Daily Apple

An Omnivore or Herbivore Diet: Which is Better?

Welcome to the Daily Apple, a new page on Your Health Forum that addresses questions that you may be curious about and are likely to come up in clinic visits. The goal is to answer questions in a useful format to allow quick learning and application in an article about 500 words or less.

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Which diet provides the most significant benefit?

While there are no “one-size-fits-all” diets, there are certainly better options to consider. There is much debate on which is the ideal dietary pattern for humans: to be an omnivore, or someone who eats both meat and vegetables, or to be an herbivore, or someone who eats a plant-based diet.

When deciding on which of these diets is best, one only needs to look at which foods are best managed by the body. Here ae a few ways of looking at the optimal diet.


The shape of an animal’s teeth predicts its diet. In humans, the front teeth, the canines, and incisors pierce and tear food apart. The premolars and the molars grind and chew on food. While human dentition may suggest omnivores, scientists and anthropologists appreciate the tame size of human canines and incisors compared to carnivores.

Maybe this places humans as mostly herbivores and opportunistic carnivores. The large human brain enabled us to develop skills like hunting, cooking, and tool-making to eat meat.

While I am mentioning teeth, a diet high in refined carbohydrates, non-plant proteins, and saturated fatty acid all have an effect increasing periodontal inflammation; a healthy diet had anti-inflammatory effects.

Diet and Microbiome “Behavior”

It has become increasingly clear that the state of one’s microbiome reflects on their health. In general, a more diverse microbial environment portends a healthier outlook on the human. The variety comes from a similarly diverse diet, high in vegetables and fiber. The intake of highly processed foods contributes to less microbial diversity. Here is a YHF article on the microbiome.

A touted benefit of an abundant microbiome is the fermentation of dietary fiber and its byproducts, short-chain fatty acids (SCFAs). The production of SCFAs, e.g., butyrate, acetate, and propionate, is associated with decreased colon inflammation, protection from colon cancer, and decreased systemic inflammation. These fatty acids can also beneficially affect gut hormone production and immune cells.

Not only does microbiome diversity protect from chronic disease conditions like metabolic syndrome, diabetes, and obesity, a less diverse environment has also been linked to anxiety and stress (Johnson, K).

What we eat also feeds our bacteria. A study compared wild versus captive colobine monkeys and found differences in their gut microbiota. Captive monkeys receive more significant amounts of fruit and cornmeal; their microbiome reflected bacteria more capable of digesting these sources, Prevotella and Bacteroides. Instead, monkeys in the wild had a different microbiome, including Lanchnospiraceae and Ruminococcaceae, to digest diverse plants. These species produce short-chain fatty acids.

What about meat and the microbiome? A molecule known as trimethylamine-N-oxide (TMAO) is produced by the microbiome in response to L-carnitine, present in red meat. TMAO is a toxic product that is associated with atherosclerosis and colon cancer.

Looking at what creates a diverse microbiome, a plant-based diet high in indigestible fiber is ideal.

The microbiome is a strong predictor of diet.

Fiber Density and Insulin Levels

Fiber comes from the plant cell wall. Processed foods are devoid of fiber. The processing steps take natural food, break it down, and concentrate it. What is left is a high sugar food with little to no fiber (See images below). Sadly, the average American eats an estimated 60% of their diet as ultra-high processed foods daily.

Another point to consider is density. A high-processed diet is a concentrated, dry food of minimal benefit. If you take a cookie and compare it to how much broccoli would achieve the same calories, you would find yourself eating much more broccoli. Additionally, the plant-based foods are replete in fiber, vitamins, and minerals.

Insulin is a hormone secreted by beta islet cells in the pancreas to metabolize glucose. The pancreas responds to the glucose level in the enterohepatic circulation. It secretes insulin to reduce levels of glucose in the bloodstream, as a way to metabolize it. A plant-based diet does not elicit the same insulin response; fiber is protective against rapid glucose absorption.

What about meat intake and insulin levels? While meat is protein, the intake of regular meat led to an increase in insulin resistance in nondiabetic women. However, this relationship was not found with very lean meat.

So when comparing highly processed versus plant-based diets, plant-based diets are protective from chronic diseases.

gingerbread cookie
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plant-based diet means more food

Centenarian Studies

One strategy to determine the ideal human diet is to look at what diet is associated with longevity. Starting with the Blue Zones, which are hot spots for longevity, we can discover the typical foods eaten by centenarians, those older than 100 years. These populations consume as much as 95% of their diet as plant-based, whole foods, high in legumes, fruits, vegetables, whole grains, and nuts. Additionally, leafy vegetables have garnered a reputation for slowing cognitive decline with aging.

The Blue Zone Locations

  • Okinawa, Japan
  • Ikaria, Greece
  • Adventists of Loma Linda, California
  • Nicoya Peninsula (Costa Rica)
  • Ogliastra, Sardinia

Other centenarian studies support daily vegetable intake in this population (89%). The Blue Zone information endorses a plant-based diet as the best choice for longevity.

Does primarily plant-based mean vegetarian or vegan? No. The effective term is “primarily plant-based.” While meat is on the menu most days in the usual American household, the individuals in the blue zone locations eat meat much less frequently – a few times a week or month – and it is locally sourced and free range.


A clear theme emerges, whether it is the shape of human teeth, the microbiome, the structure of food, hormone response, or centenarian studies. First of all, we are what we eat. Next, a diet that is primarily plant-based gives the greatest gift of health and longevity.

In conclusion, humans are herbivores with a propensity towards being opportunistic carnivores.

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