Dietary glutamic acid and aspartic acid in diabetic retinopathy
What it found
In 2067 people with type 2 diabetes followed for a median of 5 years, neither glutamic acid nor aspartic acid intake changed the risk of developing diabetic retinopathy.
Lower aspartic acid intake was linked to a higher risk of the more severe form, proliferative diabetic retinopathy.
What they found
Studies in people
Retinopathy risk overall
After adjusting for other factors, the risk of developing diabetic retinopathy was about the same across low, medium and high intakes of glutamic acid and aspartic acid. This was true whether intake was measured in milligrams or as a share of total protein.
Severe retinopathy and aspartic acid
People with the highest aspartic acid intake had a lower risk of proliferative diabetic retinopathy than those with the lowest intake. The link held after adjusting for other factors.
Intakes in the retinopathy group
At the start, people who went on to develop diabetic retinopathy ate less total energy, glutamic acid and aspartic acid than those who did not. They were also older and had higher HbA1c, longer diabetes duration, lower education and lower income.
Glutamic acid and severe retinopathy
Proliferative diabetic retinopathy tended to be more common with low glutamic acid intake, but the difference was not statistically significant.
Other findings
Why intake may not matter
The authors note that glutamic acid and aspartic acid are made in the body, so blood levels may depend more on the body's own production than on how much is eaten.
What the authors conclude
“In conclusion, the dietary glutamic acid and aspartic acid did not affect the incidence of DR. However, aspartic acid intake was negatively correlated with PDR.”
Also in their conclusions
- They conclude that dietary glutamic acid and aspartic acid did not affect the incidence of diabetic retinopathy.
- They state that aspartic acid intake was negatively correlated with proliferative diabetic retinopathy.
- They suggest that metabolites absorbed from the diet may not directly affect their concentrations in blood and body fluids.
How it was done
The authors wanted to see whether these dietary amino acids could help predict diabetic retinopathy, since screening rates are low and current biomarkers are not accurate enough. An earlier study of theirs had found a link but could not show cause and effect.
They followed 2067 patients with type 2 diabetes and no diabetic retinopathy at the start, from 12 hospitals in Korea, for a median of 5 years. Food intake was recorded over 3 days at the start and every 3 years, and eye exams were done every year.
What it can’t tell you
- This study followed people over time, so it can show links, not cause and effect.
- Food intake was recorded only at the start and every 3 years, so it may not reflect usual intake over the whole period.
- The findings are from Korean patients with type 2 diabetes and may not apply to other groups.
Who paid
- Conflicts
- The authors declare no competing interests.
- Authors work at
- Kyung Hee University Hospital, Republic of Korea; Kyung Hee University, Republic of Korea; Il San Gospel Hospital, Republic of Korea
The paper
- Title
- Dietary glutamic acid and aspartic acid as biomarkers for predicting diabetic retinopathy
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Park SY, Kim J, Son JI, et al (2021). Dietary glutamic acid and aspartic acid as biomarkers for predicting diabetic retinopathy. Scientific reports. doi:10.1038/s41598-021-83165-5Free full textPubMed 33790305DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error