If you suffer with hay fever you may well have given quercetin a go hoping it might ease your itchy eyes and runny nose. Likewise, if you’ve been finding the transition to menopause has brought with it a host of symptoms you weren’t expecting, like headaches, joint pain and digestive disturbance. But is quercetin helpful for these situations? We set out to learn more.
What is quercetin?
Quercetin is a type of plant compound called a flavonoid. As such it has anti-inflammatory, anti-histamine and antioxidant properties, this means it helps protect our body’s cells from damage, including those often associated with conditions of aging, such as heart disease and cancer.
Quercetin is found in many everyday fruit and vegetables including asparagus, chilli peppers, blueberries and tomatoes as well as drinks like green tea and coffee. It’s also available as a dietary supplement in both powder and capsule form.
Some of the benefits associated with quercetin include:
- May reduce inflammation
- May act as a natural anti-histamine
- May have cancer protective effects
- May support the heart and circulatory system
- May reduce blood pressure
- May help manage cholesterol
- May support blood sugar levels
- May support the menopausal transition
Discover our full range of health benefit guides and check out our guide on natural approaches to get you through the allergy season and our top 20 low-histamine foods.
What is quercetin used for?
A popular use of supplementary quercetin is for calming the symptoms of histamine overload, this immune chemical is best known for its role in allergy but that’s not all it does. When our body fails to manage levels of histamine and it becomes too high, we’re likely to experience symptoms of excess such as itching, sneezing, headaches, joint pain and digestive issues. Quercetin may be helpful because as well as providing an anti-inflammatory action, it calms the immune cells called mast cells, that release histamine.
Some of the other uses for quercetin are based on its protective role as a flavonoid and include reducing the risk of heart disease, cancer and degenerative brain conditions.
Top 8 health benefits of quercetin
1. May reduce inflammation
In a laboratory setting quercetin has been seen to reduce inflammatory markers including tumour necrosis factor alpha and interleukin-6, which can be associated with chronic age-related diseases such as heart disease and cancer. An eight-week study of women with rheumatoid arthritis reported that 500mg of quercetin per day resulted in significant improvements in clinical symptoms including reduced pain in the morning and after activity. More trials are underway, with findings to date looking promising.
2. May act as a natural anti-histamine
Animal studies suggest quercetin may be a useful natural anti-histamine because of its ability to inhibit histamine release. An interesting study of oral supplementation in rodents showed quercetin suppressed peanut-related allergy symptoms. While a human study that involved hay fever sufferers supplementing with 200mg of quercetin daily suggested some improvements. These findings are encouraging and suggest a potential role for quercetin in managing allergy symptoms.
3. May have cancer protective effects
As a flavonoid, quercetin has protective, antioxidant properties and may therefore be useful in our fight against cancer. Laboratory studies and animal models suggest quercetin may suppress cell growth and induce cell death in prostate cancer. Likewise, it may have similar effects for liver, lung, breast and colon cancer. Although these findings are encouraging, further clinical trials are needed to fully understand the mechanisms behind them and to establish the supplement’s safety in such situations.
4. May support the heart and circulatory system
Thanks to its anti-inflammatory and antioxidant properties quercetin may improve how our blood vessels work and help prevent atherosclerosis and other cardiovascular diseases. It may also be useful for those who have already suffered a cardiac event, such as that illustrated by a randomised study of 88 heart attack patients who reported lower levels of inflammatory markers and a higher level of total antioxidant capacity, when supplemented with 500mg quercetin daily. That said, we need more high quality clinical trials to fully assess quercetin’s value as an adjunct to conventional drug therapies.
5. May reduce blood pressure
Studies suggest that quercetin may help reduce blood pressure by bestowing a relaxing effect on blood vessels. The results of a review of nine human trials found taking more than 500mg of quercetin daily provided a statistically significant reduction in both systolic and diastolic blood pressure. Again, more clinical trials are needed to establish the use of quercetin for this purpose.
6. May help manage cholesterol
Levels of fats in the blood, most notably low-density lipoprotein (LDL cholesterol) have been shown to be directly related to atherosclerosis, more commonly known as ‘furring of the arteries’, which is one of the main causes for stroke and ischaemic heart disease. The inflammation in the walls of the arteries and the accumulation of fats that is characteristic of this condition may be eased by protective compounds like flavonoids, including quercetin.
7. May support blood sugar levels
Both human and animal studies suggest that quercetin may reduce fasting glucose levels and provide protection against the complications of diabetes.
8. May support the menopausal transition
Quercetin may help with this important life stage by increasing the body’s antioxidant capacity, reducing inflammation and by reducing the effects of histamine overload that is often caused by oestrogen fluctuations. Some research suggests it may also help with mood disorders like depression as well as genitourinary symptoms. However, human data is limited and more research is required to confirm quercetin’s efficacy and safety for menopausal symptoms.
Dietary sources of quercetin
The amount of quercetin we typically get through our diet varies depending on numerous factors, including seasonality, but it’s typically between about 15mg to 20mg per day. You can increase your dietary intake by including these quercetin-rich foods and drinks:
- Apples
- Asparagus
- Blueberries
- Broccoli
- Capers
- Chilli peppers
- Cocoa powder
- Coffee
- Coriander
- Dill
- Elderberries
- Fennel
- Green tea
- Kale
- Onion
- Oranges
- Red wine
- Rocket
- Tomato
How to take quercetin supplements
There is no recommended dose of quercetin and therapeutic amounts may vary depending on your age, weight and specific circumstances. However a typical adult dose may be between 200mg-1000mg per day. Quercetin is poorly absorbed so you may see products that combine it with other nutrients or plant compounds. For example, a popular combination may include vitamin C, digestive enzymes or other flavonoids like resveratrol, genistein and catechins.
Refer to your GP or healthcare practitioner, especially if you have a diagnosed health condition and/or you are on prescribed medication. This is important because supplements may interact with medication. Those relevant to quercetin include, but are not limited to, antibiotics and blood pressure meds.
Quercetin side effects
Safe for the majority of us when used short term, quercetin has been used safely in doses of up to 1g per day for 12 weeks. Above this dose it may trigger mild symptoms and it is important to know that the safety of longer periods of supplementation has not yet been established.
Who should not take quercetin?
Currently, there is not enough reliable information to establish whether quercetin is safe during pregnancy and breastfeeding and as such is best avoided in these circumstances.
Overall, is quercetin good for you?
Quercetin is one of the most abundant flavonoids found in our diets. It has been linked to a number of health benefits including reduced inflammation, better blood pressure, improved aging and fewer allergy symptoms. However, although the evidence appears encouraging, there remains a need for more high quality human trials.
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Kerry Torrens BSc. (Hons) PgCert MBANT is a BANT Registered nutritionist® with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including Good Food.
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