Listening to the radio this morning I learned about plans in New York to ban heart-stopping ‘trans fats’ from foods served in restaurants and fast food outlets. Apparently, a voluntary scheme for the removal of these fats from food has not worked out so well, and now the city’s health commissioner, Thomas Frieden, is reigniting the initiative with a series of public hearings which may lead to trans fats disappearing of NYC menus in all but minute amounts.
Although a liberal at heart and a believer in the principle of personal responsibility, I nevertheless applaud the seemingly draconian measures that are planned in New York. It is simply not realistic to expect the manufacturers and vendors of fast and processed food to regulate themselves. That, to me, is a bit like asking drug dealers to regulate themselves. I believe the public needs some protection from dietary elements that appear to have damaging effects on health.
It’s curious to me that, generally, our Governments take a relatively relaxed attitude to unhealthy food. While there seems to be a lot of political capital in appearing to help individuals avoid things that can kill them quickly (such as gun crime and terrorism), there seems to be much less urgency about factors that are likely to kill people more slowly (like trans fats).
The generally laissez-faire attitude regulatory agencies have to potential poisons in the diet is, no doubt, connected to the short-termism that pervades politics, but it is also a testament to the power food companies wield at the highest level. Despite their well-recognised health hazards, there is still no law here in the UK that compels food companies to declare the trans fat content of the foods they produce. I don’t know about you, but that strikes me as a very puzzling situation indeed. Many of us simply don’t know whether we’re eating trans fats or not. With this in mind, I’ve added here an account of trans fats: what they are, where they come from, what likely effects they have on health and, importantly, how to avoid consuming them.
What are trans fats, and where do they come from?
Most trans fats in the diet start out life as vegetable oils including sunflower, soya, or safflower oil. In food processing, these oils can be heated to high temperature and then reacted with hydrogen to produce what are known as ‘partially hydrogenated fats’. The hydrogenation of fats allows vegetable oils to be solidified, which is obviously critical in the manufacturing of solid fats such as margarine. The other ‘benefit’ of hydrogenation is that it makes fats less liable to turn rancid (go off), which extends their shelf life.
The production of partially hydrogenated fats can result in the formation of related fats known as ‘trans fatty acids’ or ‘trans fats’. The word ‘trans’ refers to the chemical shape of these molecules. In general terms, these fats are a different shape to their counterparts found naturally in nature (which have a different – ‘cis’ ” shape).
Some trans fats in the diet are found naturally in food such as butter, but industrially-produced trans fats are the major source of these fats in the diet, and can be found in a a wide range of processed foods including chips, fast food (such as burgers and chicken nuggets), margarine, biscuits, cakes, pastries, pizza and crackers.
What effects do trans fats have on health?
In general terms, we need to be wary of any food or foodstuff that is a relatively recent addition to the diet. The chances are we will not be well adapted to such foods, and they therefore will tend to have considerable potential for adverse effects on our health. The evidence suggests this certainly seems to be true for industrially-produced trans fats.
Trans fats and the heart
Trans fats have been linked with adverse effects on heart health. For instance, in one study, individuals who had suffered a heart attack were found to have significantly higher levels of trans fats in their bodies compared to health individuals [1]. Those with the highest concentrations of trans fats were found to be, on average, more than 2 ½ times more likely to suffer from a heart attack than those with the lowest levels.
A number of other studies also support the concept that trans fats are bad for the heart. Of four studies that have examined this potential association over time, three found that consuming just 2 per cent of our calories from trans fats is associated with an increased risk of heart disease of 28-93 per cent [2,3,4].
Trans fats and cancer
Trans fats have been associated in several studies with an increase risk of cancer. For instance, one piece was research found that higher levels of trans fats in the body were associated with an increase risk of cancers of the breast and colon [5].
Trans fats and diabetes
Trans fats seem to have the ability to disrupt the effects of the hormone insulin [6,7]. Other research has found an association between increased trans fat intake and enhanced risk of diabetes [8].
Trans fat and pregnancy
Trans fats also seem to have an association with adverse effects on pregnancy. One study, for instance, found that trans fats were associated with an increased risk of a condition called pre-eclampsia which is can result in fitting in the mother [9]. Another study has found that higher levels of trans fats are associated with shorter length of gestation and lower birth weight [10].
