Darmkrebs und Osteoporose: Calcium- und Vitamin D-Therapie enttäuschten

Zu den Standardempfehlungen die Ärzte älteren Frauen geben gehört der Rat nach Beginn der Wechseljahre Calcium und Vitamin D einzunehmen, um die Wahrscheinlichkeit von Knochenbrüchen zu reduzieren. Quasi als erwünschte Nebenwirkung wurde den Frauen in der Vergangenheit ein Rückgang des Darmkrebs-Risikos in Aussicht gestellt. 
Nun belegen zwei neue Studien, daß beide Hoffnungen durch Einnahme der Nahrungs-Ergänzungsmittel nicht einzulösen sind.  Zwar nahm die Knochendichte unter langjähriger Calcium- und Vitamin-D-Gabe tatsächlich um magere  1% zu, doch die Zahl der Knochenbrüche ging dadurch nicht wie erhofft zurück. Die erhöhte Knochendichte von 1% wird andererseits mit einer deutlichen Zunahme von Nierensteinen erkauft.

Wurde Calcium und Vitamin D von den älteren Frauen  sieben Jahre lang eingenommen, so konnte diese Therapie die Häufigkeit von bösartigen Darmtumoren nicht senken. Möglicherweise ist dafür eine weitaus längere Einnahme erforderlich.

N Engl J Med. 2006 Feb 16;354(7):669-83 

    Erratum in: N Engl J Med. 2006 Mar 9;354(10):1102. 

    Comment in: N Engl J Med. 2006 Feb 16;354(7):750-2. 

Calcium plus vitamin D supplementation and the risk of fractures. 

Jackson RD, LaCroix AZ, Gass M, Wallace RB, Robbins J, Lewis CE, Bassford T, Beresford SA, Black HR, Blanchette P, Bonds DE, Brunner RL, Brzyski RG, Caan B, Cauley JA, Chlebowski RT, Cummings SR, Granek I, Hays J, Heiss G, Hendrix SL, Howard BV, Hsia J, Hubbell FA, Johnson KC, Judd H, Kotchen JM, Kuller LH, Langer RD, Lasser NL, Limacher MC, Ludlam S, Manson JE, Margolis KL, McGowan J, Ockene JK, O'Sullivan MJ, Phillips L, Prentice RL, Sarto GE, Stefanick ML, Van Horn L, Wactawski-Wende J, Whitlock E, Anderson GL, Assaf AR, Barad D; Women's Health Initiative Investigators.   

Division of Endocrinology, Ohio State University, 485 McCampbell, 1581 Dodd Dr., Columbus, OH 43210, USA. jackson.20@osu.edu

BACKGROUND: The efficacy of calcium with vitamin D supplementation for preventing hip and other fractures in healthy postmenopausal women remains equivocal.  

METHODS: We recruited 36,282 postmenopausal women, 50 to 79 years of age, who were already enrolled in a Women's Health Initiative (WHI) clinical trial. We randomly assigned participants to receive 1000 mg of elemental [corrected] calcium as calcium carbonate with 400 IU of vitamin D3 daily or placebo. Fractures were ascertained for an average follow-up period of 7.0 years. Bone density was measured at three WHI centers.  

RESULTS: Hip bone density was 1.06 percent higher in the calcium plus vitamin D group than in the placebo group (P<0.01). Intention-to-treat analysis indicated that participants receiving calcium plus vitamin D supplementation had a hazard ratio of 0.88 for hip fracture (95 percent confidence interval, 0.72 to 1.08), 0.90 for clinical spine fracture (0.74 to 1.10), and 0.96 for total fractures (0.91 to 1.02). The risk of renal calculi increased with calcium plus vitamin D (hazard ratio, 1.17; 95 percent confidence interval, 1.02 to 1.34). Censoring data from women when they ceased to adhere to the study medication reduced the hazard ratio for hip fracture to 0.71 (95 percent confidence interval, 0.52 to 0.97). Effects did not vary significantly according to prerandomization serum vitamin D levels.  

CONCLUSIONS: Among healthy postmenopausal women, calcium with vitamin D supplementation resulted in a small but significant improvement in hip bone density, did not significantly reduce hip fracture, and increased the risk of kidney stones. (ClinicalTrials.gov number, NCT00000611.).

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1: N Engl J Med. 2006 Feb 16;354(7):684-96.          

    Erratum in: N Engl J Med. 2006 Mar 9;354(10):1102. 

    Comment in: N Engl J Med. 2006 Feb 16;354(7):752-4. 

Calcium plus vitamin D supplementation and the risk of colorectal cancer.

Wactawski-Wende J, Kotchen JM, Anderson GL, Assaf AR, Brunner RL, O'Sullivan MJ, Margolis KL, Ockene JK, Phillips L, Pottern L, Prentice RL, Robbins J, Rohan TE, Sarto GE, Sharma S, Stefanick ML, Van Horn L, Wallace RB, Whitlock E, Bassford T, Beresford SA, Black HR, Bonds DE, Brzyski RG, Caan B, Chlebowski RT, Cochrane B, Garland C, Gass M, Hays J, Heiss G, Hendrix SL, Howard BV, Hsia J, Hubbell FA, Jackson RD, Johnson KC, Judd H, Kooperberg CL, Kuller LH, LaCroix AZ, Lane DS, Langer RD, Lasser NL, Lewis CE, Limacher MC, Manson JE; Women's Health Initiative Investigators.

Department of Social and Preventive Medicine, University at Buffalo, 270 Farber Hall, Buffalo, NY 14214, USA. jww@buffalo.edu

BACKGROUND: Higher intake of calcium and vitamin D has been associated with a reduced risk of colorectal cancer in epidemiologic studies and polyp recurrence in polyp-prevention trials. However, randomized-trial evidence that calcium with vitamin D supplementation is beneficial in the primary prevention of colorectal cancer is lacking.

METHODS: We conducted a randomized, double-blind, placebo-controlled trial involving 36,282 postmenopausal women from 40 Women's Health Initiative centers: 18,176 women received 500 mg of elemental calcium as calcium carbonate with 200 IU of vitamin D3 [corrected] twice daily (1000 mg of elemental calcium and 400 IU of vitamin D3) and 18,106 received a matching placebo for an average of 7.0 years. The incidence of pathologically confirmed colorectal cancer was the designated secondary outcome. Baseline levels of serum 25-hydroxyvitamin D were assessed in a nested case-control study.  

RESULTS: The incidence of invasive colorectal cancer did not differ significantly between women assigned to calcium plus vitamin D supplementation and those assigned to placebo (168 and 154 cases; hazard ratio, 1.08; 95 percent confidence interval, 0.86 to 1.34; P=0.51), and the tumor characteristics were similar in the two groups. The frequency of colorectal-cancer screening and abdominal symptoms was similar in the two groups. There were no significant treatment interactions with baseline characteristics.  

CONCLUSIONS: Daily supplementation of calcium with vitamin D for seven years had no effect on the incidence of colorectal cancer among postmenopausal women. The long latency associated with the development of colorectal cancer, along with the seven-year duration of the trial, may have contributed to this null finding. Ongoing follow-up will assess the longer-term effect of this intervention.

(Clinical Trials.gov number, NCT00000611.)