Fats, Omegas and Cholesterol
In this fact sheet: Fats, Omegas and Cholesterol
Fats are an essential part of our diet but it is important that we do not eat too much. Understanding the role fats play in the human body can help us include the right type of fat in our diet.
Fats help with the absorption of the ‘fat soluble’ vitamins - vitamin A and the carotenoids, vitamin D, vitamin E and vitamin K. Fatty acids, the building blocks of many important substances in the body, are essential to cell membranes, maintaining a regular heart beat, providing an anti-inflammatory function, regulating cholesterol and contributing to brain and eye development in a developing baby. Fats provide a concentrated source of energy (calories) therefore eating too much can lead to weight gain. The optimum amount of fat in our diet depends on our stage of life. Extremely low fat diets will limit the amount of fat soluble vitamins and essential fats in our diet.
There are 3 main types of fats: saturated fatty acids (SFAs) and two types of unsaturated fatty acids - monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs).
For adults fat intake should not exceed more than 33% of total food energy intake, limiting saturated fat to 11% of food energy intake. This equates to a maximum overall daily fat intake of 95g for men and 70g for women, of which saturates should be no more than 30g and 20g respectively. Mono- and poly- unsaturated fats should each provide around one third of our fat intake.
Vegan and vegetarian diets tend to be lower in saturated fat than diets containing meat. However, both saturated and hydrogenated fats are found in some vegetarian foods.
Saturated fats are mainly in animal products such as butter, cream and hard cheese, but also in palm oil and coconut products. Palm oil and hydrogenated fat (which is chemically altered to remain hard at room temperature) are used extensively in the production of biscuits and pastries.
Saturated and hydrogenated fat have harmful effects on health such as weight gain which is associated with diabetes, and raising blood cholesterol levels. High levels of cholesterol cause atherosclerosis, increasing the risk of developing heart disease.
Healthier, unsaturated fats are mainly from plant sources such as fruit, seeds, nuts and vegetables. Sources of monounsaturates are olive oil and rapeseed oil. Sources of polyunsaturates are sunflower, soya, sesame and corn oils. Mono- and poly-unsaturated fats can help lower blood cholesterol levels and blood clotting.
The PUFAs are classified into the omega-3 and omega-6 families. Referred to as the omegas, the omega-3 fatty acid is alpha-linolenic acid (ALA) and the omega-6 fatty acid is linoleic acid (LA). Both these are essential nutrients for health.
An adequate intake of omegas may prevent and control a number of inflammatory conditions such as heart disease, arthritis, macular degeneration, and immune dysfunction (e.g. asthma, eczema). However, omegas utilise the same enzymes for their metabolic pathway, so it is important to balance their intakes appropriately. The ideal ratio of LA to ALA acid (O6:O3) is 3:1. However, the Western diet which is heavily dependent on fried and processed foods tends to have a ratio closer to 15:1. The activity of enzymes can be affected by excessive intakes of saturated fats, alcohol, caffeine, and sugar, as well as deficiencies in zinc, magnesium and vitamins B and C which can be common in Western diet. Under these circumstances omega 6 fatty acids inhibit the conversion pathway of omega 3 fatty acids. Omega 3 deficiency can therefore occur and this creates hormone-like substances which encourage platelet stickiness, inflammation and water retention, leading to high blood pressure.
LA is widely available in a vegetarian diet from nuts, seeds, maize (corn) and soya beans. ALA is found in flaxseed, walnuts and hempseed. Both LA and ALA are found in green leafy vegetables, milk and eggs.
The health benefits of omega-3 are suggested to come from docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) which the body makes from the parent essential fatty acid ALA. In nature, marine algae is the primary source of DHA and EPA. A non-vegetarian source of omega-3 is oily fish because it is rich in DHA and EPA from marine algae. There are a number of vegetarian supplements for DHA and EPA available (see approved products) if you are concerned about your intake.
There is no recommended daily intake for Essential Fatty Acids (or EFA's) in the UK. Most guidelines are based on an intake of oily fish which is unhelpful for vegetarians. However, the European Food Safety Authority guidelines for daily intake, which were revised in 2009, recommend 2-3g ALA or 250mg EPA/DHA and 10g LA to support cardiovascular health and neurodevelopment. A tablespoon of flaxseed oil per day would fulfil this.
