Introduction

The body requires nutrients from food and drinks - protein, fats, carbohydrates, vitamins, minerals, and water. Nutrition is the process of getting the food that is required for proper development and health. Health is necessary to have a strong body that is able to fight disease, live long, and have proper brain and body functioning. Nutrition has a lot of impact on this and is very important in brain and body development. Good nutrition results in better health, stronger immune system, less risk of getting non-infectious diseases, better productivity and ability to learn, longer life, and safer pregnancy and childbirth. Inadequate nutrition leads to malnutrition, which very greatly affects health, and is a very large problem in low and middle income countries. Malnutrition includes undernutrition (stunting and wasting), deficiency of vitamins and minerals, overweight, obesity, and diet related chronic diseases. Nutrition involves three main parts - ingestion, digestion, and absorption. The digestive system breaks the nutrients into small parts and is able to absorb them to use properly for energy, growth, and cell repair.

Digestion & Digestive system

Ingestion

Malnutrition

Diet

Absorption & Assimilation of nutrients

Disclaimer:

The information on this website is not provided by a professional, if further interested in nutrition please find information from a doctor or nutritionist.

Nutritional processes

Ingestion is the act of taking in food. It is necessary for food to be broken into smaller particles so that the nutrients are able to be absorbed later in the process. The main process of ingestion is mastication. Mastication (chewing) happens in the mouth to physically break down food. This needs to happen because digestive enzymes only work on the surfaces of the food particles, meaning that if the food particles are larger the digestive enzymes will not do their job properly. During mastication, saliva is released from glands, and enzymes in the saliva (amylase and lipase) chemically process the food to start to break it down. After the food is fully chewed, it is able to be swallowed and go down the esophagus to the stomach.

Ingestion

Digestion is the mechanical and chemical breakdown of food into small organic particles so that the nutrients can be absorbed. The gastrointestinal (GI) tract consists of the mouth, esophagus, stomach, small intestine, pancreas, liver, and large intestine. The food moves through by a process called peristalsis. Cells in the stomach lining and small intestine release hormones that signal the body to make digestive enzymes. Pancreas secretes trypsin, chymotrypsin, amylase, and lipase to break down carbohydrates, lipids (fats), and proteins, as well as the liver creating bile to help digest lipids and some vitamins. Carbohydrates are broken down first in the mouth with the enzyme amylase which breaks down the starches in the carbohydrate into maltose. In the duodenum, chyme (fluid from stomach) mixes with digestive enzymes to break maltose into enzymes - maltases, sucrases, and lactases, which can then be absorbed and used for energy. Protein is broken down into peptides by the enzyme pepsin in the stomach. Then in the duodenum, the peptides are broken down into smaller peptides by the enzymes trypsin, elastase, and chymotrypsin. The small peptides are broken down further by peptidases (enzymes) into single amino acids, which are then absorbed into the bloodstream. Lipids are digested with lipase enzymes (including lingual lipase, gastric lipase, and pancreatic lipase) and bile in a process of emulsification. This is when the large lipid globules are broken down into smaller lipid globules. This needs to happen so that the lipases can work efficiently on the lipids (which can only happen when they are broken down into small globules). Because lipids are hydrophobic, meaning that they don’t mix with water, the bile is added to emulsify it as bile contains bile salts which have both hydrophobic and hydrophilic sides. When the lipids, bile, and water are mixed the emulsification happens and the small globules are formed. Then lipases act on the lipids to break them down into fatty acids and glycerides, which can pass into the epithelial cells of the intestinal lining and be absorbed for energy. There are two types of vitamins - water soluble and lipid soluble. Water soluble vitamins are able to be absorbed directly into the bloodstream in the small intestine, whereas lipid soluble vitamins have to be absorbed like lipids. 

Digestion

Absorption or assimilation of nutrients is how the nutrients are able to get into the body and bloodstream from the food after digestion. The small intestine will finish breaking down the carbohydrates, lipids, and proteins by mixing bile and pancreatic secretions. Water also moves from the blood into the small intestine to help break down. In the intestinal lining, there are cells that absorb the nutrients into the bloodstream. After absorption, they are delivered to the liver, where it stores, processes, and delivers nutrients when needed. The large intestine absorbs water to be used. After absorption, the digestion processes are finished when the bacteria in the large intestine breaks down remaining nutrients and turns them into vitamin K and the rest of the products (waste) is excreted.

Absorption of nutrients

Maas Clinic. Your Guts and Digestion. https://www.themaasclinic.com/guides/your-guts-and-digestion/. Accessed 18 Jan. 2023.

Malnutrition

What is it?

Malnutrition is deficiencies, excesses, or imbalances in energy intake or nutrients. It can be wasting (low weight for height), stunting (low height for age), underweight (low weight for age), lack of vitamins and/or minerals, overweight, and obesity. It is a major health problem, and can even result in noncommunicable diseases such as heart disease, cancer, and diabetes.

How is it caused?

It can be caused by many things including: not having enough food to eat, an infectious disease that would cause wasting or underweight, undernutrition, or too many calories consumed with too little energy burned. Overweight and obesity happens because more and more people are consuming more food and drink that have increased calories, sugars, and fats, and less people have been exercising because of different forms of work, transportation, and increased urbanization. Some of the major factors that affect risk of malnutrition include socioeconomic status (poverty and low income), mental health, illness, and inappropriate care of children. People at more risk of malnutrition are women, infants, children, teenagers, and low income. However, malnutrition also creates a cycle of poverty by increasing health care expenses, lowering productivity, and slowing economic development.

