Are Onions Keto Friendly?

  • Date: September 4, 2021
  • Time to read: 6 min.

We all love onions, be it in a supporting role as the base of a sauce, or if they are center stage, battered, or stuffed, but are s ok to eat on a keto diet? To answer this question, it’s important to know why people might classify a vegetable as not keto-friendly; in this article, we are going to explore this and answer the questions, are onions keto-friendly?  Read on to find out more!

What are the Health Benefits of Onions?

Health Benefits of Onions on A Keto Diet?

Onions are rich in nutrients and are low in calories. They are high in vitamin C and potassium, both of which are great on a keto diet. Especially, potassium, which is lacking in most Western diets.

Onions also contain antioxidants, which are thought to assist in preventing cancer.

On top of this, they have been linked to helping heart health as well as aiding digestion and controlling blood sugar. All in all, onions are very good for a healthy diet

Did you know that the average person eats around 20 pounds of Onions a year? Crazy, isn’t it!

How many net carbs are in Onions?

Onions contain around 5.5 grams of net carbs per 100 grams. An average ‘large’ size onion weighs around 400g, meaning that this would be 22 grams of net carbs per onion.

Yes, I know that that is a shocking amount of carbs, however, when was the last time you ate a whole large onion to yourself, in one day?!

In reality, you may use a large onion split between 6-8 portions, meaning that you will be eating in the region of 2.75 grams of net carbs per portion that you are eating.

To put this into perspective, a 400-gram onion, diced, is going to fill around 5 cups – that’s a lot of onion!

Different Types of Onions

Do Any Varieties of Onions have Fewer Carbs?

There are many varieties of onions including:

  • Sweet Onions
  • Yellow Onions
  • White Onions
  • Spring Onions (also known as Green Onions or Scallions)

Despite these all being very different in taste, they all contain a similar carb count; 3-4 grams per 100 grams.

However, the fiber count in each of these varied quite dramatically, as you can see from the table below;

All below quantities are per 100-gram weight of the onion

Sweet Onions = 1 grams fiber

Yellow Onions = 1.5 grams fiber

White Onions = 1.5 grams fiber

Spring Onions = 2.5 grams fiber

What does this mean?

This means that Spring Onions (Scallions) is the winner in terms of net carbs per 100 grams, making them the most keto-friendly onion. Which is great news for me as I love these in my salads to give them a bit of a kick!

Are Onions full of sugar?

The carbs in onions consist of starch and sugars, these consist mostly of simple sugars, such as glucose, fructose, and sucrose. Although Onions contain some sugar, they can be enjoyed in moderation on a keto diet.

To understand more, and assess whether Onions are suitable for a keto diet, let’s look at the nutritional value of onions.

Nutritional Value of Onions

The nutrition value of 100 grams of Onions are:

  • Carbs: 7 grams.
  • Protein: 1 gram.
  • Fat: 0.2 grams.
  • Fibre: 1.5 grams.
  • Sugar: 4 grams.
  • Calories: 40 cal

Don’t forget that with keto we deduct the amount of fiber from the total carb count. This means that for 100 grams of Onions there are 7 grams of net carbs, (7 grams of Carbs – 1.5 grams of Fibre = 5.5 grams of Net Carbs)

Onions are not high in fat (high-fat is desirable for a keto diet), but let’s face it, there are not many vegetables that are.

If keto is new to you, why not check out our Keto Starters Guide?

SUMMARY: 100 grams of Onions there are 5.5 grams of net carbs

Can Onions be eaten on a Keto Diet?

Although Onions aren’t as low in carbs as some of the other vegetables, such as leafy greens, like broccoli or spinach, they’re not as high in carbs as many other root vegetables (potatoes, parsnips and turnips, etc), which should be avoided on a keto diet.

A keto diet is focused on eating fewer than 20 grams of carbohydrates a day; in order to stay within your macros.

For more on Keto macros, check out this article.

Normally, on a keto diet, a good rule of thumb is that if a vegetable grows below the ground; (vegetables such as onions, potatoes, sweet potatoes, and other root vegetables) you should avoid them.

For me, I do eat onions on keto. I certainly have cut down on the amount that I would have eaten in my pre-keto life!

Onions, a bit like Carrots are a vegetable that you need to need to monitor how much you are eating to ensure that you stay in ketosis!

Check out some of our favorite keto recipes with onions below.

Can Onions be eaten on a low-carb diet?

A low-carb diet will normally see a person eating fewer than 100 grams of carbs a day. 100 grams of carbs is considerably more than the 20 grams of carbs that people will eat on a keto diet.

With 100 grams of carbs to play with, you can be a lot more liberal with what carbs that you eat, therefore, onions can be eaten on a low-carb diet.

Are Shallots Keto Friendly?

We’ve spent a lot of time talking about the different varieties of onions, and whether they are keto-friendly, however, you will note that up to this point, we have not discussed shallots.
Shallots belong to the Allium family, the same onions, garlic, and leeks.

However, they are distinctly different in their cousins, onions,  not only in look but also in taste. Shallots have a lovely sweet flavor, this is from the fructans, glucose, fructose, and sucrose that are packed inside.

Shallots have around 14 grams of net carbs per 100 grams, which makes them a lot higher in carbs than regular onions.

Although you are only likely to eat shallots in the same quantity as regular onions, you will be eating over double the amount of carbs for the same volume of onion. This makes these a no-go on a keto diet.

Does how Onions are cooked alter the carb content?

With some vegetables, how they are cooked (over, steamed, fried) can alter the carb content. However, with onions, the difference between raw and cooked onions is negligible. This means that it does not make a difference if they are eaten cooked or even raw.

I have previously read somewhere that freezing onions can slightly reduce the carb content, however, I cannot find a reference to this anywhere. If somebody knows whether this is true or an urban myth – let me know in the comments below! 

To err on the side of caution – I do slice and freeze my onions in bulk sometimes. This is more out of laziness of not wanting to slice onions all of the time, however, if there are additional carb benefits, I’m all for it!

Keto-friendly recipes which have Onions (yummy!)

I have a few favorite recipes that I will use onions in.

  • Keto Onion Rings
  • Keto Stuffed Onion wrapped in bacon
  • As a base to soups

These are just a few of my favorite keto recipes containing onions. If you have a favorite keto recipe with onions or have found an imaginative way to serve them – let us all know in the comments below!

If the Carbs in Onions are too much for you, why not try some of these alternatives?

If you decided that there are too many carbs in onions for you, why not try some of these low carb, keto-friendly onion alternatives for you;

  • Asparagus: 2.5 grams of net carbs per 100 grams
  • Broccoli: contains 4 grams of net carbs per cup per 100 grams
  • Brussels Sprouts: 5 grams of net carbs per 100 grams
  • Cabbage: 4 grams of net carbs per 100 grams
  • Carrots: 7 grams of net carbs per 100 grams (check out our keto carrots guide)
  • Cauliflower: contains 3 grams of net carbs per cup 100 grams
  • Celery: contains 1.5 grams of net carbs per 100 grams
  • Courgette: 3.5 grams of net carbs per 100 grams
  • Fennel: 4 grams of net carbs per 100 grams (check out of keto fennel guide)
  • Green Beans: 5 grams of net carbs per 100 grams

In Summary; are Onions Keto Friendly?

In comparison to other, leafy green vegetables, onions do contain slightly more carbs than the average keto vegetable. Here, we have outlined all of the health benefits of onions, we have also been through the nutritional value of onions. So in summary, in moderation, onions are ok to eat on a keto diet.

Happy eating!

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