Healthy Diet

What is a healthy, well-balanced diet?

A well-balanced diet includes food from the five main food groups. These are:

• bread, cereal (including breakfast cereals) and potatoes (starchy foods),
• fruit (including fresh fruit juice) and vegetables,
• meat and fish,
• milk and dairy foods, and
• fat and sugar.

Most people should be eating three main meals a day. Most people need to eat more starchy foods and more fruit and vegetables, as well as reduce their fat intake, drink less alcohol and eat less salt. Look for labels that say food is low in fat (particularly saturated fat), low in salt and sugar-free.

Fruit and vegetables are packed with vitamins and minerals, low in calories and high in fibre. Eating lots of fruit and vegetables keeps the HEART and body healthy. They are also an ideal alternative to eating crisps and chocolate as snacks between meals.

Diet - Definition

Diet

Definition

Healthy eating is about maintaining a balanced diet. This means eating foods from all the different food groups in the right amounts.

There are five main food groups, and each one contains nutrients that are essential for your body's growth, energy and body maintenance. Nutrients are vitamins and minerals that regulate your body's chemical processes and functions and help to keep you fit and healthy.

The five main food groups are:

Carbohydrates

Carbohydrates include foods like bread, pasta, potatoes, cereals, low fat oven chips, rice, oats, noodles, couscous, maize and cornmeal. They provide energy and should make up about one third of your diet.

Carbohydrates are divided into two groups - refined and unrefined. Refined carbohydrates include white bread and sugary cereals that have had the fibre removed. Unrefined carbohydrates include brown and wholemeal bread, pasta and rice, and you should choose these options whenever possible.

Some people think starchy foods are fattening. However, it is the fats that are added to them, such as butter and cheese, which can make them unhealthy. Avoid frying these foods and choose healthier alternatives, such as low fat oven chips rather than fried chips.

Fruit and vegetables

Fruit and vegetables are rich in vitamins and minerals which are essential nutrients that your body needs in order to work properly. As well as keeping your skin and hair healthy, they can reduce your risk of getting heart disease and some cancers.

You should aim to eat five portions of fruit and vegetables each day. They can be fresh, frozen, canned or dried. One portion counts as a large piece of fruit, such as an apple or banana, three heaped tablespoons of vegetables, or one glass of 100% fruit or vegetable juice (although this only counts as one portion regardless of how much you drink). Beans and pulses, such as baked beans or lentils, also contribute to this group, but they only count towards one portion no matter how many different types you eat.

Protein

Protein helps to build and repair your body. Foods rich in protein also contain minerals, such as iron, zinc and magnesium, as well as important B vitamins. They should make up about one fifth of what you eat each day.

Sources of protein include meat, fish and eggs, as well as non-animal products, such as beans and nuts. To keep it healthy, trim fat from meat, remove the skin from chicken, drain fat away after cooking, and try to eat two portions of fish each week. One of these fish portions should be oily fish, such as salmon, mackerel or fresh tuna. Canned tuna does not count as oily fish because the canning process removes the beneficial oils. Avoid frying meat and fish, and try to grill, roast or microwave instead.

If you are a vegetarian, you can get the protein that you need by including seeds, nuts, tofu, soya products and beans in your diet. These foods provide protein, fibre and iron but, unlike the non-vegetarian examples, they do not provide much zinc or vitamin B12 unless they are fortified (have had vitamins or minerals added to them).

Dairy

Cheese, milk, yoghurt and calcium fortified soya alternatives are all examples of dairy foods (cream and butter are in the fats group, and eggs fall under protein). Dairy products are rich in calcium, which is important for strong bones and teeth. You should aim to get 700mg of calcium each day, which is roughly the same as a pint of milk, or two small yoghurts. Choose lower fat versions, such as semi-skimmed milk, low fat yoghurt and reduced fat cheese.

If you do not drink cow's milk or eat dairy products, you can get calcium from soya milk and yoghurts with added calcium, and from vegetables such as broccoli and cabbage.

Fat and sugar

Fats and sugars contain more energy than any other food group and should make up the smallest part of your diet. Foods such as butter, mayonnaise, chocolate, crisps, cakes, soft drinks, jam, sweets and ice cream, all usually contain high amounts fat.

Fats are divided into two groups - saturated and unsaturated. Saturated fat is found in cream, margarine, and fried foods. This type of fat can contribute to heart disease. Unsaturated fat is found in vegetable oils and oily fish. Eating a small amount of unsatuated fat will help to keep your IMMUNE SYSTEM healthy and can reduce CHOLESTEROL levels.

