Eating too much of low-fat dairy foods such as skimmed milk
and yoghurt may harm women's fertility while eating whole fat dairy products
such as whole fat milk and ice cream may have a protective effect against
infertility, a new study suggests.
In the study published on February 28 in Europe's leading
reproductive medicine journal, Human Reproduction, U.S. researchers found an
association between a low-fat dairy diet and increased risk of infertility due
to lack of ovulation or anovulatory infertility.
Women who ate two or more servings of low-fat dairy foods per
day were 85% more likely to experience ovulation-related problems compared to
those who ate less than one serving per week. In contrast, women who ate at
least one serving of high fat dairy foods per day had a 27% reduced risk of
anovulatory infertility compared to those who ate one serving or less per week.
Dr Jorge Chavarro, lead author of the study and a research
fellow in the Department of Nutrition at Harvard School of Public Health in
Boston was cited as saying that more research is needed to confirm or refute
the association between low-fat dairy foods and anovulatory infertility because
the information in this area is scarcely available to support this link.
Chavarro said it is particularly important to clarify the
role of dairy foods on fertility as the current U.S. Dietary Guidelines
recommends men and women eat three or more servings of low fat diary foods
If confirmed, the 85% higher risk
of infertility could be the basis for women who want to become pregnant to
adjust their diet.
In the study, Dr Chavarro and his colleagues identified
18,555 women aged 24 to 42 who participated in The Nurses' Health Study II.
Women without a history of infertility when entering the study had tried to
become pregnant or become pregnant between 1991 and 1999.
The women were surveyed every two years to see if they had
tried to become pregnant for more than a year without success and what caused
the problem if they failed to conceive. Also their dietary habits were
questioned with regard to what they ate and how often certain foods during the
In the course of the
study, 438 women reported infertility due to an ovulatory disorder.
With all possible factors considered including age, parity,
body mass index, total calorie intake, physical activity, smoking, drinking and
contraceptive use, Dr. Chavarro found eating two or more servings of low fat
dairy foods a day apparently increased the risk of infertility by 85% compared
to eating one serving or less per week whereas eating one or more servings per
day of high fat dairy foods appeared to lower the risk by 27% compared to
eating one serving or less per week.
But no association was found between infertility and the
total intake of dairy foods.
was an inverse association between high fat diary foods and the risk of
developing the fertility disorder.
means a high consumption of high fat diary foods may lead to a lower risk of
The researchers also investigated the effect of individual
dairy food on the risk of infertility.
One extra serving of low fat dairy foods such as yoghurt would result in
an 11% increase in the infertility risk whereas one extra serving of high fat
diary products such as whole milk would reduce the risk by 22%, both
associations were based on the condition that the total calories in two groups
were the same.
A more significant finding was that the more ice cream a
woman ate, the lower her risk of infertility was.
Women who ate two or more servings of ice
cream a week were 38% less likely to develop infertility than those who used
less than one serving per week.
The researchers believe that the presence of a fat-soluble
substance, which improves ovarian function, might explain the lower risk of
infertility from high-fat dairy foods. "The intake of dairy fat, or a
fat-soluble substance present in dairy foods, may partly explain the inverse
association between high-fat dairy foods and anovulatory infertility," Dr
Chavarro did not elaborate what the fat soluble substance
was, but the researchers found there was not any association between
anovulatory infertility and intake of calcium, phosphorus or vitamin D.
A scientist affiliated with foodconsumer.org suggests that
if the association between dairy fat and fertility, then fat soluble hormone(s)
in milk might be the reason. Anovulatory infertility was likely caused by an
imbalance of hormones caused by prolonged strenuous exercise, anxiety and other
emotional stress and dietary hormones from dairy may influenced the imbalance.
A Mongolian scientist working at Harvard has earlier said
U.S. milk has high
estrogen levels than Mongolian milk as
US farmers collect milk even during
a period in which dairy cows produce high levels of estrogen in their milk.
Another possibility is that those who ate low fat dairy foods were more health
conscious than others, probably because they may have known some preexisting
condition directly or indirectly related to infertility.
Anovulatory infertility can may also result from a number of
other factors including eating disorders, hypothalamic dysfunction,
hyperprolactinemia, polycystic ovary syndrome, luteal phase defects, tumors of
the pituitary gland adrenal gland or ovaries and use of certain medications.
The foodconsumer.org scientist suggests that women should
not rush to eat tons of ice cream to protect against infertility as ice cream
is not a good food from a nutrition viewpoint.
He point out eating dairy foods with high fat and protein was linked
with chronic diseases such as cancer, according to Dr. T. Colin Campbell, a
University nutritionist who described
the link in his famous book titled “The China Study”.
Early studies have already raised concern over high
consumption of milk because lactose is digested into glucose and galactose, the
latter clinically and experimentally appears toxic to ovarian germ cells.
One study published in the Feb. 1994 issue of American Journal
of Epidemiology (AJE) found fertility declined faster with aging in women who
had higher consumption of milk and greater capability of digesting lactose.
This means, milk consumption may affect ovarian function.
The toxicity was also demonstrated in other
studies, which have associated milk consumption with higher risk of ovarian
cancer. One such study was published in the November 1989 issue of AJE.
The foodconsumer.org scientist comments it does not matter
the results of the current study are accurate and reliable or not.
Eating ice cream or dairy foods is not the
way to go when it comes to protection against infertility.