Protein–energy malnutrition

Protein–energy malnutrition (or protein–calorie malnutrition) refers to a form of malnutrition where there is inadequate protein intake.

Disability-adjusted life year for protein–energy malnutrition per 100,000 inhabitants in 2002.^[1]

  no data

  less than 10

  10–100

  100–200

  200–300

  300–400

  400–500

  500–600

  600–700

  700–800

  800–1000

  1000–1350

  more than 1350

Types include:^[2]

• Kwashiorkor (protein malnutrition predominant)
• Marasmus (deficiency in calorie intake)
• Marasmic Kwashiorkor (marked protein deficiency and marked calorie insufficiency signs present, sometimes referred to as the most severe form of malnutrition)

Note that this may also be secondary to other conditions such as chronic renal disease^[3] or cancer cachexia^[4] in which protein energy wasting may occur.

Protein–energy malnutrition affects children the most because they have less protein intake. The few rare cases found in the developed world are almost entirely found in small children as a result of fad diets, or ignorance of the nutritional needs of children, particularly in cases of milk allergy.^[5]

Prenatal protein malnutrition

Protein malnutrition is detrimental at any point in life, but protein malnutrition prenatally has been shown to have significant lifelong effects. During pregnancy, one should aim for a diet that consists at least 20% protein for the health of the fetus. Diets that consist of less than 6% protein in utero have been linked with many deficits, including decreased brain weight, increased obesity, impaired communication within the brain. Even diets of mild protein malnutrition (7.2%) have been shown to have lasting and significant effects. The following are some studies in which prenatal protein deficiency has been shown to have unfavorable consequences.

• Decreased brain size: Protein deficiency has been shown to affect the size and composition of brains in rhesus monkeys. Monkeys whose mother had eaten a diet with an adequate amount of protein were shown to have no deficit in brain size or composition, even when their body weight amounted to less than one-half of that of the controls, whereas monkeys whose mothers had eaten low-protein diets were shown to have smaller brains regardless of the diet given after birth.^[6]

• Impaired neocortical long-term potentiation: Mild protein deficiency (in which 7.2% of the diet consists of protein) in rats has been shown to impair entorhinal cortex plasticity (visuospatial memory), noradrenergic function in the neocortex, and neocortical long-term potentiation.^[7]

• Altered fat distribution: Protein undernutrition can have varying effects depending on the period of fetal life during which the malnutrition occurred. Although there were not significant differences in the food intake, there were increased amounts of perirenal fat in rats that were protein-deprived during early (gestation days 0–7) and mid (gestation days 8–14) pregnancy, and throughout pregnancy, whereas rats that were protein-deprived only late in gestation (gestation days 15–22) were shown to have increased gonadal fat.^[8]

• Increased obesity: Mice exposed to a low-protein diet prenatally weighed 40% less than the control group at birth (intrauterine growth retardation). When fed a high-fat diet after birth, the prenatally undernourished mice were shown to have increased body weight and adiposity (body fat), while those who were adequately nourished prenatally did not show an increase in body weight or adiposity when fed the same high-fat diet after birth.^[9]

• Decreased birth weight, and gestation duration: Supplementation of protein and energy can lead to increased duration of gestation and higher birth weight. When fed a supplement containing protein, energy, and micronutrients, pregnant women showed more successful results during birth, including high birth weights, longer gestations, and fewer pre-term births, than women who had consumed a supplement with micronutrients and low energy but no protein (although this finding may be due to the increase of energy in the supplements, not the increase of protein).^[10]

• Increased stress sensitivity: Male offspring of pregnant rats fed low-protein diets have been shown to exhibit blood pressure that is hyperresponsive to stress and salt.^[11]

• Decreased sperm quality: A low-protein diet during gestation in rats has been shown to affect the sperm quality of the male offspring in adulthood. The protein deficiency appeared to reduce sertoli cell number, sperm motility, and sperm count.^[12]

• Altered cardiac energy metabolism: Prenatal nutrition, specifically protein nutrition, may affect the regulation of cardiac energy metabolism through changes in specific genes.^[13]

• Increased passive stiffness: Intrauterine undernutrition was shown to increase passive stiffness in skeletal muscles in rats.^[14]

From these studies it is possible to conclude that prenatal protein nutrition is vital to the development of the fetus, especially the brain, the susceptibility to diseases in adulthood, and even gene expression. When pregnant females of various species were given low-protein diets, the offspring were shown to have many deficits. These findings highlight the great significance of adequate protein in the prenatal diet.

See also

• Protein (nutrient)

References

Further reading

• Bistrian, Bruce R.; McCowen, Karen C.; Chan, Samuel (1999). "Protein–energy malnutrition in dialysis patients". American Journal of Kidney Diseases 33 (1): 172–5. doi:10.1016/S0272-6386(99)70278-7. PMID 9915286. 
• Protein–Energy Undernutrition at Merck Manual of Diagnosis and Therapy Professional Edition