Sugary foods are bad for your teeth and are full of calories. You should therefore eat them sparingly, as a special treat.

DIET - INTRO

Diet

Introduction

Good health is fundamental to leading a full and active life, and getting the right nutrition is an important step towards good health.

The word diet is often used to describe an eating plan intended to aid weight loss. However, diet really refers to the foods a person eats in the course of a day, or week. The more balanced and nutritious the diet, the healthier the person can expect to be. A balanced diet means eating the right amount of foods from all food groups.

The benefits of a balanced diet are numerous. No single food contains everything the body needs so it is important to eat a wide variety. The right amount of vitamins and nutrients can increase life expectancy by keeping the HEART and body healthy, and preventing many long-term illnesses.

Body weight can also be kept to an acceptable level through healthy eating, leading to a fitter and more active lifestyle.

Magnetism

Magnetism

This Revision Bite is about magnetism. It has these parts in it: Bar magnets Magnetic fields The Earth's magnetic field Electromagnets Using electromagnets

Bar magnets

Bar magnets are permanent magnets. This means that their magnetism is there all the time and cannot be turned on or off. They have two poles:

• north pole (short for north-seeking pole)
• south pole (short for south-seeking pole).

The north pole is normally shown as N and the south pole is normally shown as S.

A bar magnet

Magnets are made from magnetic materials. These are metals that can be magnetised or will be attracted to a magnet. Most materials are not magnetic, but iron, cobalt and nickel are magnetic. Steel is mostly iron, so steel is magnetic too.

Attract and repel

If you bring two bar magnets together, there are two things that can happen:

• if you bring a north pole and a south pole together, they attract and the magnets may stick together;
• if you bring two north poles together, or two south poles together, they repel and the magnets push each other away.

We say that unlike poles attract, and like poles repel.

Remember that unmagnetised iron, steel, cobalt and nickel objects will be attracted to either pole of a magnet. This means you can only show that an object is a magnet if it repels a known magnet.

Magnetic fields

Magnets create magnetic fields. These cannot be seen. They are the space around a magnet where magnetic materials are affected by forces, and so may be attracted or repelled.

Although we cannot see magnetic fields, we can detect them using iron filings. The tiny pieces of iron line up in the magnetic field.

It would be difficult to draw the results from the sort of experiment seen in the photograph, so we draw simple magnetic field lines instead. In the diagram, note that:

• the field lines come out of N and go into S
• the field lines are more concentrated at the poles.

The magnetic field is strongest at the poles, where the field lines are most concentrated.

Attraction and magnetic fields

Iron filings can show the magnetic field between two magnets where unlike poles face each other, and so attract.

If we look at the field lines, we see that they go from the north pole of one magnet to the south pole of the other magnet.

Magnetic field lines between two attracting magnets

Repulsion and magnetic fields

Iron filings can also show the magnetic field between two magnets where like poles face each other, and so repel.

If we look at the field lines, we see that they do not go from one magnet to the other, and they do not cross.

Magnetic field lines between two repelling magnets

The Earth's magnetic field

The Earth does not contain a giant bar magnet, but it behaves as if it does. The Earth has a magnetic north pole and a magnetic south pole. Compasses work because bar magnets can line up in the Earth's magnetic field and point north. Make sure you understand these things:

• the north pole of a bar magnet is actually called the 'north-seeking pole', and it points to the Earth's magnetic north pole;
• the south pole of a bar magnet is actually called the 'south-seeking pole', and it points to the Earth's magnetic south pole.

Compasses point towards the Earth's magnetic north pole

Small compasses called plotting compasses can be used to show the magnetic field around a bar magnet, instead of using iron filings. The needle in each compass turns and lines up along the field lines.

A line of plotting compasses follows a field line

If we arrange some plotting compasses around a bar magnet, we see that the needles point away from the magnet's north pole and towards its south pole.

Plotting compasses in a circle

When you do this experiment, it is important to keep iron or steel objects away, otherwise the compass needles might point to them instead

Electromagnets

A magnetic field is produced when an electric current flows through a coil of wire. This is the basis of the electromagnet. We can make an electromagnet stronger by doing these things:

• wrapping the coil around an iron core
• adding more turns to the coil
• increasing the current flowing through the coil.

