The tastiest, most surprising foods you can eat on the keto diet

It's about 80% fat, with no carbs. Clearly a keto food.

This is the fattiest stuff that comes out of a cow's udders — the rich substance that rises to the top of the milk pail and has around 35% fat. Just make sure it's not sweetened with any added sugar.

Keto dieters have to be careful about eating too much of certain vegetables like carrots, but many greens, such as broccoli, kale, and spinach, can be great keto staples.

Walnuts are beloved by keto-ers because they contain a kind of omega-3 fatty acid called alpha-linolenic acid (ALA), one of two essential fatty acids that the body can't produce on its own. Almonds and Brazil nuts are also good choices for keto followers.

Still, not all nuts are keto-friendly: You'd have to eat less than a cup of cashews or pistachios to stay within the daily carb limit.

Nuts are a good snack for anyone who's not allergic, since eating them regularly can help keep your heart healthy and lower levels of "bad" LDL cholesterol in the body.

A half cup of fresh tomatoes has 4 grams of carbs, so keto-ers can't eat too much of the juicy fruit, but it's fine as a salad topping.

Besides, one of those four grams of carbohydrates is from fiber, and since all fiber essentially passes straight through your body, you don't have to factor it into your daily carb intake, according to keto rules. That means a half cup of tomatoes has a net carb intake of just 3 grams. That's well within the 20-50 gram daily limit.

Blackberries and raspberries have some of the lowest carb loads of any fruit, but contain a generous helping of antioxidants, which help keep the cells in your body healthy.

Much of the carb dose in these berries comes from fiber, which, again, is subtracted in keto calculations. So it's ok to nibble on them in moderation.

There's also another important keto-friendly berry...

Avocado is a weirdo in the fruit family. By weight, avocados have more than twice the protein of any other fleshy fruit. They also lower your "bad" LDL cholesterol while raising the good stuff, and contain healthy monounsaturated fat along with very low doses of saturated fat.

Zucchini can serve as a staple food for strict keto-ers. It is often used as a creative replacement for forbidden foods like pastas and crusts.

From chicken with the skin on to a fatty cut of pork chop, all meat is allowed on keto.

But there is still reason to eat meat in moderation. Proteins in meat are more dangerous for your heart health than those in nuts, and eating more meat can up your risk of death.

Plus, ketogenic diets are not designed to be protein-rich. Protein should only constitute about 15% of a day's calorie intake for a person to remain in optimal keto mode.

Bone broth — stock that's been cooked with meat or fish bones — has developed a devoted following in recent years as a collagen-rich food.

But don't be fooled into thinking that this savory sipping juice will help your nails or joints; gut experts say that's nonsense.

"Since we don't absorb collagen whole, the idea that eating collagen somehow promotes bone growth is just wishful thinking," William Percy, a pharmacologist and associate professor at the University of South Dakota, told NPR.

However, bone stock can be a decent source of protein-rich amino acids, which are crucial building blocks for your body's cells. The briney liquid will keep you well hydrated, too.

In cocoa beans, there's a hefty dose of butter: cocoa butter, that is. So dark chocolate can be a good keto treat it it doesn't have too much sugar and milk.

Only the really dark, low-sugar variety will do: a few squares of a bar that's around 80% cocoa (or higher) is a good choice.

Regular milk isn't great for keto followers since it contains sugar. But coconut milk — the fatty, creamy base of many curries and sauces — is rich, dairy-free, and keto-approved.

Nutritionists are quick to offer caveats about coconut, though, since it's terribly high in saturated fat, which isn't great for your health.

Karin Michel, a professor at the Harvard TH Chan School of Public Health recently pointed out that coconut oil is worse for your arteries than lard, and her colleague Walter Willett cautions that coconut oil should probably be used sparingly in your diet. The health benefits of unsaturated fats and oils like olive oil are more proven.

Fish offers generous helpings of healthy fat. It's a great source of omega-3 fatty acids, which can reduce the risk of abnormal heartbeat, slow the rate of heart-clogging plaque growth, reduce the amount of fat in your blood, and lower blood pressure a bit.

The American Heart Association recommends adults eat oily fish twice a week or more.

Eggs are also a good source of omega-3s, and the cholesterol in eggs probably won't have much of an effect on your blood cholesterol, so they're a safe and filling keto choice.

Urologists say it's vitally important to stay hydrated on the keto diet, especially if you're swapping out carbs for more meat.

But drinking lots of water every day is sound advice anyone hoping to maintain a healthy weight in the long run.

One 2016 study of more than 18,000 people in the US found that those who drank more water were consistently more satisfied and ate fewer calories on a daily basis. They also consumed lower amounts of sugar, fat, salt, and cholesterol than more dehydrated participants, no matter what kind of diet they chose.