Polyunsaturated vegetable oils and cataracts

[Guest guest]

" Naomi Giuliano " <n.giuliano

Polyunsaturated Vegetable Oils Cataracts,

Research Suggests

 

http://theomnivore.com/vegetable_oil_cataracts.html

 

by Anthony Colpo

May 15, 2005

 

Last year, an Aussie doctor appeared on one of

Australia's most

widely-viewed current affairs shows stating that

refined vegetable

oils played a major role in causing macular

degeneration.

 

His comments didn't exactly win him many friends in

the powerful

vegetable oil industry, but newly published research

by Boston

researchers further supports the contention that

refined vegetable

oils can indeed be hazardous to your eyesight.

 

LA linked to cataracts in Boston

 

In their first study of women participating in a

nearly-30-year-old

diet-and-health study, the researchers link the

primary fat in many

popular vegetable oils, linoleic acid (LA), to

incipient cataracts,

called opacities, in the lenses of the women's eyes.

In this study,

this single fat accounted, on average, for roughly 5

percent of

calories consumed each day, and more than 85 percent

of

polyunsaturated-fat intake.

 

Lens opacities are " a sensitive marker for the

development of

cataracts " but don't initially cause vision loss,

notes Paul F.

Jacques, director of nutritional epidemiology for the

Agriculture

Department's Jean Mayer Human Nutrition Research

Center on Aging at

Tufts University.

 

The second study by the same researchers included

women who had

undergone surgery for removal of cataracts. Compared

with

similarly-aged women who never had such a procedure,

these women were

much less likely to have eaten omega-3 fatty acids,

the type found in

fish oils. In this study, eating vegetable oils didn't

appear to be

linked with cataracts, but eating mayonnaise and salad

dressings did.

Refined vegetable oils are a primary ingredient of

mayonnaise and

salad dressings.

 

The types and ratios of fatty acids we consume affect

the flexibility

and permeability of cell membranes throughout the

body. Cataracts are

associated with changes in lens-membrane structure and

function and

could thus be affected by dietary fats.

 

You ought to be…saturated

 

In the April American Journal of Clinical Nutrition,

the scientists

report that women whose diets were richest in

polyunsaturated fats

were significantly more likely to have incipient

nuclear cataracts,

while those whose diets were lowest in these fats were

least likely. A

higher risk of early nuclear cataracts was also

associated with diets

high in vegetable oils and trans fats.

 

Adding to the mountain of studies contradicting the

prevailing

anti-saturated fat paranoia, no increased cataract

risk was associated

with intake of saturate-rich animal fats.

 

When the researchers focused on the various types of

polyunsaturated

fats, cataract risk appeared to be most associated

with two fatty

acids: linoleic (LA) and alpha-linolenic (ALA).

 

LA is the primary fatty acid found in safflower,

sunflower, corn,

soybean, and cottonseed oils. Although ALA is found in

many plant

oils, its highest concentrations tend to be in flax,

soy, walnuts, and

canola. Dietary trans fats, meanwhile, are most

abundant in margarines

and shortenings. These are produced by subjecting

unsaturated oils to

chemicals and special manufacturing technologies that

make them solid

or semisolid at room temperature.

 

The researchers urge caution before indicting ALA for

causing

cataracts. First, two previous studies by other

researchers found

almost no alpha-linolenic in the eye's lens. Secondly,

ALA occurs in

many of the same sources as LA does, but in smaller

quantities, and

may simply serve as a marker for LA intake. Also, the

body converts

some of its ALA into docosahexaenoic acid (DHA) and

eicosapentaenoic

acid (EPA), two long-chain omega-3 fats found in fish

oils.

 

Fishy findings

 

The second study by Jacques and his team encompassed

dietary

information supplied by some 71,000 women between 1984

and 2000. To be

included for this analysis, a woman had to be free of

cataracts,

cancer. During the study, over 4,000 women in the

group had cataracts

diagnosed after age 45 and then had surgery. Roughly

60 percent of

these cases involved nuclear cataracts.

 

One finding stood out, Jacques notes: Women who

developed cataracts

were far less likely to be big fish eaters. In

contrast, women who

consumed dark-meat fish, such as salmon or tuna, at

least once a week

had a 15 percent lower risk of cataracts than did

women eating fish

less frequently. Dark-meat fish are the ones that tend

to be

especially rich in DHA and EPA.

 

References

 

Lu M, et al. Prospective study of dietary fat and risk

of cataract

extraction among U.S. women. American Journal of

Epidemiology, May 15,

2005; 161: 948-959.

http://aje.oupjournals.org/cgi/content/abstract/161/10/948

 

Lu M, et al. Dietary fat intake and early age-related

lens opacities.

American Journal of Clinical Nutrition, Apr 2005; 81:

773-779.

http://www.ajcn.org/cgi/content/abstract/81/4/773

 

---

 

About the Author

Anthony Colpo is an independent researcher and

certified fitness

consultant with 20 years' experience in the physical

conditioning

arena. To contact: contact

 

Correspondence Policy

Reader feedback is always welcome, but please read

TheOmnivore.com

Correspondence Policy before writing.

 

 

 

 

 

 

 

_____