Food, Diet and Nutrition

A Healthy, Balanced Diet Contains...

Protein

Protein supplies essential amino acids, the body’s building blocks.

All the organs, including the skin, are made from protein. Without adequate protein in our diet, we cannot build and replace muscle and repair any damage. We also need protein for our immune systems to work properly.

The recommended daily amount in the US is currently 0.8g of protein per kg of body weight. The British Heart Foundation says that adults need about 0.75g of protein per kg of body weight per day.

However, the amount of protein you need varies by activity level and your stage of life.

Children and pregnant women need more protein to support growth, as do those who are very active such as those doing a lot of sport, or working in active jobs. Guidelines from athletics governing bodies generally recommend that athletes should consume around double the recommended daily amount. One study suggested that they should consume around 2.2g of protein per kg of body weight per day, although this is clearly stated to be the author’s opinion (Antonio, J. (2018). High-protein diets in trained individuals. Research in Sports Medicine, 27, 195–203).

Older adults may also need to be careful that they consume enough protein to remain healthy.

Good sources of protein include animal products (meat, eggs, fish, dairy products) and beans, especially soya.

See our page What is Protein? for more.
A Source of Fuel, Usually Fat or Carbohydrate.

Fats have often been cast as the villains of diet, but it is now clear that some fat is essential in the diet. Many vitamins are fat-soluble, which means that you need to eat fats to obtain them, and you also need fats to provide essential fatty acids. These are used to provide insulation, and protect organs from damage, as well as helping the heart and immune system to function effectively.

Fat

Fats are a much more efficient source of fuel than carbohydrate, so you need much less for the same number of calories. Indeed, there is an argument that we should aim be getting more of our calories from fat—although this may only apply to some people, and not everyone. The real issue is that different people metabolise different sources of nutrients in different ways. Unfortunately, government guidelines tend to try to provide a single approach that will work for everyone—and this is simply not realistic.

See our page What is Fat? for more information. You may also find our datasheet on cooking oils and fats helpful.

Carbohydrate

For most people, carbohydrates are the main source of fuel in the body.

They provide the energy needed to power muscles and organs, including the brain. There are two main types, simple (mostly sugars) and complex carbohydrates such as starch and cellulose, both found in plant cells. Many carbohydrates in our diet now are refined: that is, they have been processed to remove a lot of the ‘food matrix’ from around them.

Carbohydrates are rapidly broken down in the digestive system into glucose and other sugars, and passed directly into the blood stream. This can lead to ‘spikes’ of blood glucose, which are associated with problems such as mood swings, acne, and other health issues. Refined carbohydrates are particularly likely to be broken down rapidly, and therefore cause glucose spikes.

There is growing evidence that the problem with eating sugars is not the sugar itself, but the effect on our metabolism via these glucose spikes. Scientists are starting to suggest that we should try to ‘flatten’ these spikes by changing our habits. For example, eating vegetables first seems to flatten the spike.

See our pages on Carbohydrates, What is Sugar? and Complex Carbohydrates, Sugar and Diet for more information about carbohydrates, including avoiding blood glucose ‘spikes’.
Fibre (Fiber)

Fibre, usually plant material, is well-known to help our guts to work properly. We lack the enzyme to digest fibre, so it was thought to simply ‘pass through’.

However, more recent research has shown that it also has other important effects on our general health and immune system that cannot be explained if fibre is considered ‘inert’.

For example, people who eat plenty of fibre are less likely to get heart disease or various types of cancer. This is now thought to be the result of the action of our gut bacteria, or microbiome. These bacteria have enzymes that humans lack and can therefore turn fibre into short-chain fatty acids. These are hugely beneficial to the body and are thought to have an anti-inflammatory effect.

Fibre is obtained from eating fruit and vegetables, and is one of the key reasons why we are encouraged to eat ’five a day’.

WARNING! Smoothies and juice don’t provide fibre!

Bottles of fruit juice and smoothies often have labels saying things like ‘Contains one of your five a day!’ or ‘This bottle contains half a banana, half an apple and three grapes’.

This type of labelling is very misleading.

When food is liquidised (ground or mashed), the food matrix (structure) is changed. All or most of the fibre is lost. Instead, you have rapidly accessible calories in the form of glucose, which is likely to cause a sugar spike. Yes, you will still obtain any vitamins or minerals—but you lose much of the benefit.

