By: Nutrition expert- Vidula Kozarekar, Mumbai.
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Dietary fat is a fundamental component of a healthy diet and provides energy, a source of essential fatty acids (linoleic and alpha-linolenic fatty acids), and is necessary for the absorption of fat-soluble vitamins (A, D, E, K). Dietary fats are important for gastric emptying, digestion, and satiety. They are also principal components of hormones, including steroid and sex hormones.
Their metabolic and overall health effect may not be adequately predicted by the general classification of saturated versus unsaturated fatty acids. There is evidence to suggest that chain length of individual fatty acids, processing methods, dietary source, and the dietary pattern associated with consuming fat may be more helpful in predicting a physiologic effect (1), (2), (3), (4).
There are different types of fats including poly- and mono-unsaturated fats; saturated fats; and trans fatty acids. The type of fat consumed is more important for health than the total amount of fat consumed.
Dietary fats and their food sources: (5)
- Dietary fats are mostly triglycerides, with each triglyceride molecule containing three fatty acids on a glycerol backbone
- The structure and function of dietary fatty acids can vary greatly depending on chain length (6-24 carbon units); number of double bonds—saturated (with no double bonds), monounsaturated, or polyunsaturated; and whether the double bonds are in a cis (same side) or trans (opposite side) position
- Polyunsaturated fats with double bonds that are 3 carbon atoms or 6 carbons from the n-terminal end of the fatty acid (n-3 or n-6, respectively) are considered essential—that is, they must be obtained from the diet because they are not synthesised in the body. Both have important structural and physiological functions
- Different fatty acids have distinct biochemical properties and can therefore produce different metabolic and physiological effects with different clinical manifestations, such as cardiovascular, neurological, or other
Food sources of dietary fats:
- Food sources of individual fatty acids vary within each class. For instance, within the omega 3 polyunsaturated fatty acid class, alpha linolenic acid comes from plants, including some nuts and seeds such as walnuts and linseed, whereas eicosapentaenoic acid and docosahexaenoic acid come mostly from fish and other marine sources
- Many food sources contain different types of fatty acids. For example, olive oil is a good source of monounsaturated fatty acids but also contains saturated and polyunsaturated fatty acids in smaller proportions. Animal products are rich in saturated fats but some also contain large proportions of monounsaturated and polyunsaturated fatty acids
- Saturated fats (or saturated fatty acids) occur naturally in animal products like meats, eggs and dairy products as well as some plant-based and vegetable oils such as coconut, palm and palm kernel oil. These fats can be used during production of baked goods, fried and highly processed food products.
Dietary recommendation: (6), (7), (8)
The 2015 Dietary Guidelines Advisory Committee, the Dietary Guidelines for Americans 2015–2020, and many other organizations consistently recommend a limitation on intake of saturated fat, typically to <10% of energy. In contrast, Canada’s Heart and Stroke Foundation recently removed any specific limitation on saturated fat, stating instead that their dietary guidelines do “not include a threshold or limit for saturated fat and instead focus on a healthy balanced dietary pattern”.
Facts about Saturated Fats:
- Reviews of research have shown that full fat dairy intake has a neutral or protective effect on heart disease risk, while coconut oil intake has been shown to boost HDL (good) cholesterol and may benefit weight loss (9), (10).
- Consuming processed foods rich in saturated fats, including fast food and fried foods, has been consistently linked to an increased risk of obesity, heart disease, and numerous other health conditions (11), (12).
- There is an association between Dietary patterns rich in unprocessed foods and protection from various conditions, including obesity and heart disease, and reduction of disease risk factors, regardless of dietary macronutrient composition (13), (14).
- Some important cell signalling molecules such as ceramides and diacylglycerols include saturated fatty acids in their structure.
- Saturated fatty acids may also influence gene expression via actions on transcription factors (15).