Nutrition is the study of food nutrients, how they are used by the body and the relationship between nutrition, health and disease.
In order to understand how nutrients affect the human body, nutritionists use ideas from molecular biology, biochemistry and genetics.
Nutrition also focuses on how people can make use of dietary choices to minimize disease risk, what happens if a person has too much or too little of a nutrient and how allergies work.
Nutrients provide food. All foods are proteins, carbohydrates, fat, vitamins, minerals, food, and water. When people in their diet do not have the correct nutritional balance, their risk of developing other types of health rises.
This article should clarify when and why a person needs the different nutrients. It’ll also look at the role of nutritionist and dietitian.
Macronutrients are relatively large amounts of nutrients that people need.
Carbohydrates Examples of carbohydrates include sugar, starch, and fiber.
Sugars are just carbohydrates. The body breaks down quickly and consumes sugars and starch production. They can provide energy quickly but they don’t leave a person feeling full. They may also cause blood sugar levels to spike. The recurrent sugar spikes increase the risk and complications of type 2 diabetes.
Fibre is a starch too. Many examples of fibers are broken down by the body and used for energy; others are metabolized by gut bacteria, while other forms move through the bloodstream.
Complex carbs are fibre and unprocessed starch. Complex carbs need some time to break down and penetrate the body. A person will feel full for longer after eating fibre. Fiber can also reduce the risk of diabetes, heart disease and colorectal cancer. Complex carbs are a healthier choice compared with sugars and refined carbs.
Proteins consist of amino acids, which are naturally occurring organic compounds.
Some foods have complete protein, meaning they provide all of the essential amino acids the body needs. Other foods contain diverse amino acid combinations.
Most plant-based foods don’t contain complete protein, so a person who follows a vegan diet needs to eat a range of foods that provide the essential amino acids throughout the day.
Fats are essential for:
- lubricating joints
- helping organs produce hormones
- enabling the body to absorb certain vitamins
- reducing inflammation
- preserving brain health
Too much fat can result in obesity, high cholesterol, hepatic disease, and other health issues.
The type of fat a person eats, however, does make a difference. Unsaturated fats, such as olive oil, are healthier than saturated fats which tend to originate from animals.
The adult human body is up to 60 per cent water, and for many processes, it needs water. Water does not contain calories, and contains no steam.
Most people recommend drinking 2 liters of water a day, or 8 glasses, but it can also come from dietary sources like fruit and vegetables. Adequate hydration leads to pale yellow urine.
Requirements will also depend on the body size and age of an person, environmental factors, levels of activity, health status etc.
The small amounts of micronutrients are important. They contain vitamins and minerals. Often producers add those to foods. Types include rice and fortified cereals.
The body needs nitrogen, carbon, hydrogen and oxygen.
It also requires dietary minerals, including magnesium, potassium etc.
A diverse and nutritious diet will most likely provide the minerals a person needs. If there is a deficiency a doctor can prescribe supplements.
Here are a few of the minerals which the body needs to work well.
Potassium is an electrolyte. This enables proper functioning of the liver, heart, muscles and nerves. The 2015–2020 American Dietary Guidelines suggest that adults eat 4,700 milligrams (mg) of potassium a day.
Too little can lead to hypertension, stroke, and kidney stones.
Too much is potentially harmful to people with kidney disease.
Good sources are avocadoes, coconut water, bananas, dried fruit, squash, beans, and lentils.
Sodium is an electrolyte that helps:
- maintaining nerve and muscle function
- regulates fluid levels in the body
Too little can lead to hyponatremia. Symptoms include lethargy, tiredness and uncertainty.
Too much can lead to high blood pressure, which increases the risk of heart and stroke disease.
A common condiment is table salt, which is composed of sodium and chloride. Most those, however, consume too much sodium, since it occurs naturally in most foods.
Experts urge people not to supplement their diet with table salt. It is recommended that current guidelines consume no more than 2,300 mg of sodium a day or around one teaspoon.
This guideline covers both natural sources and salt that an person adds to their food. Those with hypertension or kidney disease should eat less.
In order to form bones and teeth, the body needs calcium. It also supports the nervous system, heart health and other functions.
Too little can cause weakening of bones and teeth. Symptoms of a severe deficiency include finger tingling and changes in heart rhythm, which can have life-threatening effects.
Too much can lead to constipation, stones in the kidney, and decreased other mineral absorption.
Current guidelines suggest eating 1,000 mg per day for adults and 1,200 mg for women over 51 years of age.
