The Science of Plant-based Nutrition: How to Enhance the Power of Plants for Optimal Health: The Sunday Times Bestseller

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GENERAL NUTRITION

General Nutrition | CONTENTS

Why is nutrition so important?

How do our bodies process nutrition?

How does metabolism work?

What is meant by gut health?

What are common problems with digesting food?

What are macronutrients?

What are micronutrients?

What role does hydration play?

What are the basics of healthy nutrition?

What are the benefits of good nutrition?

How can I avoid poor nutrition?

How does poor nutrition impact health?

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Why is nutrition so important?

The food we consume contains vitamins, minerals, and nutrients that can be beneficial to our health alongside providing us with the energy needed to grow and flourish. Good nutrition is important for all areas of our health and well-being from before we are born.

What is nutrition?

Nutrition is the way you eat and how the food and drink that you consume delivers the nutrients you need to have a healthy body and mind. The nutrients we all require to maintain optimum health are carbohydrates, fats, fiber, protein, minerals, vitamins, and water. We should consume a healthy balance of these nutrients to grow and develop to our optimum height and stay as healthy as possible with a strong level of immunity. If you have good nutrition, you will fuel your body and brain. From conception and throughout life, nutrition provides a vital role in helping us grow optimally and stay disease-free.

Thanks to modern nutritional science, we now know a lot about the importance of good nutrition for our growth and development. If you eat a healthy, nutritionally balanced diet (see What are the basics of healthy nutrition?), it can help reduce your chances of developing serious health conditions, including diabetes, heart disease, stroke, and cancer. What you eat may also affect your brain development, mood, and mental health. Public health nutritional guidelines around the world vary from country to country and are based upon the minimum requirements needed to maintain an optimal health status and be free from disease and poor health.

The first thousand days

Good nutrition is important even before we are born. The health outcome of a child throughout its life is shaped by what their mother eats from the time of conception up to their second birthday (the first 1,000 days). Research in the fields of neuroscience, biology, and early childhood development provides powerful insights into how nutrition, relationships, and environments in the 1,000 days between a woman’s pregnancy and a child’s second birthday shape future outcomes (see Is a plant-based diet safe during pregnancy?, Is plant-based weaning safe for babies?, Can I raise my children vegan?, and How can I avoid nutrient deficiencies in babies and young children?). In countries where investment into the health and well-being of mothers and children during this crucial period is lacking, it appears that healthcare costs are higher and economic productivity lower. With a healthier and more prosperous future in mind for generations to come, several of the world’s leading economists are calling for greater focus and investment in the nutrition, health, and well-being of women, babies, and toddlers during this period of growth and development.

A brighter future?

With everything we know about nutrition and the availability of whole foods, you would think that the population of the world would be in a healthier position than ever before, but sadly that is not the case. Around 37 million children are now overweight, and we are facing an obesity crisis (see Will a plant-based diet help with obesity?), not only in the western world but in some lower and middle-income countries, too. This is because food systems and rising food prices are leading to more of us eating food that does not contain adequate nutrition and can result in malnourishment.

Plant-based eating and encouraging the consumption of more whole foods could be an approach that is beneficial for our nutrition and the planet. Nutrition is key to our health and happiness and everyone in the world deserves equal access to it.

Scurvy prevention

From the 16th to the 18th centuries, more than 2 million sailors died at sea from scurvy.

This was discovered to be due to a lack of fresh food supplies and in particular vitamin C. The Royal Navy became known as Limeys for carrying limes and lemons to prevent scurvy aboard their ships. Today, nutritional deficiencies are usually identified quickly and often completely eradicated in western countries, thanks to access to good nutrition and supplementation.

veggies

Vegetables are parts of plants that are consumed by humans or animals as food

fruit

A fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering

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How do our bodies process nutrition?

The human body is a true wonder, built perfectly to process the food we eat and draw the nutrients we require from our diets. It is far more complex than simply eating and swallowing the food we consume.

The process of breaking down and absorbing the food we eat is designed to give us energy and nutrients to live and function optimally. Nutrients are then taken in the bloodstream to where they are needed in the muscles, tissues, and organs, with any waste products excreted.

MOUTH

The process of digestion begins in the mouth where food is broken down into smaller pieces by our teeth when we chew. Digestive enzymes in our saliva work to chemically break the food down further and help create a bolus—a ball of chewed up food—that is swallowed and goes through the esophagus.

