Article pp.47-55 du Vol.23 n°1 (2003)

(1)

FOCUS : JSMTV

Micronutrient intakes from meat

A. Chanson, P. Brachet, P. Grolier and E. Rock¹

INTRODUCTION

By definition, micronutrients represent food components brought in small quan- tities, but ensuring biological functions susceptible to prevent, if not to improve, the health and wellbeing of individuals. The main classes of micronutrients are minerals and trace-elements, vitamins, carotenoids and polyphenols, to which can also be associated micronutrient some metabolites such as retinoic acid, the active form of vitamin A and conjugated linoleic acids or CLAs. Thus, the concept of micronutrient refers to a very heterogeneous and complex family of compounds, present in all foods at more or less high levels; it should be noted that “empty calories” or refined food products have a very low nutritional density in micronutrients.

It is necessary to distinguish the "essential" micronutrients, like vitamins and certain minerals as, when insufficient, their intake can induce characteristic symp- toms (vitamin C and scurvy), from those like most carotenoids and polyphenols that seem to contribute essentially to long-term improvement of health (phytooes- trogens and osteoporosis). The French recommended dietary allowances (FRDAs), slightly different from American DRI (Dietary reference intakes), have been defined for essential micronutrients (see Table 1 for those brought by meat and liver). They represent average nutritional needs allowing to cover 97.5% of the population. Regarding nonessential micronutrients, a distinction should be made between those brought by animal products (typically CLAs) and those brought primarily by vegetal products, namely phytomicronutrients (carotenoids, polyphenols or phytosterols) that cannot be synthesised by the mammals.

Researches on the absorption and biological effects of micronutrients (either natural or synthetic), free or included into their native food matrix, have shown that the bioavailability of a given micronutrient can depend on its possible interactions with other components of the food matrix (phytic acid and absorption of minerals).

Lastly, the importance of micronutrients is also in keeping with the evolution of nutrition in our society, in particular the change from food scarcity to abundance.

1. Unité Maladies Métaboliques et Micronutriments, INRA – THEIX, F-63122 Saint-Genès Champanelle

(2)

Such an evolution has resulted in the parallel evolvement of important diseases associated with micronutrient insufficiencies and of chronic or degenerative pathologies related to food excesses. This has led to the princeps idea of nutritionists to establish ideal diets aiming to promote optimal health and longevity.

Accordingly, epidemiological observations show the existence of relationships between the risks for developing degenerative pathologies and certain dietary modes. Thus, contrary to the "Western" diet , the "Mediterranean" or "Asian" diet has a positive impact on health. The preponderance of vegetal products in these protective dietary modes, but also the significantly decreased exposure of vegetarians to degenerative pathologies, led to a scientific consensus assuming that an increased consumption of vegetal foods, concurrent with a moderate intake of animal products, should allow to increase the health potential of individuals.

Moreover, fundamental and applied researches on factors susceptible to decrease the risk for major pathologies in the population of industrialised countries (cardiovascular diseases and cancers) have shown the preponderance of micronutrients and, in particular, of phytomicronutrients.

It is in this general context that micronutrient intake from meat will be analysed.

First of all, the definition of the word “meat” on a nutritional standpoint is complex. It can take into account several aspects, including meat as such from various species and many meat products, processed industrially and/or traditionally. We will deal here with micronutrient intakes from red meat. Such an intake will depend on the ini- tial content and bioavailability in micronutrients. Intakes of micronutrient from meat are essentially restrained to some minerals, trace-elements and B vitamins (Table 1), as well as vitamin A which is almost exclusively brought by offal (liver). Obviously, meat is not a major source of carotenoids and polyphenols. The FRDA, as well as the functions and physiological effects of micronutrients, have been comprehensi- vely described in a recent book (ANONYMOUS, 2001) edited by the French Food Safety Agency (AFSSA “Agence Française de Sécurité Sanitaire des Aliments”).

