Juicing involves removing and drinking only the juice from fruit and vegetables. It's different than blending fruit to make a smoothie. Juice has far less fiber than whole fruit, but it’s a more concentrated form of other nutrients such as enzymes. Enzymes exist in all fruits and vegetables, but they are destroyed by high heat and other methods of processing. Drinking fresh fruit and/or vegetable juice ensures that you get active enzymes, although the method of juice extraction impacts the amount of enzymes you get.
Enzymes are catalysts for biochemical reactions, which means that they make it easier for compounds to interact with each other to make new substances or recycle old ones. Some enzymes that occur in your body are meant for digesting food. Some classes of enzymes break down protein, while others reduce complex sugars to simple sugars. Without enough metabolic enzymes, digestion is reduced, energy levels drop and health is compromised. Your body is able to produce enzymes, but getting them from fresh, raw foods is very helpful. Types of enzymes that are commonly found in fruit and vegetables include amylase, protease and lipase.
Amylase represents a category of digestive enzymes, which break down complex carbohydrates into glucose. Glucose is the simplest sugar and is often called “blood sugar” because it travels in the bloodstream and is used by all cells to produce energy. The salivary glands and pancreas make a few different types of amylase, although production can become dramatically reduced with aging and from a variety of disease conditions. Drinking fresh juice, especially from such good sources as wheatgrass and carrots, can help promote healthy carbohydrate metabolism.
Protease represents a category of digestive enzymes that break down foreign proteins into amino acids, which are the building blocks needed to construct protein in your body, such as muscle tissue and skin. Amino acids are also required for the synthesis of hormones, antibodies and other types of enzymes. Two well-known proteases are found in high concentrations in papaya and pineapple. Papayas contain papain, which is a powerful protease. People who live in papaya-growing regions commonly eat or drink the fruit after consuming meat to help with digestion. Pineapples contain bromelain, another powerful protease. Perhaps this explains why pineapple is often combined with chicken and used as a tenderizer for other meats.
Lipase is the third category of digestive enzymes. Lipases break down fat into smaller fatty acids, which are absorbed in the small intestine. Lipases are made in the pancreas and work with bile to metabolize fat, but the small amount found in fresh fruit and vegetable juice is helpful. Wheatgrass, sprouts, avocado and coconut contain more lipase than most other vegetables or fruit.
Varying Amounts of Enzymes
The type of juicing machine that you use affects the amount of active enzymes in the juice. Simple, mechanical press devices produce juice with the highest concentration of enzymes, while centrifugal-type electric devices produce the least, according to "Contemporary Nutrition: Functional Approach." The overall difference can be as high as 2.5 fold, or 250 percent more enzymes in mechanically pressed juice compared to fancy machines that seem to damage enzymes. Sometimes going old school can pay off.
- Encyclopedia of Human Nutrition; Benjamin Caballero et al.
- Textbook of Nutritional Medicine; Melvyn Werbach and Jeffery Moss
- Contemporary Nutrition: Functional Approach; Gordon M. Wardlaw et al.
Sirah Dubois is currently a PhD student in food science after having completed her master's degree in nutrition at the University of Alberta. She has worked in private practice as a dietitian in Edmonton, Canada and her nutrition-related articles have appeared in The Edmonton Journal newspaper.