Is onion OK on keto?

The keto diet has become incredibly popular in recent years as a way to lose weight and improve health. But with any restrictive diet, questions arise about which foods are keto-friendly and which should be avoided. One food that often causes confusion is onions. Can you eat onions on the keto diet? Let’s take a look at what the science and experts say.

What is Keto?

The ketogenic or “keto” diet is a very low-carb, high-fat diet that shares similarities with the Atkins diet. The goal is to put the body into a metabolic state known as ketosis.

Here’s how it works:

By severely restricting carbs to usually less than 50 grams per day, the body’s preferred source of energy (glucose from carbs) becomes in short supply. This causes the body to turn to burning fat for fuel instead, producing compounds called ketones.

Ketones can be used by the body and brain for energy, meaning you can lose body fat while still feeling energetic. Achieving a state of ketosis generally requires limiting carbs to 5-10% of total daily calories.

The keto diet was originally designed to treat epilepsy in children but has since become popular for weight loss, diabetes control and other health benefits. However, it remains a controversial diet requiring strict carb restriction.

Keto Diet Guidelines

The standard keto diet typically recommends getting:

– 60-75% of calories from fat
– 15-30% of calories from protein
– 5-10% of calories from net carbs

Net carbs are total carbohydrates minus fiber. Fiber is subtracted because it is indigestible and does not raise blood sugar or insulin levels like other carbs.

Keto diets emphasize high-fat foods like meat, fish, eggs, oil, butter and very low-carb vegetables. Foods to avoid include sugar, grains, legumes, most fruits, starchy vegetables, milk and honey.

Low-carb vegetables allowed on keto with little restriction include leafy greens, cauliflower, broccoli, peppers, zucchini, asparagus, cucumber and others. In moderation, onions and tomatoes are often allowed as well.

Are Onions Keto-Friendly?

So can you eat onions on the keto diet or not? The short answer is yes, onions can fit into a keto diet when consumed in moderation. Here is a breakdown of their carb contents:

– Raw onions: 9 grams of carbs per 1 cup chopped, 4 grams fiber, 5 grams net carbs

– Cooked onions: 14 grams of carbs per 1 cup chopped, 3 grams fiber, 11 grams net carbs

As you can see, onions contain a moderate amount of carbs so they cannot be eaten freely on keto. But when portioned correctly, onions can be included.

Let’s compare the carb counts of onions to other keto-approved vegetables:

Vegetable Total Carbs Fiber Net Carbs
1 cup raw onion 9g 4g 5g
1 cup raw broccoli 6g 2g 4g
1 cup raw bell pepper 5g 2g 3g
1 cup raw spinach 1g 1g 0g

As you can see, onions are higher in net carbs than leafy greens but comparable to other low-carb veggies. And cooked onions have slightly more net carbs than raw since cooking reduces fiber.

So to stay keto, onions should be watched closely and limited to 1/2-1 cup per day max, keeping net carbs under 50g total for the day. Less is recommended when starting keto to account for hidden carbs.

Onion Benefits

Onions, especially raw red onions, provide some impressive health benefits including:

– Rich in antioxidants – Onions contain over 25 different antioxidant compounds including quercetin and anthocyanins which help fight free radicals and reduce inflammation.

– May improve heart health – Onions contain sulfur compounds and quercetin that may lower blood pressure, cholesterol and triglycerides according to studies.

– Anti-cancer properties – Onions are high in anti-cancer compounds like quercetin, fisetin and anthocyanins that may inhibit tumor growth.

– Anti-microbial effects – Onions have antibacterial, antiviral and antifungal properties that help kill potentially harmful microbes.

– Management of diabetes – Compounds in onions may help lower blood sugar, improve insulin sensitivity and reduce diabetes complications.

– Gut and bone health – Onions are prebiotics that feed beneficial gut bacteria. They also contain bone-supporting manganese and vitamin K.

So onions provide powerful health benefits. While limited on keto due to their carbs, they can still be enjoyed in moderation.

Choosing Low-Carb Onions

All types of onions can fit into a keto diet plan when a portion is measured out. But some have slightly fewer carbs than others.

Yellow onions tend to be the highest in net carbs while red, white and scallions are a little lower:

Type of Onion Net Carbs Per 1 Cup Raw
Yellow 5g
White 4g
Red 4g
Shallots 5g
Leeks 3g
Scallions 1g

As shown above, scallions (aka green onions) are lowest in net carbs by a small margin. So opting for scallions and leeks may allow for slightly bigger portions. Just keep the differences minor.