Sources of omegas:
Flaxseed oil 1 tbspn (14g):
- Total EFA's - 8.9g
- Omega 6 - 1.7g
- Omega 3 - 7.2g
- Ratio omega 6 : omega 3 - 1:4
Flaxseed ground 1 tbspn (7g):
- Total EFA's - 2.0g
- Omega 6 - 0.4g
- Omega 3 - 1.6g
- Ratio omega 6 : omega 3 - 1:4
Hulled hempseed 1 tbspn:
- Total EFA's - 3.9g
- Omega 6 - 3.0g
- Omega 3 - 0.9g
- Ratio omega 6 : omega 3 - 3:1
Rapeseed oil 1 tbspn (14g):
- Total EFA's - 3.9g
- Omega 6 - 2.6g
- Omega 3 - 1.3g
- Ratio omega 6 : omega 3 - 2:1
Walnuts 1oz (25g):
- Total EFA's - 13.2g
- Omega 6 - 10.7g
- Omega 3 - 2.5g
- Ratio omega 6 : omega 3 - 4:1
Flaxseed seeds and oil are a very good source of omega 3 fatty acids. Flaxseeds should be freshly crushed or milled in order to ensure nutrient absorption. The seed contains fibre and compounds called lignans. Lignans have an effect on hormone balance so the intake of flaxseed should be restricted during pregnancy. Hemp seeds have an ideal O6:O3 ratio and contain significant amounts gamma-linolenic acid and stearidonic acid. Rapeseed oil is also a good source of omega 3 and should be used cold-pressed because heating changes the oil’s properties.
Other foods can add to your ALA intake. Most of the fat in leafy green vegetables is ALA, for example broccoli has 0.13g per 100g and cabbage 0.11g per 100g. Occasionally you will find small levels of ALA or DHA in eggs, if the hens have been fed on flaxseeds or algae. Although organic milk has been heralded as having 60-70% higher levels of ALA than ordinary milk it is worth remembering that its overall level of polyunsaturated fats is low, even though it has a good O6:O3 ratio.
Essential fatty acids can generate free radicals once they are subjected to heat, light and oxygen. For cooking it is recommended to use oils which are high in mono-unsaturated fats, such as olive or groundnut. Flaxseed oil is also best purchased in dark bottles and stored away from heat or light.
Cholesterol is essential to life. It has several functions including helping to build cell membranes, bile acids, insulating nerve fibres, and it is an essential building block for hormones, such as sex hormones and adrenal gland hormones.
Raised blood cholesterol is a risk factor for cardiovascular disease (CVD) which includes stroke, heart disease and atherosclerosis. The liver manages cholesterol levels by turning the fat in your blood to cholesterol. The cholesterol enters the blood to be transported around the body. There is a harmful form and a protective form of cholesterol so not all cholesterol is bad for you. The harmful form is known as low-density lipoprotein (LDL). The protective form is known as high-density lipoprotein (HDL).
It is recommended to reduce the amount of fat and consider the balance of fats in your diet to favour those that help reduce cholesterol levels. There are different types of fat in food:
• Foods high in saturated fats such as cakes and biscuits, pastries, cream, cheese and coconut/palm oil, increase cholesterol levels.
• Processed foods rich in trans and hydrogenated fats, such as margarine, have a similar effect on cholesterol levels as saturated fats.
• MUFAs help lower harmful cholesterol levels. Examples of foods high in mono-unsaturated fats include olive oil and rapeseed oil.
• PUFAs lower both harmful and protective cholesterol levels. Examples of foods high in polyunsaturated fats include sunflower oil and soya oil.
When you're shopping for food, compare the labels so you can pick those with less total fat or less saturated fat. Choose lower fat versions of dairy foods, such as semi-skimmed or skimmed milk, and reduced-fat yoghurt.
If you have high cholesterol levels there are several ways in which a vegetarian diet may help. Vegetarian sources of protein such as tofu, soya mince and Quorn are excellent alternatives for avoiding saturated fat. If you want to cut down on saturates by reducing your dairy intake, soya milk and soya yoghurt are useful alternatives. Rice and oat milk are more widely available and low in saturated fat and high in PUFAs.
Omega-3 and fibre, which is abundant in vegetarian diets, can help to reduce cholesterol levels. Foods that are part of a healthy vegetarian diet include pulses such as chickpeas and kidney beans. These can be helpful in reducing cholesterol as they represent a good source of protein without the associated saturated fats of some meats, and have the added bonus of protective fibre.
There is some scientific evidence for the link between diet and cholesterol levels. A small Canadian study involving 13 people who had the inherited form of hyperlipidemia suggested that a change in diet had a beneficial effect on cholesterol levels. Participants consumed a diet for one month based on four main components:
• soy proteins
• viscous fibres (found in oats and barley)
• plant sterols (found in vegetable oils and leafy green and non-starch vegetables).
The diet had the effect of reducing LDL cholesterol levels by 29% - a similar effect to that achieved with statins medication (Jenkins, D (2002). Journal of Metabolism)
Changing your diet
If you are thinking of changing your diet or have been encouraged to by your health professional, read our Going Veggie section for help with your first steps and what to expect. Changing to a vegetarian diet with more fibre can produce changes in your digestive system which may cause bloating and gas as the friendly bacteria adjust. A higher fibre diet also increases your need for fluid as fibre absorbs more water from your gut than other foods, so remember to drink plenty of water.
Adopting an active lifestyle and losing weight are also important factors in remaining healthy.