The Lowdown on Caffeine

An excerpt from Marilyn M. Shannon’s book, Fertility, Cycles & Nutrition.


Caffeine is a good slave but a bad master. When you use it only occasionally or in moderation, it provides a lift that many people enjoy. However, it affects the nervous system, and can cause anxiety and irritability. It can deprive you of a good night’s sleep, sometimes just in small amounts, because it powerfully reduces the “sleep hormone,” melatonin. Used to excess, caffeine depletes the body of B vitamins and raises blood glucose by over stimulating the adrenal glands. The latter effect triggers the insulin response, ultimately causing hypoglycemia, fatigue, and the craving for more caffeine.

Caffeinated beverages are a factor in premenstrual syndrome (PMS), at least for some women.[1] In amounts exceeding 300 mg per day (about two to three cups of coffee), using caffeine relates to a delay in achieving pregnancy.[2] A higher incidence of miscarriage once pregnancy occurs has been found related to consumption of more than 200 mg of caffeine per day (about two cups of coffee).[3] Higher intakes increase these risks.

Coffee is the most familiar source of caffeine, but soda pop, non-herbal teas, and chocolate also contain caffeine or related compounds which have similar effects. Here is a chart of the caffeine levels found in coffee, tea, and other beverages.

Caffeine affects blood vessel constriction, so if you are trying to cut back on a heavy-duty caffeine habit, it is better to reduce your caffeine consumption gradually — over a period of two or three weeks — to avoid withdrawal headaches. If you don’t want to give up on sipping on a hot drink, you can still enjoy flavor, aroma, warmth, and low calories by selecting phytonutrient-rich green teas, white teas, or other herbal teas. Some of these may contain small amounts of caffeine, but the small amounts are not problematic, according to studies referenced above.

— Marilyn M. Shannon is a tenured, part-time instructor of biology at Indiana University Purdue University at Fort Wayne, Indiana, where she has taught human anatomy and physiology for more than 30 years. Her book, Fertility, Cycles & Nutrition is a staple for many NFP families and is available here

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[1] Gold, E., Bair, Y., Block, G., et al. “Diet and lifestyle factors associated with premenstrual symptoms in a racially diverse community sample: Study of women’s health across the nation (SWAN)” (J. Women’s Health 2007, 16:641-656); Rossignol, A., and Bonnlander, H. “Caffeine-containing beverages, total fluid consumption, and premenstrual syndrome” (Am. J. Public Health 1990, 80:1106-1109).

[2] Derbyshire, E. “Dietary factors and fertility in women of childbearing age” (Nutrition and Food Science 2007, 37:100-104).

[3] Weng, X., Odouli, R., and Li, D. “Maternal caffeine consumption during pregnancy and the risk of miscarriage: A prospective cohort study: (J. Obst. Gynecol., January 2008, pp. 1e1-1e8).