Almost double the adult RDI for Vitamin A (9400IU)
Over 5 times the adult RDI for Vitamin K (445µg)
A third of the adult RDI for Folate (130µg)
One fifth of the adult RDI for Magnesium (75mg)
As with all non-starchy vegetables, spinach is nutrient dense rather than energy dense and is also a great source of fibre (2.2g per ½ cup cooked serving).
Vegetarian Source of Iron
Firstly, it is important to distinguish between the two main type of dietary iron; haem iron (from animal sources such as red meat, chicken, fish and eggs) and non-haem iron (from plant sources such as spinach, tofu and cashews).
Although a half cup serving of cooked spinach provides 3.2mg (10-22% of adult daily requirements) per ½ cup cooked serving, it is important to consider that this iron is in the non-haem form which is not as bioavailable as haem iron (Hurrell & Egli 2010). This is the reason that those following a vegan/vegetarian diets actually require 14-32mg iron per day (14mg for men, 32mg for pre-menopausal women) as opposed to 8-18mg per day for meat-eaters.
Consuming non-haem sources of iron (including spinach) in the presence of a vitamin C source increases its absorption (Siegenberg et al 1991). Try adding a squeeze of lemon juice or some capsicum to a spinach-based salad or have some fresh fruit such as orange or strawberries on the side.
Be Wary of Oxalates
Oxalic acid (oxalates) are naturally occurring chemicals in plants (especially leafy green vegetables), nuts, seeds and soy.
The amount consumed from foods (spinach contains 750mg per 100g) is not high enough to exert toxic effects although it binds with minerals such as calcium (Heaney et al 1988) and magnesium (Bohn et al 2004), hindering their absorption.
The good news is that the negative effects of oxalates have been shown to be neutralised during the cooking process (Chai & Liebman 2005) so consuming spinach in the cooked form may actually be more beneficial than eating it raw. Lightly steaming rather than boiling for long periods of time will both neutralise the effects of oxalates as well as ensure other heat sensitive and water soluble nutrients are retained.
Spinach is an excellent source of carotenoid antioxidants (lutein and zeaxanthin) which is stored in the macular of the eye (Johnson et al 2000), playing important roles in maintaining healthy vision and preventing conditions such a macular degeneration (Snodderly 1995).
Lutein and zeaxanthin are stored in the macular (the part of the eye that shields it from the damaging effects of sunlight), absorbing blue light blue light which is particularly damaging to the retina of the eye (Carpentier et al 2009).
Carotenoid antioxidants are also fat-soluble nutrients so consume in the presence of fat to aid absorption (e.g. olive oil or avocado in spinach salads) (van het Hof et al 2000).
Chlorophyll is the green pigment used by plants during the process of photosynthesis.
It works synergistically alongside lutein (Serpeloni et al 2013) to promote the natural detoxification process in the body by stimulating the production of phase 2 liver enzymes (Fahey et al 2005) as well as having potent antioxidant action.
How to Enjoy Spinach
Whether you choose to consume spinach in its raw form or cooked as part of a meal, the following are some simple suggestions to help you include this wonderful green vegetable in your daily diet:
- Use fresh baby spinach leaves as the base of salads.
- Lightly sauté spinach leaves in olive oil and garlic with a squeeze of lemon for the perfect side dish.
- Spinach is a great addition to omelettes, frittatas and quiches. Wilted spinach also pairs well with poaches eggs for breakfast.
- Try a simple spinach dip (blend 400g baby spinach leaves with 1 clove garlic, 1 cup plain yoghurt, 1/3 cup fresh coriander leaves and a pinch of salt in a food processor). Get extra veggies in by serving with carrot and celery sticks.
- Add a handful of baby spinach leaves to a fruit smoothie. The sweetness of the fruit masks the flavour and you won’t even taste it, I promise!
Stay tuned for a tasty recipe featuring spinach I’ll be sharing soon.
Bohn et al (2004), ‘Fractional magnesium absorption is significantly lower in human subjects from a meal served with an oxalate-rich vegetable, spinach, as compared with a meal served with kale, a vegetable with low oxalate content’, British Journal of Nutrition, 91(4): 601-606.
Carpentier et al (2009), ‘Associations between lutein, zeaxanthin, and age-related macular degeneration: an overview’, Critical Reviews in Food Science and Nutrition, 49(4): 313-326.
Chai & Liebman (2005), ‘Effect of different cooking methods on vegetable oxalate content’, Journal of Agricultural and Food Chemistry, 53(8): 3027-3030.
Fahey et al (2005), ‘Chlorophyll, chlorophyllin and related tetrapyrroles are significant inducers of mammalian phase 2 cytoprotective genes’, Carcinogenesis, 26(7): 1247-1255.
Johnson et al (2000), ‘Relation among serum and tissue concentrations of lutein and zeaxanthin and macular pigment density’, American Journal of Clinical Nutrition, 71(6): 1555-1562.
Heaney et al (1988), ‘Calcium absorbability from spinach’, American Journal of Clinical Nutrition, 47(4): 707-709.
Hurrell & Egli (2010), ‘Iron bioavailability and dietary reference values’, American Journal of Clinical Nutrition, 91(5): 1461S-1467S.
Serpeloni et al (2013), ‘Effects of lutein and chlorophyll b on GSH depletion and DNA damage induced by cisplatin in vivo’, Human and Experimental Toxicology, 32(8): 828-836.
Siegengerb et al (1991), ‘Ascorbic acid prevents the dose-dependent inhibitory effects of polyphenols and phytates on nonheme-iron absorption’, American Journal of Clinical Nutrition, 53(1): 537-541.
Snodderly (1995), ‘Evidence for protection against age-related macular degeneration by carotenoids and antioxidant vitamins’, American Journal of Clinical Nutrition, 62(6): 1448S-1461S.
van het Hof et al (2000), ‘Dietary factors that affect the bioavailability of carotenoids’, Journal of Nutrition, 130(3): 503-506.