Diet (nutrition)

In the study of nutrition, a diet is defined as the total sum of food consumed by an organism.

While the word often implies a specific plan for health or weight management, it describes the actual intake of nutrients. Humans are biologically classified as omnivores, meaning they can eat both plants and animals. However, individual dietary choices are shaped by personal tastes, ethical beliefs, or cultural traditions. These choices can influence a person's quality of life, their overall health, and their longevity.

To function correctly, the body must undergo the processes of ingestion and absorption. This means taking in and utilizing specific chemical building blocks. Complete nutrition requires the intake of vitamins and minerals. It also requires essential amino acids, which are found in protein. Additionally, the body needs essential fatty acids from fat-containing foods. Finally, the body requires food energy, which it obtains from carbohydrates, proteins, and fats.

These components work together to maintain both mental and physical health.

Dietary patterns can be categorized by which food groups are included or excluded. Exclusionary diets are those where certain foods are avoided for health or personal reasons. Some people choose to avoid animal products entirely. This includes vegetarians, who avoid meat, and vegans, who avoid all animal products. There are also levels like pescetarianism, which includes fish, or flexitarianism. People may choose these paths for morality or to reduce their environmental impact. While these diets can be balanced, individuals may need to focus on specific nutrients like protein, iron, calcium, zinc, and vitamin B12.

Weight management is another major reason people change their dietary intake. This process is often called "dieting." It works by altering the body's energy balance. If a person consumes more calories than they burn, the body increases the amount of fat it stores. If they burn more calories than they consume, they may lose weight. This can help prevent diseases like heart disease and diabetes. However, rapid weight changes can be harmful to the body. Unintentional rapid weight change can also signal medical issues like cancer or thyroid problems.

Meat consumption is a significant part of many diets, especially in Western countries. Meat is categorized into red meat, such as beef, pork, and lamb, and white meat, such as chicken and turkey. Red meat provides energy, protein, vitamins, minerals, and fatty acids. However, meat can be processed through methods like smoking, salting, or canning. The International Agency for Research on Cancer (IARC) states that processed meat causes cancer, specifically colorectal cancer. They also list all red meat as a "probable" cause of cancer. Because of these risks, the World Cancer Research Fund suggests limiting red meat to three servings per week.

Dietary choices also have a massive impact on the global environment.

The entire food system, including transport, packaging, and processing, accounts for approximately one-quarter of all greenhouse gas emissions. Agriculture can also drive biodiversity loss, climate change, and soil degradation. To make more sustainable choices, people can eat more plant-based foods instead of meat or dairy. Choosing foods from sustainable farming practices can also reduce the impact on the Earth.

Finally, religion and culture play a central role in what people eat. For example, Judaism requires Kosher foods, and Islam requires Halal foods. In Hinduism, vegetarianism is considered the ideal way to eat. Jains follow even stricter rules; they are vegetarian and do not eat roots like carrots or potatoes. While Christianity has no official restrictions on animal types, many Christians choose the Mediterranean diet. These traditions show how diet is not just about biology, but also about identity and belief.