Trans Fats

Trans Fats

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 
association (9).

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 
infants (7). 

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 
hydrogenated oils. 

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 
7.4 percent. 

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. 

Checked 8/3/12