Table 1

Micronutriment composition of meats and calf liver (for 100 g)*

Types Mg

mg P mg

K mg

Na mg

Se µg

Zn mg

Fe mg

B2 mg

B3 mg

B12 µg

B9 µg

B6 µg Meats

Grilled beef steak

25 230 400 60 3 0,26 5 2 15 400

Braised beef 24 200 270 60 4 0,3 3 2 8 300

Grilled entrecôte 21 180 320 50 2,6 0,3 6 2 16 300

Grilled sirloin Flank (raw)

25 19

240 200

400 320

60

70 Average values : 6-8 5-6

3 2,5

0,2 0,3

4,5 4,1

2 2

15 9

400 300

Flank (cooked) 19 170 250 52 3,5 0,24 3 2 7 270

Roast beef Bungundy beef

25 23

230 240

400 320

65 68

3,5 3,7

0,25 0,3

5 4

2 2

14 10

400 300

Beef stew 10 170 250 52 3,4 0,19 2,6 1,9 7 300

Ground Steak 5%

Ground steak 15%

27 22

241 171

439 331

74 82

2,9 2,2

0,22 0,23

4,4 3,9

1,9 1,9

9 8

370 320

«ANC»**

Intake%

400 6

800 25

400-600 ¶ –

6-8 g –

60 µg 10

12 mg 50

9-16 33

1,5-1,6 16

14 33

2,4 83

330 3

1 800 23

Calf liver 25 320 365 92 – – 6 3 13,7 65 300 710

(*) From FAVIER J-C et al; (**): per day; (¶):average requirement;

(3)

TRACE-ELEMENT (Fe, Zn, Se) AND MINERAL (P, K, Na) INTAKES

Iron Intake

As illustrated in Table 1, a 100 g portion of meat brings approximately 3 mg of iron, which represents 30% of the “ANCs” for this element. Offal, that are much richer than meat, can contribute up to 60% of the “ANCs”. In the Western diet, cereals can also contribute up to 30% of iron intakes; however, the heminic form of iron in meat products is much better assimilated (approximately 25%) than the nonheminic form found in vegetal and dairy products (lower than 10%). An Australian study on vegetarian and omnivorous women, showed that the serum concentration of ferritin was lower in the vegetarians comparatively to the omnivores, in spite of a similar iron intake for the 2 groups (BALL et BARTLETT, 1999). In France, data from the "Val-de-Marne" study show that meats and fishes bring approximately 25% of the dietary intake of iron. In addi- tion to its involvement in many metabolic reactions, iron contributes to the for- mation of myoglobin and haemoglobin. This explains for a great part the appearance of anaemia described as “ferriprive” during dietary iron deficiency.

Deficient status can be defined by usual measurement of plasma ferritin and/or saturation of transferrin, but also by circulating transferrin receptors, that have been recently proposed as indicators of iron status (BAYNES et al., 1994). In any cases, these assays must be carried out in individuals presenting no inflam- matory syndrome, which tends to increase the serum level of ferritin indepen- dently of the state of iron stores. Iron deficiency is a major health problem in the world, that is partly due to decreased intake and/or insufficient absorption of dietary iron. The SU.VI.MAX. study in France (GALAN et al.,1998) showed that 4,4% of women in age to procreate present a deficiency intense enough to involve a “ferriprive” anaemia, and the “Val-de-Marne” study (PREZIOSI et al., 1994) had shown that iron deficiency also concerns the infants (29% of children aged less than 2 y) and adolescent girls (15%). Another recent study on Swe- dish adolescent girls confirms the French observations. The authors point out that a reduced intake of animal products is accompanied by a decrease in iron intake and by iron stores insufficient to ensure erythropoiesis and iron require- ments (SAMUELSON et al., 2000). Factors considered as favourable for iron absorption include meat products and vitamin C, whereas phytates or tannins even polyphenols could inhibit intestinal absorption of iron. It should be noted that depletion of iron stores increases iron absorption but does not allow however to compensate for the inhibiting effect of vegetal products (phytates and polyphenols), in particular when the diet is low in heminic iron.

Zinc Intakes

Body zinc (Zn) is mainly stored in bones (30%) and muscles (60%). This explains the substantial role of meat and meat products for Zn intakes in human diet. Moreover, Zn bioavailability from animal products is higher than from vegetal products, in particular because of the richness of vegetal foods in phytates which, as for iron, chelate Zn and hinder its absorption. A recent study confirmed such a higher absorption in children weaned with ground beef meat as compared with children weaned with cereals (JALLA et al., 2002). In adult women, data on Zn concentration in plasma suggest that a reduction of red meat consumption in favour of cereal consumption could

(4)

impair Zn intake and bioavailability (GIBSON et al., 2001). Taking into account the better bioavailability of Zn from meat products, the last FRDAs proposal by French experts vary according to the food richness in animal products.

