Wednesday, December 12, 2012

The Mediterranean Diet Secret: Olive Oil or Low Fat Plant-Based 200 Days A Year?

In the early 1950s, the population of Greece had a very low incidence of cardiovascular disease, particularly on the island of Crete, compared to the incidence in the U.S..  In 1948 the Rockefeller Foundation did a majory epidemiological study on the island of Crete, part of which included investigation of the food habits on Crete. 1

The following table shows the results of that investigation by a seven day food record. 

 The table shows the following:

    •    Cereals, pulses, potatoes, nuts, vegetables, and fruits supplied 61 percent of the total energy in the diet of Crete, compared to only 37 percent of energy in the U.S. food supply.
    •    Items of animal origin provided only 7 percent of the total energy in the Cretan diet, compared to 29 percent of the energy in the U.S. food supply.
    •    Table oils and fats, primarily olive oil, supplied 29 percent of the energy in the Cretan diet.

Cereals provided thirty-nine percent of the 2500 kcal of energy supplied by the Cretan diet, or 975 kcal.  Since cereals supply about 70 percent of energy as carbohydrate, cereals alone supplied 170 g of carbohydrate in the Cretan diet.

Since 28 g (1 ounce) of bread supplies about 60 kcal, the typical diet of someone living in Crete about 1950 may have included up to 16 ounces of wheat bread daily. 

Regardless of relative proportion of bread and pasta in the Cretan diet, a very low rate of heart disease occurred in Crete in conjunction with a high intake of wheat.

Meat, fish, eggs, and dairy products provided only seven percent of energy of the Cretan diet, about 178 kcal per day.

Dairy products such as feta cheese and yogurt supplied only three percent of energy, or about 75 kcal per day.  Since one cup of Greek yogurt (10% milkfat) supplies 290 kcal, and one ounce of feta cheese supplies only 75 kcal (6 g fat, 4 g saturated, 25 mg cholesterol), apparently in 1950 the people of Crete consumed no more than one ounce of cheese or about one-quarter of a cup of yogurt (6 g fat, 4 g saturated fat, 19 mg cholesterol) daily, far less than the three servings daily currently recommended by the USDA food guide. 

Meat, fish, and eggs supplied about four percent of calories or 103 kcal per day.  One egg supplies about 80 kcal, and one ounce of roasted goat flesh or grilled sardine (items consumed historically in Crete) supplies about 40 kcal, so the Cretan diet of 1950 contained an average of no more than 2.5 ounces of meat or fish daily for individuals expending 2500 kcal per day, or about one ounce of animal flesh per thousand kcal consumed (i.e. someone consuming only 2000 kcal would consume only two ounces daily).

Two and one-half ounces of roasted goat meat supplies only 19 g protein, 2 g of total fat, 0.5 g saturated fat, and 52 mg cholesterol, and 2.5 ounces of grilled sardines supplies about 12 g protein, 7 g of total fat, about 2 g saturated fat (yes, 29 percent of the fat in sardines consists of saturated fatty acids, a higher proportion than in the goat flesh). and 100 mg cholesterol (yes, the sardines supply more cholesterol than the goat meat).

Thus, from meat, fish, and dairy products, the Cretan diet circa 1950 would have on average supplied  8 to 13 g total fat, 5 to 6 g saturated fat, and 70 to 125 mg cholesterol per day.   In comparison, NHANES found that the average U.S. male consumes 307 mg cholesterol daily, and the average U.S. female 225 mg, two to four times the amount consumed by individuals in Crete 62 years ago. 2

Evidently, in 1950, people in Crete ate a starch-based diet with quite limited amounts of animal flesh, eggs, and milk.

Seven Countries Study Links Olive Oil To Health

In 1986, Keys et al reported the results of a 15-year follow-up on 15 cohorts in the prospective ecological Seven Countries Study  (which by the way involved original data collection from the 15 cohorts, not sorting through and arbitrarily selecting previously collected data, as so often incorrectly claimed):
"Death rates were related positively to average percentage of dietary energy from saturated fatty acids, negatively to dietary energy percentage from monounsaturated fatty acids, and were unrelated to dietary energy percentage from polyunsaturated fatty acids, proteins, carbohydrates, and alcohol. All death rates were negatively related to the ratio of monounsaturated to saturated fatty acids. Inclusion of that ratio with age, blood pressure, serum cholesterol, and smoking habits as independent variables accounted for 85% of variance in rates of deaths from all causes, 96% coronary heart disease, 55% cancer, and 66% stroke. Oleic acid accounted for almost all differences in monounsaturates among cohorts. All-cause and coronary heart disease death rates were low in cohorts with olive oil as the main fat. Causal relationships are not claimed but consideration of characteristics of populations as well as of individuals within populations is urged in evaluating risks."3
Notice that Keys et al specifically disclaimed assertion of causal relationships based on their data.  However, the team found a strong positive relationship between saturated (i.e. animal) fat intake and coronary heart diseaes, cancer, and stroke; and a negative relationship with olive oil. 

