Guide to the Key Nutrients

Which nutrients does your body need?

The human body is an amazingly complex mix of interconnected biochemical, electrical and physical processes which we are still trying to unravel. To get the best out of it we should make sure it is supplied with the correct food and drink.

In this section we can take a closer look at each of the common nutrients and how to ensure that our bodies have enough of them to function effectively.

You can follow these quick navigation links to a particular topic:

• Water
• Protein
• Carbohydrate
• Fat
• Fibre
• Salt
• Vitamins and Minerals

Do I really need to know about nutrients and my diet?

In short, no you don’t. In general, adults who are in good health, enjoy outdoor activity and eat a diet with a broad selection of commonly available foods which are grown, stored and cooked in a nutrient-friendly manner will be unlikely to suffer from significant nutrient deficiencies.

If you fit that description then you should probably just keep doing what your already doing.
...too much salt in the diet also makes the body retain extra fluids...

Unfortunately many of us do not fall into that group. We are more likely to buy food that has been picked before it has reached its nutritional peak (so that it doesn’t over-ripen whilst being transported long distances). Then it is processed or over-cooked into something else which can seriously reduce the value of the nutrients available in the original food, in some cases to almost nothing.

So by gaining even a little understanding of the role that nutrients play in our bodies and diets you can make better choices about selecting and preparing nutrient rich, sustaining foods.

Which nutrients are we talking about?

The human body relies on a broad spectrum of compounds to get us safely from one day to the next. Many of these are combined and constructed within the body but we need a consistent source of raw materials to keep the whole complex process running smoothly. We get these nutrients from the food and drink we give ourselves. The key ones introduced here include:

Water

When you consider that roughly two thirds of our bodies are made from water it is not surprising that it is one of the most important raw materials we can give to ourselves. If we were to remove any of the other nutrients from our diets for a period of time we might fall ill and may even cause some long term damage to ourselves. The effect of removing water from our diets is much more dramatic – fatality after just four days is common.

Water is a fundamental part of our body’s chemistry and construction. When it is in short supply the processes in our body slow down or stop altogether. Ensuring that you are getting sufficient water for your body’s needs is the best first step towards a healthy diet you can take. It is also the least expensive and can be the easiest to implement.

We lose water from our bodies through perspiration, respiration and through waste products i.e. going to the toilet. Urination typically accounts for around 1,500ml daily and a further 150ml leaves in bowel movements; sweating loses almost half that again at 750ml; and we breathe out around 400ml per day, though we commonly only notice that if on a frosty morning or if we breathe onto cold glass.

Someone who is more active or who is in a warmer environment will sweat more than average. Remember that we sweat all the time to regulate our body temperature but don’t usually notice. We only get to see the beads of sweat when we produce it faster than it can evaporate away from our skin surface or clothing.

All this water has to be continually replaced. We can get quite a lot of the water we need contained within the food we eat but the majority comes from drinking water and water-based fluids. The best available advice is to drink a further 1½ to 2 litres of water per day which equates to about 3½ pints. That’s 6 to 8 standard glasses of 250ml each. Follow this link to find suggestions on how to ensure you get enough water.

Protein

After water protein is the largest constituent of our bodies, in muscles, organs and other lean body tissues. It typically accounts for about a fifth to a quarter of weight in a healthy individual. Protein in our diet provides the primary source of building materials for our bodies as they grow, repair and defend themselves.

Proteins are made up of combinations of amino acids which can be thought of as the bricks from which other body parts are constructed.

There are twenty or more amino acids which combine with each other to make our bodies’ component parts. Many of these can themselves be made within the body. But there are 8, known as the essential amino acids, which must come from our diets. It is very important to include foods which contain these essential amino acids in your day to day dietary choices.

The best sources of proteins which supply these essential amino acids come from:

• Animal proteins such as meat, poultry, fish and dairy products
• Plant proteins such as soya and quorn as well as pulses, cereals and nuts

The plant proteins tend to be available in smaller quantities so it is important to use a broad range of foods if these are to be your primary source.

Carbohydrates

Carbohydrates are normally the body’s main fuel source. The carbohydrates in our diet are broken down into sugars and these are transported through our bloodstream to our liver and muscles for storage as glycogen. We typically store enough energy in this way to keep us going for about one day without food, and less than that if we are particularly active.

Carbohydrates have a lower calorie density than fat or alcohol so they can be used to bulk up meals. By including them at every meal the body’s glycogen energy stores can be kept topped up through the day.

