sign up to the Foodproof.co.nz blog here
Fat for fuel
Fats provide fuel for the body. From the three macronutrients, fat provides the greatest amount of energy per kg. This is twice as much as the same weight of carbohydrate or protein.
The word fat refers to both fats and oils
Fats are trending and topical because of uncertainty within the research arena but a common theme is there are healthy fats which we should all eat along with a good dose of vegetables.
Foods with a high-fat content include butter, cream, nuts, olives, avocados, seeds, eggs, cheese and obviously fatty meats, salami, sausages.
What do fats do?
Fats provide energy for the body and the brain. Eating too much fat will make you fat, but fat is an essential component of the diet.
- Fats are valuable for transporting fat-soluble vitamins and fat-soluble anti-oxidants around the body.
- Fats are integral to the cell structure – the cell membrane is made up primarily of fat.
- Fats insulate body organs
- Fats are involved in the manufacture of hormones
Fats have many functions and there are different types of fat. Fats are categorised by their chemistry and can be considered either healthy or unhealthy.
Fats have different structures
Understanding fat is about understanding the physical structure of the fat, in particular triglycerides, which are the main type of fat in the diet.
A triglyceride is three fatty acids held together by a glycerol. Think of an “E” – the vertical part is the glycerol and the three horizontal bars are the fatty acids. The fatty acids attached to the glycerol can be the same or different.
A fatty acid is a chain of carbons with hydrogens attached. It is the way those carbons are holding hands which defines whether it is saturated or unsaturated. The saturated fatty acid has a simple hand hold whereas the unsaturated fatty acid has a more intricate handhold. It may be a mono (single) or poly (many) handholds in a ‘cis’ or a ‘trans’ grip.
The length of the fatty acid – short, medium or long chain fatty acid – determines the melting point of the fat. A long chain fatty acid will have a lower melting point and will be liquid at room temperature e.g. oils and a short chain fatty acid will have a higher melting point and will be solid at room temperature e.g. butter. The medium chain fatty acid is in between e.g. coconut oil.
The length of the fatty acid determines whether the fat is solid or liquid at room temperature and the type of carbon bonds (handholds) determine the fats saturation.
Recommended daily intake of total fats
A total fat recommendation has not been set by New Zealand Ministry of Health as it is the type of fat consumed which is important rather than the overall fat intake but there are guidelines of between 20 – 35% of energy intake (1). Eating insufficient fat can be detrimental to maintaining weight and it becomes very difficult to meet all nutritional requirements (1).
Using the above guidelines 20 – 35% of total energy intake for a 30 year old woman (1.6 m high) with mild physical activity requires 8800 kJ/day of energy this equates to 47 – 83 g of fat per day.
Nutrition Information Panel
Total fat content is required on the New Zealand Nutrition Information Panel per 100g of food and per serving. Saturated fat is also required as a separate entry.
On the chocolate Nutrition Information Panel below, it has nutritional information per serving (20 g), % daily intake of the three macronutrients per serving and per 100 g of chocolate. The fat in 20 grams of this chocolate provides 7% of your suggest fat intake based on a daily intake of 8700 kJ and a suggested total fat intake of 32% of total energy.
Nutrition Information Panels are confusing, perhaps a blog on Nutrition Information Panels is required – sign up for an alert when my Foodproof blogs are released.
Summary
Food confusion is evident with fat, the science is changing and the literature is not clear on the right direction. Fats are vital to our diet and understanding the difference between good and not so good fat is a great start. From here, it becomes easier to focus on replacing the not so good fats with the good fats in the diet.
This blog has touched on the differences in the structure of fat. The next blog will look more closely at saturated fats – sign up by email.
Reference
- Ministry of Health, National Health and Medical Research Council. Nutrient reference values for Australia and New Zealand including recommended dietary intakes: NHMRC Publications, 2005.
