Flavonoids are polyphenolic molecules that are water soluble and contain 15 carbon atoms. To visualize them, you can picture two benzene rings joined by a three carbon chain. There are six major subgroups of flavonoids including isoflavonoids, anthocyanins, flavanone, flavonol, flavone and chalcone. There are many health benefits of flavonoids, most notably for its anti-cancer properties. This article explains all the benefits of flavonoids and sources of flavonoids.
Health Benefits of Flavonoids
In addition to having antioxidant activity, flavonoids provide a variety of other health benefits which make them very popular. Some of these properties include:
- Anti-viral
- Anti-inflammatory
- Antioxidant
- Anti-cancer
- Anti-allergic
In addition, flavonoids have been linked to other benefits including:
- Reducing the risk of heart disease
- Preventing low-density lipoprotein (LDL “good” cholesterol) from oxidizing, reducing the risk of developing atherosclerosis
Here are some of the benefits of specific sources of flavonoids:
- The flavonoid quercetin can relieve asthma, sinusitis, eczema and hay fever
- Red wine contains quercetin and rutin and many experts feel this is why French have less coronary heart disease (compared to their European counterparts) despite eating many cholesterol rich foods
- Tea flavonoids can lower triglyceride levels as well as cholesterol levels and prevent LDL cholesterol from oxidizing
- Isoflavones (soy flavonoids) can ease menopausal symptoms, prevent osteoporosis and reduce cholesterol
The daily intake of flavonoids can vary ranging between 50 and 500 mg, affecting its contribution towards antioxidant activity.
Food Sources of Flavonoids
Almost all herbs, spices, fruits and vegetables contain flavonoids and you can also find them in other foods such as dry beans (they provide the color for speckled, red and black beans) as well as grains (usually providing a yellow color). In most cases any product of the foods listed above will contain various flavonoids.
The flavonoid family is incredibly complex but it is important to know some things about it. Berries are the fruits with the high quantity of anthocyanins, a chemical category within flavonoids. Black raspberries can have 100 mg of anthocyanins in just one ounce.
Green tea contains catechins, a flavonoid component, at a large quantity of about a gram in just one cup. The general rule is that if a food item is more colorful it will have a higher flavonoid concentration (picture the skin of fruit). Oranges are an exception, however, as their white and pulpy interior of the skin contain most of the flavonoids.
| Common Dietary Sources of Flavonoids | ||
|---|---|---|
| Blue, red and purple berries |
Chocolate |
Kale |
| Purple and red grapes |
Apples |
Broccoli |
| Red wine |
Citrus fruits (lemons, oranges and grapefruits) |
Parsley |
| Green tea and black tea |
Yellow onions |
Soybeans |
| Legumes |
Celery |
Hot pepper |
Watch a video for comprehensive flavonoids sources:
Ideal Ways to Get Flavonoids
The ideal way to consume flavonoids is by eating fresh fruits and vegetables each day. Experts recommend having five servings of vegetables and four of fruit aiming for ones with deeper colors as they will have higher flavonoid content. Men shouldn’t have more than two glasses of wine a day while women shouldn’t have more than one. You can have as much green tea as you want (as long as you aren’t caffeine-sensitive) but should only have one ounce of chocolate.
You can also try taking a flavonoid supplement but you should always pay attention to the dosage information. Keep in mind that experts still are not sure what levels of flavonoids are ideal and if excesses can be harmful.
Safety Concerns of Flavonoids
1. Side Effects
So far experts haven’t associated any side effects with consuming high amounts of flavonoids from natural, plant-based sources. However, some people taking large quercetin supplements (of 1,000 mg/day for over a month) had side effects. In addition, liver toxicity and other side effects have been linked to overconsumption of tea extracts.
2. Pregnancy and Lactation
Experts haven’t determined whether flavonoid supplements are safe during pregnancy and lactation so you should always be cautious and avoid their use.
3. Drug Interactions
Certain drugs have had interactions with flavonoids. Cytochrome P450 (CYP), an intestinal drug metabolizing enzyme, has been negatively affected by grapefruit juice as well as flavonoids. The same is also true of P-glycoprotein which is an efflux transporter which is responsible for decreasing levels of absorption of various drugs. Taking high quantities of flavonoids from dark chocolate (over 235 mg/day) or purple grape juice (over 500 ml/day) can inhibit aggregation of platelets, possibly increasing the bleeding risk for people taking anticoagulant or anti-inflammatory drugs.
4. Nutrient Interactions
Flavonoids can react with certain nutrients. They may bind nonheme iron making it harder for the intestine to absorb it. Some flavonoids also prevent vitamin C from being transported into cells. Because of this, it is recommended to avoid having foods or beverages rich in flavonoids while consuming nonheme iron or vitamin C for optimum results.