---
title: "Human nutrition"
chunk: 6/20
source: "https://en.wikipedia.org/wiki/Human_nutrition"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:55:25.210940+00:00"
instance: "kb-cron"
---

The intestines contain a large population of gut flora. In humans, the four dominant phyla are Bacillota, Bacteroidota, Actinomycetota, and Pseudomonadota. They are essential to digestion and are also affected by food that is consumed. Bacteria are essential for metabolizing food substrates and thereby increasing energy output, and produce a great variety of metabolites, including vitamins and short-chain fatty acids that contribute to the metabolism in a wide variety of ways. These metabolites are responsible for stimulating cell growth, repressing the growth of harmful bacteria, priming the immune system to respond only to pathogens, helping to maintain a healthy gut barrier, control gene expression by epigenetic regulation and defending against some infectious diseases.

== Global nutrition challenges ==

The challenges facing global nutrition are disease, child malnutrition, obesity, and vitamin deficiency.

=== Disease ===
The most common non-infectious diseases worldwide, that contribute most to the global mortality rate, are cardiovascular diseases, various cancers, diabetes, and chronic respiratory problems, all of which are linked to poor nutrition. Nutrition and diet are closely associated with the leading causes of death, including cardiovascular disease and cancer. Obesity and high sodium intake can contribute to ischemic heart disease, while consumption of fruits and vegetables can decrease the risk 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 five 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 individuals.
Childhood malnutrition is common and contributes to the global burden of disease. Childhood is a particularly important time to achieve good nutrition status, because poor nutrition has the capability to lock a child in a vicious cycle of disease susceptibility and recurring sickness, which threatens cognitive and social development. Undernutrition and bias in access to food and health services leaves children less likely to attend or perform well in school.

=== Undernutrition ===