Do we get all your carbohydrates by eating food from plants? The Full Answer

January 3, 2026 •

3 min read

While plants are overwhelmingly the most common source of dietary carbohydrates, a significant misconception is that they are the only source. Certain animal products, such as milk and some shellfish, also contain carbs in the form of lactose and glycogen, respectively.

Quick Summary

Investigating whether all carbohydrates originate from plants reveals that animal products like milk and shellfish contain carbs, primarily lactose and glycogen. Additionally, the human body can produce its own glucose from other sources.

Key Points

Plant Sources Are Primary: Most carbohydrates come from plant foods like grains, fruits, vegetables, and legumes, in the form of starches, sugars, and fiber.
Animal Sources Exist: Some carbohydrates are derived from animal products, primarily lactose in milk and glycogen found in certain shellfish.
Glycogen is Negligible in Most Meats: The glycogen stored in animal muscles and liver is largely gone by the time it is consumed, so fresh meat contains virtually no carbohydrates.
The Body Can Produce Its Own Carbs: The human body can synthesize its own glucose from non-carbohydrate sources like protein and fat through a process called gluconeogenesis.
Not All Carbs Are Essential: Because the body can produce glucose internally, dietary carbohydrates are not considered essential nutrients for human survival, though they are a primary energy source.
Source Impacts Nutrition: The overall nutritional profile differs significantly between plant and animal carbohydrate sources, particularly concerning fiber content.

The Primary Source: Carbohydrates from Plants

Plants are indeed the most abundant and common source of dietary carbohydrates for humans. Through photosynthesis, plants produce sugars and starches which serve as their primary energy storage. The carbohydrates from plants are categorized into different types, providing various nutritional benefits.

Sugars, Starches, and Fiber

Sugars: Simple carbohydrates found naturally in fruits and some vegetables, including fructose and glucose. Honey, while produced by an animal, is derived from flower nectar and is also a source of simple sugars.
Starches: Complex carbohydrates found in staple plant foods like potatoes, corn, rice, and whole grains. Your body breaks down these starches into glucose for energy.
Fiber: A complex carbohydrate present in plant-based foods that the human body cannot fully digest. It is crucial for digestive health, blood sugar regulation, and satiety. Good sources include legumes, nuts, seeds, and the skins of fruits.

The Often Overlooked Animal Sources

While less significant in overall dietary intake for many people, animal-based foods do contain carbohydrates. The two most prominent forms are lactose and glycogen.

Lactose in Dairy Products

Milk and other dairy products contain lactose, a disaccharide often referred to as 'milk sugar'. Lactose is composed of glucose and galactose molecules. A cup of whole milk can contain around 12 grams of carbohydrates, all in the form of lactose. Many people have lactose intolerance, meaning they lack the enzyme needed to break down this milk sugar.

Glycogen in Meats

Glycogen is the primary storage form of carbohydrates in animals, analogous to starch in plants. It is stored primarily in the liver and muscles of animals. However, once an animal is slaughtered, its muscle glycogen is rapidly broken down and converted into lactic acid. This means fresh meat contains very little to no glycogen. There are some exceptions, notably shellfish like oysters and mussels, which can contain some detectable glycogen.

Gluconeogenesis: The Body's Internal Carb Production

Remarkably, humans and other animals do not require dietary carbohydrates to produce the glucose necessary for vital bodily functions. The body has a process called gluconeogenesis, which literally means 'creation of new sugar'. The liver, and to a lesser extent the kidneys, can synthesize glucose from non-carbohydrate precursors like glycerol from fats and certain amino acids from proteins. This is a critical metabolic pathway that ensures a steady supply of glucose for organs like the brain, which relies heavily on it.

Comparison of Plant and Animal Carbohydrate Sources


Feature	Plant-Based Carbohydrates	Animal-Based Carbohydrates
Primary Function	Energy storage (starch), structural support (fiber), sugars	Energy storage (glycogen), milk sugar (lactose)
Dominant Form	Complex (starch, fiber) and Simple (sugars)	Simple sugar (lactose), glycogen (trace)
Food Examples	Grains, legumes, vegetables, fruits	Milk, yogurt, some shellfish
Nutrient Profile	Often accompanied by fiber, vitamins, minerals	Often accompanied by protein and fat
Fiber Content	Can be very high in fiber	Contains no fiber

How This Affects Your Diet

Understanding the various sources of carbohydrates is essential for making informed dietary choices. Whether you follow a plant-based, omnivore, or low-carb diet, these facts are relevant:

Plant-Based Diets: Rely heavily on plant sources for carbs, fiber, vitamins, and minerals. Requires a wide variety of whole grains, legumes, fruits, and vegetables to ensure balanced nutrient intake.
Omnivore Diets: Include both plant and animal carbs. Dairy provides lactose, and while meat is not a significant carb source, other nutrients must be considered.
Low-Carb Diets: These diets leverage gluconeogenesis. The body's ability to produce glucose from fat and protein means that zero dietary carbohydrates are not necessary to survive. Focus shifts to protein and fat, with some carbohydrate intake from low-carb vegetables.

Conclusion

In conclusion, the assertion that we get all our carbohydrates from plant-based foods is a myth. While plants are the most significant dietary source of carbohydrates for most people, animal products like milk contain lactose and some shellfish retain glycogen. Furthermore, the human body is capable of producing its own glucose through gluconeogenesis, ensuring our energy needs are met even in the absence of dietary carbohydrates. A balanced understanding of these various sources is crucial for navigating dietary choices and understanding nutritional science. For additional detail on carbohydrate metabolism, one can explore scientific resources like the National Institutes of Health.

Frequently Asked Questions

Fresh, unprocessed meat contains virtually no carbohydrates because the glycogen stored in muscle tissue is converted to lactic acid after slaughter. Some shellfish, however, may contain a small amount of glycogen.

The main carbohydrate found in milk and dairy products is lactose, a type of sugar. Lactose is a disaccharide made of glucose and galactose.

Plant-based carbs exist as sugars, starches, and fiber, often accompanied by vitamins and minerals. Animal-based carbs are limited to lactose in milk and trace amounts of glycogen, and contain no fiber.

Glycogen is the carbohydrate storage form in animals and is primarily found in the liver and muscles. However, it is largely depleted in meat after slaughter.

Yes, through a metabolic process called gluconeogenesis, the human body can synthesize glucose from non-carbohydrate sources like protein and fat. This is why dietary carbs are not strictly essential.

Yes, some shellfish, including oysters and mussels, do contain glycogen, which is a carbohydrate stored in their tissues.

Honey is technically an animal product made by bees, but its sugars are derived from the nectar of flowers. Therefore, it is a carbohydrate source that originates from plants but is processed by an animal.