Should I Avoid Drinking Coffee While on a Low-Carb Diet?

Low-carbohydrate diets, especially ketogenic diets, can be fairly restrictive. Many beverages, even ones that would typically be considered healthy, aren't considered to be suitable keto drinks. Fortunately, most coffee-based beverages can be consumed freely, regardless of how strict your low-carb diet is.

Black coffee has no carbohydrates. (Image: Thanakorn Phanthura / EyeEm/EyeEm/GettyImages)

Tip

There’s no need to avoid drinking coffee while you're on a low-carb diet since black coffee has no carbohydrates.

Standard vs. Low-Carb Diets

According to the Food and Drug Administration, people tend to obtain most of their calories from carbohydrates, specifically sugar and starches. The daily value for carbohydrates is 300 grams per day. This total amount of carbohydrates includes fiber, sugar, starches and sugar alcohols.

People following low-carbohydrate diets ingest fewer carbohydrates and instead replace this macronutrient with increased amounts of fat. However, the exact amount of carbohydrates that they consume varies depending on the diet.

Counting Net Carbs

Typically, low-carb dieters count net carbs. Net carbs are calculated by taking the total amount of carbohydrates in a food and subtracting carbs from fiber and sugar alcohols.

Low-carbohydrate diets may be fairly liberal, like Atkins 100, which allow dieters to consume 100 grams of net carbohydrates each day. On the other end of the spectrum are ketogenic diets. These diets are stricter and typically only allow people to consume between 20 and 50 grams of carbohydrates per day.

Low-Carb and Keto Drinks

The strictness of most low carbohydrate diets means that many beverages are highly restricted. Regardless of whether it's a carbonated soda or a fruit drink, drinks tend to be filled with sugar and other sweeteners. In one cup (8 fluid ounces), you'll find:

  • 30.5 grams of carbohydrates in orange soda
  • 25.8 grams of carbohydrates in orange juice
  • 28 grams of carbohydrates in apple juice
  • 22.5 grams of carbohydrates in chocolate almond milk
  • 12.2 grams of carbohydrates in skim milk

These carbohydrates may come from natural sugars for certain freshly prepared fruit juices or milk products. They may also be added sugars for beverages like sodas or plant-based milk products. Regardless of whether they contain added or natural sugars, one cup of any of these beverages is poorly suited for most low-carbohydrate diets.

Low-Carb Diet-Friendly Drinks

With the exception of milk, one cup of most commonly consumed beverages would be more than the total daily carbohydrate intake for a person following a strict ketogenic diet. Even if you were following a more liberal low carbohydrate diet like Atkins 100, one cup of the average juice, milk-based drink or soda would constitute about a third of your total daily carbohydrate intake.

People following low-carbohydrate diets and ketogenic diets have to consume diet and sugar-free drinks if they want to consume soda and juices. Although milk is too carbohydrate-rich, cream or even butter can be consumed more freely.

Unlike most other beverages, one cup of black coffee has zero carbohydrates. This makes coffee a beverage well suited to low carbohydrate diets, unlike the majority of other popularly consumed drinks.

Low-Carb Diets and Coffee

Since there are no carbs in coffee, it isn't usually restricted in low-carbohydrate diets. In fact, certain low-carb diets, like the Atkins diet, advocate for its consumption. Coffee is considered beneficial for a variety of reasons: It has healthy antioxidants, can promote gastrointestinal motility and increase metabolic activity.

However, it's important to remember that there are only zero carbs in coffee if you choose to drink your beverage without any added sweeteners. This means that people can't consume sweetened plant-based milks, sweetened creamers, sugars and most commercially prepared coffee beverages. However, sugar alcohols and other low calorie sweeteners like erythritol, xylitol and stevia can be used instead.

Since milk products are also carbohydrate-rich, people following low- carbohydrate diets should also avoid these drinks and many creamers. As an alternative, certain people on low-carbohydrate diets consume a beverage called bulletproof coffee. This coffee is typically made by blending medium chain triglyceride (MCT) oil and butter into your coffee until it forms an emulsion.

Bulletproof Coffee on Keto Diets

Since low-carbohydrate dieters need to increase the amount of fat they're consuming each day, bulletproof coffee is a very popular alternative to breakfast. It provides about 50 grams of fat per serving.

While starting your day with so much fat may seem unhealthy, drinking bulletproof coffee on a keto diet can actually increase your body's resting energy expenditure and fat oxidation rates and improve endurance. This is not only due to the caffeine content from coffee, but the medium chain triglycerides in this beverage.

MCT oil (both on its own and in bulletproof coffee) is considered a beneficial fat as it can improve satiety and promote weight loss and ketosis. Unlike most saturated fats, MCT oil is considered to be good for your health. Also, the butter used in bulletproof coffee is meant to come from grass-fed cows, which means that it has more heart-healthy omega-3 fatty acids and less unhealthy saturated fats.

Downsides of Coffee-Based Beverages

Although coffee is acceptable to consume in low-carbohydrate diets, and bulletproof coffee may even have a variety of benefits, both of these drinks may also have some downsides.

Low-carbohydrate diets, particularly strict ones like the ketogenic diet, often come with gastrointestinal side effects. These typically occur because of the dramatic change in macronutrient ratios. While these adverse side effects are usually temporary, you may want to avoid consuming large amounts of coffee or bulletproof coffee if you're already experiencing gastrointestinal issues.

Bulletproof Coffee's Side Effects

It's well known that coffee consumption can cause gastrointestinal side effects, especially when consumed in large amounts. MCT oil can increase these side effects in people following strict ketogenic diets and may also lead to increased vomiting or diarrhea.

If you're drinking coffee or bulletproof coffee and experiencing gastrointestinal issues, you may need to temporarily increase your carbohydrate consumption to allow your body to adjust to your new diet. Alternatively, you may also want to switch to a less strict ketogenic diet, like the modified Atkins diet or a different type of low-carb diet.

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