Human nutrition is the most important essential nutrients which present in the food that are necessary to support human life and health. Poor nutrition may be a chronic problem often linked to poverty, food security or a poor understanding of nutrition and dietary practices. Malnutrition and its consequences are large contributors to deaths and disabilities worldwide. Good nutrition is important for youngsters to grow physically, and for normal human biological development.

The physical body contains chemical compounds like water, carbohydrates, amino acids (found in proteins), fatty acids (found in lipids), and nucleic acids (DNA and RNA). These compounds are composed of elements like carbon, hydrogen, oxygen, nitrogen, and phosphorus. Any study done to work out nutritional status must take under consideration the state of the body before and after experiments, also because the chemical composition of the entire diet and of all the materials excreted and eliminated from the body (including urine and feces).

Nutrients

There are 7 classes of nutrients are fats, fiber, carbohydrates, minerals, proteins, vitamins, and water. Nutrients are often grouped as either macronutrients or micronutrients (needed in small quantities). Carbohydrates, fats, and proteins are macronutrients, and supply energy. Water and fiber are macronutrients but don't provide energy.

• Undernutrition, which incorporates wasting (low weight-for-height), stunting (low height-for-age) and underweight (low weight-for-age)
• Micronutrient-related malnutrition, which incorporates micronutrient deficiencies or insufficiencies (a lack of important vitamins and minerals) or micronutrient excess
• Overweight, obesity and diet-related non communicable diseases (such as heart condition, stroke, diabetes and a few cancers).

In developed countries, the diseases of malnutrition are most frequently related to nutritional imbalances or excessive consumption; there are more people within the world who are malnourished thanks to excessive consumption. consistent with the United Nations World Health Organization, the best challenge in developing nations today isn't starvation, but insufficient nutrition – the shortage of nutrients necessary for the expansion and maintenance of important functions. The causes of malnutrition are directly linked to inadequate macronutrient consumption and disease, and are indirectly linked to factors like “household food security, maternal and child care, health services, and therefore the environment.”

Insufficient diet

Excessive diet

Unbalanced diet

When an excessive amount of 1 or more nutrients is present within the diet to the exclusion of the right amount of other nutrients, the diet is claimed to be unbalanced. High calorie food ingredients like vegetable oils, sugar and alcohol are mentioned as "empty calories" because they displace from the diet foods that also contain protein, vitamins, minerals and fiber.

Illnesses caused by underconsumption and overconsumption

Global nutrition challenges

There are many challenges which are facing global nutrition are disease, child malnutrition, obesity, and vitamin deficiency

Disease

The most common non-infectious diseases worldwide, that contribute most to the worldwide death rate, are cardiovascular diseases, various cancers, diabetes, and chronic respiratory problems, all of which are linked to poor nutrition. Nutrition and diet are closely related to the leading causes of death, including disorder and cancer. Obesity and high sodium intake can contribute to ischemic heart condition, while consumption of fruits and vegetables can decrease the danger of developing cancer.

Food-borne and infectious diseases can result in malnutrition, and malnutrition exacerbates infectious disease. Poor nutrition leaves children and adults more susceptible to contracting life-threatening diseases such as diarrheal infections and respiratory infections. According to the WHO, in 2011, 6.9 million children died of infectious diseases like pneumonia, diarrhea, malaria, and neonatal conditions, of which at least one third were associated with undernutrition.

Child malnutrition

According to UNICEF, in 2011, 101 million children across the globe were underweight and one in four children, 165 million, were stunted in growth Simultaneously, there are 43 million children under five who are overweight or obese. Nearly 20 million children under 5 suffer from severe acute malnutrition, a life-threatening condition requiring urgent treatment. According to estimations at UNICEF, hunger will be responsible for 5.6 million deaths of children under the age of five this year. These all represent significant public health emergencies. This is because proper maternal and child nutrition has immense consequences for survival, acute and chronic disease incidence, normal growth, and economic productivity of people.

Undernutrition

This is defined insufficient food intake and repeated infectious diseases due to lack of nutritious food. This has been estimated that undernutrition is the cause for 35% of child deaths

Adult overweight and obesity

Malnutrition in industrialized nations is primarily due to excess calories and non-nutritious carbohydrates, which has contributed to the obesity epidemic affecting both developed and some developing nations. In 2008, 35% of adults above the age of 20 years were overweight (BMI 25 kg/m2), a prevalence that has doubled worldwide between 1980 and 2008. Also 10% of men and 14% of women were obese, with a BMI greater than 30. Rates of overweight and obesity vary across the globe, with the highest prevalence in the Americas, followed by European nations, where over 50% of the population is overweight or obese. Obesity is more prevalent amongst high income and higher middle income groups than lower divisions of income. Women are more likely than men to be obese, where the rate of obesity in women doubled from 8% to 14% between 1980 and 2008. Being overweight as a child has become an increasingly important indicator for later development of obesity and non-infectious diseases such as heart disease in several western European nations.

Vitamin and mineral malnutrition

Vitamins and minerals are essential to the proper functioning and maintenance of the human body. Globally, particularly in developing nations, deficiencies in iodine, iron, and zinc among others are said to impair human health when these minerals are not ingested in an adequate quantity.