean diet, and Costa advocated this for people with long COVID, noting that “the Mediterranean diet, a consistently recommended dietary choice, is characterized by its richness in bioactive compounds, such as monounsaturated fats, omega-3 fatty acids, vitamins, minerals, and phytochemicals.”
“These compounds have demonstrated anti-inflammatory and antioxidant activities, providing a powerful tool against diseases associated with long-term, low-level inflammation,” she added.
With evidence building that inflammation might be responsible for many of the symptoms of long COVID, scientists from Keck Medicine at the University of Southern California, are running the first controlled trial of an anti-inflammatory diet to treat long COVID.
The 50 participants in the 30-day dietary trial will be divided into two groups. One will eat a low-carbohydrate diet to lower blood glucose (sugar) levels in combination with a medical food that raises blood ketone level. The other group will have no dietary intervention.
A study in rats linked a ketogenic diet with reduced oxidative stress and inflammation. And a review has animal studies linking the diet with reduced neuroinflammation.
Dr. Rao, who is an investigator on the trial, explained:
“A keto diet is essentially a low-carb, high-protein fat diet. […] [I]t is postulated that by controlling high-glucose fluctuations that we will be able to drive the inflammatory state in the body down.”
Costa welcomed the study, saying that its “exploration of a low-carbohydrate diet and medical food to elevate blood ketone levels could potentially offer a novel approach to managing long COVID-19 symptoms.”
“By transitioning the body’s metabolic state to a fat-dependent ketogenic state, this intervention may reduce inflammatory responses, enhance antioxidant defenses, and improve DNA repair mechanisms,” she added.
Throughout the trial and at the end of the 30 days, the researchers will test inflammatory markers in both groups, assess how well the intervention group is tolerating the diet and check long COVID symptoms in both groups. If the diet group shows positive effects, they will expand the clinical trial to a larger population.
“We chose 30 days as the intervention, because we believe that we will start to see a signal in the inflammatory state in that period of time and we will be able to monitor the safety of effects of the nutritional supplement,” Dr. Rao explained
“Though in its early stages, this research hints at the power of dietary interventions and their potential to impact the body’s immune and metabolic functions. Hopefully, it will contribute to developing effective long COVID treatment strategies,” Costa reflected.
General advice for managing long COVID is to follow as healthy a lifestyle as possible, including:
- resting and relaxing
- setting achievable targets
- getting quality sleep
- limiting alcohol intake
- limiting caffeine intake
- not smoking
- following a healthy diet.
In addition to potentially relieving long COVID symptoms, adopting these lifestyle changes will reduce the risk of many other conditions.
However, as people’s symptoms vary widely, individual management strategies are most likely to work in mitigating long COVID symptoms, as Costa explained:
“While diet alone is not a cure for post-viral conditions […] it can play an essential role in managing symptoms and supporting overall health and well-being. Therefore, working with a dietitian to develop personalized dietary strategies is highly recommended.”
