Caffeine.(Women's Health Adviser)

Caffeine is the world's most popular psychoactive substance, a potent adenosine receptor antagonist that stimulates the central nervous system and heart, increases gastric acid production, and induces diuresis.

The average daily caffeine consumption is about 200-250 mg--about two cups of coffee. Moderate caffeine consumption has never conclusively been shown to pose a health risk for women or their fetuses or nursing infants. Caffeine has never been linked to any teratogenic syndrome, and only if a lactating mother consumes large amounts (300-500 mg/day) is a nursing baby apt to show any ill effects (usually fussiness or sleeplessness).

Postmenopausal women should be cautioned about consuming too much caffeine. A 2001 study concluded that the consumption of 18 ounces of coffee per day (about 500 mg) accelerated bone loss. Women with the tt genetic variant of the vitamin D receptor appeared to be at greatest risk, but the authors did note that calcium supplementation could offset the deleterious effect of caffeine (Am. J. Clin. Nutr. 74[5]:694-700, 2001).

Breast tenderness is purported to be worsened by caffeine intake but most studies have failed to corroborate this.

Caffeine isn't all bad, and may even be beneficial in some respects. Users are less drowsy and less tired. Newly published research indicates that moderate consumption in adults at risk for developing liver disease decreased that risk by 69%; gallstone risk decreases by 40%. A recent study concluded that people who drank up to six cups of coffee per day decreased their risk of developing type 2 diabetes by almost 60% (Ann. Intern. Med. 140[1]:1-8, 2004).

Still, no one would recommend coffee drinking as a disease preventive, and enough evidence exists to urge women--especially those who are pregnant and lactating--to moderate their daily intake to no more than 300 mg. That's the equivalent of about three 8-ounce cups of coffee or two cups of coffee and a couple of soft drinks.

Most experts say that it's unnecessary for pregnant or nursing women to eliminate caffeine from their diet. But women who are regularly consuming more than 300 mg/day should cut back.