All-in-all, the evidence suggests, as we would expect from primal theory, that trans fats are thoroughly unhealthy. In the UK, we consume an average of about 2.5-3.0 grams of trans fats per person each day [11]. This may not sound like much, except that studies show even very small amounts of these fats are associated with an increased risk of disease. In 2002, the Food and Nutrition Board of the Institute of Medicine in the USA published a report on the role of trans fats on health and made recommendations regarding safe levels of intake [12]. In the summary of this report, its authors suggest that the: tolerable upper intake level of zero. In normal language, this translates as: the safest amount of trans fats to consume is none at all.
Trans fats found naturally in the diet
Some natural foods, for example butter, contain trans fatty acids. The food industry sometimes refers to this fact, I suspect in an attempt to suggest that the industrially-produced trans fats that they feed us are somehow ‘natural’ too. However, industrially-produced TFAs and those found naturally in food have different chemical structures: industrially-produced trans fats are predominantly monounsaturated trans fats of which elaidic acid is a major component, while those found naturally in food are mainly trans vaccenic acid and conjugated linoleic acids. Most importantly, studies suggest that it is the consumption of industrially produced partially-hydrogenated vegetable fat rather than trans fat found naturally in food that is associated with adverse health effects such as increased risk of heart disease [13, 14].
Is it on the label?
Currently, in the UK, there is no obligation for food manufacturers to declare the amount of trans fats their foods contain. However, they are required to list the partially hydrogenated fats from which they are derived during processing. Therefore, if you want to avoid trans fats, avoid eating any foods which have ‘partially hydrogenated fat’, ‘partially hydrogenated oil’, or ‘partially hydrogenated vegetable oil’ listed in the ingredients. Take-away and fat food, which are notorious harbourers of trans fats, generally need to be avoided too.
References:
1. Pedersen JI, et al. Adipose tissue fatty acids and risk of myocardial infarction – A case-
control study. Eur J Clin Nutr 2000:54:618-625
2. Ascherio A, et al. Dietary fat and risk of coronary heart disease in men: Cohort follow up study in the United States. BMJ 1996:313:84-90
3. Hu FB, et al. Dietary fat intake and the risk of coronary heart disease in women. N EngI J Med 1997:337:1491-1499
4. Oomen CM, et al. Association between trans fatty acid intake and 10-year risk of coronary heart disease in the Zutphen Elderly Study: A prospective population-based study. Lancet 2001357:746-751
5. Bakker N, et al. The Euramic Study Group: Adipose fatty acids and cancers of the breast, prostate and colon: An ecological study. Cancer 1997:72:587-597
6. Christiansen E, et al. Intake of a diet high in trans monounsaturated fatty acids or saturated fatty acids. Effects on postprandial insulinemia and glycemia in obese patients with NIDDM. Diabetes Care l997;20:88l-887
7. Alstrup KK, et al. Differential effects of cis and trans fatty acids on insulin release from isolated mouse islets. Metabolism I 999:48:22-29
8. Salméron J, et al. Dietary fat intake and risk of type 2 diabetes in women. Am J Clin Nutr 2001;73:1019-1026
9. Williams MA, et al. Risk of preeclampsia in relation to elaidic acid (trans fatty acid) in maternal erythrocytes. Gynecol Obstet Invest 1998 46:84-87
10. Elias SL, et al. Infant plasma trans. n-6, and n”3 fatty acids and conjugated linoleic acids are related to maternal plasma fatty acids, length of gestation, and birth weight and length. Am J Clin Nutr 2001 73:807-814
11. Hulshof KF Intake of fatty acids in western Europe with emphasis on trans fatty acids: the TRANSFAIR Study. Eur J Clin Nutr. 1999 53(2):143-57
12. Letter Report on Dietary Reference Intakes for Trans Fatty Acids Food and Nutrition Board, Institute of Medicine 10th July 2002
13. Pietinen P, et al, Intake of fatty acids and risk of coronary heart disease in a cohort of Finnish men. The alpha-tocopherol, beta-carotene cancer prevention trial. Am J Epidemiol. 1997;145:876-887
14. Willett WC, et al. Intake of fatty acids and risk of coronary heart diseases among women. Lancet 1993;341:581-585
