Is caffeine a risk factor for bone loss in the elderly?

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American Journal of Clinical Nutrition, Vol. 74, No. 5, 569-570, November

2001

© 2001 _American Society for Clinical Nutrition_

(http://www.ajcn.org/misc/terms.shtml)

 

__

Editorial

Is caffeine a risk factor for bone loss in the elderly?1,_2_

(http://www.ajcn.org/cgi/content/full/74/5/569#FN2)

<NOBR>Linda K

From the Department of Food Science and Human Nutrition, Washington State

University, Spokane.

See corresponding article on page _694_

(http://www.ajcn.org/cgi/content/full/ajcn;74/5/694) .

2 Address reprint requests to LK Massey, Food Science and Human Nutrition,

Washington State University, 601 W First Avenue, Spokane, WA 99201-3899.

E-mail: _massey_ (massey) .

(http://www.ajcn.org/cgi/content/full/74/5/569#RFN2)

Dietary caffeine acutely increases urinary calcium loss (_1_

(http://www.ajcn.org/cgi/content/full/74/5/569#R1) ), and these losses are not

entirely

compensated for in the 24 h after caffeine consumption (_2_

(http://www.ajcn.org/cgi/content/full/74/5/569#R2) ). Overall, the evidence

indicates that younger

individuals can increase their calcium absorption to compensate for the

urinary losses, whereas the elderly are less adaptable (_3_

(http://www.ajcn.org/cgi/content/full/74/5/569#R3) ). It is not surprising that

most

cross-sectional studies of elderly populations showed no association of

caffeine consumpti

on with bone loss or bone mineral density because so many genetic and

lifestyle factors are now known to affect bone health. Previous prospective

studies

of elderly populations yielded conflicting results regarding caffeine and bone

loss. Although Cummings et al (_4_

(http://www.ajcn.org/cgi/content/full/74/5/569#R4) ) included caffeine

consumption among the risk factors for hip

fracture, Lloyd et al (_5_ (http://www.ajcn.org/cgi/content/full/74/5/569#R5) )

were unable to find any association of caffeine with bone loss in a 2-y

prospective study of 112 postmenopausal women. Similarly, Hannan et al (_6_

(http://www.ajcn.org/cgi/content/full/74/5/569#R6) ) did not find that caffeine

(or

calcium intake) was associated with bone loss in the Framingham study

population.

The interaction of caffeine intake with calcium on bone loss was reported by

Harris and Dawson-Hughes (_7_

(http://www.ajcn.org/cgi/content/full/74/5/569#R7) ). These investigators found

that bone loss from the spine and total-body

bone mineral density occurred only in postmenopausal women who had both low

calcium intakes (440–744 mg/d) and high caffeine intakes (450–1120 mg/d).

The following year, this same research team showed that response to calcium

supplementation is influenced by vitamin D receptor gene (VDR) genotype (_8_

(http://www.ajcn.org/cgi/content/full/74/5/569#R8) ), with the rate of loss at

the femoral neck being reduced by calcium only in the BB VDR subgroup. In

retrospect, it is probably not surprising that in this issue of the Journal

Rapuri et al (_9_ (http://www.ajcn.org/cgi/content/full/74/5/569#R9) ) report

that

caffeine's effect on bone loss is also associated with VDR genotype.

The new findings of Rapuri et al (_9_

(http://www.ajcn.org/cgi/content/full/74/5/569#R9) ) cause us to re-interpret

the results of previously published

studies. Rapuri et al found that caffeine intakes of >300 mg/d were associated

with bone loss in 96 women in a 3-y prospective study. Caffeine, however,

was only associated with increased bone loss in women with the tt VDR genotype.

This subgroup contained only 5 of the 33 women (15%) with higher caffeine

intakes. Bone loss in this subgroup exceeded 3%/y at all 5 sites examined

(spine, femoral neck, trochanter, total body, and total femur), although

significantly so at only 3 sites, probably because of the low number of

subjects in

the group. In the total group, only 11 of the 96 women had the tt VDR

genotype, and 6 of these 11 were apparently protected by their lower intake of

caffeine. Unfortunately, the sample size was too small to test the interaction

of

dietary calcium with caffeine and genotype. The low incidence of the

susceptible genotype helps to explain the lack of association seen in several

previous prospective studies. Only 5 of the 96 women had significant bone loss

with

higher caffeine intakes, and this small percentage would not be detectable in

studies not considering genotype.