To determine what makes a good source of carbohydrate we must consider how quickly the sugars become available in the bloodstream. This measure is called the Glycaemic Index or GI of the food. You can follow this link to another section of the site where the glycaemic index and the glycaemic load (GL) of food are explored further.

Fat

Fat is an essential part of everyone’s body make up. It forms part of the structure of cells, including those in the brain and nervous system, and forms a protective cushion around many of the major organs. Women have gender-specific fat deposits around the breasts and hips which are essential for hormone balance and menstrual function.

Fat is also used to store excess energy. This fat can be found under the skin’s surface and in additional build ups around the organs in the body cavity. Having some of this fat is also essential as it is used daily by the body to release and store energy as our activity and blood sugar levels rise and fall.

However, calorie rich diets and a reduction in the amount of energy expended through daily activities means that many modern societies have seen a very rapid increase in the number of people storing excessive fat on their bodies.

Along with the additional strain placed on the bodies, organs and systems of overweight individuals comes an increased risk of serious illnesses and early, preventable death. This is particularly noticed in those who tend to store their excess body fat around the mid-section rather than their hips and thighs.

You can follow this link to read more about the different types of fat such as saturated fats, trans fats or hydrogenated fats, monounsaturated fats and the polyunsaturated fats including the omega-3 and omega-6 families.

Fibre

The fibre in our diets helps our bodies to maintain a healthy gut, moderates the absorption of carbohydrates and encourages the passage of foods and waste through the digestive system. A lack of fibre can lead to bowel problems including constipation. On average, UK adults fall short of the Department of Health’s recommended minimum intake by between 25% and 50%.

Fibre is made up of complex carbohydrates and is often described as either insoluble or soluble. In practice many natural foods contain a mixture of both. The insoluble fibre tends to resist the efforts of our digestive tract to break it down and passes through us, gently scouring the inside surface of the gut on the way. This helps us to maintain regular bowel movements and improves digestive health. The best sources of insoluble fibre include whole wheat products, brown rice and vegetables.

Soluble fibre is broken down in the body slowly, helping to regulate the absorption of glucose into the bloodstream. Soluble fibre is common in vegetables, fruit, seeds, beans, lentils and other pulses. This fibre also helps to reduce LDL, the “bad” cholesterol.

In a weight control or weight loss diet foods which are high in fibre are very welcome as they tend to fill you up and keep you feeling fuller for longer.

Salt (or sodium)

Salt is another nutrient which is needed in order to maintain proper functioning of a wide variety of biochemical processes within our bodies. Food labelling sometimes causes confusion by quoting sodium content rather than salt content.

Grams of sodium x 2.5 = grams of salt

e.g. 1.4g sodium = 3.5g salt

The salt which is most commonly added to foods for seasoning during cooking or at the table is sodium chloride. Sea salt and rock salt is also sodium chloride but may also carry small amounts of additional minerals.

But we tend to get most salt in our diets already within prepared foods such as ready meals, breakfast cereals, soup, sauces, bread and biscuits. Indeed we usually get much more than we need for normal health and this can cause problems. Excessive sodium from salt can contribute to raised blood pressure and damage to the heart and blood vessels and increase the likelihood of suffering a stroke.

Including too much salt in the diet also makes the body retain extra fluids as it tries to dilute the excessive salt. Fluid retention tends to increase weight and is often the reason that people feel they have put on weight after eating salt laden food, such as many takeaway curries. Restaurants and cafes also tend to include more salt than you would at home as it improves the taste and life of their food.

By choosing foods with less salt content and adding less or none to our foods during cooking and at the table we can help ourselves greatly in controlling salt intake levels. It’s true that our foods may taste a little more bland initially but our taste buds will adjust to the new levels within a few weeks. After that you will find that some foods which tasted normal before will become overpoweringly salty. You’ll wonder how you ever kept some of them down...

Vitamins and minerals

In general, we must eat and drink the vitamins and minerals we need to help our bodies to function healthily. The daily food choices we make to fulfil this need are vital. Indeed, it is particularly important for anyone who is considering cutting down their calorie intake in order to control weight that they choose to “spend” their calorie allowance on food which will provide a full complement of vitamins and minerals in their diet.

Many of the foods we commonly eat have been refined and processed such that they provide energy/calories, carbohydrates, protein and fats but very little in the way of vitamins and minerals. Sliced white bread is one obvious example but there are many more such as cakes, biscuits and sugary drinks. These foods will use up your calorie allowance without earning their keep – they are best dramatically reduced or removed altogether from a healthy diet.