It is therefore best to avoid juice and smoothies, and eat fruit or vegetables whole if you want the full benefits of consuming them.

See our page What is Fibre? for more. You can find out more about the microbes that live in our digestive system in our page on Understanding and Improving Your Gut Microbiome.
Vitamins and Minerals

Vitamins and Minerals are trace substances found in various foods. There are 13 vitamins which are essential to human life, and they are used to support multiple functions of the body. For example, Vitamin C is essential for producing and maintaining connective tissue, which holds the body together. Shortages of vitamins cause some really horrible diseases, such as scurvy (Vitamin C), rickets (Vitamin D) and spina bifida in newborn babies (folic acid, otherwise known as Vitamin B9).

If you are eating a reasonably balanced diet, with protein, fat, complex carbohydrates and fibre, especially from fresh fruit and vegetables, you will almost certainly obtain all the vitamins and minerals that you need.

See our pages on Vitamins and Minerals for more.

To Supplement or Not to Supplement?

When you feel like you might be a bit short of one or more vitamins, or that your lifestyle is not all it should be, it can be tempting to use vitamin supplements to fill the gap.

However, is this a case of trying to have your cake and eat it?

The evidence suggests that this view may not be far off the mark.

In fact, studies have shown that supplements generally don’t improve our health, and in some cases may actually be harmful. Overdosing is a very real possibility given the number of foods ‘fortified’ with various vitamins.

You are far better off eating a balanced diet with plenty of fresh fruit and vegetables than trying to fill an imaginary deficit by ‘popping a pill’.

There is more about this in our page on Dietary Supplements.

Diet, Excess Weight and Obesity

There has been considerable discussion over many years about diet, and whether particular diets make you more likely to become overweight or obese.

The answer, it now seems, is that what you eat certainly does have an effect on whether you become obese. It would be foolish to believe otherwise. However, it is not the whole story—and nor is there a single ideal diet that will suit everyone and result in nobody becoming obese or ill.

It seems that how you eat also plays a part in how your body metabolises and deals with particular foods and food groups. For example, when you eat is important for both general health and weight. The order in which you eat foods also matters, because there is considerable evidence that eating vegetables first, before any protein or carbohydrate, can have a strong influence on how your body deals with the energy released from food. The timing of exercise also matters: exercising has a very different effect before and immediately after eating.

Most importantly, it seems that we all respond to different foods slightly differently. There is no ideal diet because there is no ‘ideal’ person.

A personalised approach to nutrition is essential—although we could probably all benefit from eating more fruit and vegetables, and rather less processed food.

Measuring overweight and obesity

There are various measures of overweight and obesity, the best-known of which is probably Body Mass Index, or BMI. This is a fairly arbitrary measure that says that your weight should be related to your height.

There are problems with this as a measure, of course, because muscle weighs more than fat. This means that athletes tend to show up as obese on the scale. However, it is a reasonable guide for most normal people.

For more about this, see our page on Body Mass Index (BMI). You may also be interested in our page on Measures of Wellness, which discusses other ways to measure your wellness and wellbeing beyond simply weight.

Specific Diets

Although the word ‘diet’ describes everything that we eat, it is most often used for particular choices of food, such as a gluten- or dairy-free diet, a vegan diet, eating organic food, or a diet for weight loss.

Following these diets is generally a specific lifestyle choice, and often related to a health issue, such as a feeling of bloating after eating certain foods, or being overweight.

Warning!

As a general principle, most people need to eat a reasonably well-balanced diet for health. Specific diets, which cut out whole food groups such as dairy, or anything containing gluten, should only be followed over the long-term on the advice of a healthcare professional such as a nutritionist or doctor.

If you suspect that you or your child has a food intolerance, and may need a special diet, it’s a good idea to discuss it with a healthcare professional before taking action.

There is more about this in our page on Food Allergies and Intolerances.

The choice to follow a vegan diet, or eat mostly or completely organic food, is usually very much a lifestyle choice.

Many people follow these diets for ethical reasons, especially avoiding cruelty to animals, or because they are more sustainable. There is certainly a reasonable amount of justification for these choices. Organic farming, after all, is designed by its very nature to be sustainable.

There is more about this in our pages on Organic Food and Veganism and Plant-Based Diets.

Others choose these options for health reasons. Again, there is some justification for this thinking, especially if it leads to you eating more fresh fruit and vegetables. However, moving from meat-based to plant-based ultra-processed foods is not likely to make much difference to your health.

