Difference in status of key nutrients for the brain between PKU patients and healthy controls

Orphanet Journal of Rare Diseases published ‘Status of nutrients important in brain function in phenylketonuria (PKU): a systematic review and meta-analysis.’  To the best of our knowledge, this is the first systematic review and meta-analysis of published studies (no language restriction) that investigated the difference status of multiple nutrients1 involved in brain function between PKU patients and healthy controls.

The dietary management of PKU consists of a low-phenylalanine (phe) diet, measured amounts of natural protein intake, combined with phe-free amino acid-based protein supplements and low protein foods. The nutritional intake of PKU patients is designed to be optimal for phe as the priority, but may not be optimal for other nutrients, which may impact brain function.

This systematic review and meta-analysis compared the status of those nutrients known to be important for brain development and functioning between individuals with PKU and healthy controls.


Current data show that PKU patients have lower levels of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and cholesterol. DHA, EPA, cholesterol, but also phospholipid and choline are key structural components of neuronal membranes.

Given the key role of specific nutrients in brain function, it is important to assess the status of these nutrients where limited data is currently available (e.g. choline and iodine).
No significant differences in zinc, vitamins B, E and D, calcium, iron and magnesium were found between PKU patients and controls.

Although this meta-analysis provides valuable insight into nutrient status, the authors recommend a standardized approach to reporting on observational studies. This would allow more definitive conclusions to be drawn and strengthen the outcomes from meta-analyses. This is especially necessary given the small number of patients with rare conditions who participate in research and to be able to better understand the nutritional status of this diseases.

About PKU

Phenylketonuria (PKU) is a rare genetic metabolic condition. Those with PKU miss an enzyme, that allows the body to convert phenylalanine (an amino acid) to tyrosine (another amino acid). As a consequence, the phenylalanine builds up causing impaired brain development and function. Phenylalanine is found naturally in all proteins. People with PKU can prevent complications by avoiding protein-rich foods and following a special – phe restricted – diet and/ or by taking medications. To ensure optimal outcome in PKU, patients’ micronutrient and fatty acid status should continuously be monitored. All under supervision of a doctor and / or dietitian.


Nutrients: DHA, EPA phospholipids, selenium, vitamins B6, B12, E, C, A, D, folic acid, choline, uridine, calcium, magnesium, zinc, iron, iodine and cholesterol.