Abstract:
Nowadays, vegetarian diets are becoming more popular in many countries,
including Thailand. Many scientific studies support health benefits of vegetarian diets.
The main source of protein in the Thai vegetarian diets is from soyfoods. Soyfoods not only
provide good quality protein but also a good source of phytoestrogen, especially
isoflavones subclasses. Interestingly, isoflavones can exert partial estrogenic and
antiestrogenic effects. This is believed to be associated with a reducing risk of chronic
diseases such as cancer, cardiovascular disease and osteoporosis, as well as relieving
menopausal symptoms. However, there is no data about isoflavone content in mixed
dishes. Therefore, this study aimed to determine the isoflavone content and composition
as well as nutritive value in selected vegetarian foods containing soyfoods in order to
investigate the benefits of Thai vegetarian diets.
Ten side dishes and five one-plate dishes from 4-5 food shops in Bangkok were
selected. The ten side dishes were Kaeng jued tao hu, Kaeng kheaw whan, Larb, Pad kaphrao,
Pad pak ruam mit, Pad prig khing protein ka-set, Tao hu song krueng, Tao hu
palo, Tom jabchaay and Tom jued ga-lum-plee. The five one-plate dishes were Guayteaw-
nam, Guay-teaw pad see-ew, Guay-teaw pad-thai, Guay-teaw rad nah and Khao
pad. Proximate composition, calcium, sodium and iron, were analyzed using standard
methods, AOAC. Their isoflavone content, both aglycone and glucoside forms, was
analyzed using HPLC.
The results based on 100g wet weight showed a wide variation of energy from the
ten side dishes. Protein and fat contributed largely to their caloric distribution. Pad kaphrao,
Pad pak ruam mit and Pad prig khing protein ka-set had a considerable amount of
dietary fiber ranging from 5.2-10.4 mg/100 g wet weight. All side dishes provided low to
moderate levels of calcium, sodium and iron except Pad prig khing protein ka-set.
According to serving size, nutrient composition of all one-plate dishes was similar. They
provided adequate caloric distribution and dietary fiber. Their sodium content was rather
high while calcium and iron content was low to moderate.
Total isoflavone content of all dishes varied, probably due to type and amount of
soyfoods used as ingredients. Total isoflavone content in side dishes ranged from 1.2 to
63.4 mg aglycone equivalents/ 100 g wet weight. The highest isoflavone content was
found in Pad prig khing protein ka-set. For one-plate dishes, it ranged from 4.4 to 14.4
mg aglycone equivalents/serving. Guay-teaw-nam showed the highest total isoflavone
content. The major form of isoflavones in most of dishes was glucoside. The
predominate isomers were genistein and diadzein.
Based on this finding, Thai vegetarian diets which contained soyfoods as
ingredients contributed total isoflavone content and had considerable nutrient
composition. However, they provided low to moderate amounts of calcium and iron.
Therefore, an addition of soy beverage and soy snack between meals should be considered
for increasing calcium and iron intake.