Diets Are About More Than Food
Analyzing the effects of diets on health is notoriously difficult. People don’t always adhere to a diet, no matter how much they desire its promised health benefits. What’s more, when researchers ask people what they eat, they may not be entirely forthcoming. Analyzing the effects of a diet should be a long-term project and such studies are expensive. An accurate comparison of several diets would require a randomized clinical trial that moved participants into a lab setting for a long period to control and monitor their food intake. Obviously, that’s not practical. Therefore, studies are usually short term, retrospective, and rely on self-reporting by subjects.
A recent literature review examined 54 studies to compare weight loss and other health effects of the ketogenic (keto), paleolithic (paleo), and vegan diets. All the studies took place in the last five years and were published in peer-reviewed journals. The three diets have all been shown to aid weight loss but differ in other health effects. They vary significantly in what foods they prescribe or forbid, but can be characterized as follows:
- Paleo: First promoted by Walter Voegtlin in his book “The Stone Age Diet”, it supposedly mimics the diet of our paleolithic ancestors. This means that dairy, grains, legumes, refined sugar, and processed oils are out. Permitted foods include wild animals, lean meats, fish, eggs, vegetables, fruit, nuts, and seeds.
- Keto: The ketogenic diet was originally developed in the 1920’s to control seizures in epileptic children. It mimics fasting by putting the body in a state of ketosis. It’s extremely low in carbohydrates, high in fat, and moderate in protein. Typically, this results in food intake that is high in animal products.
- Vegan: Veganism dates to the 1800’s (and longer in some cultures) and is typically adopted for health or ethical reasons. It is entirely plant based, eliminating meat, fish, eggs, dairy, honey, and any other animal by-products. It’s typically low in saturated fat and high in vitamins and minerals.
The benefits and limitations of each diet were analyzed and quantified where possible. All three diets promoted weight loss. Those on the paleo diet lost up to 2.3 kg in three weeks, or .76 kg per week. Those adopting a vegan diet shed up to 1.2 kg in one week. And those eating a keto diet dropped an average of 13.7 kg in one year, or .26 kg per week. Beyond weight loss, each diet had a variety of impacts on health, some positive and some negative. Lower LDL (bad cholesterol), along with lower blood pressure, and lower blood glucose were common benefits of all three. The paleo diet could reduce inflammation in the body and lower the risk of colorectal cancer, but both the paleo and vegan diets could also cause calcium deficiency, and deficiencies in vitamins B6, B12 and iron may result from vegan eating. Keto appeared to increase the stiffening of the arteries, possibly leading to arteriosclerosis. Paleo and keto were both effective at increasing satiety (the feeling of fullness), while the opposite was true for the vegan diet. Cancer incidence was a particular bright spot for vegans, who experience a 14% lower cancer risk compared with non-vegans.
This study had several limitations that advocates should be aware of. Nursing students, who were by their own admission inexperienced researchers, conducted the study as part of their course work. Since paywalls prevented them from having complete access to all pertinent journals, the literature on which the review was based may be incomplete. The research project was only part of their curriculum and thus did not receive their full attention. That said, the professional mentors who supervised the students presumably required that the students meet certain quality criteria. Advocates might best use this study in conjunction with others to corroborate or challenge its findings.
To that end, two recent reports could be a starting place for further exploration. Every year, U.S. News and World Report (USN&WR) produces its list of best diets. For 2020, it ranked 35 diets on a range of criteria, and categorized them on effectiveness for specific medical conditions. To conduct this annual study, it assembled a panel of diet and nutrition professionals to scour medical journals, government reports and other sources for information about the various diets. They used the information to construct in-depth profiles of each eating plan and to analyze its benefits and risks.
In the most recent rankings, they ranked the vegan diet at #17. Like the nurses’ study, USN&WR identified nutritional deficiencies, along with effort required to maintain the diet, as downsides. The Paleo diet came in at #29. Cons included its complete elimination of grains and dairy. Eliminating entire food categories is often a red flag for diet plans. It’s also pricey since it emphasizes wild and grass-fed meats. Keto landed at #34, almost at the bottom of the rankings. It’s extreme nature and extremely low carb limits were its primary limitations.
The second study to consider is a meta-analysis of 121 randomized clinical trials published in the British Medical Journal (BMJ). While this study did not examine keto or vegan diets specifically, it did look at a generic low carb diet, which could be a stand-in for keto. Most interestingly, it found that, at 12 months, there was little difference in the effects on weight loss or cardiovascular health measures across any of the 12 named diets or two generic versions. As a result, the authors suggested that the key is for a person to find a diet they like and can stick with.
Well known diet rankings such as the USN&WR list, may help explain the popularity of various diet programs. Unfortunately, many of the most popular regimens, particularly the low carb plans, are heavy in animal products. But the BMJ study may offer animal advocates a significant opportunity. Diet choice is about more than medical considerations — ethics and environment are also important. Veg*n diets are unique in that they check both boxes. Not only are they good for physical well- being, they benefit animals and the planet as well. We shouldn’t gloss over the potential deficiencies of veg*n diets, but instead make sure we can address them. Since, enjoyability, affordability and practicality play large roles as well, advocates can work to lower these barriers. By offering veg*n food to sample and being ready with resources, we can add to our ranks. And while they may come for the food, we can create a welcoming community to encourage new veg*ns to stay for all the other reasons we cherish.