Every food you eat, from a strawberry to a steak, is built from the same handful of chemical ingredients: water, carbon-based molecules, and a small but critical set of minerals. The proportions shift dramatically depending on the food, but the raw building blocks are remarkably consistent across everything in your kitchen.
The Elements Behind Every Bite
At the most basic level, food is made of atoms. Just four chemical elements, oxygen, carbon, hydrogen, and nitrogen, account for roughly 96% of the mass in living things. That applies to the plants and animals on your plate just as much as it applies to your own body. These four elements combine in different arrangements to form every major component of food: sugars, fats, proteins, and the water that holds it all together. The remaining few percent comes from minerals like calcium, potassium, phosphorus, sodium, and iron, plus trace amounts of elements like zinc, copper, and iodine.
Water: The Largest Ingredient
Most whole foods are mostly water. Leafy greens like iceberg lettuce and romaine are around 95 to 96% water by weight. Spinach and cabbage sit at about 92%. Fruits follow a similar pattern, with watermelon, strawberries, and peaches all above 85%. Even foods that don’t feel wet contain significant water: raw chicken breast is roughly 65% water, and a cooked egg is about 75%.
Dry foods are the exception. Grains like rice and oats, nuts, crackers, and dried beans have had most of their water removed either naturally or through processing, bringing their water content down to around 5 to 15%. This is a big reason dry foods last longer on the shelf. Bacteria need moisture to grow, so removing water is one of the oldest preservation methods.
The Three Macronutrients
Once you subtract the water, most of what remains in food falls into three categories: carbohydrates, proteins, and fats. These are the molecules your body breaks down for energy and raw materials.
Carbohydrates are chains of sugar molecules. Simple carbohydrates, like the fructose in fruit or the sucrose in table sugar, are short chains that your body absorbs quickly. Complex carbohydrates, found in potatoes, rice, and bread, are long strings of sugars that take more time to break apart. Your body converts all of them into simple sugars during digestion. Carbohydrates provide about 4 calories per gram.
Proteins are built from amino acids, small molecules strung together in specific sequences. Your body breaks dietary protein back down into these individual amino acids and then reassembles them into whatever proteins it needs, from muscle tissue to enzymes. Meat, eggs, beans, and nuts are all protein-rich foods. Protein also provides about 4 calories per gram.
Fats are made of fatty acids attached to a molecule called glycerol. Fat is the most energy-dense macronutrient at 9 calories per gram, more than double what carbohydrates or protein deliver. Oils, butter, nuts, avocados, and the marbling in meat are all high in fat. Your body uses fats for long-term energy storage, insulation, and building cell membranes.
Fiber: The Carbohydrate You Can’t Digest
Fiber is technically a carbohydrate, but your body can’t break it down the way it breaks down starches and sugars. It passes through your digestive system largely intact, and that’s exactly what makes it useful. It comes in two forms.
Soluble fiber dissolves in water and forms a gel-like substance during digestion. It’s especially abundant in oats, barley, legumes, and berries. Insoluble fiber doesn’t dissolve in water at all. It adds bulk and helps move food through your intestines. Wheat bran, brown rice, celery, and whole grains are rich sources. Most high-fiber foods contain both types in different ratios.
Vitamins and Minerals
Vitamins and minerals make up a tiny fraction of food by weight, but they’re essential for keeping your body running. Vitamins are organic compounds, meaning they’re carbon-based molecules produced by living things. They split into two groups: fat-soluble vitamins (A, D, E, and K) that dissolve in fat and can accumulate in your body over time, and water-soluble vitamins (C and the B vitamins) that dissolve in water and need to be replenished regularly since your body doesn’t store them well.
Minerals are inorganic elements pulled from soil and water. Plants absorb them through their roots, and animals get them by eating plants or other animals. You’re probably familiar with calcium, sodium, and potassium, but your body also needs trace minerals like copper, iodine, and zinc in very small amounts. A single serving of spinach or a handful of almonds delivers dozens of these micronutrients at once, which is part of why whole foods are nutritionally different from supplements.
Phytochemicals: Color, Flavor, and More
Plants produce thousands of compounds beyond basic nutrients. These phytochemicals are bioactive molecules that serve the plant’s own purposes, like attracting pollinators, repelling insects, or protecting against UV damage, but they also affect your body when you eat them.
Carotenoids are the pigments responsible for the bright yellow, orange, and red colors in carrots, tomatoes, and peppers. Polyphenols are a broad category of compounds found in berries, tea, coffee, and dark chocolate. Other groups include phytosterols, saponins, and isoprenoids. These aren’t classified as essential nutrients because you won’t develop a deficiency disease without them, but research has linked their consumption to lower risks of cardiovascular disease, diabetes, and certain cancers. They’re a major reason why “eat more fruits and vegetables” remains such consistent dietary advice.
DNA in Your Dinner
Every whole food that was once alive, which is nearly all of them, contains the genetic material of the original organism. DNA molecules are present in large numbers in all raw and unprocessed food. When you eat a chicken breast, you’re eating chicken DNA. When you eat a tomato, you’re eating tomato DNA. Cooking and processing degrade much of it, breaking long strands into fragments, but traces remain. Your digestive system breaks most dietary DNA down into its component parts and recycles them, the same way it breaks down proteins and carbohydrates.
What Processed Foods Add
When food is manufactured rather than grown, additional substances enter the picture. Food additives are ingredients not naturally found in the food itself, added to change texture, extend shelf life, boost flavor, or improve appearance. They fall into a few functional categories.
Thickeners and emulsifiers, like xanthan gum, guar gum, and soy lecithin, create smooth, stable textures that keep ingredients from separating. You’ll find them in salad dressings, ice cream, and plant-based milks. Preservatives like sodium benzoate and citric acid slow bacterial growth and prevent spoilage. Flavor enhancers intensify taste without adding significant amounts of any macronutrient. Maltodextrin, a common additive derived from starch, improves both texture and flavor in everything from protein powders to snack chips.
A packaged food might contain dozens of these additives alongside its whole-food ingredients. Reading a nutrition label on a minimally processed food like plain oatmeal reveals a short list: oats. Reading the label on a flavored instant oatmeal reveals sugars, thickeners, flavorings, and preservatives layered on top of the same base ingredient. The oats haven’t changed. The additions are what make the ingredient list longer.