Polyphenols types, benefits, and food
sources
Polyphenols are beneficial
compounds found in many plant foods and can be divided into flavonoids,
phenolic acids, polyphenolamides, and other polyphenols.
Polyphenols are a
class of plant compounds that have multiple health benefits.
Regular consumption of
polyphenols is thought to promote digestive and brain health, as well as
prevent heart disease, type 2 diabetes, and even certain cancers.
Among the most well-known sources are berries, dark chocolate, tea, and red wine.. However, many
other foods also provide large amounts of these compounds.
Everything you need to know about polyphenols, including potential food sources, is covered in this article.
What are polyphenols?
Polyphenols are a
class of compounds that occur naturally in plant foods, such as fruits,
vegetables, herbs, spices, teas, dark chocolate, and wine.
They act as
antioxidants, which means they can neutralize harmful free radicals that would
otherwise damage your cells and increase your risk of diseases such as cancer,
diabetes, and heart disease (1).
Polyphenols are also
thought to reduce inflammation, which is considered the root cause of many
chronic diseases. （2, 3）。
Types of polyphenols
More than 8,000
polyphenols have been identified. They can be further divided into 4 main
groups (4, 5):
- Flavonoids. These account for about
60% of all polyphenols. Examples include quercetin, kaempferol, catechins,
and anthocyanins, which are found in foods such as apples, onions, dark
chocolate, and red cabbage.
- Phenolic acids. This group accounts for about 30% of all polyphenols.
Examples include styrene and lignans, which are mainly found in fruits,
vegetables, whole grains, and seeds.
- Polyphenol amides. This category includes capsaicin in chili peppers and
data-mine in oatmeal.
- Other polyphenols. This group included resveratrol in red wine, ellagic
acid in berries, curcumin in turmeric, and lignans in flaxseed, sesame,
and whole grains.
The amount and type of
polyphenols in a food depends on the food, including its source, maturity, and
how it is cultured, transported, stored, and prepared.
Supplements containing
polyphenols may also be used. However, they may not be as beneficial as
polyphenol-rich foods (6).
Summary: Polyphenols are beneficial to plant
compounds with antioxidant properties that can help you stay healthy and
prevent a variety of diseases. They can be subdivided into flavonoids, phenolic
acids, polyphenolamides, and other polyphenols.
Health benefits of polyphenols
Numerous health advantages have been connected to polyphenols.
May lower blood sugar levels
Polyphenols may help
lower blood sugar levels, thereby reducing the risk of type 2 diabetes.
This is partly because
polyphenols prevent starch from breaking down into simple sugars, reducing the
likelihood of blood sugar spikes after meals. （7）。
These compounds may
also help stimulate the secretion of insulin, a hormone needed to transport
sugar from the bloodstream into cells and keep blood sugar levels stable. （7）。
Various studies have
further linked a polyphenol-rich diet to lower fasting blood glucose levels,
higher glucose tolerance, and increased insulin sensitivity —all of which are
important factors in reducing the risk of type 2 diabetes. （8）。
In one study, people
who consumed polyphenol-rich foods had a 57% lower risk of developing type 2
diabetes over 2 to 4 years compared with those who consumed the least amounts. （9）。
In polyphenols,
studies have shown that anthocyanins may provide the most effective
anti-diabetic effects. They are commonly found in red, purple, and blue foods,
such as berries, blackcurrants, and grapes (10, 11).
May reduce your risk of heart disease
Adding polyphenols to
your diet can improve heart health.
Experts believe that
this is mainly due to the antioxidant properties of polyphenols, which help
reduce chronic inflammation, which is a risk factor for heart disease. （3, 12, 13）。
Two recent reviews
have linked polyphenol supplements to lower blood pressure and LDL (bad)
cholesterol levels, as well as higher HDL (good) cholesterol. （14, 15）。
Another review found
that people with higher enterolactone levels had a 45% lower risk of dying from
heart disease, and enterolactone levels were a marker of lignan intake. Lignans
are polyphenols commonly found in flaxseed and whole grains (16).
Can prevent blood clots
Polyphenols may reduce
your risk of forming blood clots.
When the platelets
circulating in the blood begin to clump together, blood clots form. This
process is called platelet aggregation and can be used to prevent excessive
bleeding.
However, excessive
platelet aggregation can lead to blood clots, which can have negative health
effects, including deep vein thrombosis, stroke, and pulmonary embolism. （17）。
According to the test
tube and animal studies, polyphenols may help reduce the process of platelet
aggregation, thereby preventing the formation of blood clots. （18, 19, 20）。
Cancer can be prevented
Research has
consistently linked diets rich in plant-based foods to a lower risk of cancer,
and many experts believe that polyphenols are part of the reason for this (5, 21, 22).
Polyphenols have
strong antioxidant and anti-inflammatory effects, both of which are beneficial
for cancer prevention (23).
According to a recent analysis of research conducted in test tubes, polyphenols may prevent certain cancer cells from proliferating and developing.（5, 24）
In humans, some studies
have linked high blood markers of polyphenol intake to a lower risk of breast
and prostate cancer, while other studies have found no effect. Therefore, more
research is needed before strong conclusions can be drawn (25).