Why is it a problem?

Malnutrition is a problem because nutrients allow the body to function properly and to grow and develop and produce necessary things such as enzymes and hormones. Malnutrition also often leads to NCDs (noncommunicable diseases), heart disease, diabetes, stroke, some cancers, musculoskeletal disorders, which a lot of time lead to death. According to the World Health Organization, 1.9 billion adults are overweight or obese, and 462 million adults are underweight. About 45% of deaths of children under 5 are caused by malnutrition. In 2020, 149 million children were stunted, 45 million children were wasted, and 38.9 million children were overweight or obese.

Diet

Healthy diet

A healthy diet leads to good nutrition and will help prevent malnutrition and risk of getting NCDs. It should include legumes, vegetables, fruits, staple foods such as grains or starchy roots, and animal products. Unhealthy diets and lack of exercise are very large global risks to health, so it is very important that you have a healthy diet, however it does depend and vary for each person. Things that affect diet can include age, gender, lifestyle, amount of physical activity, culture, available food, etc. For a regular adult with a diet of about 2000 calories, there should be:

  • 400g fruits/vegetables (excludes starchy vegetables such as potatoes)

  • <50g in added sugars and natural sugars in honey, syrups, and fruit juices

  • <30% of energy intake in fats

    • <10% saturated fats

    • <1% trans fats

  • <5g of salt

Fats should consist of mostly unsaturated fats (such as fish, avocado, nuts, sunflower/canola/soybean/olive oil) and some saturated fats (fatty meat, butter, palm/coconut oil, cream, cheese, ghee, lard). Trans fats (unsaturated fatty acids) increase LDL (bad) cholesterol and decrease HDL (good) cholesterol, which increases the risk of coronary heart disease and therefore death, and have no known health benefits. Trans fats include baked/fried foods, pre packaged foods and snacks, and industrially produced trans fats should be fully avoided. Highlight processed foods should also be fully avoided. Processing/refining food removes fiber, iron, and vitamin B which are all necessary nutrients. Most people consume about 9-12g of salt per day, which means that they will have high sodium and low potassium intake, which can eventually lead to high blood pressure and then heart disease or stroke. The plate should consist of ½ plant-based food, ¼ protein, and ¼ whole grains, thinking of vegetables as the main part of the meal. 

How to achieve this

Vegetables/Fruit:

  • Always have vegetables in meals

  • Eat fresh fruits and vegetables as snacks 

    • Cooking loses vitamins

    • If canned/dried, buy without added sugar/salt

  • Eat many different types of fresh fruit and vegetables

Fats: 

  • Steaming or boiling instead of frying 

  • Replacing butter/lard/ghee with soybean/canola/corn/safflower/sunflower oil

  • Eat reduced fat dairy foods

  • Eat lean meats

  • Reduce the amount of baked, fried, and pre-packaged foods that have trans-fats

  • Limit use of high sodium condiments in cooking - soy sauce, fish sauce, bouillon

Sugars & salts:

  • Don’t put salt or high sodium sauces with food

  • Limit amount of salty snacks eaten

  • Buy low sodium products

  • Limit amount of foods and drinks with high sugar content (soft drinks, sugary snacks, candy, fruit or vegetable juices, concentrates, energy/sports drinks, pre packaged tea and coffee, etc.)

  • Replace candy/sugary snacks with fresh fruit or vegetables

Diets

Diets can be used for weight loss as well as improving health and habits. They can focus on calorie intake, lifestyle changes, reduce/increase food intake, and limiting certain foods. Some of the best (healthiest) diets include the mediterranean diet, the DASH diet, plant-based and flexitarian diets, the MIND diet (mediterranean and DASH diet together), WW (weight watchers) diet, intermittent fasting, the volumetrics diet, the mayo clinic diet, and low carb diet. 

Plant based

Vegetarianism and veganism are the most popular versions of plant based diets. These avoid animal products because of environmental, health, and ethical reasons. Plant based diets can reduce the risk of developing chronic diseases, with better metabolic health, decreased blood pressure, and a reduced risk of getting diabetes. They can also help to lose weight when combined with exercise, etc. However, some people feel too restricted with these diets which is why flexitarian diets also exist. 

Low carb diets - keto, atkins, LCHF (low carb high fat)

Restricts carb intake to replace with protein and fat. Helps decrease appetite, raise metabolism, and keep muscle mass. Can reduce risk of heart disease (cholesterol and blood pressure levels), improve blood/sugar insulin for type II diabetes, and aid weight loss. However, it could raise LDL (bad) cholesterol levels.

Gaining/losing weight:

The diets mentioned above can help to lose weight, however one way to lose weight healthily that can also be used with these is a calorie deficit. This entails burning more calories than taking in, meaning that you need to consume less calories or burn more calories by increasing physical activity levels. To not make it unhealthy, a deficit of 500 calories is recommended for a sustainable weight loss. This can be achieved by removing sugary beverages, processed foods, and eating home cooked meals. 

To gain weight/muscle in a healthy way, a calorie surplus is one way to do it. This entails consuming more calories than you burn, usually 10-20% more. This gives the body the extra calories that are necessary for new muscle and tissue to be built. However, all diets can affect people differently depending on factors such as weight, age, exercise routine, etc., and each person should do more research into the diet if they are interested in doing it.