Quercetin

The Research

Quercetin (Que) is one half of rutin compound. For Allergies study. Here is the last line in study conclusion: "Que is a promising candidate as an effective mast cell inhibitor for allergic and inflammatory diseases, especially in formulations that permit more sufficient oral absorption."

Pretty good research on antioxidant properties and as anti-histamine for hay-fever. There is some talk about cancers, especially ones like ovarian cancer since quercetin has phytoestrogen properties*. ref**  ref 

Quercetin is showing some neuroprotective properties as well. ref

But, since it also has phytoestrogen activities, some precaution is warranted and more research is needed in this area. It may work with progesterone and estrogen and at certain doses, hinder adverse effects, especially on EM tissues. ref

Just for interest since only a rodent study of quercetin on fertility.

Vital Coronavirus Impact

 Quercetin and zinc together are under study for Coronavirus, as well as vitamin C and quercetin. While Quercetin acts to reduce inflammation, it is the ability of quercetin to function as a zinc ionophore to increase zinc uptake by cells that is critical in Covid-19. In test tubes, this combination stops the coronavirus. Obviously, a test tube is not the same as in the body study, thus the reason for continuing research. article

NOTE: It is interesting to note that the malaria drug, hydroxychloroquine is also a zinc ionophore. This ionophore might just be the best. ref Zinc is the main necessary ingredient to take with the drug. Sadly, negative results from a recent large study on hydroxychloroquine for COVID-19 cast doubt on it's usage. BUT, the study results have now been retracted and the results that it increased heart disease risks are not longer valid. Far to many problems exist with the gathered data to confirm the results. Hydroxychloroquine effects on coronavirus are still in limbo. But zinc uptake may be the real issue.  Due to less possible side effects, Quercetin is a viable option to use with zinc for preventative activity.

STUDY for COVID-19 starting July 2020 now here.

* The term "phytoestrogen" might ilicit strange connotations for males consuming such products. Here is report that covers this topic. Notice that phytoestrogens can work opposite directions. One to block estrogens, or one to increase estrogen actions. As males age, estrogen levels increase, so blocking effects of phytoestrogens might extend maleness somewhat. Some females might hope for the opposite actions. Lowering prostate and breast cancer risk probably trumps.

** Copied form this study: "Furthermore, significant number of studies focused on anti-cancer properties of this bioactive compound. Several pathways have been identified which are affected by quercetin in different cancers [11, 12]. Based on available evidences, quercetin can inhibit a broad range of cancers such as breast [13], lung [14], nasopharyngeal [15], kidney [16], colorectal [17], prostate [18], pancreatic [19], as well as ovarian [20] cancers. According to the previous literature, consuming vegetables that are rich in quercetin has been associated with lower risks of ovarian cancer [21]. Similarly, consuming fruits with high levels of quercetin, including apples as well as citrus or their juice can decrease occurrence of ovarian cancer [22]. 

Quercetin is not harmful for healthy cells, while it can impose cytotoxic effects on cancer cells through several mechanisms, making it a good candidate to treat ovarian cancer or to be employed as a supplementary factor along with other anti-cancer medications [23]. In this review, we summarized the recent and eminent researches on quercetin properties in cancer therapy, especially ovarian cancer."

This is only a two year old study. Here is summary of actions for Quercetin from authors: "Quercetin is reported to have several beneficial effects on human health such as anti-inflammatory effects, cardiovascular protection and anticancer activity. It can act as an anti-cancer, anti-tumor, anti-ulcer, anti-allergy, anti-viral, anti-inflammation, and anti-diabetes agent, exerting gastro-protection, anti-hypertension, immune-modulation, as well as anti-infection features are among its advantageous effects [27]." <lists 141 reference studies and reports.

Keep eating vegetables and fruits, and drinking green tea. 

1.  Onions

All onions contain quercetin, but since it’s a pigment, red and yellow onions contain the most. To keep the quercetin, peel off as little as possible of the outer layers. Onions contain many other vitamins and minerals, and they are especially rich in the vitamin biotin.

2. Kale  

Kale has a well-deserved reputation as a nutritional powerhouse. Besides quercetin, it’s also a rich source of vitamin A, vitamin C, and fiber. Half a cup contains only 18 calories.

3. Cherry tomatoes

All tomatoes are good sources of quercetin. Cherry tomatoes are the best because they have the highest ratio of skin to flesh. They make a great low-calorie snack, with only 37 calories per dozen.

4.  Broccoli

Along with quercetin, broccoli is rich in vitamin K and vitamin C. It also contains another flavonoid, kaempferol, that offers potent antioxidant capabilities. A one-cup serving provides 5 grams of fiber.