ESOPHAGUS

This is a large muscular tube that extends from the epiglottis (a small flap of tissue at the back of the throat) to your stomach, transporting the food you have eaten from one end to the other. Once it reaches the stomach, the lower esophageal sphincter acts as the stomach’s gateway and allows food to enter the stomach.

STOMACH

The stomach is an acidic environment where digestive enzymes and stomach acids further break down food. Muscles in the gut contract to churn and mix the food to help chemicals break it down, and the acid kills off unwanted and potentially harmful microbes found in foods. This process sends signals to the body to release a hormone called leptin, which regulates appetite by signaling that you’re full. In the stomach, food is turned into chyme, a souplike consistency substance that enters the small intestine in the next phase of digestion.

SMALL INTESTINE

Food spends between 2–6 hours in the 23 ft long small intestine, being broken down by digestive enzymes so nutrients can be absorbed from the chyme into the bloodstream and to be delivered where needed to fuel and support bodily processes.

Once the nutrients have been absorbed, the remaining material moves into the large intestine.

LARGE INTESTINE

Remaining food is turned into waste in the large intestine. Undigested food can spend up to 12–30 hours here and goes from a liquid consistency to form stools, as the water is absorbed back into the body. Far from being merely a waste processor, the large intestine is home to the majority of our immune cells and a community of trillions of microbes. These gut microbiota perform many crucial processes, interacting with and supporting the immune system, hormone production, and the brain (among others) as they feed on and ferment undigested nutrients (see What is meant by gut health?).

RECTUM AND ANUS

Finally, the semisolid waste material known as feces is excreted. This is collected in the rectum and is passed into the anus via two anal sphincters. Contraction and relaxation of the anal muscles push the stool through the sphincters and out of the anus.

Nutrient extraction As food travels through different parts of the digestive tract, it is broken down and absorbed into the bloodstream.

STOMACH

water

ethyl alcohol

copper

fluoride

iodide

molybdenum

DUODENUM

calcium

copper

folate

iron

magnesium

phosphorous

riboflavin

selenium

vitamins A, B1, B3,

B7 (biotin), D, E, K

JEJUNUM

lipids (fats)

monosaccharides (carbs)

amino acids (proteins)

small peptides (proteins)

calcium

chromium

folate

iron

phosphorous

magnesium

manganese

molydenum

pantothenic acid

riboflavin

vitamins A, B1, B3, B6,

B7 (biotin), C, D, E, K

zinc

ILEUM

bile salts

folate

magnesium

vitamins B12, C

vitamins D, K

LARGE INTESTINE

water

short-chain fatty acids

potassium

sodium

chloride

vitamins B7 (biotin), K

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How does metabolism work?

Metabolism is responsible for every single chemical reaction that takes place in any living cell or organism, and it is needed to keep us alive. The food you consume provides the nutrition that gives you the energy to fuel metabolism.

What we eat provides the raw materials for metabolism, enabling it to do the essential job of creating the energy to fuel every process in the body, from energy production, growth, repair and the regulation of the cells to physical activity.

Anabolism and catabolism

Metabolism involves two processes working simultaneously: the building up (anabolism) and breaking down (catabolism) of molecules. Anabolic processes take place when smaller molecules called monomers are joined together to create larger molecules called polymers. For example, starch and cellulose are polymers made from the glucose monomer. Proteins are polymers of the amino acids monomers. Fats (lipids) are made from fatty acid and glycerol molecules. Because of this, fats are not polymers. Catabolic processes involve the breakdown of complex molecules into simpler ones, which causes them to release energy. This happens to the proteins, carbs, and fats that you consume in your diet. The energy is then stored and transported within cells as adenosine triphosphate (ATP).

Monomers

Small molecules that can join together to form polymers

Polymers

Larger complex molecules made from smaller molecules

Metabolism and calories

Your basal metabolic rate (BMR) equates to the number of calories you need to sustain life when you are not moving. This rate varies from person to person, and there is no fixed number of calories we need to thrive. Lifestyle changes like diet, exercise, and sleep cannot boost your metabolism as is often claimed, but you can choose a diet and lifestyle that supports the system, making it work more efficiently. Many factors contribute to the rate of your metabolism, including:

Age

Muscle mass

Body size

Physical activity levels

Mitochondria

Mitochondria are known as the powerhouses of a cell as they release most of the energy produced. The more energy you release, the more efficient your metabolism. Individuals who have more muscle have a higher number of mitochondria within their cells. Those who are obese tend to have a less effective metabolism (see Will a plant-based diet help with obesity?).

