Learn more about the similarities and differences between these two diets. Plus, find out more about the health benefits and cons of each diet plan, which foods are allowed and off limits and how decide what's right for you.

Lainey Younkin, M.S., R.D., L.D.N.
November 24, 2020
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One diet is meat-heavy while the other eliminates all animal products. Are there any similarities between keto and vegan? Actually, yes. For starters, if you're looking to try either, it will require research, planning and probably working with a professional like a dietitian who can help you prevent nutrient deficiencies. Keep reading to find out the important questions to ask your dietitian—and yourself—if you're considering going vegan (that vegan lentil soup, pictured above, may be for you) or keto (learn more about a vegetarian keto diet and what foods you can eat).

What is a vegan diet and why do people follow it?

A vegan diet excludes all animal products—including meat, seafood, poultry, eggs and dairy products—and any foods with ingredients from an animal, like gelatin. Some vegans avoid honey too.

People choose to go vegan for environmental reasons, animal welfare and for the nutritional benefits of following a plant-based diet. According to the Humane Society International, eating a meat-free diet can cut our water footprint in half. Producing meat also creates more CO2 emissions and pollution than growing plants. And there's no denying that eating a plant-based diet is linked to longer life and reduced risk of chronic diseases like heart disease and cancer. Research shows that plant-based diets are low-cost, effective interventions for lowering body mass index, blood pressure, blood sugar (A1c) and cholesterol.

What is a keto diet?

https://www.eatingwell.com/recipe/276395/slow-cooker-citrus-salmon-with-melted-leeks/attachment/7851257/

The keto (ketogenic) diet is a high-fat, moderate-protein, very-low-carbohydrate diet initially created in the 1920s for the treatment of epilepsy. Today, the keto diet has become a popular weight loss diet. When carbohydrate intake is extremely low, like on the keto diet, and the body's stores of glucose (glycogen) run out, the body begins to breakdown fat in the form of ketone bodies to provide energy. This is called ketosis and as long as carbohydrate intake is very low, and ketones are being used for fuel, the body will stay in this state of metabolism. (Here's a complete list of what you can and can't eat on a keto diet.)

Key differences between vegan and keto

A vegan diet eliminates all animal products, while the keto diet strictly limits carbohydrates. There are no restrictions on calories or macronutrients on a vegan diet.

The keto diet restricts carbohydrates in order to put your body into ketosis and convert the body's normal metabolism of glucose for energy to the metabolism of ketones for energy.

There are technically no foods or food groups eliminated on keto. As long as you stick to about 80 percent of daily calories from fat, 15-20 percent from protein and less than 5 percent from carbohydrates, any foods are allowed.

While a vegan diet is usually chosen for nutritional, ethical, religious and/or environmental reasons, the ketogenic diet is chosen for treatment of seizures, or more commonly nowadays, for weight loss.

Key similarities between vegan and keto

Both diets emphasize eating whole foods as much as possible, especially vegetables. But on keto you have to be careful with starchy vegetables like potatoes and corn, which could drive carb intake too high, depending on what else you're consuming that day.

Healthy fats are encouraged on both diets. The vegan diet recommends healthy fats to support overall health and wellbeing, while fat is the cornerstone of the keto diet, in order to keep the body in ketosis. However, because fat intake is so high on keto, many end up eating a lot of meat, cheese, butter and eggs—foods that are eliminated on a vegan diet. Plant-based sources of fat like olive oil, avocados, nuts and seeds are allowed on both diets.

Vegan and keto both encourage protein intake, but most keto dieters get protein from meat and dairy, while vegans may have a harder time getting enough protein in their diets, since plant-based proteins usually contain less protein per serving than animal products. The best protein sources for vegans are beans, legumes, tofu, whole grains, nuts and seeds. (Here's a complete list of the top 10 vegan proteins.)

Is either diet healthy?

The most important question to ask when deciding what type of diet to follow is: Is this sustainable for me? Can I keep eating like this for the long-term?

With the keto diet especially, you may see rapid weight loss while following it, but if you can't sustain following the diet, you'll most likely gain the weight back once you stop the diet. It also depends on the foods choices you're making. A double bacon cheeseburger (hold the bun) and a salmon dinner with cucumber avocado salad are both keto dinners, but the salmon plate would provide you with more beneficial nutrients.

Even if you don't follow it forever, any period of eating a plant-based or vegan diet, will most likely deliver benefits in terms of reduced risk for chronic diseases and healthy cholesterol, blood sugar and blood pressure levels. You can also feel good about doing your part to help the environment. Some people choose to go partially vegan, meaning they may eat mostly vegan at home but not when eating outside the home, where it can be difficult to be fully vegan when you aren't doing the cooking. You can also eat mostly healthy plant-based foods, like fruits, vegetables and whole grains or consume mostly refined grains and vegan cookies.

Vegan pros and cons

Vegan diets are typically high in fiber, magnesium, folic acid, vitamins C and E, iron and antioxidants and phytochemicals, which fight off free radicals and decrease inflammation (here are some of the best inflammation-fighting foods to eat). Vegans generally consume fewer calories, less saturated fat and no cholesterol, since cholesterol is only found in animal products.

