The Scientific and Chemical Terminology
While “diglyceride” is a common term, its more accurate scientific name is diacylglycerol, often abbreviated as DAG or DG. This name describes its structure: two (“di”) fatty acid chains (“acyl”) attached to a glycerol molecule. Diacylglycerol or DAG is preferred in scientific research.
The Chemical Structure of Diacylglycerol (DAG)
A diacylglycerol is a type of glyceride with two fatty acids linked by ester bonds to a glycerol molecule. Glycerol has three carbon sites for fatty acid attachment. In a diglyceride, two sites are occupied, leaving one free hydroxyl group. The arrangement of fatty acids on the glycerol backbone determines the two main forms: 1,2-diacylglycerols and 1,3-diacylglycerols.
Diglycerides, Monoglycerides, and Triglycerides
These related molecules are all glycerides and differ in the number of fatty acids attached to glycerol. This difference dictates their properties and functions.
| Feature | Monoglyceride | Diglyceride | Triglyceride |
|---|---|---|---|
| Fatty Acids | One | Two | Three |
| Chemical Makeup | One fatty acid + glycerol | Two fatty acids + glycerol | Three fatty acids + glycerol |
| Polarity | Partially polar; good emulsifier. | Partially polar; emulsifier. | Non-polar; doesn't mix with water. |
| Presence | Small amounts in natural fats; produced during digestion. | Natural in foods and metabolism. | Most common dietary and stored fat. |
The Dual Role of Diacylglycerol in Biology and Food
Diacylglycerols are important in biological processes within the body and as additives in food.
DAG as a Biological Second Messenger
In biological systems, diacylglycerol is a vital second messenger involved in various cell signaling pathways. Activation of certain cell receptors leads to the production of DAG and IP3 from a membrane lipid. DAG stays in the cell membrane and activates protein kinase C (PKC), initiating a series of intracellular events. DAG also serves as a precursor for endocannabinoids.
Diglycerides as Food Additives (E471)
Diglycerides are partially polar and effective emulsifiers, enabling them to blend oil and water. This makes them useful food additives, often used with monoglycerides and labeled as E471. They are widely used in the food industry to enhance texture, extend shelf-life, and prevent ingredient separation in many products, including baked goods, ice cream, peanut butter, margarine, salad dressings, and chocolate.
Health, Production, and Labeling
Regulatory bodies like the FDA have long considered mono- and diglycerides safe. However, concerns exist regarding their use in ultra-processed foods, which can be high in sugar and fat, and the potential for trace amounts of trans fats or processing contaminants. Specialized diglyceride-rich oils have been studied for their potential to help manage body weight by altering fat metabolism. These oils are processed differently, sending fatty acids to the liver for oxidation rather than storage. To identify diglycerides in food, consumers should check ingredient lists for “mono- and diglycerides,” E471, or broader terms like “partial glycerides,” “monoacylglycerols,” or “glycerolipids,” which can sometimes refer to these compounds. For a deeper understanding of cellular messaging, see the NCBI Bookshelf Basic Neurochemistry chapter on Diacylglycerol.
