Question: Is there any hard facts about the use uf gamma linoleic aci ( Starflower
or Evening Primrose oils) in the prevention or treatment of Osteoporosis?
Answer:The prostaglandins generated by the omega-6 and omega-3
longer-chain fatty acids like DGLA and EPA affect calcium absorption through
their generation of various prosaglandins, but it's not yet known whether
increased absoprtion will lead to enhanced bone mineral density (it does seem
a good possibility though).
The balance between omega-6's and 3's seems especially important. Here's a
brief summary of a paper titled "THE EFFECT OF OF DIFFEENT N-6/N-3
ESSENTIAL FATTY ACID RATIOS ON CALCIUM BALANCE AND BONE IN RATS"
(SOURCE: Prostaglandins Leukot. Essent. Fatty Acids, Vol. 53, #1, July 1995:
Linoleic acid (LA, an omega-6) and Alpha-linolenic acid (ALA, an omega-3 EFA)
were given in a ratio of 3:1 to rats in a control group. The conversion of LA
and ALA to their prostaglandin precursor EFA's (longer chain ones like DGLA
and EPA) occurs by enzyme action and is slow and limited by the amount of the
delta 6 desaturase enzyme. Therefore gamma linolenic acid (GLA which
converts to DGLA and arachidonic acid) and EPA ( essential fatty acids beyond
this delta-6 rate-limiting step) were given to different groups of rats in
ratios of 3:1, 1:1, and 1:3 to test the different impacts on calcium
absorption. Intestinal calcium absorption was increased by 41.5% in the 3:1
ratio group compared to the controls. The decrease in urinary calcium
excretion correlated with the increased retention. The calcium balance and
and bone calcium increased significantly 41.5% and 24.7% in the 3:1 group
compared to the control. The researchers hypothesize that the positive
effects might be due to an EFA-induced increase the circulating prostaglandins,
One caveat is that rats don't necessarily metabolize fatty acids the same way
humans do. For example, erucic acid (found in older varieties of canola
plants) was thought to be toxic to humans since rats developed heart problems
in feeding trials. But the same thing happens when rats are fed sunflower oil
(no erucic acid).
The omega-6/omega-3 ratio in the typical US diet is close to 20:1 mainly due
to hydrogenation of soybean oil (the process destroys a good portion of the
omega-3 ALA), the popularity of high omega-6 oils ( corn, sunflower, and
safflower), and the relatively low consumption of fatty fish (rich in omega-3
EPA and DHA). Most experts agree that a healthy omega ratio is somewhere
around 3:1 to 7:1 as far as reduced risk of heart disease, stroke, and even
depression . PREVENTION MAGAZINE has a good article on omega fats in the
January, 1997 issue.
