- Low protein or calorie intake, or inflammation can lead to lower levels.
- Nutrient cofactors of phenylalanine catabolism include tetrahydrobiopterin (BH4), nonheme iron, vitamins B6 & B3, copper, niacin, vitamin C, magnesium, SAMe.
- Lower plasma phenylalanine levels seen in depression and associated with lower neurotransmitter levels.
- A higher protein intake or supplementation results in higher levels.
- Elevated levels of phenylalanine compete with other large neutral amino acids.
- Higher phenylalanine levels have been found in type 2 diabetes, and with increased BMI, schizophrenia, and rheumatoid arthritis.
- Inflammation can impair the function of phenylalanine hydroxylase, leading to elevated phenylalanine levels and reduced tyrosine levels. In animal studies cortisol increased the activity of phenylalanine hydroxylase.
- Elevated phenylalanine in PKU has been shown to inhibit HMG-CoA reductase and can result in lower CoQ10 and cholesterol.
Phenylalanine (Plasma)
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