Thus, for adult men and women, respectively, the FRDA are 14 and 9 mg/d if the diet is rich in vegetal products, and 12 and 7 mg/d if consumption of animal food is high. Meats contains 5 to 6 mg of Zn/100 g. It can therefore contribute effectively to 60-80% of the Zn FRDAs. Based on plasma Zn concentration, the SU.VI.MAX. study showed that more than 7% of the French population studied present a value lower than 10.7 µM, which is considered as a cut-off value for biological deficiency. Zn is involved in many enzymatic reactions, but its physiological impact is at the protein synthesis level (activa- tion of DNA and RNA polymerases, histone regulation and start of genome reading), fatty acid metabolism and prostaglandin synthesis, as well as in reactions against the oxidative stress (superoxide dismutase, membrane sta- bilisation and competition with transition metals).

Selenium intakes

The half of total body selenium (Se) is stored in muscular cells. Protein-rich foods like meat and offal, but also milk and cereals, constitute Se sources for human diet. Dietary Se is mainly made up of seleno-methionine and seleno-cys- teine. Both forms are predominant as well in meat products as in cereals. The FRDAs “ANCs” are 50 to 80 µg/d for adolescent and adult subjects. Meat consumption thus can contribute to fulfil 10 to 20% of the recommendation

“ANCs”. Most of the biological functions of Se are through selenoproteins like glutathione peroxidases (antioxidant defences), thioredoxine (regeneration of reduced vitamins C and E) and desiodases (thyroid function).

Macroelements intakes

Meats, as most biological tissues, contain phosphorus, sodium (Na) and potassium (K). The average intake of phosphorus in industrial countries is 1500 to 1600 mg/d, and all food categories contribute to this intake. However, it would be desirable to decrease intakes of polyphosphates that are largely used in food technology in order to prevent an excessive consumption of phosphorus (higher than 2500 mg/d), in particular when it is associated with insufficient calcium intakes. Under such conditions of unbalanced intake, side effects might occur on calcium metabolism and bone mineralisation as a result of a reduction in ionised calcium in the organism. Likewise for Na and K, it is obvious that all food categories contribute to a largely excessive daily intake of these elements.

However, data on K and Na content of processed meat products, such as smoked ham, raise a fundamental question about the health effect of high Na intake. Indeed, considering that muscle contains on average 300 mg of K/100 g and 70 mg of Na/100 g, the consumed smoked ham displays a K amount of approximately 450 mg/100 g, but a Na amount able to reach 1600 mg/100 g (LALAU et al., 1996). Confirmation of high Na intake is supported by a British study showing that meats provide the quarter of the daily consumed 8 g of salt, the currently recommended amount (DRÜEKE et LACOUR, 2001). This results in an increase in the Na/K molar ratio to values higher than 1, which are considered as harmful to the circulation system due to arterial hypertension particu- larly evoked by the increase in Na.

(5)

VITAMINS INTAKES

Liposoluble vitamins (A and E)

Vitamin intakes from animal products mainly concern vitamin A. However, many studies have been carried out on vitamin E in order to improve the tech- nological characteristics of meat and meat products, in particular regarding the oxidation processes susceptible to alter meat colour and sensorial qualities. As shown in Table 1, the vitamin E content of meat (0.2-0.4 mg/100 g) is far from meeting the vitamin FRDA “ANCs” (12 mg/d). The situation is different for vitamin A. Indeed, animal products like liver of farm animals contain high amounts of this vitamin, able to reach values of 10000-20000 retinol-equivalent (RE), whereas the present recommendations are between 600 and 800 RE/d (AZAÏS- BRAESCO et GROLIER, 2001). From a safety viewpoint, it is recommended to avoid intakes of vitamin A higher than 3000 RE owning to the teratogene properties of this vitamin.

Hydrosoluble vitamins – Riboflavin (B2) intake

Vitamin B2 enters flavoprotein composition as flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). Flavoproteins catalyse electron transfers in the mitochondrial respiratory chain and in dehydrogena- tion reactions. In Western countries, food brings a sufficient amount of vitamin B2 to meet the needs, except maybe for certain high-risk groups like the elederly. The Burgundy survey (COSTA DE CARVALHO et al., 1996) showed that 70% of riboflavin intakes come from animal products, with 35% from meat, fish and eggs. The FRDAs “ANCs” are 1.5-1.6 mg/d and vitamin B2 concentrations in red meat are approximately 0.3 mg, thus covering 18% of the recommendation. The highest concentrations are found in animal livers (e.g. calf [see Table 1] and pig).

