Vegan, Paleo, Mediterranean, Carnivore, Keto, Plant-based, Flexitarian, etc. There’s a flood of different popular diets out there. Each one has a list of foods you should and shouldn’t eat. Each one also has a vocal group of followers saying their diet is the best. And many base their diets (rightly or wrongly) on what our ancestors ate. The debates become so heated they’re right up there with politics and religion.

But is there such thing as the ideal diet? Is one diet really better than any other? Or is it personal preference? And is there anything we can learn from what ancient humans truly ate?

Better in what way?

In order to know if one diet is better than another, we need to decide what better means. Does it mean better at preventing disease? Better for the environment? Or one that will make you live the longest? And the most common factor associated with any diet, is weight loss.

All of these outcomes are worthy of study. But when it comes to studying nutrition, it’s a messy process.

The most common method is the observational study. In these studies, people report their eating habits at a point in time and are followed for a number of years to see who develops disease or dies. However, these studies often don’t take into account changes in diet over the years. Plus, they use the unreliable method of self-report to determine food intake. Therefore, they only provide suggestions and not answers. Because of this, the nutrition debates can continue endlessly.

To truly determine which diet is the best, we need to do randomized studies. But these studies are incredibly expensive and hard to do. Only one diet has been studied to see its effect on preventing disease. This is the Mediterranean diet, a diet high in fruits and vegetables, with plant-based oils, fish and limited meat that reduced the chances of getting heart disease.

Comparing Diets

Many studies have compared various risk factors. When low fat and low carbohydrate diets were compared both improved blood pressure and cholesterol levels compared to a general diet. Studies also suggest the Paleo diet reduces blood pressure and cholesterol too. But when compared to the Mediterranean diet, the Paleo diet was no different in improving blood sugar metabolism. Similar findings have been reported when the Keto diet was also compared to the Mediterranean diet. In addition, the Keto diet increased LDL-cholesterol.

But it’s weight loss where diets have been compared the most. Many of these studies don’t use popular diet names and instead adjust the amount of carbohydrates, fats and protein. For example, an early study randomized participants to diets of high and low carbohydrate, high fat, and high protein. After two years, there was no difference in the amount of weight loss. A later study comparing diets of low fat to low carbohydrate also found no difference. These studies demonstrate that when it comes to weight loss, it’s not as important what you eat, but how much you eat.

Few studies have compared plant and animal-based studies to each other. When vegan, vegetarian, pesco-vegetarian, semi-vegetarian and omnivorous diets were compared, the vegan diet resulted in twice as much weight loss after six months than the others.

However, what may work in a controlled research setting may not be the same as in the real-world. When a group of 20 adults were housed in a clinic and given free access to either a plant-based low-fat diet or a low-carbohydrate keto-type diet, the plant-based diet resulted in a greater reduction of calories, suggesting a plant-based diet may be more filling.

How Our Ancestors Ate

Often entering into the debate is how our ancestors ate. Advocates of Paleo or Carnivore diets often state our cavepeople ancestors ate meat for hundreds of thousands of years. And therefore, conclude humans are meant to eat meat. On the other side, plant-based advocates say we’ve descended from apes, whose diets are almost all plants.

But let’s not forget, the average lifespan of a caveperson ranged from 25 to 40 years. Less than half of what it is today. While there are many reasons for this shortened lifespan, one can’t ignore a lack of nutrition may be involved.

The earliest evidence of ancient humans eating meat comes from more than 2 million years ago. And it’s believed this meat was scavenged from dead animals. It wasn’t until 500,000 years ago the first evidence of hunting tools appeared, which were made of stone. While this opened the door to hunting, chasing down animals with primitive tools wasn’t that easy.

Hunter and Gatherer Communities of Today

Looking at the diets of the few remaining hunter and gatherer communities around the world can tell us a lot about what our ancestors ate. Apart from the Inuit, whose diet consists of almost exclusively of meat, most hunter-gatherer communities are more gatherer than hunter.

The Tsimane living in Bolivia have a diet with over 60% of calories from plants, with 30% from animals (predominantly fish). Similarly, the Hadza in Tanzania have a predominantly plant diet. And while both populations eat meat, their intake fluctuates as the hunting season changes. During the wet season in Tanzania, meat may comprise <15% of the Hadza diet. This is despite using equipment such as bows and arrows, and guns (Tsimane only). It’s likely to have been much harder for ancient humans to get meat using only stone tools.

These diets (and other aspects of their lifestyle) appear to ward of many diseases. The Tsimane have the lowest levels of heart disease in the world. And their brains exhibit slower ageing. The Hadza also have low levels of risk factors for heart disease.

In contrast, the Inuit have a high-fat diet consisting of almost entirely of meat (caribou, birds, marine mammals and fish). Traditionally, Inuit populations have been believed to have lower rates of diabetes and heart disease. What may be fine for Inuit people may not be fine for the rest of us. It’s believed a genetic adaptation in Greenland Inuit may help them process their high-fat diet. An adaptation that’s extremely rare in other populations.

Is there really a best diet?

When 33 health and nutrition experts were asked to rate 24 different diets based on health, the Mediterranean diet came first. This was followed by other diets which were predominantly plant-based with fish as the main animal source. The Paleo and Keto diet were ranked 19^th and 20^th, respectively.

One thing common to all of these diets, is not what they have, but what they don’t have. None of these diets include the consumption of high and ultra-high processed foods. Making a switch from processed foods to less processed foods, is always a healthier choice. And keep in mind, for a diet pattern to work for you, it needs to be something that fits in with you life. Diets that are too restrictive are usually harder to maintain.

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