The simple onion is a staple ingredient in most kitchens.
Sure, cutting them can be a tear-ridden experience, but most of us end up including onions in many different dishes.
The focus is almost always on cooked onions.
After all, onions become a bit sweeter once they have been cooked, which always makes them easier to eat.
But, what about health?
Are raw onions good for you?
It turns out that they are, and they may be an even better option for health than cooked onions – provided you can stand the taste, of course.
Historically, onions have been associated with a large range of health benefits and were even thought to prevent the plague.
Now, I highly doubt that is true, but there are a lot of health benefits of onions that have much more scientific backing and are more relevant for the modern day.
What You Should Know About Onions and Cooking
It’s no surprise that cooked food tastes very different than raw food, because the process of cooking can significantly change aspects of the food.
So, you end up with a completely different food than you started with.
This is why you can’t un-cook food; once it’s cooked, it’s cooked.
By extension, the process of cooking has implications for health.
After all, you are changing the composition and prevalence of some of the compounds in your food. In some cases, this might make the food healthier (especially as cooking can make food easier to digest), but in most cases, the process is going to damage some of the key nutrients.
The process of cooking can decrease the amount of flavonoids significantly – although some types of cooking are better than others (2).
One study highlighted on this pattern by looking at the percentage loss of onion flavonoids across a range of different cooking approaches (3), as shown below.
So, if you are going to cook onions, frying and sautéing are the worst ways to go.
This pattern also provides a pretty strong answer for the question, are raw onions good for you, as raw onions do contain significantly more of the health promoting flavonoids.
Another compound of interest is allicin.
Allicin is important because it has the ability to combat bacteria (4), as well as some diseases and some types of cancers.
The antibacterial action of allicin has been observed against a number of different types of bacteria, as well as fungi and parasites, suggesting it’s application in the human body may be highly significant (5).
Additionally, allicin provides support for the colon and for the heart, and has the ability to aid in the treatment of open wounds.
This makes allicin particularly important for people who are sick, or who have compromised immune systems, and can help to reduce how frequently people get colds or the flu.
This is the same important chemical that is associated with many of the health benefits from garlic (6).
Onions can also play a role in blood pressure levels, helping people to remain a healthy level of blood pressure and reducing the likelihood of cardiovascular problems (7).
These health benefits are present in both cooked and raw onions, however, they are much stronger in raw onions.
Experimental research has indicated that the intake of onion extract can significantly decrease the concentration of plasma glucose among diabetics (10).
Another study found that the consumption of onion powder was able to significantly decrease the level of HDL cholesterol among study participants (11).
There are also many more studies that I haven’t highlighted here.
All of these outcomes highlight the potential of onions to play a role in diabetes treatment.
Even though most of these studies didn’t use raw onion, the health benefits of raw onion are likely to be more significant, as it can be more bioactive and the compounds have not degraded.
The Health Potential of Onions
Onions tend to be seen as an ingredient to make meals better – rather than as something to eat because of health.
Certainly, onions don’t have the reputation of products like kale, spinach or pomegranate when it comes to health.
But, that doesn’t mean they should be overlooked.
As I mentioned above, they have been strongly associated with improvements in diabetic outcomes.
As with plants in general, the health potential of onions really comes from the natural compounds in onions (16).
Of these, quercetin is an especially interesting compound and it is in multiple cultivars of onion (19).
It is promoted for a range of potential health benefits, including anti-inflammatory action as well as the potential to help reduce the risk of heart disease and perhaps to play a role in cancer prevention (20,21,22).
Getting the Most out of Onions
The healthy compounds in onions aren’t evenly distributed across the different layers.
Instead, many of the healthy compounds are located in the outer layers of the onion.
This distribution has a lot of implications for health.
After all, people peel onions before they use them.
Often this involves peeling away the first few layers of the onion. In some cases, a person might end up peeling away a third or more of the onion.
This is a huge waste, when everything but the outermost layer can actually be used. At the same time, you end up peeling away the parts of the onion that have the most potential for health.
For example, the onion peel contains a high concentration of multiple key compounds (23).
A Note on Onion Storage
Cooking isn’t the only thing that can affect the compounds in onions.
One research study found that the exposure to different types of light could alter the profile of the quercetin compounds and quercetin glucosides within the onion, both of which may be relevant for health.
The authors found that the impacts varied across different light types and the different parts of the onion.
In particular, the pulp of the onion had the lowest level of the glucosides when under fluorescent light (24).
That outcome is highly significant because grocery stores rely on fluorescent lighting.
So, even the lighting can affect some of the compounds in onions – although the effect is probably not as significant as the impact of cooking.
This does suggest that you might get more health benefits from growing your own onions, rather than getting them from the store.
Raw onions aren’t the only way to get the most health benefits from onions.
One alternative approach is making onion soup.
If you simmer onions when making soup, the cooking process does not have as dramatic of an impact on the onions or their healthy components.
At the same time, any nutrients that are lost are likely to end up in the water used to make the soup – which means that you still actually get them.
Actually Eating Raw Onions
I started this post with the idea of are raw onions good for you? That’s something I want to go back to.
Studies on onions have been all over the place.
Many have looked at supplements of onion or of the active ingredients in onions. Studies that have considered onions themselves have also varied in whether this is cooked or not.
So, there is little evidence that raw onions offer more health benefits as such.
Yet, some healthy compounds in onions do decrease with cooking.
This offers a strong indication that raw onions have more healthy compounds, which should make them better for health.
Nevertheless, actually eating them can be a challenge for many people.
After all, regular white onions have a pretty sharp taste, which can seem pretty unappealing.
If you don’t like the taste of raw onions, one of the best ways to eat them is in veggie dips or in something that has a strong taste of its own.
Some people choose to use raw onions on top of chili dogs for example, because the taste of chili often overpowers the onion.
Another option is to crush raw onion with raw garlic (which also has considerable health benefits) and use this mixture on top of baked potatoes.
Raw onions are also used commonly in sandwiches or salads, and some people even eat them like an apple (although they are a minority).
The way that you eat raw onions is not as important as whether you eat them or not.
Additionally, you can mix up what type of raw onion you are eating, such as choosing between white, red, green and yellow, depending on the food and your personal preference.
In fact, red onions have an appealing taste and they have their own special implications for health.
While the answer to the question of are raw onions good for you is certainly yes, it’s important to note that even cooked onions offer significant health benefits, and these may be a better option if you really hate the taste of raw onions.