The Role of Sulfur Amino Acids in Risk of Kwashiorkor
Fitzpatrick, Merry Colleen.
Abstract Kwashiorkor is a form of severe acute malnutrition identified more than 80
years ago as a syndrome and still affects hundreds of thousands of children each year,
yet its etiology remains unknown. A better understanding of its etiology is necessary to
develop effective preventive strategies. Although kwashiorkor is only found in regions
where protein intake and sanitation ar... read moree poor, study findings comparing the dietary
protein intake of children with and without kwashiorkor have been conflicting. Protein
quality has not been explored and the large array of signs characterizing kwashiorkor
can plausibly be explained by a deficiency of sulfur amino acids (SAAs). Children with
kwashiorkor have low circulating sulfur amino acids (methionine and cysteine) and their
metabolites, and their metabolism of SAAs is altered. The aim of this research is to
provide evidence upon which to design preventive interventions, hypothesizing that
children in higher-prevalence populations will have lower intakes of SAAs, and that low
intake of SAAs will be a stronger predictor of the risk of kwashiorkor than other
factors. Additionally, due to its low nutrient content and potentially high cyanide
content, cassava intake was hypothesized to be a stronger predictor of risk than food
security. An anthropometric survey of all children in one Health Area of eastern
Democratic Republic of the Congo located all cases of kwashiorkor among children 12 to
59 months old to aid in the selection of two populations with very different prevalence.
A commercial laboratory was used to provide amino acid profiles on market samples of key
staples and sources of proteins. Household samples of cassava flour and cooked cassava
leaves were tested for cyanogens. Interviews with caregivers of children 36 to 59 months
old recorded multiple factors of the household and the child and a 24-hour quantitative
recall of the child's diet. Among the many signs characterizing kwashiorkor, only
bipedal pitting edema is used for admission to treatment, though light-colored brittle
hair and facial edema have been reported to appear before edema in the feet, therefore
all visible signs were recorded. One urine sample was taken to compare urinary sulfate
and another for thiocyanate. Analysis included GIS mapping, direct statistical
comparisons of diets, and path analysis modeling of the multiple potential causal
factors. Together, the findings showed children in a population with a higher prevalence
of kwashiorkor had lower intakes of sulfur amino acids, methionine in particular, more
children in this population were at risk of inadequate methionine intake than other
amino acids, and methionine was the limiting amino acid in both populations. Median
intake of both methionine and cysteine was above the WHO requirement, but true adequacy
of a nutrient must take into consideration factors that raise the requirement. Children
in the HPP were more stunted, were ill more often, and their families were more food
insecure than those in a lower-prevalence population. SAA intake, followed by illness,
was the strongest predictor of a family history of kwashiorkor. A family history of
kwashiorkor, followed by illness, was the strongest predictor of early signs of
kwashiorkor. It appears that low SAA intake makes children especially vulnerable to
kwashiorkor, but illness is often the event that triggers the onset of the syndrome.
Intervention trials to reduce prevalence of kwashiorkor should simultaneously reduce
exposure to infection and increase intake of both cysteine and
Thesis (Ph.D.)--Tufts University, 2018.
Submitted to the Dept. of Food Policy & Applied Nutrition.
Advisor: Daniel Maxwell.
Committee: Shibani Ghosh, Anura Kurpad, and Christopher Duggan.
Keywords: Nutrition, Public health, and Epidemiology.read less