5.  Blueberries

Blueberries are antioxidant superstars. On top of quercetin, they contain 17 different phytochemicals including resveratrol, the antioxidant best known for appearing in red wine.    

6. Apples

Apples contain four different phytochemicals along with the beneficial fiber known as pectin. To get the benefits of quercetin, eat your apples unpeeled. Apple juice doesn’t provide the same benefits as the whole fruit.      

While the benefits appear to outweigh thses Two issues of concern, awareness might be a prudent protocol.

PRECAUTION 1: Like some nutrients, Quercetin appears to have amazing benefits (ref) along with a few potential concerns. So far, only one study with this next possibly negative result. Sometimes what looks like a negative, turns out to really be the method Mother Nature wisely harnessed for good. Remember that the body uses a damaging free radical action to help kill viruses.

This new study reveals a possible quercetin pathway leading to increased amounts of PGE-2 which are responsible for generating inflammation. The Omega 3 fatty acid EPA regulates levels of PGE2. There are far more studies on Quercetin showing an anti-inflammatory response to offset this potential negative one. ref  Quercetin levels in foods probably are not much of a factor with the presence of counter balance nutrients, but at supplement amounts, questions arise. PGE-2 also has both positive actions as well as negative ones. A positive one is to help prevent sacropenia, a muscle wasting condition, versus the major negative one of generating chronic inflammation.  ref  And even some inflammation has a value. article Balance and harmony between opposing forces are often the norm for health status.

Here is a study that found counter results that quercetin suppressed PGE-2 production. There are many more. But even with just one opposite action study, an explanation for clarification is needed. Still searching. 

Thus, until the exact ramifications of this new PGE2 aspect are analyzed and correct dosage and usage for quercetin determined, the precautionary approach might be to cycle quercetin on and off, taking only when conditions show a need.  

NOTE: Research using animals, or test tube studies with isolated cells, do not always play out the same way inside the body. More research is needed.

PRECAUTION 2: When consuming supplements of quercetin, take vitamin C at a different time, and probably better to rotate quercetin on and off. Quercetin has been shown to inhibit vitamin C transporter SVCT1. Funny, since quercetin is made from one of the vitamin C family members, rutin, it is often put together with vitamin C in supplement formulas.

There are some important links of quercetin with vitamin C functions that warrant putting the two together. Thus, why would nature add this quark of quercetin blocking out SVCT1 transportation of vitamin C. Here is one possible reason. Glucose and vitamin C are often found together in fruits. Since Vitamin C and glucose are very close in structure, quercetin ends up blocking both transporters. SVCT1&2 for vitamins C and SGLT and GLUT for glucose. The GLUTs also transport oxidized vitamin C, dehydroascorbate. The body knows it is not good to overwhelm the body with too much glucose all at once. So, taking quercetin helps to block out some of the glucose transportation.  This action of quercetin would benefit diabetics and hinder some cancers, but could it also jeopardize vitamin C intake amount and functions? 

This is why one needs to slightly increase vitamin C when taking quercetin as well as rotate quercetin off and on for different time periods. This needs more research for appropriate protocols.

Bottom Line

Nature has methods to deal with Quercetin and vitamin C together in food, as well as a sound reason. But, it may be better to take quercetin supplements at a different time of day than vitamin C. Quercetin can block a vitamin C transporter SVCT1 during absorption from the digestive tract. This should help vitamin C absorption. But once in the system, vitamin C in both reduced and oxidaized forms is continually transported around between cells and tissues. Plus, there is a process which converts the oxidized vitamin C form dehydroascorbic acid back into the active reduced form, ascorbic acid. Quercetin could negatively impact some of this transportation, but sometimes it may have a positive twist as mentioned in next paragraph. Thus, a slightly increased amount of vitamin C may be needed when taken with quercetin to offset reduced vitamin C transport. ref

Nature may have a reason for giving opposite actions to some nutrients or putting opposite nutrients together. Cancer cells such as melanoma, contain larger amounts of vitamin C than the surrounding normal tissue cells. Tumor cells gather in glucose transporters GLUT that contain the oxidized form of vitamin C.  In the tumor cells, the oxidized vitamin C is reduced back to the active vitamin C form. In this form, vitamin C ends up protecting the tumor cells from chemo-drugs. This could be one reason that querecetin and some other flavonoids like curcumin, are designed to hinder glucose transporters, especially at tumor locations. Cancer cells use glucose as their growth energy source. In animal studies, the master detox enzyme SOD given with vitamin C blocks or limits vitamin C uptake and accumulation into tumors. ref

There is more to this story that needs to be told and discovered. This will get it's own article soon.