A recent review of nutritional requirements of active people in the heat, conducted by a group of researchers at a prominent university, included the conclusion that '… there are no indications that calcium requirements are increased in the heat …'

I conducted a PubMed search for 'calcium in sweat' and found twelve relevant references from the scientific literature of the last decade or so. The references are shown at the bottom of this message.

From the references, it appears that calcium losses in sweat are variable, but generally in the range 40-70 mg/L. I have measured sweat rates exceeding 1 L/h for soldiers patrolling in hot-dry and hot-wet climates. Even higher sweat rates have been reported for endurance athletes (the highest being 3.7 L/h for Alberto Salazar during the 1984 Olympic Marathon: Armstrong, L. et al. (1986). The Physician and Sports Medicine 14(3): 73-81.

Soldiers and ultramarathon athletes who engage in vigorous physical work in hot climates, often for more than ten hours per day, could be losing hundreds of milligrams of calcium in sweat each day. Under these circumstances, I don't believe it is appropriate to conclude that '… there are no indications that calcium requirements are increased in the heat …'

What do others think about this?

Chris Forbes-Ewan

Assistant Site Manager and
Defence Scientist (Nutrition) S&T5
Defence Nutrition and Food Technology
Human Protection and Performance Division
74 George St  Scottsdale  Tasmania

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The opinions expressed in this message are those of the author, and should not be taken to represent the position of the Defence Science and Technology Organisation or of the Australian Department of Defence.

Relevant references found through PubMed:

Barry DW, Kohrt WM. (2007). Acute effects of 2 hours of moderate-intensity cycling on serum parathyroid hormone and calcium. Calcif Tissue Int. 80(6):359-65.

Bullen DB, O'Toole ML, Johnson KC. (1999). Calcium losses resulting from an acute bout of moderate-intensity exercise. Int J Sport Nutr. Sep;9(3):275-84.

Chinevere TD, Kenefick RW, Cheuvront SN, Lukaski HC, Sawka MN. (2008). Effect of heat acclimation on sweat minerals. Med Sci Sports Exerc. 40(5):886-91.

Kunstel K. (2005). Calcium requirements for the athlete. Curr Sports Med Rep. 4(4):203-6.

Martin BR, Davis S, Campbell WW, Weaver CM. (2007). Exercise and calcium supplementation: effects on calcium homeostasis in sportswomen. Med Sci Sports Exerc. Sep;39(9):1481-6.

Montain SJ, Cheuvront SN, Lukaski HC. (2007). Sweat mineral-element responses during 7 h of exercise-heat stress. Int J Sport Nutr Exerc Metab. 17(6):574-82.

O'Toole ML, Johnson KC, Satterfield S, Bush AJ, Koo WW, Klesges RC, Applegate WB. (2000). Do sweat calcium losses affect bone mass during firefighter training? J Occup Environ Med. Nov;42(11):1054-9.

Palacios C, Wigertz K, Weaver CM. (2003). Comparison of 24 hour whole body versus patch tests for estimating body surface electrolyte losses. Int J Sport Nutr Exerc Metab. 13(4):479-88.

Petrie HJ, Stover EA, Horswill CA. (2004). Nutritional concerns for the child and adolescent competitor. Nutrition.20(7-8):620-31.

Rianon N, Feeback D, Wood R, Driscoll T, Shackelford L, LeBlanc A. (2003). Monitoring sweat calcium using skin patches. Calcif Tissue Int. 72(6):694-7.

Sawka MN, Montain SJ. (2000). Fluid and electrolyte supplementation for exercise heat stress. Am J Clin Nutr. 72(2 Suppl):564S-72S.

Shirreffs SM, Maughan RJ. (1997). Whole body sweat collection in humans: an improved method with preliminary data on electrolyte content. J Appl Physiol. Jan;82(1):336-41.

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