All about fruitarianism with a long-term fruitarian, Lena

The most frequently occurring clinical indicator of vitamin A deficiency is night-blindness, which is the earliest manifestation of xerophthalmia. 

In its mild form it is generally noticeable after stress from a bright light that bleaches the rhodopsin (visual purple) found in the retina. Vitamin A deficiency prolongs the time to regenerate rhodopsin, and thus delays adaptation time in dark environments.

Night-blind young children tend to stumble when going from bright to dimly-lit areas and they, as well as night-blind mothers, tend to remain inactive at dusk and at night.

George Berkeley

To be is to be perceived.

Protein Digestibility-Corrected Amino Acid Score

The protein digestibility-corrected amino acid score (PDCAAS) has been adopted by FAO/WHO as the preferred method for the measurement of the protein value in human nutrition. 

PDCAAS = Amino Acid Score x Digestibility

The method is based on comparison of the concentration of the first limiting essential amino acid in the test protein with the concentration of that amino acid in a reference (scoring) pattern. This scoring pattern is derived from the essential amino acid requirements of the preschool-age child.

Although the principle of the PDCAAS method has been widely accepted, critical questions have been raised in the scientific community:

  1. the validity of the preschool-age child amino acid requirement values (more than 4 times greater than the EAA requirement for an adult),
  2. the validity of correction for fecal instead of ileal digestibility,
  3. the truncation of PDCAAS values to 100%.

The reference scoring pattern was based on studies performed more than 25 years ago on a limited number of 2-year-old children recovering from malnutrition.

According to the current official recommendations, a 2-year old child needs ~ 3x higher essential-to-non-essential amino acid ratio, and needs essential amino acids in different proportions than adult. Methionine/cysteine is the limiting essential amino acids for adults, and for children it is lysine or tryptophan.

The use of fecal digestibility overestimates the nutritional value of a protein because amino acid nitrogen entering the colon is lost for protein synthesis in the body and is, at least in part, excreted in urine as ammonia.

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