What to Combine Quercetin With

Quercetin is rarely sold on its own: it is added to “immune” formulas, antioxidant complexes and pre-workouts. Athletes, for their part, often take it together with protein, creatine or caffeine. The editorial team examined which combinations have scientific logic, which give nothing beyond a nice label, and which combinations are best avoided.

Principles of combining supplements

Any combination of supplements must answer a simple question: what does it give beyond taking each component separately? Three answers are possible: improved absorption, an enhanced effect (synergy) or simply convenience — one capsule instead of several. For quercetin, only some mechanisms of improved absorption are actually confirmed.

Evidence of synergy between supplements is usually weak, because combinations are hard to study: you need groups with each component separately, with their combination and with placebo. Most “synergistic” claims in advertising rely on laboratory data or on logical reasoning.

The second question is safety. Each additional component brings its own risks and possible interactions. Quercetin affects liver enzymes and transport proteins, so when combining it with substances that are metabolized by the same pathways one should be attentive.

Finally, the general context is important. The IOC consensus on supplements (Maughan et al., 2018) reminds us that supplements make sense only against the background of adequate nutrition, and quercetin belongs to the means with a limited evidence base. Complex combinations around it are rarely justified.

Combinations for better absorption

The simplest and best-justified “partner” of quercetin is food with fats. Guo and colleagues (2013) showed that fatty food increased the bioavailability of quercetin. Therefore taking a capsule together with breakfast or lunch that contains oil, nuts or dairy products is already a useful combination.

Lecithin (phosphatidylcholine) is the basis of phytosomal forms. Here the combination is technological: quercetin is pre-bound to phospholipids, which increases absorption. There is no point in additionally taking lecithin separately with ordinary quercetin — the phytosome effect depends on the technology of making the complex.

• Food with fats:a proven improvement in bioavailability, free and simple.
• Phytosomes with lecithin:a significant rise in plasma levels according to pharmacokinetic data.
• Bromelain:a popular claim about improved absorption, but there is little convincing data in humans.
• Vitamin C:theoretically “regenerates” oxidized quercetin; the clinical advantage of the combination is not proven.

The combination with bromelain is a classic of “seasonal” formulas. Bromelain has its own anti-inflammatory properties and can affect blood clotting, so for people on anticoagulants such a pair is undesirable. In addition, it can cause allergy in people sensitive to pineapple.

Vitamin C is often combined with quercetin on the grounds of an antioxidant “recycling.” This combination is safe in ordinary doses, but as a way to enhance the effect of quercetin it has no clear confirmation.

Combinations with other polyphenols and omega-3

The most sports studies of combinations were conducted by the group of David Nieman. Nieman and colleagues (2009) tested quercetin together with EGCG (the main catechin of green tea) in trained cyclists during an intensive training block. No substantial advantages regarding mitochondrial markers and immunity indicators compared with placebo were obtained.

Omega-3 fatty acids are often added to “anti-inflammatory” complexes with quercetin. Each component has its own evidence base in different contexts, but there is no convincing data that their combination works better than separate intake. If you are already taking fish oil, adding quercetin is a separate decision.

Resveratrol and quercetin are often combined in “mitochondrial” or “anti-aging” formulas. Both affect sirtuins and AMPK in animal experiments, but in humans the advantages are not proven, and an excessive combination of polyphenols during a training period may be undesirable.

Zinc with quercetin became popular thanks to laboratory data on the ionophore action of quercetin. Zinc is an important trace element, and replenishment makes sense when it is deficient, but the idea that quercetin makes zinc an “antiviral weapon” is not clinically confirmed.

Quercetin and basic sports nutrition

For most active people the practical question sounds like this: can quercetin be taken together with protein, creatine, caffeine or carbohydrate drinks? There are few direct studies of such combinations, but there are also no known mechanisms of negative interaction.

Protein and creatine can be taken together with quercetin without restrictions. Their effects concern other mechanisms — muscle protein synthesis and energy metabolism — and quercetin does not affect them in any known way.

Caffeine is often present in pre-workouts together with quercetin. Interestingly, quercetin is structurally capable of interacting with adenosine receptors, like caffeine, but an enhancement of caffeine’s action in humans has not been shown. The ergogenic effect of such a combination is provided primarily by the caffeine itself.

Carbohydrate drinks and gels during prolonged loads are one of the most effective strategies for endurance. Quercetin does not interfere with them and does not replace them. If an athlete is choosing what to spend the budget on, carbohydrate provision has a clear priority.

What to avoid

The most important thing is combining with medicines. Quercetin inhibits certain cytochrome P450 enzymes and P-glycoprotein, so with simultaneous intake with anticoagulants, immunosuppressants, digoxin or some antitumor drugs, changes in their concentration are possible. Such combinations are permissible only by a doctor’s decision.

1. Do not take several products with quercetin at the same time — check the composition of “immune” and “antioxidant” formulas.
2. Do not combine quercetin with megadoses of vitamins C and E during a period when the goal is training adaptation.
3. Avoid complexes with bromelain if you are taking drugs that affect blood clotting.
4. Be attentive with plant extracts, which also affect liver enzymes.

Ristow and colleagues (2009) showed that vitamins C and E in high doses weakened the beneficial metabolic effects of training. For quercetin this has not been proven, but the logic of “collecting as many antioxidants as possible” during a training period has no basis.

Also, it is not advisable to combine quercetin with several stimulants in complex “fat-burning” formulas. Adverse effects in such products are usually caused by the stimulants, not by quercetin, but figuring out exactly what caused the reaction becomes impossible.

Editorial conclusions

The best-justified “partner” of quercetin is ordinary food with fats, which improves its absorption, as well as the phytosomal form with lecithin.

Popular combinations with EGCG, omega-3, zinc or bromelain have no convincing evidence of an advantage over separate intake. With protein, creatine and caffeine, quercetin can be combined without known problems.

One should avoid combining with anticoagulants, immunosuppressants, digoxin and other medicines without a doctor’s agreement, as well as excessive accumulation of antioxidants during a training period.

We also recommend reading “Quercetin: Product Forms and Which to Choose,” “Who Should Not Take Quercetin” and “Resveratrol: What It Is and How It Works.”

References

1. Guo Y, Mah E, Davis CG, et al. Dietary fat increases quercetin bioavailability in overweight adults. Mol Nutr Food Res. 2013;57(5):896–905.
2. Riva A, Ronchi M, Petrangolini G, Bosisio S, Allegrini P. Improved oral absorption of quercetin from quercetin phytosome, a new delivery system based on food grade lecithin. Eur J Drug Metab Pharmacokinet. 2019;44(2):169–177.
3. Nieman DC, Henson DA, Maxwell KR, et al. Effects of quercetin and EGCG on mitochondrial biogenesis and immunity. Med Sci Sports Exerc. 2009;41(7):1467–1475.
4. Dabbagh-Bazarbachi H, Clergeaud G, Quesada IM, et al. Zinc ionophore activity of quercetin and epigallocatechin-gallate: from Hepa 1-6 cells to a liposome model. J Agric Food Chem. 2014;62(32):8085–8093.
5. Ristow M, Zarse K, Oberbach A, et al. Antioxidants prevent health-promoting effects of physical exercise in humans. Proc Natl Acad Sci U S A. 2009;106(21):8665–8670.
6. Andres S, Pevny S, Ziegenhagen R, et al. Safety aspects of the use of quercetin as a dietary supplement. Mol Nutr Food Res. 2018;62(1):1700447.
7. Maughan RJ, Burke LM, Dvorak J, et al. IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. 2018;52(7):439–455.