Pasta Food
Structure of the section

Introduction

The nutritional value of pasta, as regards its bromatological composition, is not very high, as this food is most of all rich in starch, whereas its protein contribution is significantly lower (approx. 7-8 times!). In addition, some people attach too much importance to its content in trace elements (mainly Fe and Zn), which is instead modest, compared with the main food sources of mineral salts and vitamins.

Therefore pasta essentially supplies glucides, apart from a small amount of proteins occurring in it, which, on the other hand, have a poor biological value. Actually, if one analyses the amino acid spectrum of the protein component of pasta and compares it with that of the protein component of some foods of everyday use, such as egg, milk casein or soya proteins, it appears that wheat flour and semolina proteins are characterized by a low content
in essential amino acids, particularly in lysine, thus representing the limiting amino acid which reduces the nutritional value.
Both the biological value and the factor of protein net utilization of wheat flour and, consequently, of pasta, are therefore rather low in comparison with those of meat or egg, with a variation ranging from approx. 2/3 half.

Pasta combined with seasonings

Pasta, however, unlike other carbohydrate-rich foods (bread, biscuits), is hardly ever eaten "as it is", but it is combined with a number of other high protein content foods (cheeses, meats, fish, etc.), with enhance and improve its nutritional value by means of a supplementation of their amino acid complex with that of wheat proteins. Thanks to a "synergetic effect", a notable increase is so obtained in the nutritional value of each food and, as a result, a thorough utilization of the protein total complex. A fairly reduced helping of pasta (70 g) seasoned with a little tomato sauce, containing approx. 10% of olive oil, and with 10 g of grated Parmigiano-Reggiano cheese, reaches a quite high factor of protein net utilization, respecting as well those rates of per cent contribution in calories derived from the three energy-giving nutrients (13% for proteins, 30% for lipids, and 57% for glucides), regarded as optimum by the Nutritionnists all over the world. Of course, seasonings even richer in proteins, as the meat sauce, will further increase the nutritional value of pasta. Table 1, reporting the comparison between a ration of pasta with "tomato sauce" and with "meat sauce", demonstrates that, in case of tomato sauce seasoned pasta, with Parmesan cheese added, coverages up to 25-30% of protein contribution are obtained, and of approx. 40% of Vit. C requirements. Whereas meat sauce seasoned pasta even exceeds 40% of daily protein requirements and covers as well about 25-30% of iron demands (Table 1).
Therefore, semolina made pasta, although it is not by itself a complete food for nutritional viewpoint, plays all the same a leading role in our nutrition, as, by perfectly combining with seasonings used to enrich its consumption, makes it possible to obtain nutritious and well-balanced dishes on the whole

Stuffed pasta

What we said regarding traditional pasta applies, even more so, to stuffed pasta, a more recent production of Industry which, in the wake of tried out gastronomical traditions, has developed ready-to-use products (ravioli, tortelli, agnolotti, etc.) featuring a remarkable nutritional and gastronomic value. A helping of 100 g tortellini or agnolotti with filling supplies, in fact, approx. 15 g proteins, 10 g lipids, and 46 g glucides, which are within the limits of those optimum rates of calories provided by the various nutrients (15,30, and 55%).
The meat sauce and the Parmigiano-Reggiano cheese, ordinarily added to these products, produce, however, an increase in the protein and lipid share to the detriment of the carbohydrate one, thereby fairly unbalancing the dish. But by supplementing the meal with a dish of mixed vegetables (approx. 200 g), dressed with a teaspoonful of olive oil, a roll and a fruit, this problem can be easily solved, as a total caloric contribution of approx. 900 Kcalories is obtained, divided this way: 134 from proteins, 270 from lipids, and 510 from glucides.
The per cent rate is therefore 15%, 29% and 56%. A dish of tortellini with meat sauce, a few vegetables, a roll and a fruit therefore represent an ideal meal, fully respecting these proportions. There is no significant difference if we replace the meat sauce used for seasoning with the tomato sauce as, once more, we obtain the rates of 10%, 26%, and 64% of calories supplied by proteins, lipids, and glucides, in total compliance with the suggestions of Nutritionnists.