How to make a simple electromagnet

The magnetic field around an electromagnet is just the same as the one around a bar magnet. It can, however, be reversed by turning the battery around. Unlike bar magnets, which are permanent magnets, the magnetism of electromagnets can be turned on and off just by closing or opening the switch.

Using electromagnets

Many objects around you contain electromagnets. They are found in electric motors and loudspeakers. Very large and powerful electromagnets are used as lifting magnets in scrap yards to pick up, then drop, old cars and other scrap iron and steel.

An electromagnet in a scrap yard

Electric bell

Electric bells like the ones used in most schools also contain an electromagnet.

• When the current flows through the circuit, the electromagnet makes a magnetic field.
• The electromagnet attracts the springy metal arm.
• The arm hits the gong, which makes a sound and the circuit is broken.
• The electromagnet is turned off and the springy metal arm moves back.
• The circuit is complete again.

ELECTRICAL ENGINEERING FOR HEALTH

Magnetic Resonance Imaging for Medical Diagnostics

Today's medical professionals use a variety of diagnostic tools to probe the condition of biological entities. One such technique is that of magnetic resonance imaging (MRI).

MRI works in the following manner. The patient is first placed in a strong magnetic field. The paramagnetic atoms become aligned with the direction of the field. The aligned hydrogen atoms take on resonance characteristics; that is, they can absorb energy and re-emit the energy as electromagnetic radiation at a specific frequency. A short pulse of radiofrequency (RF) waves is then sent to the body. The aligned protons (hydrogen) are excited and become deflected. Once the RF pulse is stopped, the protons realign with the magnetic field while emitting RF waves that are measured. The emitted RF waves contain information on both the physical and chemical characteristics and spatial distribution of body materials. For instance, an image representing the density of hydrogen nuclei within the body is produced.

The electromagnet experiment serves to illustrate just a fraction of the physics behind MRI. The electromagnet interacts with metal objects on a macroscopic scale whereas the object of MRI is to take advantage of interactions on an atomic scale.

The electrical engineer is involved in the development of medical diagnostic procedures in a variety of ways, including: Radiofrequency (RF) waves are studied in electromagnetics Instrumentation is developed to measure the emissions Signal processing techniques are used to analyze and enhance the images

Electromagnetism

Electromagnetism describes the relationship between electricity and magnetism. Nearly everyone, at some time or another, has had the opportunity to play with magnets. Most of us are acquainted with bar magnets or those thin magnets that usually end up on refrigerators. These magnets are known as permanent magnets. Although permanent magnets receive a lot of exposure, we use and depend on electromagnets much more in our everyday lives. Electromagnetism is essentially the foundation for all of electrical engineering. We use electromagnets to generate electricity, store memory on our computers, generate pictures on a television screen, diagnose illnesses, and in just about every other aspect of our lives that depends on electricity.

Electromagnetism works on the principle that an electric current through a wire generates a magnetic field. This magnetic field is the same force that makes metal objects stick to permanent magnets. In a bar magnet, the magnetic field runs from the north to the south pole. In a wire, the magnetic field forms around the wire. If we wrap that wire around a metal object, we can often magnetize that object. In this way, we can create an electromagnet.

Experiments Involving Electromagnetism

In order to find out more about electromagnetism, and do an experiment of your own, click on one of the pictures below. Try making your own:

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GALVANO METER

ELECTROMAGNET

ELECTRIC METER

Using Electromagnetism in Medicine

Find out how doctors use electromagnets in Magnetic Resonance Imaging (MRI) to help diagnose illnesses.

HUMAN BODY

Human Body

The human body is made up of a head, neck, torso, two arms and two legs. The average height of an adult human is about 5 to 6 feet tall. The human body is made to stand erect, walk on two feet, use the arms to carry and lift, and has opposoble thumbs (able to grasp). The adult body is made up of: 100 trillion cells 206 bones 600 muscles 22 internal organs There are many systems in the human body: Circulatory System (heart, blood, vessels) Respiratory System (nose, trachea, lungs) Immune System (many types of protein, cells, organs, tissues) Skeletal System (bones) Excretory System (lungs, large intestine, kidneys) Urinary System (bladder, kidneys) Muscular System (muscles) Endocrine System (glands) Digestive System (mouth, esophogus, stomach, intestines) Nervous System (brain, spinal cord, nerves) Reproductive System (male and female reproductive organs)

