When you’re choosing a diet, it’s only natural to consider what you will and won’t be allowed to eat.

On a vegan diet, you can’t eat meat but you can eat pasta. On the ketogenic diet, you can eat meat but you can’t eat pasta. And on the Zone diet, you can’t eat fatty red meat or pasta.

It’s natural, of course, to focus on food. But when you choose a diet plan, you should really be thinking about what you can and can’t drink, too. For instance, on the vegan and keto diets, you aren’t supposed to drink dairy milk. But on the Zone diet, it’s “the perfect snack.”

There’s an interesting, apparent contradiction in that last sentence.

Both the keto and Zone diets are considered low-carb eating plans. Yet you’re allowed to drink milk on one diet and not the other.

What’s that all about? And more importantly, what can and can’t you drink when you’re on a low-carb diet?

Let’s talk about it.

Low carb diets have been shown to help people lose weight. They may also help regulate blood sugar spikes, lower blood pressure and cholesterol levels, contribute to heart health – and reduce your appetite, too.

However, low-carb is a term of art, not science. There’s no single “right amount” of carbs you can or should consume when you’re on a low-carb eating plan.

Instead, the term simply calls for limits on one of the three macronutrient groups, carbohydrates. Each low-carb diet provides its own guidance on the ideal carb content in a daily diet – and which of the other macronutrients, fat or protein, should be emphasized more.

Here are a few examples. Keto recommends that carbs make up no more than 5-10% of daily calories. The Atkins diet starts around the same level, but then relaxes limits on carb intake. The Zone diet suggests no more than 40%, but the carbs should have a low glycemic index. Paleo (the “caveman” diet) doesn’t have a set limit, but its guidelines eliminate most carb-heavy foods simply because our ancestors didn’t eat them.

Yet all of them are considered low-carb diets.

Why does the allowable amount of carbs vary so greatly? It’s because low-carb diet rules depend on the type of low-carb diet you’re following.

Keto and the first phase of Atkins aim to put the body into the metabolic state called ketosis, which jump-starts fat burning. With the Zone diet, the goal is to prevent body inflammation by maintaining strict macronutrient ratios. And Paleo is based less on science and more on a philosophy: the cavemen didn’t contract modern illnesses because they had a healthier diet – so we should eat like they did.

(That answers one of the first questions we asked; milk is relatively high in carbs so it’s not allowed on rigorous low-carb diets like keto, but is OK on the more-forgiving Zone diet.)

No matter which low-carb meal plan you’re following, the bottom line is essentially the same. The fewer carbohydrates you ingest, the better you’ll do and the more weight you’ll lose.

Liquids provide nearly one-quarter of the calories in the average American diet. So it makes sense for low-carb dieters to know which beverages are low in carbohydrates, and which ones are way too high.

We happen to have those lists right here.

Why are we starting with our rundown of the worst beverages to drink on a low-carb diet, instead of the best?

It’s simple. Most peoples’ eating and drinking habits have been formed over a lifetime. Changing them isn’t as easy as just stocking the fridge with the beverages you’re supposed to drink; it requires a conscious decision to make changes. And many low-carb diets actually require you to keep a carb count.

If you’re at a friend’s house or a restaurant, it’s easy (and tempting) to cheat and grab a Coke instead of a low-carb beverage. If you understand why that’s such a bad idea – and if you know how quickly the Coke could destroy all the work you’ve put into your diet – it’s much easier to say “I’ll just have some water, thanks.”

So let’s get started. Here are the drinks to avoid when you’re eating (and drinking) low-carb.

Soft Drinks

Coke wasn’t just a handy example. Soda is just about the highest-carb drink you can choose because it’s loaded with added sugar – and sugar is nothing more than a sweet carbohydrate.

A 12-ounce can or bottle of Coke, Pepsi, Dr. Pepper or other cola contains around 40 grams of net carbs. (Net carbs is the important number; “total” carbs includes dietary fiber, which doesn’t really count because it can’t be digested.) Clear soda isn’t much better either; ginger ale and Sprite are in the high 30s. And root beer (45 net carbs) and orange soda (50 carbs) are even worse.

Let’s put that into perspective. A strict keto diet, and the first phase of Atkins, only allow you to consume about 20-25 grams of net carbs per day. That “cheat” can of Coke we mentioned earlier would be likely to knock you right out of ketosis, requiring you to start your diet all over again. On the Zone diet, you’d have to consume a ton of protein and fat to balance out a single soft drink – and to be honest, soft drinks are banned on the diet. As for the paleo diet, it’s easy: did cavemen drink soda? Neither should you.

Diet Soft Drinks

Ah, the perfect low-carb drink. In fact, many diet sodas these days have zero carbs. It says so, right in their name: Coke Zero, Pepsi Zero, Canada Dry Zero.

Hold your horses, friend. Yes, they are literally zero-carb and zero-calorie drinks. But that doesn’t make them a good choice on a low-carb diet.

There are a number of reasons why carb-free diet soda is still very bad for you. They’ve been tied to all sorts of health risks including diabetes, and study after study show that people who consume diet drinks are still likely to gain weight.

But there’s a bigger problem. Research shows that the artificial sweeteners in sugar-free drinks actually stimulate the brain’s reward center and increase cravings for sugar – meaning that soon after you drink a low-carb soda, you’re likely to be consuming real carbs and busting your diet.

Even though their name says they’re low-carb, these drinks should be avoided on low-carb diets.

Fruit Juice

Even though fruit is “good for you,” it’s very high in carbohydrates. So is its juice. The juices we love all contain high amounts of fructose, or fruit sugar. And as you know, sugar is basically just carbs.

Orange juice, apple juice, cranberry juice, pineapple juice – you name the juice, and an eight-ounce glass of it will contain between 25-35 net carbs. That makes them all “beverages non grata” on a low-carbohydrate diet. The only exceptions are lemon juice and lime juice; you probably wouldn’t think of downing a glass of either one, but that’s good news for the “best drinks” list that we’ll get to shortly.

Energy Drinks

Where do you think almost all of that energy comes from? That’s right, added sugar. Rockstar is the “worst” with a whopping 61 net grams of carbs per can. Red Bull’s on the low end, with 26 grams, but that’s still enough to potentially end a keto or first-stage Atkins diet. Energy shots are much, much worse. And even sports drinks like Gatorade contain nearly 20 grams of net carbs, nearly a full day’s worth just in a single bottle. Add electrolytes to a low-carb beverage instead.

Milk

Dairy milk contains lactose, and like fructose, it’s almost pure sugar. You can sneak a small glass of milk into a low-carb diet like keto, since it contains a more palatable 12 carbs; it’s just not a good idea since you’ll have to drastically limit any additional carb intake during the day. (And skim milk has just as many carbs as full-fat milk.)

The Zone diet isn’t quite as harsh on milk, since its carbs and proteins are “balanced,” but it can still only be consumed in moderation. Strict paleo bans milk because hunger-gatherers didn’t milk cows, but more “modern” followers still avoid it because of its high glycemic index.

Beer

A regular beer like Bud or Heineken contains 11 grams of net carbs, because it’s made from carb-heavy grains. Those beers definitely don’t qualify as low-carb beverages, but there’s good news on beer coming up.