Quercetin is a naturally occurring flavonoid which has recently gained popularity as a dietary supplement, particularly in relation to cancer and heart disease. The phytochemical has been in every culture’s diets for centuries, in the pigments of fresh fruits and vegetables such as citrus fruits, buckwheat and onions.
Although quercetin is quickly broken down by digestion and is not actually found in the bloodstream, the compounds that are created by the digestion of quercetin have been shown to be beneficial to the treatment of a number of physical problems. Most of the benefits come from quercetin’s anti-inflammatory affect, which is helpful in the treatment of asthma and heart disease, and the phytochemical has even been looked at for its anti-ageing possibilities.
Foods that are naturally rich in quercetin include capers, apples, tea, onion (especially red onion – the redder, the better), tomatoes, red grapes, brocoli, cherries and raspberries. Quercetin has also been found in honey from eucalyptus and tea-tree. As with a lot of nutrients, the concentration of quercetin is higher in organically grown products than commercially grown ones – although a higher dose of quercetin is not necessarily more beneficial, as some studies have found.
The specific suspected benefits of quercetin include reduction of histamine in the bloodstream (meaning a lower incidence of allergic reaction), an increase in antioxidant activity and a smaller use of vitamin C. It is suspected that quercetin could help men with chronic prostatitis and women with interstitial cystitis, although the research is still in the early stages.
When it comes to cancer, quercetin has gained a lot of attention as the latest miracle cure. As with all such claims, a certain amount of suspicion should be exercised by those seeking treatment. What a range of studies has shown is that there are certain things quercetin does: in an in vitro (cellular) study in which samples of skin and prostate cancers were treated with a mixture of quercetin and ultrasound, cancerous cells had a mortality rate of 90%, whereas normal cells did not have a visible mortality. This means that, on a cellular level at least, quercetin reduced cancerous cells. The ultrasound component of the treatment encouraged absorbtion of the quercetin, so treatment of topically applied quercetin combined with an ultrasound wand may be a treatment used some time in the future.
Another study conducted over eight years showed that quercetin and two other flavonols, kaempferol and myricetin, were associated with a 23% reduction of risk of pancreatic cancer. The participants in the study had their diets monitored for the amount of flavonols they consumed: over the next eight years the study showed a reduced risk of the cancer for participants with the required intakes of flavonols, even when the participants were current smokers.
This means that quercetin may have a beneficial effect on cancer, although exactly what this is has yet to be established. Clinical tests on quercetin supplements have not yet reached a conclusion on the subject. That said, an increase of fresh fruit and vegetables has been shown to reduce the incidence of cancer, and some scientists suspect that quercetin might be the reason – yet another reason to increase your fresh fruit and vegetable intake.
As with all dietary supplements, you should check with your doctor before introducing any major supplements into your diet.
