Prof. Alberto Hernández Cañero, M. D. , Ph.D.1
ABSTRACT: Many studies have shown the relationship between an elevated intake of dietary saturated fats, high levels of total serum cholesterol and high mortality rates from atherosclerotic diseases. The mortality curve from ischemic heart disease was rising in Cuba until 1990, when it began to drop, finally reaching 25% of the peak value. The period of higher mortality was linked to high consumption of dietary saturated fats among the Cuban population, indicated by elevated total serum cholesterol levels. The drop began with the so-called "Special Period" in Cuba, corresponding to the country's economic crisis, and was characterized by a decreased intake of dietary saturated fats, a less sedentary lifestyle and a lower incidence of obesity in the Cuban population. Yet, the reduction in mortality rates from ischemic heart disease has been less than one would have expected from the decrease in total serum cholesterol levels. This may be the result of other as yet unidentified risk factors associated with atherosclerosis in the Cuban population.
Background
Many observational, randomized studies--some of which were conducted 60 years ago--have shown the relationship between diet and mean levels of total serum cholesterol.1-8
Populations that consume high levels of dietary saturated fats and cholesterol have higher levels of serum lipids and cholesterol that those with low intakes of these elements.9,10
Epidemiological studies have shown that people with elevated levels of serum cholesterol have a higher risk of developing atherosclerosis than those with normal levels of serum cholesterol.3-5, 11
Moreover, a reduction in the levels of total serum cholesterol in a given population, due either to changes in lifestyle or to medical treatment, has been shown to decrease mortality rates from atherosclerosis-related disease.
12,13 Framingham14 demonstrated a linear correlation between decreased levels of serum cholesterol and mortality due to ischemic heart disease. In his study, a
reduction of 5 mg/dL in these levels over 6 years corresponded to a decrease of 4.3% in the mortality rate from this disease.
Mortality Rate from Ischemic Heart Disease in Cuba
Mortality rates from ischemic heart disease in Cuba from
1986 to 1997 (Fig. 1), show two markedly different tendencies: from 1986 to 1990,
In their work published in 1987, Ríos and Tejeiro reported five-year increases in calorie and protein consumption among the Cuban population since 1965.15
we find a slight increase, but thereafter,
a decrease amounting to 25% of the 1990
mortality rate, which constituted the highest peak value. The Cuban population's diet
underwent important changes during these
two periods.
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So strong was the impact of these events on the Cuban economy and on the health of the population that an outbreak of epidemic neuropathy affected nearly 50,000 people on the island between 1991 and 1993.
Nutritional studies carried out between 1991 and 1995 showed that a significant portion of the Cuban population had diets low in fats and nutrients. Among these is the 1993 study carried out by Gay et al. on the Isle of Youth 16 of epidemic neuropathy patients compared to a control group, reporting the following findings:
The intake of protein Kcals was significantly lower in epidemic neuropathy patients
than in the control group.
Fats accounted for 14.8% of calories in the 50th percentile of control subjects and
patients alike.
Carbohydrates accounted for 72% of the caloric intake in the 50th percentile of all
subjects in the study.
A similar study was conducted by Cabrera et al.,17 in 1995, with a group of railway workers in Havana, in which the following findings were reported:
The total intake of dietary fats was 23.16g in men and 18.11g in women (with a
polyunsaturated/saturate fatty acids intake index of approximately 1).
Cholesterol intake lower than 300 mg/dL.
Caloric intake similar to that found by Gay et al.16
Comparing the levels of total serum cholesterol in the Cuban population before and after 1990, we refer to a 1988 survey carried out in Havana's 10 de Octubre Municipality (Dueñas A, et al., Unpublished Observations. Debs G. Tesis de Especialidad en Cardiología) showing that 29% of men and 37.7% of women had levels of total serum cholesterol higher than 5.2 mmol/L, with the mean at 5.29 mmol/L (204.6 mg/dL). However, a 1994 survey showed a mean level for total serum cholesterol at only 4.23 mmol/L (163.6 mg/dL). That is, we observe a decrease of 1.06 mmol/L (41 mg/dL) between the two periods studied.
Cabrera, et al.17 also conducted a study between 1987 and 1988 on levels of serum lipids in railway workers, which revealed that 15.5% of men and 15.2% of women had levels of total serum cholesterol higher than 6.2 mmol/L (240 mg/dL). In 1995, the mean level of total serum cholesterol in the same population was 3.5 mmol/L in men and 3.34 mmol/L in women.
These findings indicate that the period of increasing mortality from ischemic heart disease corresponded to a diet high in calories and with a mean total cholesterol at high risk levels; while the period of decreasing mortality was characterized by a diet low in fats, with a mean total cholesterol below risk levels.
Nevertheless, according to the Framingham studies,13,14,18 such a low consumption of dietary fats (which decreased by 41 mg/dL) should have resulted not in a 36% reduction in mortality, and not the mere 25% as occurred in Cuba. So far, we have no explanation for this fact. In Cuba, as in other countries, a level of total serum cholesterol higher than 200 mg/dL is considered a risk factor for acute myocardial infarction. However, the FRICAS multinational study showed that in Cuba, 68.5% of cases with acute myocardial infarction had levels of total serum cholesterol lower than 200 mg/dL upon hospital admittance. The Cuban rates may have been influenced by the development of other risk factors.
In 1995, in the 10 de Octubre Municipality (Dueñas A, et al., Unpublished Observations) the incidence of smoking, arterial hypertension, and diabetes mellitus remained almost unaltered from 1986 to 1997, although in recent years, the incidence of obesity and sedentary lifestyles have markedly decreased.
The prevalence of other risk factors involved in the etiology and pathogenesis of ischemic heart disease, such as a deficit of antioxidants and hyper-homocysteinemia, has not yet been studied in Cuba.18
Conclusions
Despite the economic hardships that the Special Period has meant for the Cuban
population, it has contributed to detain the epidemic of ischemic heart disease in Cuba, which had already begun in 1990.
A low consumption of saturated fats is the main cause of the reduction in mortality from ischemic heart disease beginning in 1990.
Other risk factors associated with ischemic heart disease have not been effectively
brought under control in Cuba, with the exception of obesity and sedentary lifestyles.
The implementation of the Cuban National Program for the Control of Ischemic
Heart Disease, which includes nutritional surveillance, should contribute to maintaining reduced mortality rates from ischemic heart disease in Cuba.
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This article first appeared in Spanish in the Revista Cubana de Cardiología y Cirugía Cardiovascular 1999;13(1):8-12.
