Nutritionists use ideas from molecular biology, biochemistry, and genetics to understand how nutrients affect the human body.
Nutrition also focuses on how people can use dietary choices to reduce the risk of disease, what happens if a person has too much or too little of a nutrient, and how people can use dietary choices to prevent nutrient deficiencies and manage certain conditions.
This article explains the different nutrients a person needs and why, and the roles of dietitians and nutritionists.
Nutrients are compounds that the body needs to survive and grow. All nutrients fit into
: macronutrients and micronutrients.
The ideal amount of various nutrients vary depending on factors
:
age
biological sex
activity level
pregnancy status
According to the
World Health Organization (WHO)
, malnutrition can involve undernutrition, deficiencies in micronutrients, and
. In 2022, 390 million adults globally were underweight, and 2.5 billion were overweight.
Understanding nutrition and the amounts of nutrients to consume daily may help people reduce their risk of diet-related health issues.
Macronutrients
energy, support cell growth, and protect your organs. The body generally needs macronutrients in larger quantities.
Carbohydrates
Simple carbs: A chemical structure containing one or two sugars. Sugars, such as
, are simple carbs.
Complex carbs: A chemical structure containing three or more sugars.
and
are types of complex carbs.
It takes longer for the body to digest complex carbs, so they tend to have a slower effect on
than simple carbs. This can also mean complex carbs leave people feeling fuller for longer.
Proteins
Proteins
amino acids, which are natural organic compounds. Some of these are essential, meaning people need to obtain them through food. The body can make the others.
Most
do not contain all of the essential amino acids. People who follow
need to eat a range of foods throughout the day to get enough.
Fats
Fats are essential for:
lubricating joints
helping organs produce hormones
enabling the body to absorb certain vitamins
reducing
preserving brain health
However, the
a person eats makes a difference. Unsaturated fats, such as olive oil, are more healthful than saturated fats, which tend to come from animals.
Water
The adult human body is
water, and it needs water for many processes. Water contains no calories, and it does not provide energy.
Many people recommend consuming
of water a day. Factors such as a person’s body size and age, environmental factors, activity levels, and health status can also affect daily water needs.
Micronutrients are essential in small amounts. Manufacturers sometimes add these to foods.
Minerals
The body needs dietary minerals, such as iron,
, and so on.
In most cases, a varied and balanced diet will provide the minerals a person needs. If a deficiency occurs, a doctor may recommend supplements.
Below are some of the minerals the body needs to function well, including the daily
recommended dietary allowance (RDA)
from the Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine:
Potassium: Potassium enables the kidneys, heart, muscles, and nerves to work properly. Most adults need between 2,600 and 3,400 milligrams (mg) of potassium daily, depending on biological sex.
Sodium: Sodium helps regulate fluid levels in the body and maintain nerve and muscle function. Too much can contribute to high blood pressure. The RDA for adults is 1,500 mg, but most adults should consume no more than
of sodium daily.
Calcium:
supports the nervous system, cardiovascular health, and healthy bones and teeth. Most adults need between 1,000 and 1,200 mg of calcium daily.
Phosphorus:
is present in all body cells and
the health of the bones and teeth. Most adults need around 700 mg of phosphorus daily.
Magnesium: Magnesium
muscle and nerve function, and it enables the body to produce proteins, bone, and DNA. Adults require around 320 to 420 mg of magnesium daily, depending on biological sex.
Zinc:
plays a role in the health of body cells, the immune system, wound healing, and the creation of proteins. Most adults need 8 to 11 mg daily, depending on biological sex.
Iron:
is
of red blood cells, which carry oxygen to all parts of the body. Adults may need between 8 and 18 mg of iron daily, depending on biological sex and reproductive status.
People can be deficient in minerals or consume too much. Both extremes can lead to health complications. Anyone concerned about their intake of certain minerals can speak with a healthcare professional for more help.
Water-soluble vitamins
People need to consume water-soluble vitamins regularly because the body removes them more quickly, and it cannot store them easily. Below are
some key water-soluble vitamins
:
VitaminEffect of too littleEffect of too muchAdult RDAB-1 (
)•
•
unclear, as the body excretes it in the urine1.1 to 1.2 mgB-2 (
)• hormonal problems
• skin disorders
• swelling in the mouth and throatunclear, as the body excretes it in the urine1.1 to 1.3 mgB-3 (
)
•
• burning, itching, and tingling
•
•
•
14 to 16 mg of niacin equivalentsB-5 (
)• numbness and burning in hands and feet
•
•
digestive problems at high doses5 mgB-6 (
)•
• skin changes, such as an itchy rash
•
• nerve damage
• loss of muscle control1.3 to 1.7 mgB-7 (
)•
• rashes around the eyes and other body openings
•
unclear30 micrograms (mcg)B-9 (
)• weakness
• fatigue
• difficulty focusing
•
•
may increase
risk400 mcg of dietary folate equivalentsB-12 (
)• anemia
• fatigue
• tongue inflammation
•
• neurological changesno adverse effects reported2.4 mcgVitamin C (
)
•
•
• stomach cramps75 to 90 mgPeople may be unlikely to consume too much of these vitamins from dietary sources. However, the risk increases if someone takes supplements.
Fat-soluble vitamins
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.
VitaminEffect of too littleEffect of too muchAdult RDA
• severe headache
• nausea
• dizziness, skin irritation
• joint and bone pain
• orange pigmented skin color700 to 900 mcg of retinol activity equivalents
improper bone formation and weak bones•
•
•
15 to 20 mcg
•
• retinopathy
• reduced immune response
•
may reduce the ability of blood to clot15 mg
bleeding and hemorrhagingno adverse effects, but it may interact with blood thinners and other drugs90 to 120 mcgMultivitamins are available for purchase in stores or online, but people should speak to their doctor before taking any supplements to check that they are suitable for them to use. Supplements can increase the risk of excessive vitamin intake.
Antioxidants
Some nutrients also
antioxidants. These may be vitamins, minerals, proteins, or other types of molecules.
They help the body remove toxic substances known as
or reactive oxygen species. If too many of these substances remain in the body, cell damage and disease can result.
Anyone concerned about their nutritional intake may benefit from speaking with a specialist, such as a dietitian or nutritionist.
A registered dietitian nutritionist (RD or RDN) studies food, nutrition, and dietetics.
To become a registered dietitian, a person needs to attend an accredited university, follow an approved curriculum, complete a rigorous internship, pass a licensure exam, and complete 75 or more continuing education hours every five years.
Dietitians work in various settings, including private and public healthcare, education, corporate wellness, research, and the food industry.
A nutritionist learns about nutrition through self-study or formal education, but they do not meet the requirements to use the titles RD or RDN. Nutritionists often work in the food industry and in food science and technology.
Nutrition is the study of food and how it affects the body. People need to consume a varied diet to obtain a wide range of nutrients.
Some people choose to follow a specific diet, in which they focus on certain foods and avoid others. People who do this may need to plan carefully to ensure they obtain all the necessary vitamins to maintain their health.
People can work with a registered dietitian or a nutritionist if they have concerns about their nutritional intake.