– Niacin (B3) intake

Niacin is not strictly a vitamin since nicotinamide, a related substance having biological activity of niacin, can be synthesised from tryptophan by the body. Nicotinamide forms integral part of nicotinamide-adenine dinucleotide (NAD⁺/NADH) and nicotinamide-adenine dinucleotide phosphate (NADP⁺/NADPH), which both are oxidoreduction and electron transporter coenzymes. Bioavailability of niacin from NAD and NADP in meat products is higher than that of glycosylated forms of niacin that occur in cereals.

The FRDA are 11 and 14 mg/d for adult men and women, respectively. In France, the average tryptophan content of the protein fraction of the diet (14 mg) is largely enough to fulfil the niacin needs thanks to an endoge- nous synthesis. Consequently, the pre-formed vitamin of meat (3-5 mg/

100 g) can be considered as a surplus in Western diets. A Spanish study shows that niacin intake is higher in young women consuming at least 100 g of meat/d compared with those consuming less than 100 g/d (ORTEGA et al., 1998). Additionally, an Irish study (O' BRIEN et al., 2001) shows that in 20 and 6% of men and women, respectively, of 1379 studied subjects, fish and meat consumption contributes to an intake of pre- formed niacin close to the safety limit for this vitamin.

(6)

– Vitamin B6 intake

Six compounds form vitamin B6 family: pyridoxal, pyridoxine, pyridoxamine and their phosphorylated derivatives. The major forms in animal tissues are pyridoxal 5' phosphate (PLP) and pyridoxamine 5' phosphate (PMP), whereas vegetal tissues mainly contain glycosylated pyridoxine (GPN). Vitamin B6 brought by animal products contribute to 85% of the intakes. Comparatively, vitamin B6 bioavailability from plant foods is lower owning to glycosylation that decreases absorption by 50%. PLP ensures coenzyme functions in amino acid metabolism, in particular of aminotrans- ferases and of decarboxylases. The FRDA have been set to 1.5 and 1.8 mg/d for adult women and men, respectively, and at 2.2 mg/d for elderly.

Higher recommendation for old people is notably related to age-related moderate hyperhomocysteinemia, which is considered as an independent risk factor for cardiovascular diseases. Homocysteine metabolism depends on cystathionine β-synthase which requires vitamin B6 as a cofactor. Insufficient vitamin B6 intake, as suggested by studies on the relationship between vitamin B6 and hyperhomocysteinemia in healthy individuals, might reduce cystathionine synthesis and lead to homocysteine accumulation (see Figure 1). In this context, it is worth considering meat as an important source for this vitamin among animal products (more than 40% of the intakes). Meat content in this vitamin ranging from 300 to 400 µg/100 g, can contribute to 20 to 25% of the vitamin B6 FRDAs. In France, the SU.VI.MAX study shows that 16 to 19% of men and 26 to 38% of women have intakes lower than the 2/3 of that recommendations

“ANCs” (reviewed in GUILLAND et al., 2001).

Figure 1

Role of vitamins B6 and B12 in homocysteine metabolism

Methionine Cystathionine

Homocysteine

Vitamin B12 Mehionine synthase

Vitamin B6 Cystathionine ßsynthase

(7)

– Cobalamin (B12) Intakes

The physiological role of vitamin B12 mainly takes place at the level of its methylated (methylcobalamin) form, which is a donor of methyl group brought by methyltetrahydrofolate (vitamin B9) that allows methionine synthesis from homocysteine (see Figure 1). Homocysteinemia and methyl- malonic acid (MMA) concentrations are considered as biological indicators of vitamin B12 status. Thus, in spite of the central role played by folates (vitamin B9) on homocysteine metabolism, the Figure shows the interactions of vitamins B6 and B12, mainly supplied by animal products, with hyperhomocysteinemia. Contrary to vitamin B6, vitamin B12 is exclusively from animal origin. The values indicated in Table 1 show that meat, contai- ning approximately 2 µg of vitamin B12/100 g, can meet more than 80%

of the FRDA (2.4 µg/d), and that liver consumption (> 60 µg/100 g) brings noticeably excessive amounts. Although vitamin B12 deficiency is rare in the general population, risks of marginal deficiency in the vegetarians and vegetalians exist. Two independent studies (HERMANN et al., 2001;

MANN et al., 1999) have thus shown that a decreased meat intake leads to a significant increase of the plasma levels of homocysteine and MMA without changes in the plasma concentration of vitamin B12, which remains correlated with homocysteinemia. From these studies, it was con- cluded that 25% of the vegetarians exhibited a functional deficiency in vitamin B12. The elderly also represents a high-risk population for vitamin B12, and the prevalence of deficiencies in this vitamin is linked to the ele- vated incidence of atrophic gastritis at the origin of achlorhydria which decreases absorption of dietary vitamin B12.

