A healthy diet helps your physical and mental health.
It can reduce the risk and severity of conditions such as obesity, heart disease, diabetes, hypertension, depression and cancer.
Why a balanced diet?
Sometimes we eat because we enjoy the taste and experience of different foods, and sharing food and meals are important socially.
But other than for pleasure, our bodies need food to get nutrients, vitamins, minerals and energy.
Very few foods are either all good or all bad – so by having an idea of the balance in your diet, it should be easier to enjoy food and be healthy.
There are seven essential nutrients that come from a balanced diet, and a rough percentage of daily calories should come from each nutrient, see Table 10.
Table 10: Essential nutrients for a healthy balanced diet
|Nutrient||% of daily calories||Function||Source|
|Carbs||45–55%||Energy||Grains (refined & unrefined): wheat, maize, corn, millet, oats, rice, flour, pasta, noodles; potatoes; sweet potatoes, yam. Fruit (sugar).|
|Protein||10–35%||Tissue growth and maintenance||Meat, fish, nuts, eggs, soya, beans and pulses.|
|Fat||20–35% from fat||Energy, energy storage, hormone production||Nuts, seeds, plant oils, dairy products (milk, cheese).|
|Fibre||Included in carbs.||Regulates blood sugar levels, bowel function and bowel health.||Peas, beans, vegetables, fruit, oats, whole grains, brown rice, nuts, seeds.|
|Vitamins & minerals||trace||Metabolism regulation, aiding cell growth, other biochemical functions||Specific to each vitamin/mineral. A range of vegetables, lean meat, nuts and seeds will cover most peoples needs.|
|Water||0||Maintaining hydration||Drinking water, other beverages. About 20% of water intake comes from food.|
Eating a wide range of different foods will give you body the nutrients and micronutrients that it needs.
A healthy diet should include a varied selection of foods. But some types of food are better for us (”5-a-day” for fruit and vegetables) than others (cakes, biscuits etc), see Table 11.
Table 11: Eat more, eat less…
|Eat more||Raw and cooked vegetables & fruit (“5-a-day”), nuts, seeds, beans & pulses, whole grain cereals/bread, lean white meat (chicken without skin), fish (especially oily)||Linked to many aspects of better health including reducing LDL.|
|Eat in moderation||Lean cuts of beef, lamb, pork, shellfish, dairy products (low fat), unsaturated fats (olive oil, vegetable oil). Dried fruit, jams. Sucrose, honey, fructose, chocolate.||These foods can all be an important part of your diet.|
|Eat less and in limited amounts||Saturated fat (butter, margarine, lard, cheese, cream, high fat milk), trans fat, salt (less than 5g daily). Processed meats/fatty cuts of meat (sausages, salami, bacon, ribs etc).
Processed meals (high in fat, sugar and salt).
Pastries, muffins, pies, cakes, sweets, etc.
Alcohol is high is sugar and calories and is only recommended in moderation.
|These foods are not good for your health.
Some guidelines include specific recommendations.
Diet and weight
In general, if we eat fewer calories than our body needs for energy, we will lose weight and if we eat more than we need we put on weight.
But this is not the whole story. We all have an individual balance depending on how our body signals to itself to process food. Some people burn more energy and in different ways, and this explains some of the diversity in how we all look.
This can also change over time through life depending on whether we are still growing and when we get older.
Some foods are processed by our bodies in ways that are more healthy. This tends to be foods that release sugars more slowly and that contain fibre.
Other foods including saturated fats and foods that are high in salt or simple sugars can have a negative impact on health because of how the body processes them.
Calories and lifestyle
The average number of calories you need each day can vary and is influenced by many factors including sex, age, metabolism, physical activity, growth and pregnancy.
Body height, weight and size, genetics, hormone levels and any illness can affect how much energy we need.
Daily guidelines recommend around 2500 calories for men and 2000 calories for women.
Differences within nutrients
There are healthy and less healthy dietary sources of nutrients, especially for carbohydrates (carbs) and fats. These are explained below and in Table 12.
Table 12: Types of fat and their impact on your health
|Saturated||Generally solid at room temperature. Animal fat from meat and dairy fat (butter, cheese, cream). Some plant oils including coconut oil and palm oil.||Less healthy. Linked to high LDL and increase heart disease. Diets high in saturated fat are linked to raising levels of LDL; this can be a risk factor for heart disease. Saturated fat should not be excluded from the diet however, just consumed in smaller amounts (7-10% of fat intake). A range of fats is needed for healthy functioning of the body.|
|Unsaturated||Vegetable oils like olive, sunflower, and rapeseed/canola oil. Nuts, avocados.
Omega-3 (from oily fish or supplements) and omega-6.
|Improves insulin sensitivity, LDL and TG compared to saturated fats.
Replacing saturated fats by unsatruated fats and carbs reduces the risk of heart disease.
|Trans fats||Trans fats are included in processed foods.As a processed cooking oil, it was widely used by fast food outlets for frying.||Trans fats increase bad cholesterol, reduce good cholesterol and are bad for your health, especially “partially hydrogenated trans fats”.
They are banned in some countries and US states for use as cooking oils.
Carbs: simple vs complex
It is recommended that carbohydrates (“carbs”) form the basis of most diets. You should aim for half of total energy (calorie) intake to come from carbs. This food group can be separated into simple and complex carbs
Complex carbs such as wholewheat flour and pasta, and brown rice, contain larger chains of sugar molecules. These take longer to digest than procesed grains. This makes you feel full for longer, helping to control your appetite.
