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Edible Fats and Vegetable oils: do the trans Isomers Represent a Health Risk?.

The hydrogenation of fats was one of the early industrial applications of cata- lysis. In a 1913 (1913 or 1923?) edition of his three volume works entitled "Chemical Technology and Analysis of Oils, Fats and Waxes", Lewkowitsch [1] wrote that, "The production of solid fats from liquid oils by the direct addition of hydrogen to the gly- cerides of unsaturated fatty acids has grown enormously of late years". As the substitution of vegetable oils for animal fats for dietary uses has increased, catalytic hydrogenation has assumed today an even more important role.

In the US, the popular press has devoted attention to the impact of the trans

isomer of fats on the elevation of choleste- rol levels. A product linked to cholesterol levels is immediately cast in a bad light - -

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a guilt by association. The improving ability to provide a rapid and, at the same time, more complete analysis of food products has increased the number of topics that may be investigated, and the results of these studies become related to health issues. The initial concern in the area of facts was limited to two classes: saturated and unsaturated fats. Today there is con- cern about the impact of a number of ad- ditional factors that include the carbon number, the position of the unsaturation and the cis-trans configuration.

The data shown in Fig. 1 were recently published and were based on Emeken's acceptance address for the 1994 Alton E. Bailey Award [2]. The data shown in Fig. 1 are a compilation of 6 data sets that are from the older literature and 6 from more recent controlled diet studies [3-14]. The line shown in Fig. 1 is convincing and leads one to the conclusion that there is a direct relationship between the serum total cho-

l l i l l l l l l i l l l l

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o!= o!, o!6 o~.s l:0 1'.2 t'.4 1'.6 1'.8 2'.o 2t2 :! , 2!6 2!s trans/tS:2n6 Ratio

Fig. 1

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lesterol and the trans acid isomer content of the diet. On the other hand, Dutton [15], in his Lewkowitsch Memorial Lecture just 12 years earlier, wrote that "Despite incom- plete experiments on the biological effects of double bond position and configuration, certain generalizations seem to be emerg- ing. Rapid incorporation and removal of all isomers are observed in the blood lipids with no evidence of permanent accumula- tion."

Catalyst manufacturers whose busi- ness includes hydrogenation catalysts must be concerned with health issues if they wish to continue in business [16]. Data such as shown in Fig. 1 is en- countered frequently, in catalysis and in numerous other areas. An outstanding example of this is the Linear Free Energy Relationship (LFER) that is widely used in catalysis and in physical organic chem- istry. As impressive as the LFER plots ap- pear, one should always note that in nearly

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every plot the majority of the data points fall near the middle of the plot, and only a limited fraction of the data points determine the slope of the line.

The medical and biological consider- ations of the experimental approach are beyond the scope of either the writer or Appfied Catalysis. However, the validity of the conclusions are of interest. On closer examination, the data in Fig. 1 exhibit the problem encountered frequently in LFER correlations. If just two data points are omitted from consideration, the situation may be viewed in a different light. Omitting the data of the studies of De Jongh et al. [7] and of Anderson et al. [12], one obtains the plot shown in Fig. 2. The line in Fig. 2 fits the ten data points better than the line shown in Fig. 1 for the 12 data points, although neither fit is an example of preci- sion.

One could use Fig. 2 and conclude that there is no, or essentially no, impact of the

I I I

5 • •

0 I I I I I I I t I I I I I I 0.0 0.2 0.4 0.6 0.8 1.0 t . 2 1.4 i .6 t .8 2.0 2.2 2.4 2.6 2.8 3.0

t rans / tS:2n6 Ratio

Fig. 2

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..+

25

20"

15.

10-

I 1 1 1 1 1 1 1 1 1 1 1 1 1

Ell A

/

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0'.5 o'., o!6 o!81!o 1 .21!, 1!61!8 2!o 5!= =!, =!6 5!8 trans/18:2n6 Ratio

Fig. 3

trans acid isomer on the cholesterol, at least up to a ratio of the isomers of about 2.4. If one is to make a conclusion based on the data in Fig. 1, it appears that one straight line representing all of the data is not the best way to do it. It therefore ap- pears to the writer that a better repre- sentation of the 12 sets of data would be either the solid or broken lines (both hand drawn) in Fig. 3. If Fig. 3 provides a valid representation, only when a manufacturer has a catalyst formulation that is especially prone to form the trans isomer should there be reason to worry.