However, of the seven countries involved in the study (Japan, Italy, Greece, USA, Yugoslavia, Finland, and Netherlands), only two (Italy and Greece) had significant olive oil consumption.  Of these two, one had a significant brake on olive oil consumption for many days of the year, and this may have given olive oil an undeserved good reputation.

The Orthodox Mediterranean Diet Secret:  Avoid Olive Oil 180 Days A Year

Few popular or scientific accounts of the Mediterranean diet mention the fact that at least 95 percent of Greeks belong the the Eastern Orthodox Church, and a high proportion of Greeks follow the dietary directions of the Church which involve avoiding olive oil, meat, fish, milk, and dairy products on as many as 200 days every year:

"Orthodox Christian holy books recommend a total of 180–200 days of fasting per year. The faithful are advised to avoid olive oil, meat, fish, milk and dairy products every Wednesday and Friday throughout the year. Additionally, there are three principal fasting periods per year: i) a total of 40 days preceding Christmas (meat, dairy products and eggs are not allowed, while fish and olive oil are allowed except on Wednesdays and Fridays), ii) a period of 48 days preceding Easter (Lent). During Lent fish is allowed only two days whereas meat, dairy products and eggs are not allowed. Olive oil consumption is allowed only at weekends, iii) a total of 15 days in August (the Assumption) when the same dietary rules apply as for Lent with the exception of fish consumption which is allowed only on August 6th. Seafood such as shrimps, squid, cuttlefish, octopus, lobsters, crabs as well as snails are allowed on all fasting days throughout the year. The Greek Orthodox fasting practices can therefore be characterized as requiring a periodic vegetarian diet including fish and seafood." 4

Thus, on many days of the year, many Greeks eat a primarily plant-based diet without the olive oil so often identified as the secret to health and longevity.  Apparently, the Seven Countries Study did not account for this.  In fact, up until the year 2000, no scientific study, including the Seven Countries Study (SCS), had evaluated the impact of Greek Orthodox Christian fasting on serum lipoproteins or risk of cardiovascular disease or cancer.

At the ten-year follow-up of the SCS, Greece had the lowest CHD mortality of all seven countries: a remarkable 0/1000, compared to the next lowest in Japan, 7/1000. 5  This means that the Greek data would most strongly influence the appearance that a diet high in olive oil protects against CHD, when as a matter of fact, some significant portion of Greeks actually avoided eating olive oil on many days of the year. 

In 2000-2001, scientists from the University of Crete School of Medicine compared the blood lipids of Greeks who adhered to the fasting periods to those of Greeks who did not adhere during that year. They found that by the end of the year the fasters had significantly lower total cholesterol, LDL, and body mass index.  They also found that "when fasters returned to their usual dietary habits (non-fasting periods) total cholesterol and LDL cholesterol were increased by 6% and 9% respectively."4

Therefore, considering that the olive oil users of Roman Catholic Italy did not have the very low incidence of CHD and other diseases of civilization found in Greece in the 1950s, it seems possible that the Greeks enjoyed better health than the Italians because they avoided olive oil more often than the Italians, resulting in lower total cholesterol, LDL, and body fat levels.  

Greek Data Supports The Lipid Hypothesis

In 1997, an earlier team from the University of Crete School of Medicine reported that between 1962 and 1991, individuals participating in the Crete cohort of the Seven Countries Study had increased their intake of saturated fats and decreased their intake of monounsaturated fats, with corresponding increases in body mass index, adipose palmitic acid, diastolic and blood pressure, and by 1991,  "all age groups were characterized by central obesity."6
“Over time, the diet of Crete has changed remarkably and is now characterized by higher intake of saturated fat and cholesterol, and reduced intake of monounsaturated fat.  At the same time, total fat consumption has fallen.  These trends have been accompanied by a stead rise in CHD risk during 25 years of follow-up of the Cretan cohort (Menotti et al. 1999). Hence, as the Cretan diet increasingly resembles a Western diet, there has been a concurrent rise in CHD risk.”5