Complex carbs provide energy and are key sources of nutrients such as fibre, B vitamins and minerals.
The more refined complex carbs e.g. white flour, pasta and rice are digested more quickly by the body. This makes them a faster source of energy. However, these types of carbs do not offer as many additional nutrients. This is why whole-wheat and brown carbs helps improve the overall quality of your diet.
Simple carbs are the sugars. These can be natural (e.g. fructose found in fruit) or refined (e.g. sucrose or glucose in soft drinks, sweets and biscuits).
Another key carb-related term is the Glycaemic Index (GI). This relates to how quickly the sugar in either complex or simple carbohydrates is released into the blood stream.
Low GI foods release sugar slowly. This gives a prolonged supply of energy to the body. Higher GI foods give shorter bursts of energy.
The GI of a carbohydrate is affected by numerous factors including whether the carb is simple or complex but also how the food is cooked and also what it is eaten with.
Fruit and vegetables are carbohydrate foods. They include a wide range of vitamins and minerals as well as soluble fibre. You should aim for five portions of fruit and vegetables a day.
Fruit juice is counted as one of your 5-a-day, but if you are watching your weight it is better to eat whole fruit which takes longer to digest and keeps you felling full for longer.
Fat: saturated and unsaturated
Dietary fat is important for making healthy cells. It produces hormones and other signalling molecules and is a source of energy and energy storage.
Two categories of dietary fat are saturated and unsaturated. They have the same amount of calories but different effects on your health. We need to aim for a good balance between the different dietary fats to optimise our health and reduce health risks.
Saturated fats are generally solid at room temperature and these are the fats that will have a negative impact on our health. They are the naturally occurring ‘bad fats’ and are found from butter, hard cheeses, fatty meat/ meat products, cream, lard, suet and some plant oils including coconut oil and palm oil.
Unsaturated fats include the polyunsaturated, monounsaturated and Omega 3 fats and will have a positive impact on our health. Monounsaturated and polyunsaturated fats are found in oils such as olive, rapeseed and sunflower.
Omega-3 and omega-6 are known as essential fatty acids (EFA’s) because the body can only get these from diet. They are found in oily fish such as sardines, salmon and mackerel.
Trans-fats are a form of unsaturated fat that rarely exists in natural food but are associated with partially hydrogenated vegetable oils. They are often added to processed foods such as cakes and biscuits and so these should be eaten less often and in small amounts.
Trans fats as cooking oils have been banned in some regions because of their impact on cardiovascular health.
Diet and cholesterol
Cholesterol is a compound similar to fat. It is needed by the body to form the outside barrier of cells (membrane). It can be both made by the body and consumed through sources in the diet. Absorption of dietary cholesterol is complicated and other factors such as genetics can affect the overall level of cholesterol circulating in the blood.
High levels of cholesterol in the blood are associated with damaging arteries and heart disease.
Specifically, having high levels of low-density lipoprotein cholesterol (LDL) and low levels of high-density lipoprotein cholesterol (HDL) in the blood increase the risk of heart disease.
Changes in diet can make a difference though. Choosing foods with more unsaturated fats compared to saturated fats can increase levels of HDL and lower levels of LDL in the blood.
Diet and triglycerides
Similar to cholesterol, triglycerides are fat molecules that aid in metabolism and moving other fats around the body.
Like cholesterol, high levels of triglycerides in the blood have been linked to heart disease.
Dietary fibre: soluble vs insoluble
There are two types of dietary fibre. This can be classed as either soluble (which changes how other nutrients are absorbed in the digestive system) or insoluble, (which is not metabolised and which itself absorbs water).
A mixture of both soluble and insoluble fibre is needed for good health.
Soluble fibre regulates blood sugar levels and balances intestinal pH levels.
Insoluble fibre helps with digestion and elimination by speeding up the passage of food in the digestive system.
Dietary fibre typically contains a proportion of the carbohydrate cellulose, which cannot be digested by humans as we lack the enzyme to break it down.
Vitamins and minerals
Vitamins are chemical compounds and minerals are chemical elements that the body needs in small quantities. They are used by the body for a wide range of functions and very low levels (deficiency) are related to some health complications.
Unless you have a low level of a particular mineral or vitamin, there is unlikely to be a benefit from taking a supplement.
Protein is essential in maintaining the function of all cells in the body and is also a source of energy.
It is made up by complex combinations of 22 amino acids. Ten of these amino acids can only be obtained by diet.
Although protein is an essential part of your diet, this is also only needed in moderation.
What about salt?
High intake salt and high salt containing foods increases the risk of high blood pressure and therefore increased risk of coronary heart disease.
Most salt in the UK diet comes from processed foods such as pastries, convenience and savoury type snack foods. Tinned foods can also be high in salt so if in doubt check the nutritional labelling.
Recommended intake of salt varies depending on your age, health and other factors. UK guidelines recommend no more than 6 grams a day for adults, which is the equivalent to 2.4 g of sodium.
To convert sodium to salt multiply by 2.5. US guidelines are 5 g/day while recognising that actual average intake is often twice this high.
Ways of cooking?
The way that we cook and prepare food is important. Certain cooking methods are also better at retaining the nutrients within food.
Cooking techniques such as roasting and frying can be less healthy if a large amount of fat (oil or butter) is added during the cooking.
However, you can fry and roast using small amounts of healthier fats such as olive and rapeseed oil.
Grilling and steaming are widely considered to be healthier cooking techniques in most cases.
The online references for this booklet includes links for further information.
1 July 2012