The incredible onion, be it yellow, red or white, is part of just about every kitchen. Rarely, though, do we give this beautiful vegetable much thought. Years ago my friend Sunny taught me that you can serve them as an outright standalone side dish. I was intrigued, to say the least. Since then onions have become my most treasured staple because of their amazing versatility.
Written by Jillian Kubala, MS, RD — Updated
on July 20, 2023
Medically reviewed by Amy Richter, RD
Onions are highly nutritious vegetables that may have
several benefits, including improved heart health, better blood sugar
regulation, and increased bone density.
Onions are
members of the Allium genus of flowering plants, which also includes
garlic, shallots, and leeks.
They’re delicious, versatile, and relatively cheap, and they
boast a wide range of healthy vitamins, minerals, and plant compounds.
The medicinal properties of onions have been recognized
for thousands of years. Athletes in ancient
Greece supposedly used onions to purify their blood, while medieval and
traditional doctors prescribed them to help treat headaches, heart disease,
and mouth sores.
Read on to discover 9 health benefits of onions.
Onions are nutrient-dense,
meaning they’re low in calories but high in vitamins, fiber,
and minerals.
One medium onion (110 grams [g]) contains:
- Calories: 44
- Protein: 1.2 g
- Carbs: 10.3 g
- Sugar: 4.7 g
- Fiber: 1.9 g
- Fat: 0.1 g
- Potassium: 3.4% of Daily Value (DV)
- Vitamin C: 9% of the DV
Onions are high in vitamin C,
which may help regulate your immune health, collagen production, and iron
absorption.
It’s also a powerful antioxidant that could help protect your cells from unstable, damaging molecules
called free radicals.
Onions are rich in B vitamins, including folate and vitamin B6.
These play key roles in metabolism, red blood cell
production, and nerve function.
Lastly, onions are a good source of potassium,
a mineral that may help
with:
- cellular function
- fluid balance
- nerve transmission
- kidney function
- muscle contraction
The average potassium intake of Americans is less
than half the recommended DV of 4,700 milligrams (mg).
So, adding onions to your diet is a great way to increase your potassium
intake.
Onions contain antioxidants and compounds that may reduce
your risk of heart disease by fighting inflammation and
lowering triglyceride and cholesterol levels.
They contain a large amount of quercetin, a
flavonoid antioxidant and anti-inflammatory that may help lower
high blood pressure.
A small 2015
study in 70 people with overweight and hypertension suggests
that a daily dose of 162 mg of quercetin-rich onion extract may significantly
reduce systolic blood pressure by 3.6 millimeters of mercury.
Also, a small 2014 study in 54 females with polycystic
ovary syndrome found that consuming 80–120 g of raw red onions per day
for 8 weeks lowered total and LDL (bad) cholesterol levels.
However, more research is needed.
Antioxidants are
compounds that inhibit oxidation, a process that may lead to cellular damage
and contribute to diseases such as cancer, diabetes, and
heart disease.
Onions are an excellent source of antioxidants and contain
at least 17 types of flavonoids.
Red onions, in particular, contain anthocyanins, plant
pigments in the flavonoid family that give red onions their deep color. These
may protect against diabetes and certain types of cancer.
In a 2016
study involving 43,880 males, researchers found that
habitual anthocyanin intakes up to 613 mg were correlated with a 14% lower risk
of nonfatal heart attacks.
Similarly, the authors of a 2019 review concluded that consuming more anthocyanin-rich foods was
associated with a lower risk of heart disease and of death from heart disease.
4. Contain anticancer compounds
Allium vegetables such as onions and garlic may lower
your risk of developing certain types of cancer, including stomach and colorectal cancers.
In a 2015 review of 26 studies, researchers
concluded that people who consumed the most allium vegetables were 22% less
likely to receive a diagnosis of stomach cancer than those who consumed the
least.
And in a 2014 review of 16 studies involving a total of 13,333 people, researchers
suggested that people with the greatest onion intake had a 15% lower risk of
colorectal cancer than those with the lowest intake.
