Wheat gluten diets and blood amino acids in young men
What it found
In 38 young men, eating wheat gluten at levels from 170 down to 30 mgN/kg for two weeks lowered blood levels of several essential amino acids, but lysine stayed near normal.
Below 30 mgN/kg, essential amino acids rose again.
What they found
Studies in people
Essential amino acids fall
In men eating 170 to 30 mgN/kg wheat gluten, blood levels of threonine, valine, methionine, leucine, tyrosine, phenylalanine, serine, histidine and arginine fell significantly as protein intake dropped. Valine fell the most.
Lysine stays steady
Blood lysine did not clearly reflect dietary lysine. Values ranged from 146 to 194 micromoles per liter across gluten intakes from 170 to zero mgN/kg, similar to the 186 on the standard diet.
Alanine rises
Blood alanine increased significantly as protein intake fell, rising about 50% at intakes below 30 mgN/kg.
Very low protein
At 15 or zero mgN/kg, essential amino acids did not keep falling but rose slightly above the levels seen at 30 mgN/kg. Alanine and glycine continued to rise.
Protein-free diet
In nine men on a protein-free diet, branched-chain amino acids, especially valine, dropped by about 25%, while alanine and glycine rose by 73% and 37%. Lysine stayed near the standard level.
Weight and nitrogen balance
Body weight tended to decrease in all groups during the experimental period. Nitrogen balance was negative at all wheat gluten levels, even at 170 mgN/kg.
What the authors conclude
“These findings suggest that in human adults receiving a wheat gluten diet, lysine deficiency is not reflected in a decrease in the lysine concentration of the plasma.”
Also in their conclusions
- They conclude that in human adults on a wheat gluten diet, lysine deficiency is not reflected in a decrease in the lysine concentration of the plasma.
- They state that a protein intake of 30mgN/kg was of biological significance, based on plasma amino acids and nitrogen balance.
- They say the study provides further evidence for the nutritional significance of plasma free amino acids in nitrogen balance studies.
How it was done
The authors wanted to understand how blood levels of amino acids, especially lysine, change when young men eat different amounts of wheat gluten. Earlier studies in growing animals and children had given conflicting results.
38 healthy male university students, aged 19 to 24, ate a standard mixed-protein diet for one week, then a wheat gluten diet at 170, 100, 60, 30, 15 or zero mgN/kg for two weeks. Blood was taken before breakfast at the end of each period to measure free amino acids.
What it can’t tell you
- This was a small study in 38 young men, so the results may not apply to women, older adults or children.
- The men ate wheat gluten for only two weeks, so the longer-term effects are not known.
- The study measured blood amino acid levels, not health outcomes like growth, strength or disease risk.
The paper
- Title
- Effect of low protein diets on free amino acids in plasma of young men: effect of wheat gluten diet
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Fujita Y, Yamamoto T, Rikimaru T, Inoue G (1979). Effect of low protein diets on free amino acids in plasma of young men: effect of wheat gluten diet. Journal of nutritional science and vitaminology. doi:10.3177/jnsv.25.427Free full textPubMed 120426DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error