Introduction

Recently a great importance has been attached to fiber, which is able to control, due to its modulatory action on intestinal absorption of carbohydrates, the sudden peaks of glycemia resulting from a meal rich in glucides that, in the long run, prove harmful for our organism. Figure 1 clearly summarizes the phenomenon: plenty of fiber available causes a dilution of the gastrointestinal content, thereby slowing down the absorption of nutrients (especially glucose), giving rise to much more reduced glycemic variations. On the contrary, a low-fiber meal is accompanied by marked glycemic and insulin fluctuations, with a subsequent rapid drop of glycemia, which, in its turn, causes a sensation of hunger thus driving people to overfeed. On the grounds of these effects, JENKINS set a hierarchic scale of "glycemic indexes" (Table 2), reckoning the areas taken up by the glycemic varations after taking various glucide foods. Letting the glucose index be 100, JENKINS et al. pointed out a glycemic index of 70-75% for wholemeal bread, and of 50-59% for spaghetti (even of 40-49% for wholemeal spaghetti). Bread therefore shows a much less favourable index compared with pasta (Table 2). However, the same authors reported, some time later, the results of an inquiry which should raise doubts on effects of fiber.
By giving the same amount of carbohydrate in form of white bread, and spaghetti, they observed, in fact, a same trend for glycemia with the two kinds of bread (Fig. 2), whereas the trend, after the spaghetti intake, was more reduced and modulated. Moreover, the sensation of satiety after taking the three considered products (right side of the figure) was quite alike.These data would therefore challenge the role of fiber or would at least lead to assume that other factors exist capable of affecting the glycemic trend.
Subsequently, other researchers (HERMANSEN et al.) studied the trend of glycemic curves in a number of Type I diabetic patients, who took the same amount of carbohydrate (approx. 40 g starch) in form of potatoes, rice and spaghetti (Fig. 3 and Table 3). It appeared, from the comparison of the results obtained that, whereas potatoes and rice produce a quick increase in glycemia, after taking spaghetti, the trend is much less reduced. This in spite the fact that potatoes contain four times the amount of fiber found in spaghetti (Table 3). Once more the importance of fiber is questioned. That's why we should start considering other possible interference factors.

Pasta "shape", cooking times and various kind of starch

A confirmation to the results observed by Hermansen et al., also comes from other investigations. In these investigations, after comparing the glycemic variations following the intake of 50 g carbohydrate in form of white bread and spaghetti in Type I insulin-dependent and Type II non insulin-dependent, diabetic patients (Fig. 4), possible interferences in absorption due to pasta shape and cookig times (Fig. 5) were also taken into account. No significant differences were on the other hand observed. The different glycemic index found between white bread and semolina made pasta therefore could perhaps be ascribed to the kind of starch. Starting from this theory, MOUROT et al. gave 50 g starch from different source (potatoes, bread, rice, and pasta) to 12 healthy grown-up volunteers (Fig. 6).
The glycemic curves were respectively: higher for bread, intermediate for potatoes and rice, and significantly lower for spaghetti. The relevant insulin curves showed a quite similar trend.

Gastric emptying times and other interference factors

Moreover, the same authors have found, by marking the various kinds of starch with radiotechnetium 99, significantly different gastric emptying times correlated with the glycemic ranges observed (Fig. 7, Fig. 8). Therefore, after all, there would be many factors capable of modulating the glycemic response to starchy foods, such as the physical structure of starch, its content in amylase or fiber, the processing technologies undergone by the food, its digestion speed. In all cases, however, pasta has all the time clearly shown a more favourable and quite preferable behaviour, regarding all the starchy food it was compared with, both in normal subjects and Type I and Type II diabetic patients. Finally, on the basis of the unmistakable experimental controls carried out on many by MOUROT et al., an exact role could also be ascribed to the different times of gastric emptying, in their turn deeply affected by the possible concurrent presence of lipids and proteins in stomach.


