Gabe Mirkin, M.D.
Polyunsaturated fats in vegetable oils are healthful if they are
left in the vegetables. Removing fats from vegetables makes them
less stable so they turn rancid. To preserve their freshness, they
are either processed with heat, which destroys the very unstable
essential omega-3 fatty acids; or, even worse, they are converted
into harmful partially hydrogenated fats. Hydrogen atoms are added
to replace the unsaturated double bonds between carbons, to create a
very stable, more solid fat that is similar to saturated fat but has
a different chemical structure. Partially hydrogenated fats have
been linked to increased risk for cancer and heart attacks.
Partially hydrogenated fats that you eat are deposited in your body
fat. Lenore Kohlmeier of the University of North Carolina biopsied
the fat in women's buttocks. She then followed these women for
several years and showed that the amount of partially hydrogenated
fats in a woman's buttocks predicts her susceptibility to developing
breast cancer in the future (2). Other studies confirm this
Partially hydrogenated fats increase risk for heart attacks (8) by
lowering blood levels of the good HDL cholesterol, raising levels of
the bad LDL cholesterol and very bad Lp(a) and blocking arachidonic
acid to cause clotting (3). Partially hydrogenated fats lower blood
levels of omega-3 fatty acids to create a relative deficiency of the
heart attack preventing fat to increase risk for a heart attack (4).
They also raise blood levels of the bad LDL cholesterol that causes
heart attacks (5).
Babies eat too much partially hydrogenated fats, too. A letter in
the New England Journal of Medicine raised concern that infants eat
too much of the partially hydrogenated fats that increase risk of
heart attacks and cancers (6). Bruce Holub of the University of
Guelph reported that partially hydrogenated fats account for 23
percent of the fat in baby cereals and 37 percent of the fat in baby
cookies. The foods a woman eats determines what types of fats are
found in her breast milk. Partially hydrogenated fats comprise 7.2
percent of the fat in Canadian women's breast milk and the
combination of the large amount of partially hydrogenated fats in
baby food and breast milk cause the average baby to get more than
four percent of his fat from hydrogenated fats. Studies show that
partially hydrogenated fats may slow growth and development in
We have known for more than twenty years that trans fats increase
your risk for heart attacks and possibly some types of cancers such
as breast cancer. Wlter Willett, chairman of the Department of
Nutrition as Harvard School of Public Health, reported that trans
fats also increase your risk for getting diabetes (13).
Partially hydrogenated fats are still found in many prepared foods,
such a french fries, doughnuts, frozen meals, cookies or crackers.
Since labeling laws now require trans fat content to be listed in
the Nutrition Facts panel, many manufacturers have eliminated them
from their products. However, the laws allow a manufacturer to claim
ZERO if there is less than one-half gram (.5g) of partially
hydrogenated oil per serving. That doesn't sound like much, but if a
serving size is one teaspoon or one cracker, it can add up to a lot
of trans fats in a tub of margarine, a bowl of cereal or a bag of
The only way to know whether a food contains any trans fats is to
read the list of ingredients. If you see the words "partially
hydrogenated" in front of any vegetable oil, the food contains trans
fats. Look for another brand that does not include partially
1) DB Allison, SK Egan, LM Barraj, C Caughman, M Infante,
T Heimbach. Estimated intakes of trans fatty and other fatty acids
in the US population. Journal of the American Dietetic
Association 99: 2 (FEB 1999):166-174. Mean percentage of energy
ingested as trans fatty acids was 2.6 percent and the mean
percentage of total fat ingested as traits fatty acids was
2) Kohlmeier, L et al. Cancer Epidemiology October, 1997.
3) B Koletzko, T Decsi. Metabolic aspects of trans fatty acids.
Clinical Nutrition 16: 5 (OCT 1997):229-237. trans fatty acids
increase plasma LDL-cholesterol and lipoprotein (a) and reduce
HDL-cholesterol concentrations, lower arachidonic acid.
4) E Larque, F PerezLlamas, V Puerta, MD Giron, MD Suarez, S Zamora,
A Gil. Dietary trans fatty acids affect docosahexaenoic acid
concentrations in plasma and liver but not brain of pregnant and
fetal rats. Pediatric Research, 2000, Vol 47, Iss 2, pp 278-283.
5) M Noakes, PM Clifton. Changes in plasma lipids and other
cardiovascular risk factors during 3 energy-restricted diets
differing in total fat and fatty acid composition. American Journal
of Clinical Nutrition, 2000, Vol 71, Iss 3, pp 706-712.
6) Holub BJ. Letter, NEJM, October 28, 1999 341(18);1396.
7) Koletzko B. Potential adverse effects of trans fatty acids in
infants and children. Eur J Med Res 1995;1:123-5.
8) A Aro. Epidemiology of trans fatty acids and coronary heart
disease in Europe. Nutrition Metabolism and Cardiovascular
Diseases 8: 6 (DEC 1998):402-407.
9) BA Stoll. Breast cancer and the Western diet: Role of fatty acids
and antioxidant vitamins. European Journal of Cancer 34: 12
(NOV 1998): 1852-1856.
10) Trans-Fatty Acids and Colon Cancer. Martha L. Slattery, Joan
Benson, Khe-Ni Ma, Donna Schaffer, and John D. Potter. Nutrition
and Cancer 39(2):170-175, 2001.
11) Bakery foods are the major dietary source of trans-fatty acids
among pregnant women with diets providing 30 percent energy from
fat. Journal of the American Dietetic Association, 2002, Vol 102,
Iss 1, pp 46-51. SL Elias, SM Innis. Innis SM, British Columbia Res
Inst Childrens & Womens Hlth, 950 W 28th Ave, Vancouver, BC V5Z 4H4,
12) Partially hydrogenated fats made from fish oils. Lancet, 3/10/01.
13) Science News, November 10, 2001, pp. 300-301
14) Cell membrane trans-fatty acids and the risk of primary cardiac
arrest. Circulation, 2002, Vol 105, Iss 6, pp 697-701. RN Lemaitre,
IB King, TE Raghunathan, RM Pearce, S Weinmann, RH Knopp, MK Copass,
LA Cobb, DS Siscovick.