Fats, Omegas and Cholesterol
In this fact sheet: Fats, Omegas and Cholesterol
It’s important we don’t eat too much fat and yet at the same time fats are an essential part of our diet. As vegetarians understanding a little about the role they 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, in maintaining regular heart beat and anti-inflammatory function as well as regulating cholesterol and contributing to brain and eye development in the developing baby. Fats provide a concentrated source of energy and because fat is rich source of energy (calories) eating too much can make you put on weight. 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 three main types of fat or fatty acid in the diet: saturated fatty acids (SFAs) and two types of unsaturated fatty acids called monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids, the now familiar PUFAs.
For adults fat intake should not exceed more than 33% of total food energy intake with a limit on saturated fat of 11% of food energy intake. In practice this means 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.
Vegetarians consume less saturated fat on average as they avoid meat products but there are both saturated and hydrogenated fats to be found in vegetarian foods.
Saturated fats are present mainly in animal products like 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. As well as leading to weight gain which is associated with diabetes, eating a diet that is high in these fats can raise the level of cholesterol in your blood. High levels of cholesterol cause atherosclerosis which increases your chances of developing heart disease.
The healthier unsaturated fats are mainly from plant sources such as fruit, seeds, nuts and vegetables. Olive oil and rapeseed oil are the main sources of monosaturates and polyunsaturates are provided by sunflower, soya, sesame and corn oils. Mono- and poly-unsaturated fats promote health; can lower your blood cholesterol levels and the tendency for your blood to clot. Monosaturated and polysaturated fats should each provide around one third of our fat intake.
The polyunsaturated fatty acids (PUFAs) can be classified into Omega-3 and Omega-6 families. The two essential fatty acids (ESAs) which have popularly come to be known as Omegas are Alpha linolenic acid which is an omega-3 and Linoleic acid which is an omega-6 faty acid. Both these omega-3 and omega-6 polyunsaturated fatty acids must be present in the diet for normal health.
An adequate intake of both may prevent and control a number of inflammatory conditions such as heart disease, arthritis, macular degeneration, immune dysfunction (e.g. asthma, eczema). However, because these fatty acids utilise the same enzymes for their metabolic pathway, it is important that there is an appropriate balance between their intakes. The ideal ratio of Linoleic acid to Alpha linolenic acid 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. Additionally the activity of these enzymes can be affected by excessive intake of other elements common in the Western diet such as saturated fats, alcohol, caffeine and sugar as well as deficiencies in zinc, magnesium and vitamins B and C. Under these circumstances omega 6 fatty acids can not only inhibit the conversion pathway of omega 3 fatty acids but also where omega 3 deficiency occurs – its metabolic pathway creates hormone-like substances which encourage platelet stickiness, inflammation and water retention leading to high blood pressure.
Linoleic acid (LA) omega-6 is widely available in a vegetarian diet in nuts, seeds maize (corn) and soya beans. Alpha-linolenic acid (ALA) omega-3 is found most notably in flaxseed but also in walnuts and hempseed. Both LA and ALA are found in green leafy vegetables, cow's milk and eggs.
The health benefits of omega-3 are thought to come from the omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) which the body makes from the parent essential fatty acid - Alpha Linolenic Acid (ALA). In nature marine algae are the primary source of DHA and EPA and so non-vegetarian sources of DHA and EPA are oily fish which derive these DHA and EPA from marine algae. If, as a vegetarian you want a source of DHA and EPA then there are a number of vegetarian supplements available (see approved products).
Getting your omegas
There is no recommended daily intake for essential fatty acids (EFAs) in the UK and most of the 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. Clearly a tablespoon of flaxseed oil per day would fulfil this.
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. As lignans can have an effect on hormone balance the intake of flaxseed should be restricted during pregnancy. Hemp seeds have an ideal O6:O3 ratio and also contain significant amounts of the fatty acids GLA (gamma-linolenic acid) and stearidonic acid. Rapeseed oil is a good source of omega 3 fatty acids and should be used cold-pressed as heating changes the oil’s properties.
Other foods can also 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 also find eggs, where the hens have been fed on flaxseeds or algae, but the levels of ALA or DHA provided will be small. Although organic milk has been heralded as having 60-70% higher levels of ALA than ordinary milk it must be remembered that even though it has a good omega 6:3 ratio, its overall level of polyunsaturated fats is low.
Essential fatty acids can easily generate free radicals once they are subjected to heat, light and oxygen. For cooking it is better to use oils high in mono-unsaturated fats such as olive or groundnut. For the same reasons flaxseed oil is best purchased in dark bottles and stored away from heat or light.
Cholesterol is present in the body in normal health. It has several functions: cholesterol is present in the membrane (outerskin) of every cell in the body, it insulates nerve fibres, and is an essential building block for hormones, such as
the sex hormones and the hormones that are made and released by the adrenal glands.
Raised blood cholesterol however, is a risk factor for cardiovascular disease (CVD) which includes stroke, heart disease and atherosclerosis. The body manages cholesterol levels in the following way. The fat in your blood is turned into cholesterol by your liver. The cholesterol then enters your blood to be transported around your body. Not all cholesterol is bad for you; there is a harmful form and a protective form. The harmful form of cholesterol is known as LDL or low-density lipoprotein. The protective form of cholesterol is known as HDL or high-density lipoprotein.
You should reduce the amount and consider the balance of fats in your diet to favour those that help reduce your cholesterol level. There are different types of fat in food.
• Saturated fats increase cholesterol levels. Examples of foods high in saturated fat include cakes and biscuits, pastry, cream, hard cheese and products containing palm or coconut oil.
• Trans fats, including hydrogenated fats have a similar effect on cholesterol levels as saturated fats and are similarly found in cakes, biscuits and pastries as well as some margarines.
• Mono-unsaturated fats help lower harmful cholesterol levels. Examples of foods high in mono-unsaturated fats include olive oil and rapeseed oil.
• Polyunsaturated fats 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. Try and choose lower fat versions of dairy foods, such as semi-skimmed or skimmed milk, and reduced-fat yoghurt, whenever you can.
If you have high cholesterol there are several ways in which a vegetarian diet can help. If you are thinking of switching to a vegetarian diet as a way of avoiding the saturated fat associated with meat then vegetarian sources of protein such as tofu, soya mince and Quorn are an excellent alternatives. If you want to cut down on saturates by reducing your dairy intake soya milk and soya yoghurt are useful alternatives to dairy milk and yoghurt. Rice and oat milk are also becoming more widely available and all are low in saturated fat and high in polyunsaturates.
Essential fatty acid Omega-3 can help to reduce your cholesterol levels (see Omegas) and fibre, which is abundant in a balanced vegetarian diet, is also cholesterol reducing. Foods that are part of a healthy vegetarian diet include pulses such as chickpeas and kidney beans. Pulses can be doubly 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.
The Scientific Evidence for Cholesterol Lowering Effects of One Type of Vegetarian Diet
A small Canadian study lead by Professor David Jenkins, from the University of Toronto hit the headlines in 2002. Results of the study involving 13 people who had the inherited form of hyperlipidemia suggested that a change in diet has a beneficial effect on cholesterol levels.
In Professor Jenkins' study 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).
This diet had the effect of reducing LDL cholesterol levels by 29 per cent - a similar effect to that achieved with statins medication. [*Reference: Professor David Jenkins University of Toronto 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 your diet to a vegetarian one with more fibre can produce changes in your digestive system which may cause bloating and gas as the friendly bacteria in your gut 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 some more water.
Diet is not the only factor, adopting an active lifestyle and losing weight are also important.