Barley grass juice is a liquid derived from barley grass, a young cereal grass. Young barley grass is either picked fresh and processed in a juice-making machine or dried and powdered to make dietary supplements. Barley grass offers a high density of nutrients, and may provide many nutritional and health benefits.

The first cereal grain cultivated by humans, barley grass was included in the diets of Ancient Middle Eastern and Asian cultures. The barley grain is used to make beer, and it is eaten in breads, soups, salads, and many other dishes. Young barley grass is more like a vegetable than a grain, however, and is considered similar to leafy green vegetables.

Barley grass juice contains antioxidants, enzymes, and other phytochemicals that may help reduce damage from free radicals. Barley grass also contains amounts of beta carotene, folic acid, calcium, and many B vitamins, as well as vitamins C and E. It is also high in iron and certain other minerals.

One of the main elements in barley grass juice that many people find beneficial is its high chlorophyll levels. Chlorophyll is believed to help stimulate tissue growth and maintain red blood cells. There is some suggestion that chlorophyll may also help patients with cancer, but not definitive studies have yet been performed. Barley grass juice may also help to promote healthy cholesterol levels. It can also be used as a diet supplement for those trying to lose weight.

Barley grass juice, along with the related wheatgrass juice, is often served in juice bars and health food stores. It is said to have a distinctive taste which is not appreciated by all people, so it is often mixed with wheatgrass or other juices. Although fresh juice is thought to provide the most benefits, many users find the convenience of powered supplements more appealing.

The powder form of barley grass is derived from dried young leaves of the barley plant. It is easily digested by the body when mixed with liquid to create barley grass juice, so the nutrients can be used quickly. When making the juice at home, it is recommended that the user mix the powder with cold or room temperature water, not hot, so as to avoid breaking down the vitamins and other nutrients.