A Look Inside the Human Body Anatomy of the Human Body BBC: Human Body Get Body Smart Hillendale Health: Learn About Your Body Introduction to Gross Anatomy Crossword Puzzles KidsHealth Lymphatic System Medtropolis: The Virtual Body National Geographic: Explore the Human Body Smithsonian: Artificial Anatomy Southern California Orthopedic Institute Home Page Surfing Inside the Human Body Systems Youthealth

		Cardiovascular System Circulatory System Circulatory System 1 Circulatory System: The Life Pump How Your Heart Works Kids Health: Your Heart & Circulatory System Preview the Heart The Circulatory System The Human Heart Wikipedia: The Circulatory System
		How Your Immune System Works Kids' Health: The Immune System Kids Health: Your Immune System The Immune System: Defending Our Bodies Understanding The Immune System Wikipedia: The Immune System
		eSkeletons Project Human Skeleton Printout-Enchanted Learning.com Kids Health: Your Bones Skeletal System Skeletal System: The Bone Zone Skeletal System (Front View) Skeletal System (Back View) The Skeletal System The Skeleton Wikipedia: Skeleton
		Excretory System Kids Health: Your Urinary System Poison Protection Urinary System Urinary System 1 Wikipedia: The Excretory System Yucky: Armpits Yucky: Poop
		Back View Of The Muscular System Bundles of Energy: The Muscular System How Muscles Work Kids Health: Your Muscles Muscular Systems (Front View) Muscle System Overview Wikipedia: Muscular System
		Control of the Thyroid Gland Endocrine System Kids Health: Your Endocrine System The Endocrine System Wikipedia: Endocrine System Yucky: The Endocrine System
		Digestive System Digestive System 1 Food Factory How the Body Works: The Digestive System Kids Health: Your Digestive System My Body The Digestive System The Digestive System 1 The Real Deal on the Digestive System Wikipedia: Gastrointestinal Tract
		Kids Health: Your Brain and Nervous System Nervous System Nervous System: The Control Center Neuroscience for Kids Neuroscience for Kids-Explore the Nervous System Seeing, Hearing, Smelling the World Types of Neurons Wikipedia: The Nervous System
		Air Bags: The Respiratory System How the Body Works: The Respiratory System Kids Health: Your Lungs & Respiratory System Oxygen Delivery System Respiratory System The Respiratory System Your Respiratory System Wikipedia: The Respiratory System

Heart Circulatory System

Did you give your friends valentines and little heart-shaped candies on Valentine's Day? Do you ever cross your heart when making a promise that you really, really mean? Or turn on the radio to hear a guy singing about his broken heart?

We see and hear about hearts everywhere. A long time ago, people even thought that their emotions came from their hearts, maybe because the heart beats faster when a person is scared or excited. Now we know that emotions come from the brain, and in this case, the brain tells the heart to speed up. So what's the heart up to, then? How does it keep busy? What does it look like? Let's find out.

Working That Muscle

Your heart is really a muscle. It's located a little to the left of the middle of your chest, and it's about the size of your fist. There are lots of muscles all over your body — in your arms, in your legs, in your back, even in your behind.

But the heart muscle is special because of what it does. The heart sends blood around your body. The blood provides your body with the oxygen and nutrients it needs. It also carries away waste.

Your heart is sort of like a pump, or two pumps in one. The right side of your heart receives blood from the body and pumps it to the lungs. The left side of the heart does the exact opposite: It receives blood from the lungs and pumps it out to the body.

We Got the Beat

How does the heart beat? Before each beat, your heart fills with blood. Then its muscle contracts to squirt the blood along. When the heart contracts, it squeezes — try squeezing your hand into a fist. That's sort of like what your heart does so it can squirt out the blood. Your heart does this all day and all night, all the time. The heart is one hard worker!

Heart Parts

The heart is made up of four different blood-filled areas, and each of these areas is called a chamber. There are two chambers on each side of the heart. One chamber is on the top and one chamber is on the bottom. The two chambers on top are called the atria (say: ay-tree-uh). If you're talking only about one, call it an atrium. The atria are the chambers that fill with the blood returning to the heart from the body and lungs. The heart has a left atrium and a right atrium.

The two chambers on the bottom are called the ventricles (say: ven-trih-kulz). The heart has a left ventricle and a right ventricle. Their job is to squirt out the blood to the body and lungs. Running down the middle of the heart is a thick wall of muscle called the septum (say: sep-tum). The septum's job is to separate the left side and the right side of the heart.