Great sources include milk products, tofu, legumes, and leafy, green vegetables.
Phosphorus exists in all body cells and contributes to bone and teeth protection.
Too small amount of phosphorus can cause bone disease, affect appetite, muscle strength, and coordination. It can also lead to anemia, increased risk of infection, feelings of burning or prickling in the skin and confusion.
Too much in the diet is unlikely to cause health problems but problems with vitamins, drugs, and the metabolism of phosphorus may cause toxicity.
Adults will aim to ingest approximately 700 mg of phosphorus a day. Good sources include dairy products, lentils, salmon, and cashews.
magnesium contributes to the function of the muscle and nerve. This helps to regulate levels of blood pressure and blood sugar and enables the body to produce protein, bone, and DNA.
Finally too little magnesium will lead to weakness, nausea, exhaustion, restless legs, lack of sleep, and other symptoms.
Too much can lead to digestive problems and eventually heart problems.
Nuts, spinach, and beans are strong magnesium sources. Adult females require 320 mg of magnesium every day and adult males need 420 mg.
Zinc Zinc plays a role in body cell safety, immune system, wound healing, and protein production.
Too little can lead to hair loss, skin sores, taste or smell changes, and diarrhea, but it’s rare.
Too much can lead to headache and digestive problems.
Adult females need 8 mg of zinc per day and 11 mg of adult males. Oysters, beef, fortified breakfast cereals and baked beans are among the dietary sources.
Iron is essential to the production of red blood cells that carry oxygen to all body parts. It also plays a role in the development of connective tissue and in the hormone production.
Too little can lead to anemia, including digestive problems, fatigue and reasoning difficulties.
Too much can lead to problems with the digestion and very high levels can be fatal.
Great sources include fortified cereals, beef liver, lettuce, lentils, and tofu. Adults require 8 mg of iron a day but in their reproductive years, females need 18 mg.
The body uses manganese to generate energy, plays a role in blood coagulation and strengthens the immune system.
Too little can cause weak children’s bones, men’s skin rashes and women’s mood changes.
Too much, but only with very high amounts, can lead to tremors, muscle spasms and other symptoms.
Mussels, hazelnuts, brown rice, spinach and chickpeas all provide manganese. Male adults need 2.3 mg of manganese a day and females need 1.8 mg.
copper helps the body produce energy and make tissue and blood vessels connective.
Too little copper can contribute to fatigue, light skin patches, high cholesterol and disorders of the connective tissue. That is rare.
Hepatic damage, abdominal pain, nausea, and diarrhea can result in too much copper. Too much copper also reduces zinc absorption.
Good sources include sunflower seeds, beef liver, oysters, potatoes, mushrooms, sesame seeds. Every day, adults require 900 micrograms (mcg) of copper.
selenium consists of more than 24 selenoproteins, and plays a key role in reproductive and thyroid health. It’s also able to prevent cell damage as an antioxidant.
Too much selenium can cause breath of the garlic, diarrhea, irritability, rashes in the skin, brittle hair or nails and other symptoms.
Too little can lead to cardiac disease, male infertility and arthritis.
The adults require 55 mcg of selenium per day.
Brazil nuts are a good source of selenium. Certain examples of plants include lettuce, baked beans, and oatmeal. The excellent examples are salmon, ham and enriched macaroni.
People require tiny amounts of various vitamins. Some of those are also antioxidants, such as vitamin C. Through eliminating toxic molecules, known as free radicals, from the body, this means they help protect cells from damage.
Vitamins may be
Water-soluble: the eight B vitamins and the vitamin C
Fat-soluble : vitamins A, D, E and K
People need to eat water-soluble vitamins regularly because they are absorbed quicker by the body, and they can not be easily stored.
