Is Mad Cow or Coronary Heart Disease the Bigger Risk From Beef?

To the Editor:

Speculations regarding Creutzfeldt-Jakob disease (CJD) acquired from beef containing the infectious agent that causes bovine spongiform encephalopathy [1] have resulted in dramatic health policy measures and serious concerns in the lay public about dietary beef intake in Britain. We believe these concerns are out of proportion to the actual risk of CJD, especially when compared to other established risks of beef consumption, such as the development of coronary heart disease (CHD). We therefore sought to estimate a beef-eater’s risk of CJD and CHD based on currently available data.

The ten cases of CJD became manifest over a 20 month span in 1994-1995 [1]. If we suppose a uniform incubation period of 10 years for CJD, then all 10 cases were infected during a 20 month period in 1984-1985, when the mean beef intake among the 56 million Britons was 181.5 g/person/week [2] (roughly equivalent to two hamburgers per week). Assuming the attack rate remains constant, an average Briton would have a 1 in 933,000 chance of developing CJD from 10 years of beef-eating. The risk per hamburger is roughly 1 in one billion.

To determine the beef-attributable risk of CHD, we first calculate the change in serum cholesterol that results when the fat and cholesterol in lean beef [3] are consumed in place of isocaloric carbohydrate or protein. Using the average daily caloric intake in Britons (2040 kcal) [2], the Hegsted equation [4] predicts a 2.1 mg/dl increase in serum cholesterol when 181.5 g beef/week are consumed. For a 30 year-old non-smoking, non-diabetic man with a total cholesterol of 150 mg/dl, an HDL cholesterol of 45 mg/dl, and a systolic blood pressure of 120 mmHg, the Framingham equation [5] predicts that a 2.1 mg/dl increase in serum cholesterol sustained over 10 years raises the risk of CHD during this period by 1 chance in 5300. Thus the CHD/CJD relative risk is approximately 175!

Although our calculations are approximations at best, they clearly show that the risk from fat and cholesterol in beef is, for most of the adult population, orders of magnitude greater than the risk from neurotropic particles contained therein. Other diseases linked to fat intake, such as stroke and colon cancer, have not been considered here. Based on these data we believe that beef-eaters should care for their coronaries, rather thsn perseverate on prions.