The atria and ventricles work as a team — the atria fill with blood, then dump it into the ventricles. The ventricles then squeeze, pumping blood out of the heart. While the ventricles are squeezing, the atria refill and get ready for the next contraction. So when the blood gets pumped, how does it know which way to go?

Well, your blood relies on four special valves inside the heart. A valve lets something in and keeps it there by closing — think of walking through a door. The door shuts behind you and keeps you from going backward.

Two of the heart valves are the mitral (say: my-trul) valve and the tricuspid (say: try-kus-pid) valve. They let blood flow from the atria to the ventricles. The other two are called the aortic (say: ay-or-tik) valve and pulmonary (say: pul-muh-ner-ee) valve, and they're in charge of controlling the flow as the blood leaves the heart. These valves all work to keep the blood flowing forward. They open up to let the blood move ahead, then they close quickly to keep the blood from flowing backward.

It's Great to Circulate

You probably guessed that the blood just doesn't slosh around your body once it leaves the heart. It moves through many tubes called arteries and veins, which together are called blood vessels. These blood vessels are attached to the heart. The blood vessels that carry blood away from the heart are called arteries. The ones that carry blood back to the heart are called veins.

The movement of the blood through the heart and around the body is called circulation (say: sur-kyoo-lay-shun), and your heart is really good at it — it takes less than 60 seconds to pump blood to every cell in your body.

Your body needs this steady supply of blood to keep it working right. Blood delivers oxygen to all the body's cells. To stay alive, a person needs healthy, living cells. Without oxygen, these cells would die. If that oxygen-rich blood doesn't circulate as it should, a person could die.

The left side of your heart sends that oxygen-rich blood out to the body. The body takes the oxygen out of the blood and uses it in your body's cells. When the cells use the oxygen, they make carbon dioxide and other stuff that gets carried away by the blood. It's like the blood delivers lunch to the cells and then has to pick up the trash!

Kidneys Are Filters

Each time the blood circulates from the heart out to the body, about 20% (one fifth) of it goes through the kidneys. The kidneys filter out some of the waste before the blood heads back to the heart.

The returning blood enters the right side of the heart. It takes the blood to the lungs for a little freshening up. Carbon dioxide is left in the lungs to be removed when we exhale. What's next? An inhale, of course, and a fresh breath of oxygen that can enter the blood to start the process again. And remember, it all happens in about a minute!

Listen to the Lub-Dub

When you go for a checkup, your doctor uses a stethoscope to listen carefully to your heart. A healthy heart makes a lub-dub sound with each beat. This sound comes from the valves shutting on the blood inside the heart.

The first sound (the lub) happens when the mitral and tricuspid valves close. The next sound (the dub) happens when the aortic and pulmonary valves close after the blood has been squeezed out of the heart. Next time you go to the doctor, ask if you can listen to the lub-dub, too.

Pretty Cool — It's My Pulse!

Even though your heart is inside you, there is a cool way to know it's working from the outside. It's your pulse. You can find your pulse by lightly pressing on the skin anywhere there's a large artery running just beneath your skin. Two good places to find it are on the side of your neck and the inside of your wrist, just below the thumb.

You'll know that you've found your pulse when you can feel a small beat under your skin. Each beat is caused by the contraction (squeezing) of your heart. If you want to find out what your heart rate is, use a watch with a second hand and count how many beats you feel in 1 minute. When you are resting, you will probably feel between 70 and 100 beats per minute.

When you run around a lot, your body needs a lot more oxygen-filled blood. Your heart pumps faster to supply the oxygen-filled blood that your body needs. You may even feel your heart pounding in your chest. Try running in place or jumping rope for a few minutes and taking your pulse again — now how many beats do you count in 1 minute?

Keep Your Heart Happy

Most kids are born with a healthy heart and it's important to keep yours in good shape. Here are some things that you can do to help keep your heart happy:

• Remember that your heart is a muscle. If you want it to be strong, you need to exercise it. How do you do it? By being active in a way that gets you huffing and puffing, like jumping rope, dancing, or playing basketball. Try to be active every day!
• Eat a variety of healthy foods and avoid foods high in unhealthy fats, such as saturated fats and trans fats.
• Don't smoke. It can damage the heart and blood vessels.

So now you know that your heart doesn't look like a valentine, but it sure deserves to be loved for all the work it does. It started pumping blood before you were born and will continue pumping throughout your whole life.