How Fat Works – Part Two
If you missed our first post never fear, read up on Fat Part One to get a little more familiar with some of the things we’ll be talking about. In part one we briefly went over some of the common fatty terms that is associated with fat in our culture. We talked about triglycerides, trans fat, saturated fat, unsaturated fat, and two common types of cholesterol, HDL and LDL. In this post we’re going to be talking about what happens once you see a rack of rib, eat some bacon, or chomp down on a cupcake, chew it up then swallow it down into that stomach. All of these things will help you understand a little more what you can personally do about heart disease prevention.
As we talked about in our first post, triglycerides are what fat is stored as. Look into a bottle of olive oil or look at the fat on a piece of bacon and what you are seeing are triglycerides. As we talked about triglycerides are composed of fatty acids such as unsaturated or saturated fat for example. In part one we also gave the flag pole analogy that a triglyceride is a flag pole with three flags to it. Each flag represents a fatty acids while the flag pole is the backbone that holds it all together. In the case of the bacon those flag poles are primarily saturated fatty acids and in the case of the olive oil it’s mostly unsaturated fatty acids. Now let’s say you go for that olive oil and you go for that bacon and it hits your tongue and you just love how much it tastes with all that flavor and you chew it up and before you know it, that piece of bacon is in your stomach.
The beginning: Before that bacon even reaches your stomach, the fat is mashed up and lubricated with your salivary juices in your mouth (yum) and the triglycerides break off in a small amount by something called lingual lipase. Fat travels down your food tube (a.k.a. esophagus) where it reaches the stomach where food is tossed and turned some more. Everything in the stomach starts to be broken down. The protein of the bacon somewhat becomes separated from the fat but for the most part, digestion is relatively minor here compared to what happens in the small intestine. The longer the fatty acid chain, the less likely it is for the stomach to break it down. Fat can sit in your stomach for anywhere between one to three hours so some absorption of fat occurs through the stomach lining. Those smaller fatty acids that the stomach is able to break down go to the portal vein which carries it on to the liver. With the exception of the smaller fatty acid chains, fat for the most part remains a triglyceride or in a longer fatty acid chain until it hits the small intestine .
Fat Part Two
Once those triglycerides and fatty acids push into the stomach the combo sends a signal to your pancreas and gall bladder to do their job and release their digestive juices. These juices help to strip triglycerides or diglycerides (flag pole with two fatty acids attached to it instead of three) down even more into individual fatty acids. The end product is composed of several different things but for simplicity sake – and because it’s probably all you care about – we’ll just say it’s individual fatty acids and cholesterol .
So, how does it get from stomach to blood?
Well, your small intestines are covered with thousands of absorptive cells. Under a microscope they look like a bunch of hair. What happens is those cells absorb those fats and two things happen. If the fatty acid chain is smaller than about 12-carbons (a small or medium fatty acid chain) it’s usually absorbed by the absorptive cells of the intestine where it travels through the portal vein connected to the liver. The liver then packages it up then it enters the lymphatic system where it goes off to the bloodstream for use via a lipoprotein (more on that below). If it’s any longer than that then it’s repackaged inside the absorptive cell into a flagpole (triglyceride) before it prepares to be sent off to your blood stream straight from the intestine [1,2].
Okay so what happens next?