The role of co-ingestion of lipids and proteins

Several researchers studied the effects of fat co-ingestion on metabolic responses to white bread and spaghetti demonstrating that the concomitant presence of lipids, mainly if in large amounts, reduces the glycemic response, very probably by promoting a slowing down of the gastric emptying time. By increasing the lipidic content of meal, a progressive reduction of the glycemic curves occurs, which proves that fats can interfere on the speed intestinal absorption of carbohydrate. For proteins too, a similar effect was clearly demonstrated. In addition, as they tend to stimulate insulin release, they would consequently reduce the glycemic response. After all, shifting from theory to facts, it is obvious that the more fats and proteins are present in stomach along with pasta, the more the absorption of carbohydrate is slowed down and a more modulated response is obtained. From a practical point of view, very important are the recent remarks made by a team of Danish Researchers from Aarhus (Fig. 9), who clearly demonstrated in Type II diabetic patients, that industrial spaghetti produce a significantly lower glycemic and insulin response, compared with homemade spaghetti and with usual white bread, the traditional reference food for this kind of investigations. This finding takes up a noteworthy clinical-practical meaning: in fact, by reducing the postprandial hyperglycemic and hyperinsulin peak, industrial pasta presents, especially in diabetic and obese patients, a considerable advantage compared with homemade pasta or other starchy foods. Moreover, on account of these comparisons, quite insignificant are also the doubts on nutritional value of industrial pasta, due to the decreased bioavailability in lysine following the high temperature drying technological process, raised by some researchers, who are not, on the other hand, clinical nutritionnists. These observations, in fact, have in our opinion a negligible importance from a nutritional point of view, because, as previously recalled, the usual addition of seasonings particularly rich in proteins, will largely compensate for the losses of this amio acid. Quite different, instead, and very useful is the modulation of the glycemic and insulin responses which, on clinical level, makes industrial pasta more advantageous and preferable.


Comments and conclusions

To conclude, on the grounds of the scientific documentations here reported, we could undoubtedly state that pasta, especially industrial pasta, is definitely to be preferred as regards other starchy foods (bread, rice, potatoes, fruit). It produces in fact more reduced glycemic variations, lower postprandial hyperglycemic peaks and less quick drops in glycemia, and a more prolonged sensation of satiety. We should therefore regard this food as an ideal source of carbohydrate in the dietetic prescription of a diabetic patient, both insulin-dependent and non insulin-dependent, as well as in insulin-resistant subjects, as typically found in obese persons.
In spite of that, an article published these days on the front page of the New York Times (Fig. 10) asks the American population, whose 25% insulin-resistant and overweight, to cut down on pasta consumption, as it causes important glycemic fluctuations, hyperinsulinemia, hypertriglyceridemia, hypertension, and Type II diabetes (the so called X syndrome by Gerald Reaven). Such statements about the danger and the possible harmful implications linked to pasta consumption, even in a "risk" population as it is the North-American one, are without precedent in the international scientific literature. Therefore those who have supported them either do not know the medical-scientific literature or have distorted what reported in it. This second theory would seem to be the most likely, as no one of the influential Scholars mentioned in the article (Fig. 10) maintains that the United States population should cut down on pasta consumption. The suggestion instead is of reducing total calories, especially those derived from fats, simple sugars and starchy foods in general. One would better charge, instead, the overconsumption, by the American people, of snacks, potato chips, bakery products, and soft drinks. Also pizza, undoubtedly the most widespread food in the world, as regards pasta, should be looked at with more suspicion, due to its excessive hyperglycemic response, recently found in young diabetic patients, if compared with a control meal similar as to its glycidic and caloric content.
After all, just on account of the special metabolic-humoral and clinical effects following the taking of a pasta based meal, it appears that there are good reasons for still considering pasta as the best among starchy foods. Pasta, in fact, due to its bromatologic properties and metabolic distinctive qualities, can hold a very important place in our daily nutrition. Not only under physiological conditions and/or at times of high or particular energetic requirements (during growth, at the pre-competition meal, during special athletic performances, intense sports activity, etc.), but also in given clinical states, such as in diabetes both of Type I and II. In all these cases, several experimental and clinical investigations have very recently recognized its preferential use, towards the other starchy foods, thanks to its more reduced and modulated metabolic-humoral responses.