Because vegans only consume plants, they tend to have a higher intake of fruits and vegetables, which is associated with lower cholesterol, lower incidence of stroke and lower risk of mortality from stroke and heart disease. Vegans have higher consumption of whole grains, soy and nuts, which help keep your heart healthy.

However there are some "junk food vegans," who eat mostly processed vegan foods and not enough whole foods. They do not reap the same benefits of vegans who consume mostly whole foods.

Vegans are at risk for some nutritional deficiencies. Iron is not as readily absorbed from plants as it is from meat, but pairing foods with iron with foods high in vitamin C can increase absorption so throw some peppers on that spinach salad.

Other crucial nutrients that vegans lack are omega-3s - specifically EPA and DHA, the type found in fatty fish like salmon. EPA and DHA are important for heart, eye and brain health and must be consumed, as the body does not make them. Vegans can get ALA, another omega-3 from walnuts and chia seeds (these top vegan omega-3 foods can help you get your fill).

Vitamin D intake is a concern for some, but spending time in the sun each day can help. Some mushrooms, which are exposed to UV light, are high in vitamin D too.

Many vegans may need to supplement vitamin B12, which is mostly found in animal products and is essential for keeping nerves and blood cells functioning properly. Nutritional yeast is a vegan favorite, is high in B12 and can be sprinkled on popcorn or salads. Vegans should also monitor protein intake and aim to pair complementary sources like beans and grains.

Keto pros and cons

The keto diet shows promising results for reducing seizures in pediatric patients, and in neurological disorders such as epilepsy, demenetia, ALS, traumatic brain injury, acne, cancers and metabolic disorders.

It can also lead to rapid weight loss—at least in the short-term, but weight loss from a ketogenic diet is often not sustained long-term. Emerging research shows that a keto diet may improve glucose control, insulin sensitivity, blood pressure, cholesterol and triglyceride levels and could be useful for those with type 2 diabetes (learn more about the ketogenic diet and if it's right when you have diabetes).

On the flip side, LDL ("bad") cholesterol could increase on a keto diet, due to high consumption of animal products like meat, cheese and butter. The keto diet is difficult to follow long-term and long-term studies are lacking at this point. Potential long-term concerns include the buildup of fat in the liver (hepatic steatosis), kidney stones and vitamin and mineral deficiencies. Plus, the keto diet is lacking in many plant-based foods associated with longevity and reduced risk of cancer like fruits, vegetables, whole grains and beans. If people primarily eat red and processed meats, they could in fact be increasing their risk for cancer.

Finally, keto has some less than desirable short-term side effects, often called "keto flu." Keto-goers report nausea, vomiting, headache, fatigue, dizziness, insomnia, difficulty in exercise tolerance and constipation. Ensuring adequate fluid and electrolyte intake can help counter some of these symptoms.

Things to decide before going vegan or keto:

  • Before deciding to do any diet, ask yourself why you are going on the diet. Is it for nutritional, environmental or ethical reasons? Are you trying to lose weight or improve a health condition like diabetes or cholesterol? This can help guide you toward the diet best suited for you and your goals.
  • Check with your doctor to see if it is healthy for you given your medical history and nutrient status to start eating vegan or keto.
  • If choosing a diet for weight loss, ask yourself, "What plans have I tried in the past, and why did they fail?" Were the food choices too restrictive? Did you lose motivation? Were you always hungry? Understanding what works and does not work for you and talking to your health care providers, including your physician and a dietitian, to determine which diet is best for you based on your goals, will be most successful.
  • Review your current lifestyle and how much time you have to devote to food preparation or calculating macronutrients like carbs in your diet. Do you eat outside the home a lot? Does your schedule allow for food preparation? It's not impossible to do vegan or keto while traveling or eating out, but (as with most diets) preparation and planning are key—as is working with a professional who can guide you.

Bottom line

Vegan diets eliminate all animal products for either nutritional, environmental or ethical reasons. The keto diet keeps carbohydrate intake low (less than 5% of daily calories) but doesn't technically limit food groups, as long as they fit within your carb range. Before deciding on either, determine why you want to do it and if it fits within your lifestyle. There are short and long-term benefits of going vegan, including reduced risk of chronic diseases, not to mention the positive impact on the environment. Keto is effective for treatment of epilepsy in kids and leads to rapid weight loss. However, long-term studies are lacking on those who follow keto long-term. Some concerns include high cholesterol, not eating enough fruits and vegetables, buildup of fat in the liver and weight regain, due to the difficulty of following keto over many months and years. We always recommend checking with your doctor and a dietitian before choosing either diet.

Lainey Younkin, MS, RD, LDN is a Boston-based weight loss dietitian who helps women ditch diets and change habits for a healthy lifestyle that lasts. She helps frustrated women, who feel like they eat healthy and workout but still can't lose weight, work smarter not harder to lose weight and keep it off. Follow along on Instagram at @weight.loss.dietitian.