What can we tell our patients about dietary recommendations to prevent

osteoporosis in the increasingly complex scenario of diet-gene interactions?

Making dietary recommendations to prevent osteoporosis is becoming increasingly

difficult as we learn more about the genetics of osteoporosis (_10_

(http://www.ajcn.org/cgi/content/full/74/5/569#R10) ). However, the studies of

Harris and

Dawson-Hughes (_7_ (http://www.ajcn.org/cgi/content/full/74/5/569#R7) ) and

Krall et al (_8_ (http://www.ajcn.org/cgi/content/full/74/5/569#R8) ) show

that adequate dietary calcium seems to counteract much of the negative effects

of higher caffeine consumption. The findings of Rapuri et al (_9_

(http://www.ajcn.org/cgi/content/full/74/5/569#R9) ) are also consistent with

previous

reports suggesting that a moderate caffeine intake is not associated with

increased bone loss. Until we can know an individual's genotype, as well as

diet-gene interactions, we must make recommendations based on the assumption

that

each person may have a genetic susceptibility to osteoporosis. On the basis

of the studies conducted to date, it seems prudent to recommend both adequate

dietary calcium and a moderate caffeine consumption for elderly individuals.

Moderate caffeine consumption seems likely to be 300 mg, 16 oz (473 mL)

brewed coffee, 32 oz (946 mL) brewed tea, or 6, 12-oz (355-mL) cans of most

caffeinated soft drinks (_3_ (http://www.ajcn.org/cgi/content/full/74/5/569#R3)

).

REFERENCES

1. Massey LK, Whiting SJ. Caffeine, urinary calcium, calcium metabolism

and bone. J Nutr 1993;123:1611–4._[Medline]_

(http://www.ajcn.org/cgi/external_ref?access_num=8360789 & link_type=MED)

2. Kynast-Gales SA, Massey LK. Effect of caffeine on circadian

excretion of urinary calcium and magnesium. J Am Coll Nutr 1994;13: 467–

72._[Abstract]_

(http://www.ajcn.org/cgi/ijlink?linkType=ABST & journalCode=jamcnutr & resid=13/5/46\

7)

3. Massey LK. Caffeine and the elderly. Drug Aging 1998;13:45–50.

4. Cummings SR, Nevitt MC, Browner WS, et al. Risk factors for hip

fracture in white women. Study of Osteoporotic Fractures Research Group. N Engl

J

Med 1995;32:767–73.

5. Lloyd T, Johnson-Rollings N, Eggli DF, Kieselhorst K, Mauger EA,

Cardamonte Cusatis D. Bone status among postmenopausal women with different

habitual caffeine intakes: a longitudinal investigation. J Am Coll Nutr

2000;19:256–61._<NOBR>[AbsFree Full Text]_

(http://www.ajcn.org/cgi/ijlink?linkType=ABST & journalCode=jamcnutr & resid=19/2/25\

6)

6. Hannan MT, Felson DT, Dawson-Hughes B, et al. Risk factors for

longitudinal bone loss in elderly men and women: The Framingham Osteoporosis

Study. J Bone Miner Res 2000;15:710–20._[Medline]_

(http://www.ajcn.org/cgi/external_ref?access_num=10780863 & link_type=MED)

7. Harris SS, Dawson-Hughes B. Caffeine and bone loss in healthy

postmenopausal women. Am J Clin Nutr 1994;60:573–8._<NOBR>[AbsFree Full Text]_

(http://www.ajcn.org/cgi/ijlink?linkType=ABST & journalCode=ajcn & resid=60/4/573)

8. Krall EA, Parry P, Lichter JB, Dawson-Hughes B. Vitamin D receptor

alleles and rates of bone loss: influence of years since menopause and calcium

intake. J Bone Miner Res 1995;10:978–84._[Medline]_

(http://www.ajcn.org/cgi/external_ref?access_num=7572323 & link_type=MED)

9. Rapuri PB, Gallagher JC, Kinyamu HK, Ryschon KL. Caffeine intake

increases the rate of bone loss in elderly women and interacts with vitamin D

receptor genotypes. Am J Clin Nutr 2001;74; 694–700.

10. Hobson EE, Ralston SH. Role of genetic factors in the

pathophysiology and management of osteoporosis. Clin Endocrinol

2001;54:1–9._[Medline]_

(http://www.ajcn.org/cgi/external_ref?access_num=11167918 & link_type=MED)