Exercise-Trained Young Men Have Higher Calcium Absorption Rates and Plasma Calcitriol Levels Compared with Age-Matched Sedentary Controls

Abstract

The effect of physical activity on human calcium (Ca) metabolism is still not completely understood. Thus, we investigated fractional Ca absorption using a stable strontium test (Fc(240)), calciotropic hormones, and renal Ca excretion in 31 young men with a high activity level (GH) and in 26 age-matched sedentary control subjects (GL). Weekly hours spent on physical activity, obtained with a questionnaire were 15.0 +/- 6.6 (GH) and 1.0 +/- 1.4 (GL), respectively. Serum testosterone levels were significantly lower in GH compared with GL (P < 0.005). Dietary Ca intake (4-day food record) was twice as high in GH compared with GL men (P < 0.001). GH had significantly higher serum calcitriol levels and Fc(240) values than GL (P < 0.001 and P < 0.01, respectively). In a stepwise multiple regression analysis including serum levels of 25-hydroxyvitamin D, calcitriol, testosterone, and dietary Ca intake, only calcitriol was significantly correlated with Fc(240) (P = 0. 017). Twenty-four hour renal Ca excretion was only slightly higher in GH compared with GL (P < 0.05). However, additional Ca losses might have occurred through the extensive sweating of GH, as indicated by a difference of 1.7 liter between fluid intake and renal fluid excretion (P < 0.001). In summary, we observed a higher fractional Ca absorption rate in physically active young men compared with sedentary controls which is probably mediated by calcitriol. The low testosterone serum levels of the athletes were obviously not a limiting factor in Ca absorption efficiency. An additional Ca retention might, however, only be obtained if absorbed Ca exceeded total obligatory Ca losses.

Endurance swimming stimulates transepithelial calcium transport and alters the expression of genes related to calcium absorption in the intestine of rats

“…In well-trained male athletes orally administered with stable strontium as a marker of calcium absorption, Zittermann et al (61) demonstrated increases in the fractional calcium absorption and serum 1,25(OH) 2 D 3 level after a shortterm moderate exercise bout. Another study (60) in male athletes with a minimum of 8 h/wk of endurance sport activities confirmed a 4% increase in the fractional strontium absorption compared with the age-matched sedentary controls. In contrast, immobilization by sciatic denervation in female rats led to a decrease in the duodenal calcium absorption, especially the passive components (58).…”

“…The mechanism of swimming-altered gene expression is currently unknown, but it might be mediated by 1,25(OH) 2 D 3 , as the plasma 1,25(OH) 2 D 3 concentration is typically elevated after endurance exercise (57,58,60). In contrast, immobilization was associated with suppressed 1,25(OH) 2 D 3 synthesis (46).…”

Calcium, dietary, and lifestyle factors in the prevention of colorectal adenomas

“…10,11 Nonsteroidal antiinflammatory drugs (NSAIDs) have been shown to be associated with a reduced risk of colorectal adenomas and cancer in clinical trials 12,13 and might potentially interact with calcium through similar biologic pathways. [14][15][16] Vitamin D and physical activity affect calcium absorption and homeostasis, [17][18][19] which could modify risk, in part, by affecting the amount of free calcium available within the lumen or cells of the colon.…”

Physical activity and bone mineral density

“…Specifični mehanizmi pomoću kojih fizička aktivnost utiče na metabolizam kostiju još uvek nisu potpuno razjašnjeni, međutim, dobro je poznato da povećanje koštane gustine nastaje usled povećanog mehaničkog opterećenja (Frost, 1988), ali izgleda da i ostali parametri, kao što su endokrine promene (Bell et al, 1988;Zittermann et al, 2000;Maimoun et al, 2003), doprinose adaptaciji koštanog sistema. Generalno, mineralna gustina kostiju je od koristi prilikom utvrđivanja snage kostiju i predstavlja primarni indikator rizika nastanka osteoporoze.…”