- Fat is made up of different types of fatty acids, some of which are essential for health in small amounts. Fatty acids are usually classified as saturated, monounsaturated or polyunsaturated depending on their chemical structure. Among the polyunsaturates there are further structural differences which determine whether the fatty acid is known as an omega 3 (n-3) or omega 6 (n-6) fatty acid. These structural differences directly influence health effects, with mono- and polyunsaturates usually being associated with health benefits when consumed as part of a varied diet. The exception to this is trans fatty acids, which are unsaturated in terms of their structure but behave in the body like saturated fatty acids.
- Fat provides energy; 1 gram provides 37 kJ (9 kcal). Foods that contain a lot of fat provide a lot of energy. Fat is a carrier of fat-soluble vitamins and is necessary for their absorption.
- A high intake of saturated or trans fatty acids can have adverse effects on health.
- In the UK, saturates currently contribute 12.7% of food energy in adults, which is above the recommendation of 11%, whereas average total fat intake is close to the 35% of food energy recommended for the population.
- Intake of trans fatty acids is now well below the population recommendation of no more than 2% of food energy, at 0.7%.
- In the UK, intakes of omega-6 polyunsaturated (principally linoleic acid) are close to the recommendation of 6.5% of dietary energy, but intakes of the long chain omega-3 fatty acids found in fish oils are low compared to recent recommendations.
Fat is the richest source of dietary energy available in the diet and so can readily contribute to weight gain. The structure of the building blocks of dietary fat – fatty acids – determines their health effects. Some fatty acids are essential components of the diet but others can be detrimental. As with most nutrients, recommendations exist to help establish dietary balance.
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