Table of Phenylalanine Content of Foods: Comparative Analysis of Data Compiled in Food Composition Tables

Abstract

Background: Knowing the phenylalanine (Phe) content of foods is essential for managing the diet of patients with phenylketonuria. Data on the Phe content of foods are scarce and sometimes vary between different Food Composition Tables (FCT). Brazil created its own table of the Phe contents of fruits and vegetables based exclusively on the chemical analysis of protein content, considering that proteins contain 3-4% Phe (TCFA/ANVISA). This study compared the protein and Phe contents of vegetables and fruits provided by the TCFA/ANVISA with those listed in international food composition tables.

Methods: The Phe content of 71 fruits and vegetables listed in TCFA/ANVISA was classified into four subgroups, and the Wilcoxon nonparametric test compared the Phe and mean protein contents provided by the FCTs. All tests considered the bilateral hypothesis, and the level of significance was set at 5%. The Spearman's correlation coefficient measured the statistical dependence between Phe and protein contents.

Results: The mean Phe content was <50 mg Phe/100 g for 15 fruits; >50 mg/100 g for 11 type-A vegetables; <50 mg/100 g for 8 type-B vegetables; ≤50 mg/100 g for 7 type-C vegetables. The percentage of Phe in protein varied from 3.13 ± 1.03% to 3.74 ± 2.55% in fruits; 3.33 ± 1.41 to 4.82 ± 1.17 in type-A vegetables; 3.46 ± 1.25% to 4.83 ± 2.46 in type-B vegetables; and 3.14% ± 1.49 to 4.62% ± 2.26 in type-C vegetables.

Conclusions: The Phe and protein contents provided by most FCTs were positively correlated, suggesting that it is possible to estimate the Phe content of fruits by multiplying its protein content by 3%. For type-A, -B, and -C vegetables, 4% may be used.

Keywords: Food composition tables; Phenylalanine; Phenylalanine restricted diet; Phenylketonuria.

Fig. 1

Phenylalanine content (mg/100 g) of fruits (a) and type-A, -B, and -C vegetables (b, c, d) provided by TCFA/ANVISA (gray dots) and eight international food composition tables (black dots): DTU FOOD/Denmark, FAO-AA, FCNT/Germany, HCNT/Canada, LPFL-PKU/USA, NUTTAB/Australia, NZFC/New Zealand, USDA-SR/USA. Legend for fruits: Grape, several varieties (Thompson, White, Niagara) (Vitis sp.); Peach, Brazilian and international (Prunus persica); Pear, Williams (Pyrus communis L.); Strawberry (Fragaria vesca L.); Mandarin, Mungote and Ponkan (Citrus reticulata “Murgote”); Melon (Cucumis melo); Mango (Mangifera indica L.); Papaya (Carica papaya L.), Apple (Pyrus malus); Kiwi fruit (Actinidia chinensis Plack.); Fig (Ficus carica L.); Persimmon (Diospyros kaki L.); Banana (several varieties) (Musa sp.); Plum (Prunus salicina Lindl.); Pineapple (Ananas comosus); Avocado (Persea americana mil.). Legend for type-A vegetables: Parsley (Petroselinum sativum), Spices, celery seed (Apium graveolens L.), Arugula (Erucata sativa), Cabbage, white and red (Brassica oleracea L.), Spinach (Tetragonia expansa Murr.), Cauliflower (Brassica oleracea L.), Kale (Brassica oleracea L.), Coriander (Coriandrum sativum L.), Chicory greens (Cichorium intybus L.), Onions spring or scallions (Allium fistulosum L.), Chicory (Chicorium endivia), Lettuce (Lactuca sativa L.), Artichokes, globe (Cynara scolimus L.), Watercress (Nasturtium officinale L.), Chard, Swiss (Beta vulgaris L. var. cicla). Legend for type-B vegetables: Tomatoes, several varieties (Solanum lycopersicon Mill., Lycopersicon sp.), Okra (Hibiscus esculentus), Pepper, sweet, red (Capsicum annuum), Pepper, sweet, green (Capsicum annuum), Pepper, sweet, yellow (Capsicum annuum), Cucumber (Cucumis sativus L.), Peas, green (Pisum sativum L.), Chayote (Sechium edule), Aubergine (Solanum melogena L.), Kent pumpkin (Cucurbita maxima), Butter, squash, (Cucurbita pepo), Pumpkin (Cucurbita spp.). Legend for type-C vegetables: Radish (Raphanus sativus), Turnip (Brassica rapa L.), Cassava (Manihot esculenta Crantz Manihot utilissima), Yam (Colocasia esculenta), Carrot (Daucus carota L.), Onion (Allium cepa L.), Taro (Dioscorea spp.), Beet root (Beta vulgaris), Sweet potato (Ipomoea batatas L.), Potato (Solanum tuberosum), Garlic (Allium sativum L.), Leek (Allium porrum L.)