Milk may impair infertility in women ... as lead can in men.
Women who would like but have failed to conceive a child may want to review how big a role dairy products play in their diet, a new study suggests. A team of researchers in the United States and Finland now reports that where per capita [Latin, By the heads or polls.] A term used in the Descent and Distribution of the estate of one who dies without a will. It means to share and share alike according to the number of individuals. milk consumption is highest, women tend to experience the sharpest age-related falloff fall·off
A reduction or decrease: a falloff in car sales.
Noun 1. falloff - a noticeable deterioration in performance or quality; "the team went into a slump"; "a gradual slack in in fertility
With the exception of certain northern European populations and their descendants, most adults lose the ability to easily digest lactose, a sugar in milk. Because lactose intolerance discourages high consumption of milk and other dairy goods rich in galactose - a sugar apparently toxic to human eggs - this trait may be beneficial, observe gynecologist gynecologist /gy·ne·col·o·gist/ (-kol´ah-jist) a person skilled in gynecology.
A physician specializing in gynecology. Daniel W. Cramer of Harvard Medical School Harvard Medical School (HMS) is one of the graduate schools of Harvard University. It is a prestigious American medical school located in the Longwood Medical Area of the Mission Hill neighborhood of Boston, Massachusetts. in Boston and his coworkers.
Five years ago, Cramer linked galactose consumption with increased risk of ovarian cancer (SN: 7/22/89, p. 52). To look for hints that this sugar might also affect fecundity fecundity /fe·cun·di·ty/ (fe-kun´dit-e)
1. in demography, the physiological ability to reproduce, as opposed to fertility.
2. ability to produce offspring rapidly and in large numbers. , his team compared published data from 36 countries on rates of fertility, per capita milk consumption, and hypolactasia - that adult inability to digest lactose. In the Feb. 1 AMERICAN JOURNAL OF EPIDEMIOLOGY, they now report a correlation between high rates of milk consumption and waning fertility, beginning in women just 20 to 24 years old.
The strength of that association - and the rate of fertility decline - grew with each successively older age group studied. In Thailand, for instance -- where 98 percent of adults are hypolactasic - average fertility in women 35 t o 39 is only 26 percent lower than peak rates (at age 25 to 29). By contrast, in Australia and the United Kingdom, where hypolactasia affects only about 5 percent of adults, average fertility by 35 to 39 is fully 82 percent below peak rates.
Many factors - including marriage customs, divorce rates, contraception use, and individual wealth - affect fertility, the authors concede. However, notes Cramer, the new analysis does offer "demographic confirmation of what we have observed both experimentally, when you feed a mouse high galactose, and clinically, in women with galactosemia galactosemia (gəlăk'təsē`mēə), inherited metabolic disorder caused by an enzyme deficiency and transmitted as a recessive trait; it results in the accumulation of the sugar galactose in the body. [an inability to metabolize me·tab·o·lize
1. To subject to metabolism.
2. To produce by metabolism.
3. To undergo change by metabolism.
to subject to or be transformed by metabolism. galactose]." Women with this disorder who have high concentrations of the sugar in tissue are infertile in·fer·tile
Not capable of initiating, sustaining, or supporting reproduction.
adj unable to produce offspring. , he observes.
... as lead can in men
Though several studies have demonstrated that high exposures to lead can impair male reproduction, no one has understood precisely how the heavy metal wreaks its havoc. Now, researchers at the University of California, Los Angeles UCLA comprises the College of Letters and Science (the primary undergraduate college), seven professional schools, and five professional Health Science schools. Since 2001, UCLA has enrolled over 33,000 total students, and that number is steadily rising. , School of Medicine report that the toxic metal may alter sperm function by suppressing circulating concentrations of the male sex hormone testosterone.
Rebecca Z. Sokol and her coworkers treated mature male rats to regular water or drinking water laced with lead. Rodents exposed to lead received enough to alter serum testosterone concentrations without affecting their apparent health. After 2 to 9 weeks, sperm from each rat were incubated with eggs from females raised on a lead free diet.
The researchers found no structural abnormalities in sperm from the lead-treated animals. However, these sperm proved about 30 percent less successful at penetrating eggs than did sperm from untreated rats. Even after penetrating an egg, lead-exposed sperm had a more difficult time fostering those initial stages of development in which one cell begins dividing into many,
In the February TOXICOLOGY AND APPLIED PHARMACOLOGY, SSokol's team concludes that by disrupting testosterone's stimulation of the testes testes
Male reproductive organs (see reproductive system). Humans have two oval-shaped testes 1.5–2 in. (4–5 cm) long that produce sperm and androgens (mainly testosterone), contained in a sac (scrotum) behind the penis. , lead appears to trigger a cascade of events that "not only impairs sperm penetrating ability, but also diminishes the ability of lead-exposed sperm to physiologically fertilize the eggs that they have penetrated."