Does a plant-based diet help our metabolism?

Some studies suggest that eating plant-based may help increase metabolism as a result of lower energy intake and weight loss. A 16-week trial of 244 Americans with a low-fat vegan diet versus a control group, which was asked to make no diet changes, found that eating a low-fat plant-based diet reduced body weight by increasing metabolism after eating and reducing energy intake. Other reviews suggest that plant-based diets help metabolic function in those with obesity and type 2 diabetes when compared to those who eat meat, but more research is emerging all the time.

Energy production There are three potential energy sources from food—protein, carbs, and fats. The pathway conversion of food to cellular energy depends on what the fuel is composed of. Hormones regulate the processes of anabolism and catabolism, which work at the same time.

proteins

The least efficient way to generate energy

carbohydrates

The body prefers to use carbs first

fats

A denser way to store energy on average

Amino acids

Organic molecules that are the building blocks of protein

mon0saccharids

The basic unit of carbohydrates (or simple sugars)

Glycerol and fatty acids

Lipids are formed from these molecules

Amino acid pool

The collective supply of amino acids

Glucose

The primary energy source for cells

Triglycerides

A means of transporting and storing lipids in the body

krebs cycle

A process by which cells generate energy in the form of ATP

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What is meant by gut health?

The gut is a term used to describe your gastrointestinal (GI) system, the health of which is generally determined by the levels and types of bacteria in your intestinal tract. Gut health refers to the overall health of your digestive system.

Large intestine This is where most of the fiber from the food you consume is broken down into smaller molecules by fermentation and bacteria.

The microbiome

Gut health is now synonymous with the microbiome of the large intestine but has a wider meaning, especially in clinical fields, relating to the health of the entire gastrointestinal tract. The gut microbiome consists of all the microorganisms, such as bacteria and fungi, that live in our gut. The gut influences all parts of our body, from the immune system to our digestive functions. It plays a key part in keeping our energy levels up and helping us avoid illness, so it is worth keeping it healthy.

Having a diet high in fibrous foods, found in abundance in a healthy plant-based diet, such as in nuts and whole grains, aids digestion. However, in order to digest fiber properly, we need to have the right balance of bacteria and other microorganisms in our gut. Bacteria thrives on the fiber in our diet.

The biochemical products made in our gut from foods play an important role in maintaining the normal functioning of the immune system, and producing hormones responsible for mood, hunger, and sleep regulation. The gut is also a production site for nutrients such as B vitamins.

Healthy gut, healthy body

Having a healthy gut means that the food and drink we consume day-to-day can be digested efficiently and the nutrients from them can be used to support regulating our appetite and mood. This, in turn, helps us stay healthy and promotes well-being. Taking steps to consume foods that are helpful to our gut is a great way to keep it healthy. However, there are also foods that can harm it. Artificial sweeteners, hydrogenated fats, emulsifiers, additives, and flavorings in processed snacks can reduce the healthier gut bacteria and cause an imbalance of microorganisms in our gut. So aim to keep these foods to a minimum. Staying hydrated and taking part in regular exercise also both help the digestive system to function normally.

The role of stress

Stress strongly influences our body’s processes and how it functions. High levels or chronic low levels of stress can alter the microbiome, unbalancing the levels of bacteria present. Stress has also been shown to reduce the strength of the gut barrier, allowing bacteria to leak into our bodies and cause inflammation. Additionally, stress can influence the types of foods we choose and can make us go for more ultra-processed foods that are high in salt, sugar, and fat, which harm rather than support our gut health. For all these reasons, implementing stress-reducing measures is crucial for gut health. Try to include short windows of mindfulness, such as breathing exercises and meditation, throughout the day to keep stress levels lowered. Regular exercise can also help reduce your stress.

Know your gut terms

In the human body, there are trillions of microorganisms. The majority of these are in the gut, where they play a vital role in our health and well-being.

Microorganisms

Tiny living organisms, such as bacteria, viruses, or fungi.

