Biology Reference
In-Depth Information
gluconeogenesis in liver and kidney, and by influencing gastric emptying.
Dietary proteins when consumed alone appear to increase insulin expression
although not as much as glucose. They have no impact on blood glucose.
The metabolic effects of proteins are conditional upon their quality. Dairy
proteins and whey protein, in particular, appears to be significantly
insulinotropic. While animal and fish proteins have also shown to be mod-
erately insulinotropic, data on vegetable proteins are equivocal. The com-
bined ingestion of proteins and carbohydrates appear to markedly attenuate
blood glucose and hyperstimulate insulin secretion. These effects also
depend upon protein quality. The reduction in glycemia and increase in
insulinemia are more marked in type 2 diabetics compared to normal indi-
viduals. Proteins may also be attenuating the glycemic response by slowing
gastric emptying. There is evidence to suggest that the ratio of animal and
plant protein in a meal can affect insulin secretions.
Individual amino acids also appear to play an important role in glucose
metabolism. The majority of amino acids when given alone at least modestly
affected insulin secretion. A few such as BCAAs and phenylalanine appear to
have a greater effect on insulin secretion. Only BCAAs seem to be able to
attenuate the blood glucose response when ingested alone. The glucose low-
ering and insulin secretion effects of amino acids are enhanced when they are
coingested with glucose. Amino acids such as arginine, proline, phenylala-
nine, glutamine, and BCAAs have greater glucose attenuating effects in this
regard. Arginine, BCAAs, and glutamine appear to be better insulin secre-
tagogues when taken in combination with glucose. The effect of amino acids
on glucose and insulin depends on amino acid type, mode of administration
(intravenous or oral), dosage, and combination. Oral administration of
amino acids stimulates glucose homeostasis metabolic pathways (involving
incretins and the liver) that intravenous dosages may bypass. While physio-
logically greater doses of amino acids often show better effects, amounts rep-
resentative of quantities typically found in food sometimes may show a lesser
impact. Amino acid combinations have been shown to have a significantly
greater effect on glycemia and insulin secretion than any given alone. This
highlights the significance of synergistic effects and the importance and
practical usefulness of considering amino acid combinations rather than
singular types.
These studies collectively demonstrate the complexity of protein's effects
on glucose homeostasis and the equivocal nature of the current state of the
art. The literature so far produces as many questions as it does answers.
A large amount of the basic knowledge in this area comes from studies
