Spinach is not Bayam

Bayam ( in Malay language ) is of the genus Amaranthus, of the family Amaranthaceae.  There are about 60 species of Amaranthus, valued as leaf vegetables, cereals, and ornamentals, and several considered as weeds.  A. dubius is widely consumed as greens in S.E.Asia. 

The word 'Amaranth' comes from the Greek ἀμάραντος (amarantos), "unfading" or "never-fading (flower)".

Amaranthus dubius（ synonym Amaranthus mangostanus）Amaranth greens, also called Chinese spinach 苋菜  ( pinyin: xiàncài ) is an annual flowering plants, grows up to 120cm in height.  It has both green ( Bayam hijau ) and red ( Bayam merah ) varieties, as well as some with mixed colours.  Green variety of A. dubius is practically undistinguishable from A. viridis.

Amaranth greens are a very good source of vitamin A, vitamin K, vitamin B6, vitamin C, riboflavin, folate, calcium iron, magnesium, phosphosur, potassium, zinc, copper and manganese.   However their moderatelly high content of oxalic acid can inhibit the absorption of calcium and zinc, and thus people with kidney disorder, gout, or rheumatoid arthritis should be more cautious consuming bayam.

Reheating cooked bayam is discouraged, particularly for consumption by small children, as the nitrates in the leaves can be converted to nitrites, similarly to spinach.

Spinach ( Spinacia oleracea ) is an edible flowering plant from the family Amaranthaceae too.  It is native to central and southwestern Asia.  Spinach is an annual plant, capable to grow up to 30cm in height.

The English word spinach' dates to 1530 and is from espinache (Fr. épinard), from O.Prov. espinarc, which perhaps is via Catalan espinac, from Andalusian Arabic asbinakh , from Arabic es-sabaanikh (السبانخ), from Persian aspanakh, meaning roughly "green hand".

Spinach is thought to have originated in ancient Persia. Arab traders carried spinach into India, and then the plant was introduced into ancient China, where it was known as "Persian vegetable" (波斯菜, 菠菜).   It is loosely named bayam in Malay, which leads to confusion to distinguish a spinach and a bayam.

Spinach is rich in vitamin A, vitamin C, vitamin E, vitamin K, magnesium, manganese,  folate, betaine, iron, vitamin B2, calcium, potassium, vitamin B6, folic acid, protein, phosphorus, zinc, niacin, selenium omega-3 fatty acids etc.

The cartoon character Popeye the Sailor is potrayed as having a strong affinity for spinach, becoming physically stronger after consuming it.   This portrayal was based on faulty calculation of the iron content by a German scientist E. von Wolf who misplaced a decimal point in an 1870 measurement of the spinach’s iron content, leading to an iron value 10 times higher than its should have been.  This faulty measurement was not notice until the 1930s.