Fats are probably the most misunderstood macro-nutrient with many people believing a low fat diet is the healthiest choice. However, certain fats are essential to human health in order for the body to perform particular functions. These essential fats, sometimes called omega 3 & 6, must be ingested through the diet as they cannot be manufactured in the body from other foods.
Types of Fat:
- poly-unsaturated, also called omega 3 & 6 or essential fats
Saturated fats and mono-unsaturated fats are non-essential but can be broken down or stored for energy. The conventional wisdom is that saturated fats should be kept to a minimum, while mono-unsaturated fats can be consumed in moderation. (However, as with all things in nutrition there is a counter argument: I have recently started reading a book on traditional diets called “Nourishing Traditions” which advocates a certain amount of saturated fats.)
The Benefits of Fats:
- Enhance flavour in cooking; make food taste good!
- Make food more filling by slowing digestion.
- Decrease the glycaemic response (jumps in blood sugar) to food.
- High energy content, though not beneficial if consumed in excess!
Some of the benefits of omega fats include:
- increase metabolism and therefore fat loss
- control inflammation thus improving recovery from injury and exercise
- have a positive affect on mood and improve cognitive performance
- improve cholesterol balance
- help transport oxygen
- form part of the structure of all cell membranes
Sources of good fats-
Poly-unsaturated (omega 3 & 6):
- seeds and nuts in particular; flax or linseed, hemp, pumpkin,brazils, sunflower, safflower, sesame
- oily fish e.g. mackerel, salmon, sardines, pilchards, herring, fresh tuna (not tinned)
- cold-pressed oil supplements
- seeds & nuts in particular, almonds, cashews, macadamia, peanuts, pecans, pistachio
Good fats gone bad; ‘Trans-fats’
Polyunsaturated fats are very sensitive to heat and light. Therefore if exposed to these factors during large scale production or cooking they can become damaged ‘trans-fats’. (See typical supermarket-shelf vegetable oils such as sunflower and corn.) Similarly, the hydrogenation process used to turn vegetable oils into semi-solid spreads such as margarines and shortenings also turns these fats into a type of trans-fat. Trans-fats are known to interfere with human health in many ways as they are a substance not recognised by the body. They can inhibit immune function, cause imbalances in cholesterol, atherosclerosis (hardening of the arteries), disrupt function of good fats. Some researchers have suggested a link between increased deaths from cancer (from 1 in 30 people in 1900 to 1 in 4 people in 1990) to the increased consumption of trans-fats, although it is difficult to prove causation.
Many health magazine articles focus on reducing omega 6 and increasing omega 3, however both are essential. This advice is often driven by 2 factors:
1) Most of the recent research has been carried out on omega 3.
2) The assumption that the reader consumes a lot of damaged omega 6 in the form of hydrogenated vegetable oils, typically found in processed food or trans-fats used to deep-fry your chicken and chips at the local take-away. Really the advice should be to consume both 3 and 6 in as unadulterated form as possible.
How much fat do you need?
Current UK NHS guidelines recommend calories from fats should represent no more than 30% of total calories consumed. At least one third of dietary fats consumed as polyunsaturated, with no more than a third saturated.
The ratio of omega 3 to 6 is a little harder to determine. Many supplements are 3:1 or 3:2, based on the assumption you are omega 3 deficient or getting a lot of omega 6 elsewhere. Udo Erasmus a pioneer in omega research suggests an ideal ratio of 3 to 1 omega 6 and 3 respectively for long-term use and between 15-20% of total calories from fats. Research in this area is relatively new and definitive answers are not really known.
- Eat a variety of fats from the above lists to include omega 3 and 6.
- Avoid like the plague – damaged fats e.g. margarines, hydrogenated spreads, trans-fats used in many processed and packaged foods, and probably your local fast food joint.
- Buy oils that are cold-pressed and avoid highly processed vegetable cooking oils e.g. sunflower oil, corn oil.
- If frying use coconut, palm or macadamia oils preferably or butter in moderation if the previous choices are unavailable. Olive oil is suitable for low temp cooking or to add to cooked food.
Sources and Further reading: