How Are Triglycerides Transported in the Blood?

Dietary triglycerides are transported through your blood in vehicles called lipoproteins.

Dietary triglycerides are transported through your blood in vehicles called lipoproteins.

Triglycerides are found in the fats and oils in your diet, and they can also be made in your body from dietary carbohydrates. Triglycerides are a type of fat composed of three fatty acids linked with one glycerol molecule. Triglycerides provide energy to your tissues when glucose is in low supply, such as during the overnight hours when you are not eating as well as when you are vigorously working or exercising. Triglycerides are oily substances that cannot be transported in the watery environment of your blood without the help of lipoproteins.

Dietary Triglycerides

The triglycerides in the fats and oils in your diet are broken down by enzymes in your small intestine in to fatty acids and monoglycerides, which are then reassembled into triglycerides in your intestinal cells. The absorbed triglycerides are packaged into very large lipoproteins called chylomicrons that pass into your lymph and then into your blood. Chylomicrons deliver the triglycerides that you had in your last meal to your tissues. With the help of an enzyme called lipoprotein lipase, dietary triglycerides are removed from chylomicrons and taken into your tissues to be used for energy or to be stored as fat.

Liver Triglycerides

Your liver can make triglycerides from the carbohydrates in your diet, especially if you ate more calories than you should have eaten and if the extra calories came from sugar-sweetened foods. Your liver can also make triglycerides from fatty acids that are recycled to your liver from your fatty tissues. Liver triglycerides are packaged into lipoproteins called very low-density lipoproteins, or VLDLs, which are shipped into your blood. VLDLs deliver triglycerides to your heart and muscles to supply energy as well as to your fatty tissues for storage.

LDL and HDL

As triglycerides are moved from the VLDLs in your blood into your tissues, the VLDLs are converted into low-density lipoproteins, or LDLs. The LDLs are the main cholesterol transporters in your blood, but they also contain some triglycerides. The LDLs are taken up by most of your tissues, and the triglycerides and cholesterol that they carry are used in your cells. Another type of lipoprotein called high-density lipoprotein, or HDL, can pick up some triglycerides from the other lipoproteins circulating in your blood, and the HDLs can deliver their triglycerides to your liver and other tissues for energy or storage.

Triglycerides and Nutrition

A couple of hours after a meal, when the chylomicrons have all been cleared from your blood, VLDLs are the main triglyceride transporters in your blood. The main cause of high VLDL triglycerides is too many calories from sugar-sweetened foods and too many calories from saturated fats. To keep your VLDL triglyceride levels down, strive to replace foods made with refined flours and sugars with whole-grain foods, fruits and vegetables, and replace some of the saturated fats in your diet with sources of polyunsaturated fats.

 

About the Author

Michael Peluso is a semi-retired scientist in the field of nutritional biochemistry. He received his M.S. in nutrition from the University of California, Davis and Ph.D. in nutrition from the University of Missouri. Peluso's work has appeared in scholarly publications such as the "Journal of Nutrition," "Lipids" and "Experimental Biology and Medicine."

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