|Vitamin||Effect of too little||Effect of too much||Sources|
|Unclear, as the body excretes it in the urine.||Fortified cereals and rice, pork, trout, black beans|
|B-2 (riboflavin)||Hormonal problems, skin disorders, swelling in the mouth and throat||Unclear, as the body excretes it in the urine.||Beef liver, breakfast cereal, oats, yogurt, mushrooms, almonds|
|B-3 (niacin)||Pellagra, including skin changes, red tongue, digestive and neurological symptoms||Facial flushing, burning, itching, headaches, rashes, and dizziness||Beef liver, chicken breast, brown rice, fortified cereals, peanuts.|
|B-5 (pantothenic acid)||Numbness and burning in hands and feet, fatigue, stomach pain||Digestive problems at high doses.||Breakfast cereal, beef liver, shiitake mushroom, sunflower seeds|
|B-6 (pyridoxamine, pyridoxal)||Anemia, itchy rash, skin changes, swollen tongue||Nerve damage, loss of muscle control||Chickpeas, beef liver, tuna, chicken breast, fortified cereals, potatoes|
|B-7 (biotin)||Hair loss, rashes around the eyes and other body openings, conjunctivitis||Unclear||Beef liver, egg, salmon, sunflower seeds, sweet potato|
|B-9 (folic acid, folate)||Weakness, fatigue, difficulty focusing, heart palpitations, shortness of breath||May increase cancer risk||Beef liver, spinach, black-eyed peas, fortified cereal, asparagus|
|B-12 (cobalamins)||Anemia, fatigue, constipation, weight loss, neurological changes||No adverse effects reported||Clams, beef liver, fortified yeasts, plant milks, and breakfast cereals, some oily fish.|
|Vitamin C (ascorbic acid)||Scurvy, including fatigue, skin rash, gum inflammation, poor wound healing||Nausea, diarrhea, stomach cramps||Citrus fruits, berries, red and green peppers, kiwi fruit, broccoli, baked potatoes, fortified juices.|
The body absorbs fat-soluble vitamins through the intestines with the help of fats (lipids). The body can store them and does not remove them quickly. People who follow a low-fat diet may not be able to absorb enough of these vitamins. If too many build up, problems can arise.
|Vitamin||Effect of too little||Effect of too much||Sources|
|Vitamin A (retinoids)||Night blindness||Pressure on the brain, nausea, dizziness, skin irritation, joint and bone pain, orange pigmented skin color||Sweet potato, beef liver, spinach, and other dark leafy greens, carrots, winter squash|
|Vitamin D||Poor bone formation and weak bones||Anorexia, weight loss, changes in heart rhythm, damage to cardiovascular system and kidneys||Sunlight exposure plus dietary sources: cod liver oil, oily fish, dairy products, fortified juices|
|Vitamin E||Peripheral neuropathy, retinopathy, reduced immune response||May reduce the ability of blood to clot||Wheatgerm, nuts, seeds, sunflower and safflower oil, spinach|
|Vitamin K||Bleeding and hemorrhaging in severe cases||No adverse effects but it may interact with blood thinners and other drugs||Leafy, green vegetables, soybeans, edamame, okra, natto|
Multivitamins are available for purchase in stores, but before taking any supplements, people can talk to their doctor to make sure they are safe for use.
Many foods serve as antioxidants, as well. These may be vitamins, minerals, proteins, or any other molecular form. They help the body remove toxic substances or reactive oxygen species known as free radicals. If too many of these substances stay in the body it can result in cell damage and disease.
Dietitian vs. nutritionist
A registered dietitian nutritionist (RD or RDN)studies food, nutrition, particularly diet. A person needs to attend an accredited university to become a registered dietitian, follow an approved program, complete a rigorous internship, pass a licensing review and complete 75 or more hours of continuing education every 5 years. Dietitians are working in private and public hospitals, education, corporate wellness, science, and the food industry.
A nutritionist learns about nutrition through self-study or formal education, but the requirements for using the names RD or RDN are not met. In the food industry, and in food science and technology, nutritionists also work.
Nutrition is food science, and how it affects the body. People need to eat a varied diet to get a wide array of nutrients.
Many people choose to take a specific diet, concentrating on certain foods and eliminating others. Those who do this might need to plan carefully to ensure they get all the nutrients they need to protect their health.
A diet rich in plant-based foods that reduces added animal fats, processed foods, and added sugar and salt is highly likely to benefit the health of a person.
Find out about different diets here:
- Plant-based diet
- Mediterranean diet
- DASH diet
- Vegan diet
- Raw food diet
- Paleo diet
- Gluten-free diet
- Keto diet
Do you recommend any particular type of diet for overall health?
I firmly believe that there is not a one-size-fits-all diet. Genetics, family history, diagnoses, sustainability, and more factors influence what is the best diet for someone.
However, the basis of any diet that I do recommend for a specific person (whether it is low carb, Mediterranean, Dash, paleo, or keto) is that it is plant-heavy, providing adequate fiber to feed gut bacteria, as well as antioxidants, phytochemicals, and nutrients for optimal health.Natalie Butler, R.D., L.D.
Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.