Starches come from plants, which store them for future energy use. The plants richest in starches are grains, such as wheat, rice, corn, rye, millet, barley and oats. Tubers, such as potatoes, and legumes, such as beans, lentils and peas, also are common sources of starches.
Function
Plants store energy by synthesizing glucose molecules through photosynthesis to create polymers called starches. When humans eat starches, their digestive systems convert the starches back to glucose. Glucose is an important source of energy. Specifically, 1g of starch provides 4 calories of energy. Proteins provide 4 calories per gram as well. Fats provide 9 calories per gram.
Carbohydrates
In addition to carbohydrates in the form of starches, plant foods provide carbohydrates in the form of sugar and fiber. Your body converts sugar to glucose, as it does starches, but starches take longer to digest because they are more complex. Consequently, starches are called complex carbohydrates, and sugars are called simple carbohydrates. Fiber passes through your body undigested, but eating a sufficient amount is vital to ensure healthy digestion.
Use
Whole starches such as potatoes, rice and grains are mainstays of diets worldwide. Food industries also use the thickening capabilities of starches to improve the texture, appearance and taste of many foods, including sauces, cream soups, gravies, salad dressings, puddings and commercial baked goods. Essentially, starches form a temporary suspension when mixed with water--unlike salt and sugar, which dissolve in water to form a solution. After you heat starch granules mixed with water, the swelling of the starch granules due to water absorption becomes permanent, which is why starches are effective thickening agents.
Considerations
Vegetables that are high in starches, such as potatoes, also provide many calories. Consequently, if you're cutting back on your calorie intake, non-starchy vegetables might be more effective dietary choices. Non-starchy vegetables typically contain fewer carbohydrates but more water, making them low in calories but still filling. For example, tomatoes, broccoli, celery, cucumbers, mushrooms, water chestnuts, peppers and salad greens can satiate you without providing many calories.
