Balance of Essential Fats May Prevent Bone Loss After Menopause
19 Jul 2005

Maintaining a proper balance of dietary fats may ward off much of the
bone loss associated with post-menopausal osteoporosis, according to a
recent study by scientists at Purdue University and the Indiana
University School of Medicine.

The researchers found that diets with a low ratio of omega-6 fatty
acids to omega-3 fatty acids minimized the bone loss typically brought
on by estrogen deficiency, which is common in post-menopausal females.
Omega-6 fatty acids are typically found in foods such as grains and
beef, while omega-3 fatty acids are found in foods such as walnuts and
salmon.

"Our lab and others have shown that omega-3 fatty acids help promote
bone formation," said Bruce Watkins, professor and director of Purdue's
Center for Enhancing Foods to Protect Health. "We also have shown that
higher intakes of omega-6 fatty acids lead to an increased production
of compounds associated with bone loss."

The current study, which is in press in the Journal of Nutritional
Biochemistry, assessed bone mineral content and bone mineral density in
female rats. These measurements are used as indicators of bone mass and
bone strength, respectively.

Half the rats in the study had their ovaries removed, a procedure that
leads to a rapid drop in estrogen levels. This mimics menopause and is
the standard model for studying compounds that mitigate osteoporosis,
said Mark Seifert, a professor of anatomy and cell biology at the
Indiana University School of Medicine and the study's co-author.

"Bone loss due to estrogen depletion in the adult female rat is very
similar to that which occurs in post-menopausal women," he said.
"Studies like this will help us and other researchers assess drugs or
nutraceuticals that may reduce the bone loss that sets in with
menopause, " he said.

In the study, groups of these rats were fed diets containing different
ratios of omega-6 to omega-3 polyunsaturated fatty acids.

While both types of fats are essential for human health, diets with a
high ratio of omega-6 fatty acids to omega-3 fatty acids are often
associated with cardiovascular disease, cancer and inflammatory and
autoimmune diseases. A low ratio of omega-6 to omega-3 fatty acids,
however, is believed to promote cardiovascular health, improve memory
and, as the current study shows, protect bone health.

After 12 weeks, rats with the lowest ratio of omega-6 to omega-3 fatty
acids in their diet experienced significantly less bone loss than rats
in the other dietary groups.

"We saw in this study that omega-3 fatty acids are associated with a
better blood profile of bone health, and with higher bone mineral
density, in the absence of estrogen," Watkins said.

"A 5-to-1 dietary ratio of omega-6 to omega-3 fatty acids led to a
conservation of bone mineral content that we didn't see with a 10-to-1
ratio," Watkins said.

While he cautions against translating these results to humans, Watkins
does agree that omega-3s are an important part of a healthy diet.

"As a nation, we don't consume enough of these fats, but we're heading
in the right direction," he said.

The average American dietary ratio of omega-6 to omega-3 fatty acids is
approximately 10 to 1, a ratio inflated by the types of foods people
eat and the methods used to produce those foods, especially those
containing vegetable oils, Watkins said.

"Our foods are different today than they were yesterday," he said.

"Omega-6 fatty acids have been an important part of our diet, but over
the past 80 years, the human diet has shifted in a way that increased
the ratio of omega-6 to omega-3 fatty acids. In the past century, we've
relied on high omega-6 grains like corn to feed livestock."

Animals such as cattle naturally feed on pasture grasses, which have a
lower omega-6 to omega-3 ratio than grains like corn, Watkins said.

The omega-6 fatty acids in today's animal feed incorporate right into
the animals' tissues where they become part of the eggs, poultry, meats
and pork served in households and restaurants across the country.

"The expression 'you are what you eat' is truer than you think,"
Watkins said.

Seifert suggests the bone-protective effects of omega-3 fatty acids may
be linked to their previously established role in minimizing
inflammation in the body.

"We believe omega-3s may minimize bone loss with estrogen deficiency in
association with their anti-inflammatory effects," he said.

Inflammation is caused by a number of compounds, including a class of
molecules called cytokines. These compounds also stimulate bone
breakdown, a natural part of a body process known as the bone cycle.

"Many people don't realize it, but our bones are not static
structures," Seifert said.

Bones undergo a process called "remodeling," in which they are
continuously broken down and rebuilt. Two types of cells found in bones
govern this process - bone resorption cells, which remove small
portions of bone, and bone building cells, which fill in the gaps.

Estrogen blocks some of the inflammatory compounds associated with bone
resorption, which may explain why osteoporosis typically progresses
after estrogen levels fall with the onset of menopause. Likewise,
Watkins' previous studies have shown omega-3 fatty acids may reduce the
production of these same inflammatory compounds, accounting for their
bone-protective effect.

"Omega-3s change the behavior of cytokines in a way that is consistent
with the role of omega-3s in mitigating cardiovascular disease,"
Watkins said.

Watkins and Seifert have spent the last 10 years investigating the role
of lipids on the biology of bone. "We began to question years ago how
lipids may affect bones," Watkins said. "Our studies have laid the
groundwork for other researchers today who have started to look for
lipid effects on bone health in humans."

Yong Li, with the Purdue Center for Enhancing Foods to Protect Health,
also participated in this research. The Indiana 21st Century Research
and Technology Fund provided funding.

Purdue University
1132 Engineering Administration Bldg.
West Lafayette, IN 47907
United States
http://www.purdue.edu/UNS

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