Plant-based Vegan vs. Ketogenic diets: the Pros and Cons

Updated: Jul 12, 2019

Plant Based Vegan vs. Ketogenic Diet: Pros and Cons

by Helen Ross February 28, 2019

Are you confused about which type of diet you should be following for optimal health? While there’s been an increase in the popularity of both vegan and ketogenic diets, it can be difficult to know which one is best for our long-term health. You wouldn’t be blamed for wondering which is healthiest, as it seems it’s a confusing topic with many advocates of both dietary extremes vouching for their benefits.

Statistics show a 600% increase in Americans following a vegan diet in the last 3 years, while in the U.K., there has been a 350% increase in people identifying as vegan over the last 10 years (1). While the keto craze is fast on its tracks, there does appear to be conflicting evidence suggesting pros and cons for both of these very different dietary approaches. It’s important to do your research and to look at the positives and negatives of following these diets.

Vegan Diet

Photo Credit: Ella Olsson

Ethical, moral, environmental, and health factors are often the reasons behind those opting to turn vegan. Research shows that, when followed correctly, a vegan diet may be effective for weight loss (2), it can reduce the risk of heart disease and diabetes (3,4), it may promote a reduction in symptoms of rheumatoid arthritis (5), and it may improve the diversity of beneficial gut bacteria of the microbiota (6).

Typically, a vegan diet is plant-based with no animal products at all, including meat, fish, poultry, dairy products, eggs, and even honey. Unfortunately, many unsuccessful vegan diets may result in nutrient deficiencies and suboptimal health. It is important to know what nutrients are missing in your vegan diet and to supplement accordingly in order to maintain good long-term health. While a plant-based diet is high in protective and antioxidant phytonutrients, fibre, and many other vitamins and minerals, we know that a vegan diet is lacking in vitamin B12. Vegan diets may also be prone to deficiencies in omega-3 long-chain fatty acids EPA and DHA, iron, zinc, calcium, vitamin K2, as well as vitamins A and D.

Photo Credit: Ella Olsson

In order to stay healthy, vegans need to ensure an adequate supply of protein and healthy fats. Some plants contain all of the essential amino acids, and these include quinoa, amaranth and soybeans Flaxseeds, hemp seeds, walnuts, and chia seeds are plant proteins that also contain short-chain ALA omega-3 fats, however they are not easily converted in the body to the long-chain fats required by the brain (EPA and DHA), and this conversion may only be around 10% efficient.

Furthermore, many other plant-based proteins are incomplete proteins. Amino acids are the building blocks of protein, and a complete protein has all of the essential amino acids necessary for human physiological requirements. There are 22 different amino acids required by the body to effectively function. Thirteen of these are made in the body, however the remaining nine must be obtained from diet; this why they are called essentialamino acids. Unfortunately, many plant-based protein sources are incomplete proteins, meaning that they need to be combined with other protein sources to make them complete proteins. Examples of this include combining beans and brown rice, and hummus and wholegrain bread. Because of the need to combine many plant-based protein sources, vegans often fall short of their protein requirements.

Humans also need a good supply of B vitamins, most of which can be found in vegetable sources, however B12 is mostly found in animal sources. B vitamins are necessary for energy production, cell division and metabolism, and B12 deficiency may lead to neurological disorders and megaloblastic anaemia. B12 deficient infants may be at risk of irreversible symptoms similar to autism (7). Plant sources of B12 include seaweed (nori in particular) and fermented soy beans (tempeh), and trace amounts can be found in other fermented foods such as kimchi. Edible mushrooms such as black trumpet, shiitake, chanterelles, and lion’s mane all contain vitamin B12, although it would be necessary to consume very large quantities to meet the daily requirement (8). It is usually recommended that vegans supplement their diet with B12 to ensure an adequate supply of this essential nutrient.

Ketogenic Diet

Ketosis is a state in which your body burns ketone bodies (fat) as opposed to carbohydrates (glucose) for energy. Ketogenic diets have been therapeutically used for the treatment of epilepsy for almost a century, and they became popular for weight-loss during the 1960’s and 70’s. More recent research has shown therapeutic potential for many other pathological conditions such as neurological diseases, diabetes, polycystic ovary syndrome, cancer, and a reduction in the risk of cardiovascular and respiratory disorders (9).

Prosciutto and Cheese Egg cups with Cracked Pepper and Green Onions

Typically, the ketogenic diet focuses on a high intake of fat. Fats are generally 70% – 80% of the diet, proteins are 10% – 20%, and only around 5% comes from carbohydrates. Studies show that eating a lower carbohydrate, higher fat diet is beneficial in preventing heart disease, achieving weight loss, and managing the risk of diabetes (10). The main benefit of a very low carbohydrate diet is weight loss, but this could also be seen as a disadvantage to those individuals not wanting to lose weight. Overall improved health, sporting performance, and endurance are among other advantages reported from this style of eating.

