Soybean Nutritional Properties: The Good And The Bad About Soy Foods Consumption - A Review|
Consumption of soy foods is increasing worldwide mainly due to their acclaimed
health benefits. However, nutritional demerits associated with soy foods consumption
exist. Proteins and lipids, some vitamins and minerals, are major nutritionallyimportant
components of soybeans; carbohydrates are major constituents
quantitatively. Whole soy foods are also good sources of dietary fibre, B-vitamins,
calcium, and omega-3 essential fatty acids. This review examines the merits and
demerits of consuming soy foods. The amino acid composition of soybean protein
complements that of cereals. Also, the high biological value of soy proteins increases
their value as feedstuff. Processing generally increases digestibility of soybean
protein; soy protein concentrate and isolate have higher digestibility than soy flours.
Trypsin and chymotrypsin inhibitors in flours lower protein digestibility. However,
despite demonstrated growth inhibition in animals, due to antinutrients, methionine
supplementation in infants is useful only when dietary protein intake is marginal.
Although processing considerably reduces antinutrient levels, care must be taken not
to reduce protein nutritional value by excessive heating, which can result in loss of
thermolabile amino acids. Significant lowering of plasma cholesterol has been
reported in hypercholesterolemic subjects with hyperlipoproteinemia, when soy
protein replaced animal protein in diets. Also, a dose-response relationship has been
shown with isoflavones, particularly genistein, in lowering low-density lipoprotein
cholesterol in human kinetic studies. However, questions are being raised about soy
isoflavones, especially when consumed as concentrated supplements by segments of
the population. Data suggest that genistein may prompt growth of breast tissue in
male mice, while other data suggest the opposite effect. Studies also showed that
infants consuming soy formula had higher blood levels of isoflavones than women
receiving soy supplements who show menstrual cycle disturbances. Also, some
animal and human study results have linked soy isoflavones to goitre. Nevertheless,
data linking soy consumption to reduced risk of osteoporosis, prostate, breast and
colon cancers exists, despite the data being inadequate to make definitive conclusions.
Despite concerns on soy isoflavones, the FDA-sanctioned claim on soy protein,
covers a component generally accepted as heart-healthy. Nevertheless, the need for
more research is emerging as well as caution on soy foods inappropriate consumption.
As Africa produces small but increasing amount of soybeans, it will continue relying
on imports to meet demand. As demand for soy products increases worldwide, due to
its health benefits, African consumers are advised to take note of emerging unhealthy
side effects of consumption of large amounts of soy products.
Soybean, nutrients, health benefits, demerits