5. Feb, 2017
Magnesium is considered a major mineral. It is required for bone and heart health, and has numerous functions in the human body. Nuts, green leafy veg, whole grains, seafood & legumes are good dietary sources (Whitney et al. 2011).
Bioavailability of minerals can be an issue, so the addition of a source of vitamin C can be helpful for calcium, phosphorus, iron and magnesium absorption. Phytic and oxalic acids, found in many healthy foods, can lower the bioavailability particularly of iron and calcium (Byrd-Bredbenner et al. 2009).
Phytic acid in wheat grain fibre can bind to some minerals and prevent their absorption. If the grain is leavened with yeast, their enzymes help break down the phytic acid, making zinc more bioavailable for example.
Oxalic acid, found in leafy greens, is known as an anti-nutrient. It blocks around 95% of the calcium in spinach from being absorbed. Oxalobacter formigenes, a colonic bacteria, uses oxalic acid as an energy source before it is able to bind to minerals, however widespead antibiotic use has meant it is now only found in less than 50% of the population’s microbiome (Kaufman et al. 2008). Boiling vegetables can reduce their oxalic acid content from 30% to just under 90% (Chai & Liebman 2005).
The authors of a recent meta-analysis (where the data from many studies are put together) looked at the relationship between magnesium and both type 2 diabetes and cardiovascular disease. They found significant inverse associations between intake and the risk of stroke, heart failure, and diabetes, but not coronary heart disease or total cardiovascular disease (Fang et al. 2016).
Byrd-Bredbenner, C, Moe, G, Beshgetoor, D & Berning, J 2009, Wardlaw's Perspectives in Nutrition, 8th edn, MacGraw-Hill, New York, NY.
Chai, W & Liebman, M 2005, 'Effect of Different Cooking Methods on Vegetable Oxalate Content', Journal of Agricultural and Food Chemistry, vol. 53, no. 8, pp. 3027-3030.
Fang, X, Wang, K, Han, D, He, X, Wei, J, Zhao, L, Imam, MU, Ping, Z, Li, Y, Xu, Y, Min, J & Wang, F 2016, 'Dietary magnesium intake and the risk of cardiovascular disease, type 2 diabetes, and all-cause mortality: a dose–response meta-analysis of prospective cohort studies', BMC Medicine, vol. 14, no. 1, p. 210.
Kaufman, DW, Kelly, JP, Curhan, GC, Anderson, TE, Dretler, SP, Preminger, GM & Cave, DR 2008, 'Oxalobacter formigenes May Reduce the Risk of Calcium Oxalate Kidney Stones', Journal of the American Society of Nephrology : JASN, vol. 19, no. 6, pp. 1197-1203.
Whitney, E, Rolfes, SR, Crowe, T, Cameron-Smith, D & Walsh, A 2011, Understanding Nutrition, 1st edn, Wadsworth, South Melbourne, Victoria.