Quercetin vs. CoQ10: Different Supplements, Similar Benefits

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Two popular heart and longevity supplements as of late are quercetin and coenzyme Q10 (CoQ10), the former being an abundant dietary flavonoid and the latter an endogenous antioxidant. Consumers often mistake quercetin and coenzyme Q10 as being the same (likely due to their putative synergy as cardioprotective supplements). Though these micronutrients provide similar disease-mitigating properties and antioxidant effects in mitochondria, they are distinct molecules with unrelated chemical structures.

This article will provide an overview of quercetin and coenzyme Q10, emphasizing the former and how the two complement one another as nutritional supplements.

What Is Quercetin?​

The dietary flavonoids comprise one of the most diverse classes of plant antioxidants, and quercetin stands out as a significant flavonoid in berries, apples, cruciferous vegetables, onions, tea leaves, and many seeds and nuts [1]. Quercetin, the most prominent of all dietary flavonoids, has garnered considerable evidence as a versatile antioxidant and anti-inflammatory micronutrient.

For example, research suggests that quercetin reduces blood pressure, oxidative DNA damage, and tumor growth by attenuating oxidative stress and mediating inflammation pathways across multiple cell types [2]. Naturally, the scientific community continually investigates quercetin as a prospective treatment for related health conditions, such as hypertension, obesity, heart disease, cancer, and rheumatoid arthritis [3].

Phase 1 clinical studies of quercetin treatment began circa 2010, and the preliminary results are encouraging. One such study even found that quercetin supplementation significantly increased the expression of genes related to mitochondrial biogenesis [4]. Many consumers are drawn to quercetin for its longevity benefits, but quercetin may also provide ergogenic effects for active individuals and gym-goers, especially advanced endurance athletes [5].

What Is Coenzyme Q10?​

A coenzyme is a simple molecule essential for the normal function of specific enzyme systems in our cells. One example is that of acetyl-coenzyme A (acetyl-CoA), which participates in numerous biochemical reactions.

Coenzyme Q (CoQ), also known as ubiquinone due to its omnipresence in (most) living organisms, is a naturally occurring quinone-based coenzyme family. These coenzymes are formed from the conjugation of a benzoquinone ring with an isoprenyl side chain of varying chain length among myriad animal, plant, and bacterial species.

In the case of CoQ10, the prenyl side chain contains ten isoprenoid groups (decaprenyl), hence the name coenzyme Q10. CoQ10 is a potent antioxidant that exists in three different redox forms: ubiquinone (oxidized CoQ10), ubiquinol (reduced CoQ10), and semiquinone (free-radical CoQ10). These molecules are found in all biological membranes, especially mitochondrial and endothelial membranes and plasma lipoproteins (e.g. cholesterol).

By virtue of its role in the electron transport chain of the mitochondrial oxidative phosphorylation pathway (i.e. aerobic glycolysis), coenzyme Q10 is integral for the cellular production of adenosine triphosphate (ATP) — the veritable "energetic currency" of cells. Given that the vast majority of the human body's energy needs are met through aerobic glycolysis, metabolically privileged organs like the liver, heart, kidney, and brain have the highest concentrations of CoQ10 [6].

Since CoQ10 neutralizes free radicals and preserves ATP synthesis, supplementing with it may provide a range of health benefits, including [7]:

• Reducing blood pressure
• Controlling risk factors of heart disease
• Abating oxidative damage
• Maintaining energy production
• Fighting neurodegenerative processes
• Anti-inflammatory properties

The body produces significantly less coenzyme Q10 as we age past the age of 30 [8]. Thus, older adults and seniors tend to experience more pronounced benefits from CoQ10 supplementation.

IS QUERCETIN THE SAME AS COQ10?​

The flavonoid Quercetin is not the same as CoQ10. As mentioned above, quercetin is a dietary flavonoid found in numerous fruits and vegetables, particularly onions, kale, and chili peppers [9]. Coenzyme Q10 (CoQ10) is a biologically active quinone that plays a vital role in the mitochondrial electron transport chain.

DIETARY QUERCETIN AND COENZYME Q10​

While some foods contain CoQ10, notably organ meats, seafood, and nuts, the average dietary intake is only 3 to 6 mg per day (well below a therapeutically effective dose) [10]. As such, a CoQ10 supplement is necessary for optimal health benefits.

Likewise, quercetin supplementation may be prudent as daily intake of this flavonoid is a modest 10-15 mg despite its relative abundance in plant foods [11]. In comparison, clinical studies suggest an efficacious dose of quercetin ranges from 500 to 2,000 mg per day for controlling heart disease risk factors and 50-100 mg per day for general health benefits [12, 13].