Remember all that HDL and LDL stuff we talked about last time? The triglycerides either in your liver or the remaining ones in your small intestine are packaged up into things called lipoproteins (fatty proteins that help carry fat out to where it needs to go). Fat doesn’t really like water very much which is the base of what your blood consists of. These lipoproteins help to allow the repackaged triglycerides to cross that barrier. One such lipoprotein and a major player in health is VLDL (very low-density-lipoprotein). The VLDL helps to carry that fat from your small intestine to your lymphatic system where they are finally then dumped off into your blood stream. Another one is a chylomicron which helps take the fat from your liver to your blood stream. After they’re in the blood stream they deliver its contents for pretty much anything your body wants: energy, cell formation, growth of your waistline, hormones, etc. etc. This whole process takes anywhere from two to ten hours depending on the fat content and how much Kentucky Fried Chicken you ate the meal before. As the VLDL makes it’s deposits it becomes less dense and it ends up as the infamous LDL which is made mostly of cholesterol . As we talked about last time, the liver has a good system in place for recovering it’s LDL by using a LDL receoptor-dependent pathway, HDL, or another scavenger pathway . With the LDL receptor pathway, as LDL is transported from the liver out to the body for use, receptors on your cells pick up your LDL where they bring it into the cell and strip it’s components for use. After the LDL is stripped down the receptors surface back up to the cell where they pick up more LDL. If your body can’t use any more due to a high LDL intake through your diet, a lot of that LDL will remains circulating through your bloodstream [3,4,5,6]. This is where HDL can come in. The HDL ships off the LDL back to the liver from the blood stream. HDL is also responsible for taking chylomicron remnants back to your liver to be broken down. If you don’t have enough HDL to combat the LDL, some of that LDL remains in your blood stream where it can become oxidized (damaged) . This is where the scavenger pathway can kick in. The scavenger pathway is made up of specialized cells that helps to dissolve and engulf the damaged LDL. The problem here is that this process causes the damaged LDL to adhere to your blood vessels . Over time this dissolved LDL builds up and can contribute to heart disease .
The problem with our diets: The problem with our diets, specifically a Western diet is that we’re not burning off enough calories compared to what we’re taking in. When we take in that excess fat that our body doesn’t need to use we store it in specialized cells called our adipose tissue. Our adipose tissue is responsible for all the parts on our body that we’re not really fans of. It stores those flagpoles of fat in our body for times that we need them for extra energy – but unless we’re exerting ourselves with enough exercise, going into a starvation mode, or we’re on a low carbohydrate diet those fat reserves never really get called upon. Then by the time we hit middle age we wonder what happened. The other problem with our diets is that for the most part, we consume WAY too many carbohydrates (in the form of sugary drinks, pasta, breads, rice…you name it). The body ends up converting any unused carbohydrates into fat then stores it along with our other fat. One issue associated with high carbohydrate intake is that it releases the hormone insulin to help our cells process the sugar. It’s not talked about very often but insulin has effects on our bodies in addition to just regulating blood sugar levels . When insulin is elevated it also helps your body to build and store fat. High fat and carbohydrate intake? It’s a double whammy and recipe for disaster in the long run.
What can you do?
This is why it’s essential to know how your body works. It goes without saying that it’s important to know what you’re eating. Do you not plan on working out or getting as much activity one day as opposed to another? Cut back on your carbohydrate to decrease fat synthesis in your body – especially cut down on those carbohydrates that spike your blood sugar (cookies, cakes, breads, wheat, pasta, chips, sugary drinks, etc.). When you eat, eat a balanced meal, low in carbohydrates, include some protein, and a healthy portion of vegetables. Also include water. It will help you feel more full. The carbohydrates will give you some energy to last you through whatever you need to do, the protein will provide building blocks for your body, and the vegetables will provide some fiber to prevent too much fat from sticking to the inside of your vessels.
One thing to keep in mind: A diet can be as different as one person to the next and each diet needs to be tailored to the needs of the individual. What you eat can have effects on how your fat is absorbed. This is a general blue print of how fat is absorbed into your system when it’s ingested in a healthy individual. If you have a certain activity level or certain disease that needs a specific customization, ask us your question or Post a comment on our Facebook page.
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1. Hampl, Jeffry S. Wardlaw, Gordon, M. Perspectives in Nutrition. 7th ed. New York: McGraw-Hill Companies Inc., 2007. 130-133, 204-211. Print.
2. Boyer, Rodney. Concepts in Biochemistry. 3rd ed. New Jersey: John Wiley & Sons. 2006. 558-560, 571-587, 639-640. Print.
3. Porth, Carol Mattson, RN, MSN, PhD. Matfin, Glenn, MB ChB, DGM, FFPM, FACE, FACP, FRCP. Pathiophysiology: Concepts of Altered Health States. Philadelphia: Wolters Kluwer Health | Lippincott Williams & Wilkins. 480-481. Print.