May promote healthy digestion
Polyphenols can
promote digestion by promoting the growth of beneficial gut bacteria while
defending against harmful bacteria. （26, 27）。
For example, there is
evidence that polyphenol-rich tea extracts can promote the growth of beneficial
bifidobacteria. （28）。
Similarly, green tea
polyphenols may help fight harmful bacteria, including Clostridium difficile,
E. coli and Salmonella, and alleviate the symptoms of inflammatory bowel disease (IBD) and peptic ulcer disease (PUD) (29, 30).
In addition, emerging
evidence suggests that polyphenols may help probiotics thrive and survive.
These are good bacteria that can be taken as supplements and are present in some fermented foods. However, more research is needed (31).
May promote brain function
Consuming foods high in polyphenols can help you focus and remember things better.
One study reported
that drinking grape juice that is naturally rich in polyphenols can help
significantly improve memory in older adults with mild mental disorders in as
little as 12 weeks. （32）。
Others believe that
cocoa flavanols improve blood flow to the brain and link these polyphenols to
improved working memory and attention. （33, 34, 35, 36）。
Similarly, Ginkgo
biloba, a polyphenol-rich plant extract, appears to improve memory, learning,
and concentration. It has also been linked to improvements in brain activity
and short-term memory in people with dementia. （37）。
Summary: In conclusion, polyphenols may help lower blood sugar, minimize the risk of heart disease, and avoid blood clots. They can also promote
brain function, improve digestion, and provide some anti-cancer protection, but
more research is needed.
Foods rich in polyphenols
While tea, dark
chocolate, red wine, and berries may be the most famous sources of polyphenols,
many other foods also contain large amounts of these beneficial compounds.
Here are 75
polyphenol-rich foods by category (38).
Fruit
- apple
- apricot
- Black bitter berry
- Blackcurrants and redcurrants
- Black elderberry
- Black grapes
- Blackberries
- blueberry
- cherry
- grape
- Grapefruit
- lemon
- nectarine
- peach
- pear
- pomegranate
- plum
- Raspberries
- Strawberry
Vegetable
- artichoke
- asparagus
- broccoli
- turnip
- chicory
- potato
- red chicory
- Red lettuce
- Red onions and yellow onions
- spinach
- Shallots
Legume
- Black beans
- Tempeh
- bean curd
- Soybean sprouts
- Bean meat
- soy milk
- soy milk
- White beans
Nuts and seeds
- almond
- chestnut
- hazelnut
- Flax seeds
- walnut
- walnut
Cereals
- oats
- rye
- Whole grain
Herbs and spices
- Parsley seeds
- Celery seeds
- cinnamon
- clove
- cumin
- Curry powder
- Dry basil
- Dry Margarine
- Dried parsley
- Dried mint
- Dried mint
- Lemon verbena
- Mexican oregano
- rosemary
- wise man
- aniseed
- thyme
Other
- black tea
- Capers
- Cocoa powder
- coffee
- dark chocolate
- ginger
- green tea
- Olives and olive oil
- rapeseed oil
- claret
- Mean
Adding these
categories of foods to your diet can provide you with multiple polyphenols.
Summary: Polyphenols are naturally abundant in many plant-based meals. Increasing your intake of these healthy nutrients can be achieved by include a range of these foods in your diet.
What about polyphenol supplements?
One benefit of supplementing is that it offers a steady supply of polyphenols. They do, however, also have a number of possible disadvantages.
First, supplements
don't consistently show the same benefits as polyphenol-rich foods, and they
don't contain any of the additional beneficial plant compounds typically found
in whole foods.
Additionally, polyphenols appear to function best in naturally occurring foods when combining with a wide range of other nutrients. The effectiveness of isolated polyphenols, like those in supplements, in comparison to those in food is unknown. （6, 39）。
Finally, polyphenol
supplements are not regulated, and many supplements are more than 100 times
larger than those found in food. More research is needed to determine safe and
effective doses, and it is unclear whether these large doses are beneficial (39, 40).
Summary: Foods high in polyphenols may offer more health advantages than pills containing polyphenols. There is no known safe and effective dosage.
Potential risks and side effects
Foods rich in
polyphenols are safe for most people.
This cannot be said of
supplements, which tend to be much higher than the polyphenols typically
provided in a healthy diet (39).
Animal studies have
shown that high-dose polyphenol supplementation may cause kidney damage,
tumors, and imbalances in thyroid hormone levels. In humans, they may cause an
increased risk of stroke and premature death (39, 40).
Certain supplements high in polyphenols may interfere with the absorption of nutrients or drugs. For instance, they might make it harder for your body to absorb folic acid, iron, or thiamine. (39, 41, 42).
If you have been
diagnosed with nutritional deficiencies or are taking medication, it is best to
discuss polyphenol supplementation with your healthcare provider before taking
it.
In addition, some
foods rich in polyphenols, such as legumes and peas, may be rich in lectins.
Large-scale lectin consumption can result in uncomfortable digestive symptoms such indigestion, gas, and bloating.（43）。
If this is a problem
for you, try soaking or sprouting beans before consuming them, as this can help
reduce the lectin content by up to 50% (44, 45).
Summary: For most people, foods rich in
polyphenols are considered safe, and supplements can do more harm than good.
Conclusion
Polyphenols are
beneficial compounds found in many plant foods and can be divided into
flavonoids, phenolic acids, polyphenolamides, and other polyphenols.
They can improve
digestion, brain function, and blood sugar levels, and prevent blood clots,
heart disease, and certain cancers.
To find safe and efficient dosages for polyphenol supplements, more research is required.
Therefore, for now, it
is best to rely on food rather than supplements to increase the intake of these
healthy compounds.