Fats Flashcards
(22 cards)
Recommended fat intake, and saturated fat intake.
up to 35%, 11% for saturated fat. No more than 30g for males, 20g for females.
Roles of Fat
Form part of the cell membranes, brain tissue, myelin sheaths and bone marrow. Provide a source of essential fatty acids. Are a storage point for the fat-soluble vitamins, A,D,E, and K. Play a key role in hormone storage and modification, particularly in the female hormone, oestrogen. Cushion vital organs and insulate the body. Give food flavour, aroma, tenderness and palatability. Serves as the largest store and source of energy in the body. Slow the rate of digestion, providing a sense of fullness after a meal by activating the satiety centre in the brain.
Potential energy of stored fat in average individual?
108,000kcal
Structure and classification of fats.
Fats are made up of carbon, hydrogen and oxygen. Fats contain more carbon than carbohydrates, making them more energy dense as a result. Fats found in the body are usually in the form of triglycerides, with each triglyceride being made up of one unit of glycerol and three fatty acids.
Saturated fats.
This type of fat has the maximum amount of hydrogen atoms possible in its structure, hence the term ‘saturated’, and is generally hard at room temperature. In the medical world it is generally thought that eating a diet high in saturated fat is linked to elevatedcholesterol levels and an increased risk of heart disease.
Foods containing saturated fat: The main sources are animal products like meat, butter, lard and cheese. Plant based oils (coconut & palm) which are not solid at room temperature. Processed foods like biscuits, pastries and cake
Mono-saturated fats
This type of fat contains slightly less hydrogen than saturated fat, and tends to be liquid at room temperature but can solidify in the cold.Consumption of these fats is thought to offer the greatest health benefits as they have the most positive effect on the different types of cholesterol in our body, lowering the ‘bad’ cholesterol whilst elevating the ‘good’.
Plants are the most common source, with the richest being olive, rapeseed, groundnut, hazelnut and almond oils, as well as avocados.
Polyunsaturated fats
This type of fat contains the least number of hydrogen atoms and is always liquid at room temperature. Sources include vegetable oils and oily fish and, like monounsaturated fats, they may reduce cholesterol levels. Several polyunsaturated fats are also termed essential fatty acids as they cannot be made in the body and must be obtained from the diet.
Omega 3
The richest sources of omega 3 fatty acids include mackerel, fresh tuna, salmon and sardines. For vegetarians, linseed (flax seeds), pumpkin seeds and walnuts are all good sources, as are dark leafy vegetables.To ensure a person gets the correct amount of omega 3, the Department of Health recommends two portions of oily fish (140g) per week.
Omega 6&9
Found in commonly eaten foods such as vegetable oils, polyunsaturated margarine, and processed foods made from these oils and fats, so deficiency is less likely in these types of essential fatty acid.
Trans-Fats
Trans-fatty acids, or trans-fats as they are more commonly known, are present in small amounts in a wide range of foods and are produced when vegetable oils are hardened through hydrogenation. They are arguably the least healthy form of fats and should be consumed in limited amounts. Like saturated fats, trans-fats have a negative effect on cholesterol levels, causing them to rise.
Recommended guidelines for trans-fats: Should make up no more than 2% of the diet, which is no more than 5g per day.
Hydrogenation
A chemical process that hardens vegetable oils and turns them into solid or semi-solid fats to extend the shelf-life of a product.
Sources of trans fats
Processed foods including cakes, pastries, biscuits, and low-fat spreads; they are often found in baked goods because they extend the shelf-life. They do also occur naturally in small amounts in dairy products such as cheese and cream, as well as some meats like beef and lamb. These naturally occurring trans-fats are thought be to less dangerous than artificial trans-fats.
Cholesterol
Is essential for health, so much so that it is produced by the body and is therefore not actually needed in the diet. It is naturally found in the structure of cell walls and is used to produce steroid hormones and vitamin D, and to manufacture bile acids which aid digestion and the absorption of dietary fat.
Low Density Lipoproteins (LDL)
Low density lipoproteins (LDL) cholesterol: Their role is to transport cholesterol from the liver to the body where it is used to build new cells. It is the low density lipoproteins (LDL) that are considered to be detrimental to health if levels are too high.
Excess levels of LDL cholesterol can become embedded in the walls of arteries. Causing them damage and increasing the likelihood of clots forming, leading to strokes or heart attacks.
High Density Lipoproteins (HDL)
High density lipoproteins (HDL) cholesterol: Their role is to remove cholesterol from the body and transport it back to the liver, where it is recycled and reused or excreted.
recommended cholesterol level
The government recommends that total cholesterol level for healthy adults should be 5mmol/L with no more than 3mmol/L coming from LDL
TC:HDL ratio
This is the total cholesterol (TC) figure divided by the HDL level. A ratio over 6 is considered a high risk - the lower the figure the better.(Heart UK. The Cholesterol Charity)
Effect of different types of fat on cholesterol
Monosaturated: Increase HDL, Decrease LDL.
Polyunsaturated: Decrease HDL, Decrease LDL.
Sauturated: No effect on HDL, Increase LDL.
Trans-Fats: Decrease HDL, Increase LDL.
Impact of Fibre on cholesterol.
Increasing fibre uptake is also an effective way to reduce cholesterol levels.Unlike other nutrients, once cholesterol has been produced by the body, it cannot be broken down, only eliminated from the body as waste. An adequate intake of fibre will ensure that this process occurs as effectively as possible.
Metabolism of Fat
Once fat has been broken down into triglycerides it is stored in the body as adipose tissue, the majority of which is found around organs (visceral fat) and beneath the skin (subcutaneous fat). Some fat - around 300-400g - is stored in muscles, and this is known as intramuscular fat. Genetics and hormonal balance can effect where fat is stored in the body.
Triglycerides are the end product of digesting and breaking down fats found in food and are stored in the fatty tissues of the body. They are also produced by the liver from any excess intake of carbohydrate or protein.
Sources of energy from fat during exercise.
- Triglycerides in the adipose tissue (this is the main store)
- Triglycerides within the muscles.
- Circulating triglycerides in the blood stream.
Lipolysis
For fat to be used as an energy source the fatty acid component must be freed from the glycerol molecule: this is done through the process of lipolysis. Once freed, the fatty acids can enter the bloodstream and be transported to the muscle cells to be used to produce ATP.