The data in Fig. 1 is not atypical of many data sets used to reach conclusions re- lated to health or other political issues. It would appear that scientists should be more aware of the potential impact of their conclusions, and to examine their data from the view of their conclusion and from the opposite viewpoint.

References

[1] J. Lewkowitsch, Chemical technology and analysis of oils, fats and waxes, MacMillan Press, London, Volume 3, 1923, p. 119.

[2] E.A. Emken, INFORM, 5 (1994) 906. [3] A. Bonanome and SM. Grundy, N.

Engl. J. Med., 318 (1988) 1244. [4] R.P. Mensink and MB. Katan, N. Engl.

J. Med., 323 (1990) 439. [5] J.T. Judd, B.A. Clevidence, R.A. Mues-

ing, J. Wittes, M.E. Sunkin and J.J. Podczasy, Am. J. Clin. Nutr., 59 (1994) 861.

[6] R. Wood, K. Kubena B. O'Brien, S. Tseng and G. Martin, J. Lipid Res., 34 (1993) 1.

[7] H. de Jongh, R.K. Beerthus, C. den Hartog, L.M. Dalderup and RA. van der Spek, Bibl. Nutritio Dieta, 7 (1965) 137.

[8] D.C. Laine, C.M. Snodgrass, E.A. Daw- son, M.E. Ener, K. Kuba and I.D. Frantz, Am. J. Clin. Nutr., 35 (1982) 683.

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[9] B.A. Erickson, R.H. Coots, F.H. Mattson and A.M. Kligman, J. Clin. Invest., 43 (1964) 2017.

[10] D.E. McOsker, F.H. Mattson, H.B. Sweringen and A.M. Kligman, J. Am. Meal. Assoc., 180 (1962) 380.

[11] A.H. Lichenstein, L.M. Ausman, W. Carrasco, J.L. Jenner, J.M. Ordovas and E.J. Schaefer, Arteriosclerosis and Thrombosis, 13 (1993) 154.

[12] J.T. Anderson, F. Grande and A. Keys, J. Nutr., 75 (1961) 388.

[13] P.J. Nestel, M. Noakes, G.B. Belling, R. McArthur, P.M. Clifton and M. Abbey, Am. J. Clin. Nutr., 55 (1992) 46.

[14] P.L. Zock and M.B. Katan, J. Lipid Res., 33 (1992) 399.

[15] H.J. Dutton, Chem. Ind., January 2, 1982, pp. 10-17.

[16] J.M. Hasman and P.D. McLaughlin, Trans Isomer Minimization During the Conventional Hydrogenation of Vege- table Oils, United Catalysts, Inc., Louis- ville, Ky, 1994.

B.H. DAVIS

State Research Center of C1 Chemi- cal Engineering Technology of China

This Center was established under the administration of the State Science and Technology Committee of China and under the direct supervision of the Science and Technology Department of the Minis- try of Chemical Industry. It is affiliated to the South-West Research Institute of Chemi- cal Industry. The Center was established for the purpose of promoting the commer- cialization of research achievements in C1 chemistry, improving their maturity, inte-

grity and engineering level. The Center car- ries out research and development on State-sponsored key projects. It under- takes reaction engineering research in the field of C1 chemistry on commission from either domestic or foreign organizations. It is able to accomplish engineering scaling- up for the commercialization of existing research activities in laboratories. It is also able to carry out the techno-economic as- sessment and engineering design of com- mercial plants. The Center is open to do- mestic and foreign institutions and offers a commercial service.

The Center comprises a C1 chemistry laboratory, a development and design di- vision, a consultancy division, as well as a management department. The engineer- ing and technological research emphasis is put on methanol synthesis, methanol and formaldehyde chemistry, and the comprehensive utilization of natural gas. The South-West Research Institute of Chemical Industry has been carrying out C1 chemistry research since the 1970's and has been entrusted with many State- or Ministry-sponsored key projects. The achievements obtained have been: meth- anol synthesis technology, the C302 cata- lyst for low-pressure methanol synthesis, technology for the dehydrogenation of methanol to methyl formate, new techno- logies for the synthesis of DMF, NMF, and NFA, steam reforming of methanol into hydrogen and carbon dioxide, residential fuels, methanol to methyl trichloride, me- thane to methyl chloride, PSA for carbon monoxide concentration, etc. The techno- logies under development are methanol to DME (as aerosol propellant) and the low- pressure carbonylation of methanol to acetic acid. [Source: Chin. J. Nat. Gas

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