There is more about this in our page on Ultra-Processed Food.

Dieting for Weight Loss

There are many different weight loss diets available. Some limit the types of food you can eat, others limit when you can eat, and yet more substitute meals with ‘protein shakes’ or similar.

The problem with most of these is that dieting for weight loss is often seen as a case of ‘follow these instructions for a set period and then get back to normal’: that is, lose the weight, then go back to eating your ‘normal’ diet.

This tends to result in (some) successful weight loss, followed by regaining all the weight within a fairly short time.

Instead, dieting for weight loss should be seen as a matter of changing your lifestyle—and also a very individual issue. Diets that work for one person will not work for another—maybe not even their identical twin. For some people, it will be about reducing the amount you eat or the times within which you eat. For others, it may be about changing the type of food you eat, or perhaps a combination. Crucially, it will be different for everyone, because everyone’s gut microbiome is different (and you can find out more about the microbes that live in our digestive system in our page on Understanding and Improving Your Gut Microbiome).

For more information, see our page on Dieting for Weight Loss. You may also find it helpful to read our page on Calorie Counting and Food Labelling, which explains why calorie counting may not have the desired effect in weight loss terms.

Diet and Mental Health

The links between diet and mental health are still not entirely clear. However, there is certainly enough evidence to suggest that diet has a strong impact on your mental well-being.

The overall effect has been clear enough for some time that the Mental Health Foundation says that diet plays a part in maintaining overall mental health and in the treatment of certain conditions.

Some studies have found differences between children and adolescents who eat more fruit and vegetables, and those who eat more junk food. The children who ate more junk food were more likely to have a diagnosed condition like attention-deficit hyperactivity disorder or depression. Those who ate a ‘better’ diet, with more fresh fruit and vegetables, were less likely to experience mental health problems. Another more recent study found that women who ate a lot of ultra-processed food were significantly more likely to develop depression than those who ate less.

For more about this, see our page on Keeping Your Mind Healthy. For more about the link between ultra-processed food and various health conditions, see our page on Ultra-Processed Food.

Diet and Stress

Poor diet and dietary problems have also been related to stress.

Stress hormones cause the body to reduce blood flow to the digestive system, as digestion is less essential than, for example, running away from a tiger. While this is good if you’re being chased by a tiger, it’s less good if you’re under stress over a long period because of being busy at work, or moving house. Under those circumstances, you may find that your digestive system suffers.

The good news is that there are various things that you can do to help.

For example:

When you’re feeling under stress, avoid foods that will increase your levels of cortisol, a stress hormone. These include beans, barley and fermented milk products like yoghurt.
Keep managing your blood glucose levels to avoid spikes. These will make it harder to concentrate, and are likely to make you more irritable.

For more about the links between diet and stress, and how to reduce stress through diet, see our page on Stress, Diet and Nutrition.

In the past, scientists suggested that you should also avoid caffeine if you are stressed, because caffeine, like adrenaline, is a stimulant. It can also irritate your gut and make digestion harder. However, more recent work suggests that coffee and tea are far more than simply vehicles for caffeine. Instead, they can provide useful contributions to health, including anti-inflammatory polyphenols. Contrary to previous beliefs, therefore, coffee and tea could actually help you to manage stress by improving your general health.

There is more about this in our page on Coffee and Health.

A Word About Alcohol

Alcohol is often seen as a stress-reliever, at least in the short-term. However, there is considerable evidence that it should not be used in this way, and that consuming alcohol at even a moderate level has a detrimental effect on health.

There is more about this in our page on Alcohol and Health.

The Skills You Need Guide to Life: Looking After Yourself

In Summary

Our diet has a huge impact on the health of our bodies, both mentally and physically.

There is also considerable evidence that each of us has a slightly different response to different foods. The ideal diet for one person will certainly not work for everyone. This is because we all have different gut bacteria, or microbiomes—and these have a huge effect on how we digest and metabolise food.

It is therefore difficult to make generalisations about what foods we should eat. However, the pages on this site aim to provide information about what the science says about various food groups, and their consumption. One generalisation worth mentioning is that it does seem certain that a ‘balanced’ diet is good, and that we would all benefit from eating more fresh fruit and vegetables, and reducing our intake of processed foods as much as possible.

Continue to:
Food Intolerances and Allergies
Dieting for Weight Loss