Trends in food availability in Portugal in 1966–2003

Abstract

Background

Dietary intake has changed considerably in South European countries, but whether those changes were similar between countries is currently unknown.

Aim of the study

To assess the trends in food availability in Portugal and four other Mediterranean countries from 1966 to 2003.

Methods

Food and Agricultural Organization food balance sheets from Portugal, France, Italy, Greece and Spain. Trends were assessed by linear regression.

Results

The per capita availability of calories has increased in Portugal, France, Greece, Italy and Spain in the past 40 years. Portugal presented the most rapid growth with an annual increase of 28.5 ± 2.2 kcal (slope ± standard error), or +1000 kcal overall. In animal products, Portugal had an annual increase of 20.7 ± 0.9 kcal, much higher than the other four countries. Conversely, the availabilities of vegetable and fruit only showed a slight growth of 1.0 ± 0.1 kcal/year and 2.5 ± 0.4 kcal/year, respectively, thus increasing the ration of animal to vegetable products. Olive oil availability increased in all countries with the notable exception of Portugal, where a significant decrease was noted. Wine supply decreased in all five countries; in contrast, beer supply started to take up more alcohol share. Percentage of total calories from fat increased from nearly 25% to almost 35% in Portugal during the study period, mainly at the expenses of calories from carbohydrates, whereas the share of protein showed just a slight increase. Furthermore, fat and protein were increasingly provided by animal products.

Conclusions

Portugal is gradually moving away from the traditional Mediterranean diet to a more Westernized diet as well as France, Greece, Italy and Spain. Noticeably, the trends of diet transition were observed relatively faster in Portugal than in the other four Mediterranean countries.

Annex

Assessing the effect of several foodstuffs on the trends in caloric/nutrient availability

Briefly, let the timely change in total caloric availability be modeled by a simple linear regression:

$$ {\rm Total\,\,caloric\,\,availability} = \alpha_{\rm t} + \beta_{\rm t}.({\rm time}) $$

(1)

Where a_t is the total caloric availability at time 0 and β_t is the slope (increase/decrease) for the change in total caloric availability, for example an increase in 50 kcal/year. The time changes for animal and vegetable-derived caloric availabilities can be calculated similarly:

$$ {\rm Animal\,\,caloric\,\,availability} = \alpha_{\rm a} + \beta_{\rm a}.({\rm time}) $$

(2)

$$ {\rm Vegetable\,\,caloric\,\,availability} = \alpha_{\rm v} + \beta_{\rm v}.({\rm time}) $$

(3)

Supposing alcohol-derived caloric availability is negligible or included in vegetable caloric availability, one can postulate that:

$$ {\rm total\,\,caloric\,\,availability} = {\rm animal + vegetable\,\,caloric\,\,availability} $$

(4)

Introducing (1), (2) and (3) into (4) leads to the equation

$$ \alpha_{\rm t} + \beta_{\rm t}.({\rm time}) = \alpha_{\rm a} + \beta_{\rm a}.({\rm time}) + \alpha_{\rm v} + \beta_{\rm v}.({\rm time}) $$

(5)

At time = 0, equation (5) simplifies into

$$ \alpha_{\rm t} = \alpha_{\rm a} + \alpha_{\rm v} $$

(6)

indicating that the total caloric availability at time zero (and actually at any time) should be equal to the sum of animal and vegetable caloric availability, as stated in equation (4). Using (6) and (5) we obtain for any time

$$ \beta_{\rm t} = \beta_{\rm a} + \beta_{\rm v} $$

(7)

Which indicates that the changes in total caloric availability can be expressed as the sum of the changes in animal and vegetable caloric availabilities. Thus, the percentage of change in total caloric availability explained by changes in vegetable-derived calories can be easily calculated as

$$ {\beta_{\rm v}\over \beta_{\rm a} + \beta_{\rm v}} $$

(8)

For example, for an increase in total caloric availability of 50 kcal/year and a corresponding increase of 30 kcal/year in vegetable caloric availability, then the percentage of total caloric availability change explained by changes in vegetable-derived caloric availability is

$$ {30\over 50} = 0.6\,\,{\rm or}\,\,60\% $$

(9)

Which indicates that most of the increase in total caloric availability is due to vegetable products. Actually, equation (8) is not limited to positive (increasing) trends as, using another example, the previous increase of 50 kcal/year in total caloric availability could also be obtained by an increase of 80 kcal/year in vegetable and a decrease of 30 kcal/year in animal availability. Thus, a similar change in total caloric/nutrient availability can be obtained by completely different trends as regards the foodstuffs analyzed.