Quercetin, CoQ10 & D-Ribose and Long COVID Fatigue: What the Research Says

Quercetin, CoQ10 and D-Ribose are three "classic" nutrients that people living with Long COVID fatigue keep searching for. As a medical scientist, I wanted to look past the hype and summarise what the published research actually shows — including where the evidence is encouraging, and where it isn't.

Long COVID (also called post-COVID condition) describes symptoms that persist for weeks or months after a COVID-19 infection. Fatigue, low energy after exertion and "brain fog" are among the most commonly reported. Researchers are exploring several possible contributors, including ongoing inflammation, oxidative stress and changes in how cells produce energy in the mitochondria.

That mitochondrial and antioxidant angle is why Quercetin, CoQ10 and D-Ribose come up so often. Below is a plain-English summary of the key studies on each one.

Why Mitochondria and Cellular Energy Matter

Every cell makes its energy as ATP (adenosine triphosphate), mostly inside the mitochondria. CoQ10 is a natural part of the mitochondrial energy chain, and D-Ribose is a sugar the body uses as a building block of ATP. Quercetin is a plant flavonoid found in onions, apples and capers that is studied for its antioxidant properties. None of these is a treatment for Long COVID — but each has been studied in people with fatigue, which is why they're worth understanding.

Quercetin and Fatigue: What the Research Says

The most relevant study is a 2023 double-blind, placebo-controlled trial published in Biomedicine & Pharmacotherapy (Rondanelli et al.). It enrolled 78 adults with chronic fatigue — about a quarter of whom had Long COVID — and gave them 500mg per day of a lecithin-based form of Quercetin (Quercetin Phytosome) or a placebo for two months. The Quercetin group reported a significantly larger reduction in fatigue scores than the placebo group, along with improvements in sleep quality and daily step count. Note that the study used a specific lecithin-based form of Quercetin, so results may not apply to every form.¹

Other research has looked at Quercetin during the acute stage of COVID-19 rather than Long COVID, so those findings don't directly apply here.² A 2022 open-label study of a nine-ingredient formula that included Quercetin, Zinc and Vitamin D also reported symptom improvements in people with long-haul COVID, but because it had no placebo group and combined many ingredients, it can't tell us what Quercetin or Zinc did on their own.³

Bottom line: one small, well-designed trial is encouraging for fatigue. Larger studies specifically in Long COVID are still needed.

CoQ10 and Long COVID: Mixed Results

CoQ10 has the most direct Long COVID research of the three — and the results are mixed.

• A 2023 randomised, placebo-controlled crossover trial in The Lancet Regional Health – Europe (Hansen et al.) gave 121 people with post-COVID condition 500mg of CoQ10 per day for six weeks. It found no significant difference in symptoms or quality of life compared with placebo; both groups tended to improve over time.⁴
• A 2023 observational study in Clinical and Experimental Medicine (Barletta et al.) followed 174 people with chronic COVID syndrome and reported a greater reduction in fatigue scores in those taking CoQ10 combined with alpha-lipoic acid than in those who didn't. Because it wasn't placebo-controlled, it's weaker evidence.⁵
• Outside of COVID, a 2019 systematic review of 16 studies in Complementary Therapies in Medicine found that about two-thirds showed a significant improvement in fatigue with CoQ10, most clearly in statin-related fatigue and fibromyalgia, and called for larger, longer trials.⁶

Bottom line: CoQ10 is well established as essential for cellular energy production, but the best-quality Long COVID trial to date didn't show a benefit over placebo.

D-Ribose and Energy: Early-Stage Evidence

D-Ribose hasn't yet been studied in Long COVID specifically. The research comes from chronic fatigue syndrome (ME/CFS) and fibromyalgia:

• A 2006 pilot study in the Journal of Alternative and Complementary Medicine (Teitelbaum et al.) gave 5g of D-Ribose three times daily to 41 people with CFS and/or fibromyalgia and reported improvements in energy, sleep and wellbeing.⁷
• A 2012 multicentre follow-up in The Open Pain Journal (203 completers) reported similar improvements in energy over three weeks.⁸

Both studies were open-label with no placebo group, so the results are best described as preliminary.

Bottom line: D-Ribose plays a direct role in ATP production, and early studies in fatigue conditions are promising, but controlled trials are still lacking.

Quercetin, CoQ10 & D-Ribose: Evidence at a Glance

Talk to Your Doctor First

Long COVID is a medical condition and should be assessed and managed by a qualified healthcare professional. If you're considering any supplement, speak with your doctor first — especially if you're pregnant or breastfeeding, take blood thinners or blood pressure medication, have diabetes (D-Ribose is a sugar and may affect blood glucose), or take any prescription medicines. Supplements are not a substitute for medical care.

About BoostCeuticals Clean-Label Supplements

If you and your doctor decide these nutrients are right for you, BoostCeuticals makes vegan, clean-label versions — with no magnesium stearate, no silica and no unnecessary fillers, manufactured in GMP-certified facilities and third-party tested:

• Zinc Quercetin (Quercetin + Zinc + Vitamin C & D3) — supports normal immune function*
• CoQ10 200mg — supports cellular energy production and heart health*
• D-Ribose — supports cellular energy (ATP) production*

BoostCeuticals – Your Trusted Partner in Health and Wellness

This blog post is presented by BoostCeuticals, your source for clean-label vegan supplements. BoostCeuticals supplements are made without silica, stearates or unnecessary additives.