Test-tube studies suggest that onionin A, a
sulfur-containing compound in onions, may help decrease tumor
development and slow
the spread of ovarian cancer.
Onions also contain fisetin and quercetin, which are flavonoid antioxidants that may inhibit tumor growth.
Eating onions may help regulate blood
sugar levels, which is significant for people with diabetes or prediabetes.
A small 2010
study in 84 people with type 1 or type 2 diabetes found
that eating 100 g of raw red onion significantly reduced fasting blood sugar
levels after 4 hours.
A 2020
study showed that rats with diabetes who ate food
containing 5% dried onion powder for 8 weeks had decreased fasting blood sugar
levels and lower triglyceride and cholesterol levels than a control group.
Quercetin has also been shown to help regulate whole-body blood sugar balance by interacting with cells in
the:
- small intestine
- pancreas
- skeletal muscle
- fat tissue
- liver
Dairy gets much of the credit for boosting bone health, but
other foods, including onions, may also help support strong bones.
A small 2016 study in 24 middle-aged and postmenopausal females
found that those who consumed 100 milliliters of onion juice daily for 8 weeks
had improved bone mineral density and antioxidant activity compared to a
control group.
Also, a 2009 study in 507 perimenopausal and postmenopausal females found that
those who ate onions at least once per day had a 5% greater overall bone
density than those who ate onions once per month or less often.
Onions may help reduce oxidative stress,
boost antioxidant levels, and decrease bone loss. This may help prevent osteoporosis and
improve bone density.
7. Have antibacterial
properties
Onions may help fight
potentially dangerous bacteria such as:
- Escherichia coli (E. coli)
- Pseudomonas aeruginosa
- Staphylococcus aureus (S. aureus)
- Bacillus cereus
A 2010 test-tube study suggests that onion
extract might inhibit the growth of Vibrio cholerae, a type of bacteria
that is a major public health concern in some parts of the world.
Quercetin extracted from onions may also reduce bacteria
growth.
One review suggests that it could inhibit the growth of several strains of
bacteria, including Helicobacter
pylori, a type of bacteria associated with stomach ulcers and certain
digestive cancers.
Another test-tube study found that quercetin damaged the cell
walls and membranes of E. coli and S. aureus.
Onions are a rich source of fiber and prebiotics, which are
necessary for optimal gut health.
Prebiotics are
nondigestible types of fiber that are broken down by beneficial gut bacteria.
Gut bacteria feed on prebiotics and create short-chain
fatty acids, which may
help:
- strengthen gut health
- boost immunity
- reduce inflammation
- enhance digestion
Consuming prebiotic
foods may also help increase probiotics, such as Lactobacillus and Bifidobacterium strains,
which benefit digestive health.
Onions are rich in the prebiotics inulin and fructooligosaccharides,
which may help increase the number of friendly bacteria in your gut and improve
immune function.
Onions are a fresh and versatile staple in kitchens around
the world. They can be cooked, fried, eaten raw, and more.
To incorporate onions into your diet, you can try:
- using them in soups such as French onion soup
- using them in dips and spreads such as guacamole, salsa, and ranch
- adding them to egg dishes such as omelets, frittatas, and quiches
- making cooked toppings, such as caramelized onions, to top meat or tofu or add to savory baked goods
- using them raw as a topping for tacos, fajitas, and other Mexican dishes and savory baked goods
- adding them to salads, such as a chickpea, chopped onion, and red pepper salad
- using them in stir-fries, pasta sauces, or curries
Onions are nutrient-packed vegetables that contain powerful
compounds that may help decrease your risk of heart disease and certain
cancers.
They have antibacterial properties and promote digestive
health, which may improve immune function.
What’s more, they’re versatile and can be used to heighten
the flavor of any dish.
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Have a great week, everyone, and thank you for your support!
Blessed be… and happy cooking!
Chef Michael R