Onions can also be consumed in smaller portions such as:

– 2 thin slices of onion on a burger
– 1 tablespoon minced onion in a salad or taco
– A few rings on top of a keto-friendly pizza
– 1-2 tablespoons caramelized onions as a topping

This provides great onion flavor at only 1-3 grams of carbs.

Healthier Cooking Methods

To maximize the nutrition in onions, opt for raw onions or gentle cooking methods like sauteing. Deep frying onions adds extra fat and calories while boiling decreases anti-oxidants.

Sauteeing, caramelizing, roasting, or grilling onions are all healthy keto cooking methods. This brings out flavor while avoiding deep frying.

Keto Onion Recipes

Here are some ideas for incorporating onions into keto-friendly recipes:

– Burgers or fajitas topped with grilled onions
– Salads with thinly sliced red onion
– Egg salad, tuna salad or chicken salad with minced onion
– Chili, soups or bone broth cooked with onion base
– Stir frys with sliced onion and low-carb veggies
– Fajita stuffed peppers topped with sauteed onions
– Keto onion pizza or flatbreads
– Bacon onion quiche or frittata
– Roasted brussels sprouts with caramelized onion
– Homemade onion dip from sour cream and onion seasoning
– Crispy onion rings coated in almond or pork rind breading
– Onion soup or French onion soup topped with cheese

The key is measuring 1/2 – 1 cup onion per serving and accounting for the net carbs. This allows you to enjoy the flavor and nutrition of onions without going over your carb limit.

Onion Powder

A simple way to add onion flavor without any carbs is to use onion powder. Onion powder is dehydrated, ground onion that contains zero grams of carbs:

1 Teaspoon Onion Powder 0g Net Carbs

Onion powder lacks the fiber, antioxidants and some nutrients of fresh onion. But the flavor can spice up keto meals. Use onion powder to season meat, salads, veggies, soups, eggs and more.

Other onion-flavored seasoning ideas for keto cooking include:

– Onion salt or onion flakes
– Onion soup mix as a seasoning
– Dried minced onion
– Garlic onion herb seasoning blends
– Onion & chive cream cheese spread

A small amount of these add lots of onion taste without carbs.

What About Garlic?

Like onions, garlic is a flavorful vegetable low-carb dieters are concerned with. The good news is garlic is very keto-friendly, with just 1 gram of net carbs per clove:

1 Clove of Garlic 1g Net Carbs

Due to its medicinal properties and very low carb count, garlic is a superstar for keto. Benefits of garlic include:

– Lowers blood pressure and cholesterol
– Boosts immunity with its antimicrobial effects
– Reduces risk of Alzheimer’s, dementia and aging of the brain
– May help treat fatty liver disease and prevent liver damage
– Linked to reduced risk of certain cancers
– Contains the antioxidant allicin that fights free radicals

Garlic adds great flavor for almost zero net carbs. Use it liberally in keto recipes like sauces, salad dressings, soups, roasted veggies and more. Up to 4 cloves per day can be safely consumed.


Here are some precautions to take with onions on keto:

– Count the net carbs when meal planning, approximately 4-5g per cup
– Limit intake of onions to 1/2 – 1 cup per day
– Raw onion and garlic can cause digestive issues like bloating, gas and upset stomach in some people. Cook them to reduce this effect.
– Onions and garlic belong to the nightshade family, which some claim exacerbates inflammation and arthritis. However, most people tolerate nightshades fine.
– Due to their blood-thinning properties, talk to your doctor before consuming medicinal amounts of onion or garlic if taking blood thinners or facing surgery.
– Garlic can interact with certain medications like HIV treatments, immunosuppressants and blood pressure medications. Check with your pharmacist.
– Pre-made onion/garlic powders sometimes contain anti-caking agents and fillers that add carbs. Check labels for 100% real onion/garlic ingredients.

So those with digestive issues may need to limit onion intake. But most people can include moderate amounts of onion in their keto diet without problems.

Bottom Line

Here is the bottom line on whether onions can be eaten on the keto diet:

Yes, onions can be part of a keto diet plan. A typical serving of 1/2 – 1 cup of onions contains around 4-9 grams of net carbs after subtracting fiber.

This fits into the 50 gram daily carb limit of keto, though the total amount should be restricted. Raw onions are lowest in carbs but all types can work. Onion powder gives flavor without carbs.

Onions provide antioxidants, possible cancer-fighting properties, and prebiotics for good bacteria when eaten in moderation. Use raw onions and cooked onions to add flavor and nutrients to keto meals. Just account for the extra carbs.

With smart choices, measurements and recipes, onions can be included in a low-carb keto eating plan.

Leave a Comment