Our blood cells can use only blood glucose and the brain and other nervous tissues rely on glucose as well. This is why we often get tired, irritable and shaky when we haven’t eaten carbohydrates in a prolonged period of time. Many popular diets are based on the idea that our bodies don’t need carbohydrates and can use fats and proteins for energy. An example of this would be the Atkins diet. They claim the need for carbohydrates that are recommended are much higher than we really need but in reality the body relies on both carbohydrates and fats for energy. When we exercise, we begin to use more glucose than lipids because we can break down glucose very quickly with or without oxygen. If you are physically active, it’s important to eat enough carbohydrates to provide energy for the brain, red blood cells, and muscles.
When we don’t eat enough carbohydrates, the body looks for another alternative source of fuel for the brain and begins to break down stored fat. This process is called ketosis, which produces ketones. Ketosis is an important mechanism for providing energy to the brain during situations such as fasting, low carbohydrate intake, or vigorous exercise. Ketones also suppress appetite and cause dehydration. Because many ketones are acids, high ketone levels cause the blood to become very acidic which can lead to ketoacidosis. This interferes with body functions, causes loss of lean body mass and damages many body tissues. People with untreated diabetes are at a high risk of ketoacidosis which can lead to coma and sometimes death.
Complex carbohydrates contain fiber and other nutrients that can reduce the risk for obesity, heart disease, and diabetes. Low carbohydrate diets claim that eating carbs will make you overweight and promotes changes in blood lipids and insulin to contribute to heart disease and diabetes. However, eating carbohydrates that are high in fiber and other nutrients has been shown to reduce the risk of obesity, heart disease and type 2 diabetes. So, all carbs are not “bad” and complex carbohydrates are beneficial.
The current RDA for carbohydrate for adults 19 years and older is 130 grams a day. It’s important that this doesn’t support the daily activities a person does, but only supports the amount of carbs the brain needs to function. Most health agencies agree that most of the carbohydrates should be high in fiber, whole grain and unprocessed. And the USDA guide recommends eating at least half of your grains as whole grains.
Most Americans eat too much simple sugars which come from added sugars found in foods that are processed or prepared. The most common source of added sugar in the US diet is soft drinks, drinking an average of 40 gallons per person a year. A 12 oz. sugared cola contains 38.5 g of sugar which is almost 10 teaspoons! Other common sources of added sugars are cookies, cakes, pies, fruit drinks and candy. A surprising number of processed foods can also contain a significant amount of added sugar as well such as peanut butter and rice mixes. Foods and beverages with added sugars have lower levels of vitamins and mineral than foods that naturally contain simple sugars such as fruit and milk.
Simple carbohydrates have such a bad reputation simply because they are known to contribute to tooth decay, researchers believe eating a lot will increase the levels of unhealthful lipids in our blood, increasing our risk for heart disease and high intakes of simple carbohydrates have also been blamed for causing diabetes and obesity. There is no scientific evidence that eating a diet high in sugar causes diabetes, however have found evidence of high sugar leading to obesity.