DRINKING RED WINE FOR QUERCETIN: AN EFFORT IN FUTILITY​

A common misapprehension is that red wine protects against cardiovascular disease via the antioxidants effects of quercetin. Unfortunately, the quercetin content in red wine is too low to elicit marked vascular benefits [14].

Nevertheless, moderate red wine consumption is associated with a reduced risk of heart disease, likely attributable to the prophylactic synergy among red wine polyphenols [15].

Should Take Quercetin with Vitamin C?​

One reason sizable dosages of quercetin are necessary is to account for the flavonoid's poor oral bioavailability, which may be as low as 2% after a single dose [16]. However, concomitant ingestion of vitamin C and folate improves quercetin bioavailability, as does consistent supplementation (since it accumulates in body tissues after repeated dosing) [17]. Hence, taking vitamin C with quercetin is a viable means of enhancing the latter's efficacy.

Effects of Quercetin Supplementation​

Dietary flavonoid intake is on the decline in Western civilization. Eating more quercetin-rich foods will undoubtedly help neutralize free radicals and control oxidative stress. Still, even a full-blown vegan diet will likely fall short of an effective quercetin dose.

So, what are the effects of quercetin supplementation? Well, they're pretty extensive and go beyond the cardiovascular system. Here are some salient benefits of quercetin:

QUERCETIN SUPPORTS HEALTHY CARDIOVASCULAR FUNCTION​

Overproduction of reactive oxygen species is a known risk factor for cardiovascular diseases like congestive heart failure, atherosclerosis, and coronary artery disease [18]. The pathophysiology of these conditions is complicated, but endothelial dysfunction seems to be a major impetus.

When the endothelium is exposed to excessive reactive oxygen species, without commensurate antioxidant protection, lipids, proteins, and DNA in this tissue are liable to damage. Consequently, endothelial oxidative stress significantly erodes the function and integrity of vascular cells.

Quercetin — a potent antioxidant — holds promise as complementary medicine in preventing and treating heart conditions [19].

ANTIOXIDANT PROPERTIES OF QUERCETIN AMELIORATE OXIDATIVE DNA DAMAGE​

Oxidative stress-induced DNA damage is a culprit of cell death and may instigate tumorigenic pathways that lead to cancer. The antioxidant effects of quercetin have been shown to inhibit oxidative DNA damage, thereby protecting vital organs from chronic disease [20, 21].

QUERCETIN HELPS FIGHT CHRONIC INFLAMMATION​

Quercetin acts through a variety of mechanisms to fight oxidative stress and protect the body from chronic inflammation. Stimulating sirtuin proteins (SIRTs) is one such mechanism [22]. Sirtuins are cellular proteins involved in multiple metabolic processes of aging.

Caloric restriction is another prudent way to increase sirtuin activity [23]. In this regard, quercetin may mimic the effects of an energy deficit.

Since quercetin has strong antioxidant properties throughout the body, it can reduce inflammation and the risk of rheumatic conditions such as arthritis [24]. Quercetin scavenges reactive oxygen species and hinders the activity of cytokines and histamine — small molecules that mediate the inflammatory response.

QUERCETIN PRIMES THE IMMUNE SYSTEM​

Mast cells are a type of white blood cell (immune cell) rich in histamine and typically produce cytokines that stimulate an inflammatory response in target tissues, such as the nasal mucosa. Supplementing with quercetin can help reduce allergy symptoms (especially in the sinuses) by effectively blocking cytokine and histamine release from mast cells [25].

QUERCETIN IMPROVES FERTILITY​

Several murine studies suggest that quercetin protects Leydig cells — the cells that comprise testicular tissue — and oocytes from toxin-induced damage, thereby preserving testosterone levels and fertility [26, 27, 28].

Taking Quercetin and Coenzyme Q10 Together​

Taking quercetin is a practical way to reap the antioxidant effects of this essential dietary flavonoid. While there is only limited data investigating synergy between coenzyme Q10 and quercetin supplements, there's a plausible crossover between the mechanisms of action of these micronutrients. In fact, recent evidence suggests quercetin can act as a "coenzyme Q10-mimetic" [29].
Indeed, preliminary findings indicate that taking quercetin and CoQ10 can bolster musculoskeletal and cardiovascular functions [30, 31]. We can expect further studies to provide insights into the ergogenic and health-promoting applications of quercetin and CoQ10.