Food and Nutrition Absorption and Delivery
Food and nutrition go hand-in-hand, and in this article we will take a look at how nutrients are absorbed and delivered throughout our body. Eating food is a daily activity that we partake in multiple times per day. Most of us are not concentrating on the nutritional value and the nutrients that are in the food, we are concentrating on the food itself and how it tastes. However, if you want to move close to living a fitness lifestyle, it is important to understand how food and nutrition interacts with our body.
Food and Nutrition: Absorption
Food and nutrition absorption is controlled by the two major body systems that control digestion: the endocrine system and the nervous system. These two systems control the release of hormones and nerve impulses that regulate how food and nutrition absorption and deliver take place. The endocrine system is responsible for the release of hormones to direct the digestive system, while the nervous system is responsible for sending nerve impulses for direction. To learn in-depth about these systems click here.
This food and nutrition absorption starts when the food we eat enters into the digestive system. This is where the major nutrients we need are extracted as micronutrients and absorbed, and where the potentially harmful microorganisms are held at bay. Our digestive system is about 25 feet long and starts at our mouth and ends at our anus. Food and nutrition absorption take place along this canal where acidic secretions, alkaline secretions both combine together to breakdown the complex molecules in the food stuff we eat, into smaller and simpler molecules that can be used in the cells throughout our body.
The main objective of the digestive system is to deliver nutrients into our bloodstream for use in our cells. For this process to take place, the nutrients must cross the gastrointestinal-body barrier within our intestine. This barrier has a surface area of about 2,700 square feet, and this large intestinal surface area helps with nutrient absorption. Food and nutrition absorption and starts to make there appearance in the bloodstream within a few minutes after eating, it takes a few hours for blood nutrient levels to peak. Although the food and nutrition absorption happens rather fast, the entire digestive process can take between 18-72 hours.
Once the nutrients pass through the gastrointestinal-body barrier they will enter the blood supply of the GI tract or lymph. Next, the veins in the stomach and intestine will deliver the nutrients to their next stop, the liver. After the digestive process is when food and nutrition absorption and deliver can occur buy making there way into various cells to be used. In this process most nutrients get delivered directly to the liver where they are filtered and deemed appropriate to enter into systemic circulation. The exception is that most fatty acids bypass the liver and are absorbed into our lymphatic circulation before slowly being released into our bloodstream and then circulated to the liver. Once the nutrients have made it through the liver they are delivered to the various tissues in our body.
The liver plays an important roll in food and nutrition absorption. One of these roles is that of maintaining carbohydrate homeostasis, or in other words; the automatic tendency to maintain a relative consistent internal environment. The liver may do this by using excess glucose and store it as glycogen for later use. The liver also can remove other sugars from the blood such as fructose or galactose and turn them into glucose.
Food and Nutrition: Delivery
Now that the nutrients have been processed by the liver and have entered into the bloodstream, they need to be delivered to the various cells in our body. Once the nutrients enter into the bloodstream most of them are dissolved and carried in a free-floating manner. However, lipids are the exception. Lipids are carried by lipoprotein carriers which are commonly called by the different types of cholesterol: HDL, IDL, LDL, VLDL, and chylomicrons.
The delivery of these nutrients is critical for us to function at our physical best, and they must also be delivered effectively to some specific target tissues in the body. The most important of these targets are: the liver, the muscles, the adipose tissue, and the brain.
Liver
As we learned from above, the liver plays a vital role in digestive and absorption process where most nutrients are passed through and screened. The liver also plays a roll in the synthesizing the three major macronutrients (Carbohydrates, proteins, and fats). With carbohydrate metabolism, glucose that enters the liver can be stored for later use as liver glycogen. This glycogen can be used later to regulate the body’s blood sugar. The liver also synthesizes proteins which are formed from amino acids during the first pass through of nutrients after eating food, and also through general circulation. The liver can also synthesize amino acids into non-protein products such as hormones, glucose, or fatty acids.
Muscle
For muscles to function properly they need glucose, amino acids, and fatty acids. Glucose passed through the liver can be used by muscles cells for the production of ATP or stored as muscle glycogen. Amino acids that have passed through the liver can also be used by muscle cells and synthesized into new proteins and enzymes. Lastly, the fatty acids that are delivered to the bloodstream can be used by the muscle cells to provide energy.
Adipose Tissue
The adipose tissue (commonly referred to as fat), uses both glucose and fatty acids for long term energy storage. These cells process glucose through glucose metabolism to form glycerol and fatty acids which are joined with triglycerides. Triglycerides are the body’s main storage form of fat.
Brain
Arguable the most important deliver destination for nutrients is the brain. The brain is the body’s most sensitive and delicate organ. One of the brains protective mechanisms is a protective blood-brain barrier that protects that brain from chemicals in the bloodstream, but yet allows the vital nutrients it needs to function. The brain preferred energy source is glucose, but glucose can not be stored in the brain. Therefore, the brain needs a constant supply of glucose to function properly. In times when glucose is not in high enough supply, the brain will use Ketone bodies, which are synthesized from dietary fat in the liver.