How much is enough where nutrients are concerned?

There are several measures of all the macronutrients and micronutrients available. The difficulty is that they do not all agree with each other and none of them take the individual’s needs into account. For example, an office or factory worker who lives in an urban area, with its associated pollution, drinks in moderation, smokes cigarettes and does minimal exercise will have a different nutrient requirement from a keen sportsperson of the same weight who lives in the suburbs or countryside.
The BDA recommends that we should get our nutrients from our normal varied and well-balanced diets

For the vitamins and minerals each Government, some federal bodies and several scientific studies produce guidance amounts. These might include the minimum needed to avoid diseases and the maximum permissible to prevent damage from excessive intake, for an average adult.

You are most likely to come across the Recommended Daily Amounts or RDA’s. These originate at a European level and are the values which, by law, must appear of food packaging if that food makes claims about its beneficial nutritional content.

Reference Nutrient Intake or RNI levels are set by taking measurements of nutrient levels in healthy people and then deriving a value for the general population. These vary, sometimes considerably, from one country to the next.

You may also come across the DRV or Dietary Reference Value. These were set by the UK Department of Health in the early 1990’s and use the measure of how much of each nutrient an average person will need, the EAR – Estimated Average Requirement, and a higher value which might be sufficient for 97% of the population known as the RNI or Reference Nutrient Intake. The RNI will be more than most people need but not so much more that harm would be caused.

Still reading? It seems that more work will have to be done in this area to help clarify certain key measures:

How much of each nutrient is enough to avoid ill health?

How much is enough to ensure optimum intake?

How much is too much and may cause harm?

Until then the best course of action is to choose your food wisely using the long established guidelines of including a wide variety of food sources such as:

• Potatoes, wholegrain bread and other cereals
• Fruits and vegetables
• Lean meat, fish, pulses, nuts and seeds
• Low fat dairy products
• Healthy fats

Is it possible to have too many nutrients?

Yes, it is possible to have too many nutrients; and excessive amounts of certain vitamins and minerals can cause lasting damage to the body. But it is very unlikely to happen if a normal adult is following a well-balanced diet and not taking excessive supplements.

The British Dietetic Association recommends that we should get our nutrients from our normal varied and well-balanced diets. However, for those who want an “insurance policy” to ensure that they are getting all the nutrients they need a multi-vitamin and mineral supplement covering at least 15 nutrients at or below levels of 150% of the European RDA’s could be taken. They warn against taking single dose supplements in addition in case that puts you at risk of consuming excessive doses.

It is even possible to have too much water and some rare cases have occurred where individuals have been harmed by over-saturating, causing other nutrients to be leached away from the body. However, we are far more likely to be suffering from drinking too little water than too much. And the body has a simple mechanism for getting rid of excess liquids from the body – we will visit the toilet more often.

Selection of foods which are rich in nutrients

There are some useful rules of thumb regarding selecting food which will give a broad base of the nutrient needed by our bodies.

Choose wholegrain foods in place of more processed varieties; for example, wholemeal bread and pasta instead of white bread and pasta. Much of the grain’s nutritional value is removed along with the fibre and wheat germ. And choose brown rice in place of white rice.

Choose fruits and vegetables which have a diverse range of colours; eat a minimum of 2 to 3 portions of fruit and 3 to 4 portions of vegetables per day.

Get your proteins from a variety of sources including meats, fish, dairy products, nuts, seeds and pulses. Many of the micronutrients come along with the different protein sources.

Choose water in place of other drinks, especially if you can swap out sugared, caffeinated and alcoholic drinks.

And finally, remember that loading up on the “superfoods” will do you no addition good if you body cannot absorb their nutrients. The key measure is the bioavailability of their nutrients to the body. So a handful of superfood berries may indeed contain more of a particular nutrient than a handful of blackberries. But if your body can only make use of a limited amount of that particular nutrient then either berry will be good enough.

The body’s reaction to many nutrients often depends on how well supplied it is with all the other nutrients. So a deficiency in one mineral, say, might prevent the efficient absorption of another, even if that one is plentiful in the diet. For example, someone who has low vitamin D levels is less able to absorb and use calcium for bone building.

It is important, therefore, to take a more broad based approach to the body’s systems and ensure that a wide variety of foods in the diet ensure that all these essential nutrients are available.