Microbiota

A group of microorganisms in a particular location.

Microbiome

Entire genetic material of microorganisms in a specific environment.

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What are common problems with digesting food?

Most of us will experience a degree of digestive discomfort at some point in our lives. In fact, 66 percent of Americans have gastrointestinal issues, and 73 percent of those aged 18–44 suffer with symptoms such as bloating, constipation, and diarrhea at least a few times a month.

When food is not digested properly, it can cause stomach discomfort, like bloating and abdominal pain, and lead to nutrient deficiencies and malabsorption. This results in diarrhea or constipation, weight changes, and nutritional imbalances, all of which can disrupt the gut microbiota (see What is meant by gut health?) and affect your overall health and immune function.

The most common digestive issues are related to travel, lack of sleep, lifestyle, age, stress, and diet. If the digestive system isn’t working well, it can lead to a variety of concerns from gastrointestinal discomfort, food intolerance, irregular bowel movements, and a weakened immune system. Make sure that you seek advice from your doctor if you have any concerns.

Travel

Up to 50 percent of travelers experience gut health concerns on their trips. Flying in an airplane can impact our digestion because of the air pressure in the cabin itself. Any air trapped inside your gut will expand, causing bloating and gas, in the same way as a water bottle inflating after takeoff. Your digestion is also affected by changes in time zones that disrupt your natural sleep-wake cycle (the circadian rhythm). When you are suddenly awake at a time your body is not adjusted to, this impacts your gut microbes because they are used to working at regular times. What’s more, food you consume on vacation likely has different properties to your usual diet, and your gut bacteria will need new digestive enzymes to deal with this. Disruption to our normal routine can also cause problems related to processing nutrition.

Age and lifestyle

Apart from travel and diet, the two main factors that negatively influence the health of the intestines are reduced blood flow (caused by a sedentary lifestyle) and increased pressure on the intestines, due to the compression of the intestinal organs between the hip and the diaphragm.

If you sit in one position at a desk for long periods, this can cause compression of the digestive system. Remember to get up, stretch, and move around regularly to avoid digestive issues because of this. Stress levels also impact how well our food is digested. Studies are also now looking into the impact of sedentary lifestyles on the gut microbiome, with the majority showing a negative influence from a less active lifestyle. Our digestion also naturally slows down as we age, although diet and exercise can improve matters.

IBS and other digestive conditions

A common digestive complaint, irritable bowel syndrome (IBS) can cause symptoms like stomach cramps, bloating, diarrhea, and constipation. These tend to come and go over time and can last for days, weeks, or months. Food can pass too quickly or too slowly, and you can have oversensitive nerves in your gut. Stress can trigger the condition, and a family history of IBS may enhance your likelihood of getting it, but the cause is still unknown and there is no cure. IBS is managed through lifestyle and diet (see Is a plant-based diet good for IBS?). Some people also live with chronic conditions that impact their digestion, causing severe tummy pain and diarrhea. These include inflammatory bowel disease (IBD) and celiac disease.

IBS GLOBAL FIGURES

It is believed that irritable bowel syndrome affects more than 1 in 10 people globally. IBS has many symptoms and can be eased through diet and exercise.

Digestive issues A range of symptoms are caused by poor digestion, ranging from bloating and gas to abdominal pain. These can affect your nutritional intake from food.

bloating and gas

can be caused by travel or stress

Constipation

lack of exercise and fiber may bring about constipation

Abdominal pain

can be caused by conditions such as IBS or IBD

diarrhea

May occur with IBS or food intolerances

Eating disorders

Anorexia and bulimia are often not thought of as a cause of poor digestion, but they can cause damage by weakening muscles in the gut. Other problems are severe nausea and vomiting, esophageal erosions, heartburn, and gastrointestinal symptoms. These problems may be helped with appropriate treatment.

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What are macronutrients?

Your diet requires key components in order for your body to have enough energy and nutrition to carry out its daily tasks. The focus of these functions is largely dependent on the three macronutrients—carbohydrates, proteins, and fats.

Carbohydrates

Carbohydrates are essentially sugar molecules that are broken down in the body and used as energy. Carbohydrates are often described as simple or complex, and this relates to their chemical structure. Simple carbs provide a quick burst of energy, whereas complex carbohydrates are released more slowly (see Will I consume