Photo Credit: Stefan Johnson

Risks of a ketogenic diet include possible kidney damage due to a very high protein intake (11), however true ketogenic diets should only be relatively high in protein and higher in fat. Another potential downside to this diet is a reduced intake of vegetables due to their carbohydrate content, which results in a low intake of fibre and some plant-based nutrients. It is well known that adequate dietary fibre is essential for the maintenance of a healthy gut microbiome and for reducing the risk of colorectal disease (12). This diet may also be difficult to adhere to long-term, as it may be very socially challenging and isolating. While the ketogenic diet shows clinical promise for a range of health conditions, further studies are needed to investigate the therapeutic effectiveness, long-term safety, and the potential mechanisms of action.

Photo Credit: Jennifer Pallian

The predecessors to the ketogenic diet were the Atkins and Paleo diets (a Paleolithic style of eating is the way our ancestors would have traditionally eaten). The latest diet trend gaining popularity is the carnivore diet which is a zero-carbohydrate plan with only animal products consumed; the exact opposite of a vegan diet. Many people claim health benefits such as reduced inflammation and increased energy, and while the scientific research is lacking, the current evidence is largely anecdotal.

Environmental Concerns

Vegans claim that meat eating is largely responsible for climate change due to bovine methane emissions. However, those arguing for a more carnivorous way of eating claim that environmental damage is the result of ruminant livestock’s confinement to feedlots which prevents proper recycling of waste nutrients back into the land. It is suggested that it is not the animals that are responsible for climate destruction, but rather the humans who are responsible for the farming methods that lead to an imbalanced methane cycle (13). Wild grazing ensures a healthier ecosystem for animals, humans, and the earth herself.

It’s important to note that meat production is not the sole cause of an increase in greenhouse gases as rice production creates a lot of methane as well. In fact, rice has one of the greatest carbon footprints of any plant (14).

Rice Terraces and farming village in Longsheng, Guangxi province, China.

As a registered nutritionist, my approach is to take principles from both styles of eating to combine the positive factors and minimize the less beneficial aspects. I consider this approach to be more sustainable in the long-term for maintaining a healthy body weight and for the prevention of chronic lifestyle diseases. Eating a diverse variety of organic plant foods ensures a healthy microbiota, which is necessary for a strong immune system. It also supplies us with plant-based phytonutrient antioxidants that are anti-inflammatory and anti-carcinogenic, supporting our overall good health. Choosing organic, grass-fed meat and wild fish ensures adequate quality protein sources and beneficial omega-3 fats, which are necessary for neurotransmitter balance. This is turn aids in maintaining healthy neurological function and cardiovascular health.

As you can see, there are pros and cons for both sides of the debate. By choosing sustainable and organic farming methods for our meat, fish, and vegetables, we can help to keep ourselves well-balanced and healthy while supporting the health of our planet at the same time.

What we do know for sure is that we are all genetically individual and unique, therefore there is no one-size-fits-all when it comes to diet. What works for one person may not necessarily work for the next. Working with a registered nutritional therapist can help you to personalize the diet that is right for you.

More Info:

The Well Life Lab is a nutrition clinic run by Helen Ross, a degree qualified Registered Nutritional Therapist and health coach. Helen has a special interest in digestive disorders, detoxification, and dietary education. She uses a Functional Medicine approach, which improves patient outcomes across a wide range of chronic health conditions.

Helen gained her BSc (Hons) Nutritional Science from the Centre for Nutrition Education and Lifestyle Management (CNELM) in the UK and is a registered member of the British Association for Nutrition and Lifestyle Medicine (BANT), and the Complementary and Natural Healthcare Council (CNHC).  Helen has a lifelong love of healthy food and firmly believes that food really is our medicine.

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2. G.M. et al., 2015. Comparative effectiveness of plant-based diets for weight loss: A randomized controlled trial of five different diets. Nutrition.

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4. Barnard, N.D. et al., 2006. A low-fat vegan diet improves glycemic control and cardiovascular risk factors in a randomized clinical trial in individuals with type 2 diabetes. Diabetes Care.McDougall, J. et al., 2002.

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10. Volek, J.S. et al., 2008. Dietary carbohydrate restriction induces a unique metabolic state positively affecting atherogenic dyslipidemia, fatty acid partitioning, and metabolic syndrome. Progress in Lipid Research.Martin WF, Armstrong LE, Rodriguez NR.

11. Dietary protein intake and renal function. Nutr Metab (Lond) 2005;2:25.Simpson, H.L. & Campbell, B.J., 2015.

12. Review article: Dietary fibre-microbiota interactions. Alimentary Pharmacology and Therapeutics, 42(2), pp.158–179.Lovell, T, 2019.


14. W, 2017.

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