You can taste the sweetness of maltose if you hold a starchy food in your mouth for a minute or so. Try this with a simple food like a soda cracker. Starch is not sweet, but as the starch in the cracker begins to break down with the action of salivary amylase, maltose will form, and you'll taste the sweetness!
Sucrose is made of a glucose molecule bonded to a fructose molecule. It's made by plants for the same reason as fructose -- to attract animals to eat it and thereby spread the seeds. Sucrose is naturally-occurring in fruits and vegetables.
Most fruits and vegetables contain a mixture of glucose, fructose, and sucrose. But humans have also figured out how to concentrate the sucrose in plants usually sugar cane or sugar beets to make refined table sugar.
We also find sucrose in maple syrup and honey. The sucrose found in sweet potato is chemically identical to the sucrose found in table sugar. Likewise, the fructose found in a fig is chemically identical to the fructose found in high fructose corn syrup. As we'll discuss more later, what's different is the package the sugars come in. When you eat a sweet potato or a fig, you also get lots of fiber, vitamins, and minerals in that package, whereas sugar and high fructose corn syrup only provide sugar, nothing else.
It's not a bad thing to eat sugar. After all, it's a vital fuel for our brain and nervous system. But paying attention to the package it comes in can help us make good overall choices for health. Lactose is made of a glucose molecule bonded to a galactose molecule. It is sometimes called "milk sugar" as it is found in dairy products like milk, yogurt, and cheese. These are the only animal foods that have significant amounts of carbohydrate.
Most of our carbohydrates come from plant foods. Complex carbohydrates are also called polysaccharides, because they contain many sugars. The prefix "poly-" means "many. All three of these polysaccharides are made up of many glucose molecules bonded together, but they differ in their structure and the type of bonds. Starch is made up of long chains of glucose. If these chains are straight, they're called amylose; if they're branched, they're called amylopectin. Here is an amylose segment containing 3 glucose units.
The next figure shows an amylopectin segment containing 4 glucose units. The chemical structure is represented differently, but can you spot the place where it branches? Using our green hexagon to represent glucose, you can picture starch as something like this:. Humans have digestive enzymes to break down both types of starch, which we'll discuss on the next page. Starch is the storage form of carbohydrate in plants.
Plants make starch in order to store glucose. For example, starch is in seeds to give the seedling energy to sprout, and we eat those seeds in the form of grains, legumes soybeans, lentils, pinto and kidney beans, for example , nuts, and seeds. Starch is also stored in roots and tubers to provide stored energy for the plant to grow and reproduce, and we eat these in the form of potatoes, sweet potatoes, carrots, beets, and turnips.
When we eat plant foods with starch, we can break it down into glucose to provide fuel for our body's cells. In addition, starch from whole plant foods comes packaged with other valuable nutrients.
We also find refined starch - such as corn starch - as an ingredient in many processed foods, because it serves as a good thickener.
Glycogen is structurally similar to amylopectin, but it's the storage form of carbohydrate in animals , humans included. It's made up of highly branched chains of glucose, and it's stored in the liver and skeletal muscle.
Sucrose or table sugar, for instance, is a disaccharide of glucose bonded to fructose. Potatoes, corn, and other starches contain polysaccharides.
These typically contain a polymer of glucose, or chains of glucose molecules bonded to one another. In their simplest forms, however, monosaccharides can be consumed by eating fruit, dairy, or other disaccharide foods like honey. Furthermore, sweeteners used in processed foods generally contain glucose, fructose, or a combination of the two, although fructose is roughly 75 percent sweeter than glucose and therefore is inexpensive to use commercially, as in the form of high-fructose corn syrup.
All monosaccharides are absorbed quickly into the bloodstream and therefore provide energy much sooner than slower-digesting complex carbohydrates. Added sugars have been linked to obesity. You can find added sugars in different types of foods — even ones you may not think of as sweet, such as ketchup, bread, and canned baked beans.
That said, the main sources of added sugars are sugar-sweetened beverages, candy, desserts, ice cream, and sugary cereals Look at the nutrition facts panel on a food product to find out how many grams of added sugar it contains. This made it difficult to determine just how much added sugar you consumed. Many large food companies have already complied, making it easier to assess the added sugar content of products. The American Heart Association recommends that women and men get less than 25 grams and 38 grams of added sugar per day from their diet, respectively Getting more than these amounts makes it difficult to meet your nutrient needs while staying within your daily calorie limits Names for added sugars include:.
Labels list ingredients in descending order of predominance by weight, with the ingredients used in the greatest amount first, followed by those in smaller amounts.
This means that if a product lists sugar as the first ingredient, you know it contains more sugar than anything else. You can identify added sugars by looking at the food label and reading the ingredient list. Limiting your calories from added sugar can help you meet your nutrient needs while staying within your daily calorie limits. Yet, sugar is only one component of your diet. Research suggests that sugar only becomes problematic to your health when it comprises too much of your diet or if you get more calories than you need from sugar 10 , 33 , 34 , Besides, simple sugars are found naturally in a wide range of healthy foods, such as fruits, vegetables, and dairy.
These foods bring a variety of other important nutrients to your diet, such as vitamins, minerals, antioxidants, and fiber. Sugar is detrimental to your health when it makes up too much of your diet or you get excess calories from sugar. Therefore, limiting but not completely avoiding sugar — specifically added sugar — is worthwhile for your health. However, excess added sugar is linked to obesity and increased heart disease and cancer risk.
Carbohydrates are one of the three major nutrition group categories—carbohydrates, fats, and proteins. They provide four calories of energy per gram and are the major source of energy in the human diet. A very diverse group of foods contain carbohydrates in the forms of sugars, starches, and fibers.
There are distinct biological actions among the different carbohydrate types. Depending on the foods they are sourced in, one can have different health consequences from carbohydrates. The generally favorable sources include whole food sources such as fruits, vegetables, legumes, and whole grains and the generally unfavorable food sources are heavy in refined carbohydrate sources such as high fructose corn syrup sweetened beverages, refined sugars and flours in dessert foods, and white as opposed to brown rice.
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