Carbohydrate-rich foods naturally contain varying levels of glucose. Carbohydrates are found in fruits, vegetables, milk and milk products, grains, seeds and legumes. The body breaks down these foods and converts them into glucose for energy. Every cell uses glucose and it's the brain's only energy source.
Carbohydrates are broken down at various speeds, depending on their complexity. Simple carbohydrates, like fructose, a sugar found in fruits, rapidly enters the bloodstream as glucose for a quick source of energy. Complex carbohydrates, which contain a lot of fiber and complex starches, like barley or beans, enter the bloodstream as glucose more slowly. They provide a more sustained source of energy to the body.
Nutritionally speaking, complex carbohydrates make healthier food choices. They tend to be nutrient dense, containing important vitamins and minerals in addition to complex sugars. They also contain fiber, the part of a plant that remains undigested and passes through the body largely intact. There are two types of fiber: soluble and insoluble. Soluble fiber dissolves in water, and helps lower blood glucose and cholesterol levels. It's found in foods like beans, apples, oatmeal and lentils. Insoluble fiber adds bulk to the diet. Its laxative effect promotes regularity and helps prevent constipation. It's found in foods like brown rice, carrots and whole grain breads.