CONCLUSION

Altogether, meat products constitute an undeniable source in several micronutrients of interest like iron and B vitamins, but could also contribute to satisfy selenium or zinc intake. It should be noted that these elements play an incon- testable physiological role, and for some of them, an insufficient intake has been reported in particular in the European populations. However, recent epidemiological studies highlight deleterious association as for the impact of meat consumption on health. It seems that there is a paradox or at least a question to which hypothetical answers can be proposed. Concerning the relationship between meat and colo-rectal cancer, a recent analysis of epidemiological data (HILL, 2002) shows that the European data are not consistent with those of the United States, in particular because of the different nutritional context in which meat is consumed in these 2 continents. The author thus concludes that if fruits and vegetables have a protective effect, meat consumption would not have any role on occurrence of this cancer. Besides, epidemiological studies generally relate to a comparison between heavy-meat consumers and vegetarians. Few information are provided as for the nature the precise amounts of meat consumed and the lifestyles associated to these consumers. Other studies show a significant difference between the groups previously mentioned regarding their

(8)

everyday life habits (VOLATIER et al., 1997). Analysis of these studies suggest that meat consumers associate foods such as bread and “empty-calories”

foods, and have a lifestyle (higher cigarette smoking, alcohol drinking and little physical exercise) which is not in favour of preservation of their health. Thus, more detailed analysis and perhaps even experimentation with meat consuming volunteers, duly informed and adviced by nutritionists, should be carried out.

This would allow to establish biological parameters for the status in micronutrients of interest and for their health effect, in order to draw an objective conclusion on the health impact of meat and meat products in a general context (food and lifestyle) favourable to health maintenance.

Another question still remains on the role of saturated fatty acids (SFAs).

Indeed, consumption of meats, because of their richness in SFAs, significantly increases SFAs of plasma phospholipids, in correlation with the increases in plasma cholesterol and triglycerides (in particular, stearic acid). Thus, like other foods, as vegetal products rich in phytates, meat shows positive and negative nutritional properties. Attempts to modulate the meat SFAs content have been undertaken, but the nutritional advice to eat “varied and balanced”, with moderate amounts of energy and lipid-rich foods (animal products), remains worth in the current state of our knowledge in human nutrition. Concerning meat and meat products, it would be cautious to incite the whole population to increase their consumption and, in contrast, to recommend a reduced intake to high- meat consumers. Lastly, instead of opposing plant-based diet and animal foods, it seems possible to undertake, in particular in the communication field, an education of the population (consumers, but also professionals involved in the nutrition field) on an optimal use of meat in food practices, i.e. an association with the most suitable vegetables.

REFERENCES

ANONYMOUS, 2001. Apports nutritionnels conseillés pour la population française (3^rd Edition). Co-ordinator : Ambroise Martin.

Editions Tec&Doc.

AZAÏS-BRAESCO V., GROLIER P, 2001. Vita- mine A et caroténoïdes. In: Apports nutritionnels conseillés pour la population française (3^rd Edition). Co-ordinator:

Ambroise Martin. Editions Tec&Doc;

pp 221-228.

BALL M.J., BARTLETT M.A., 1999. Dietary intake and iron status of Australian vegetarian women. Am. J. Clin. Nutr., 70, 353- 358.

BAYNES R.D., SKIKNE B.S., COOK J.D., 1994. Circulating transferrin receptors and assessment of iron status. J.Nutr.Bio- chem., 5, 322-330.

COSTA DE CARVALHO M.J., GUIILLAND J.C., MOREAU D., 1996. Vitamin status of health subjects in Burgundy (France). Ann. Nutr.

Metab., 40, 25-51.

DRÜEKE T.B., LACOUR B., 2001. Sodium. In : Apports nutritionnels conseillés pour la population française (3^rd Edition). Co-ordinator : Ambroise Martin. Editions Tec&Doc ; pp 120-130.

FAVIER J.C., IRELAND-RIPERT J., TOQUE C., FEINBERG M., 1995. In : Répertoire géné- ral des aliments. Table de composition.

Editions INRA, CNERNA, Tec&Doc ; 2^nd edition.

GALAN P., YOON H.C., PREZIOSI P., VITERI F., VALEIX P., FIEUX B., BRIANCON S., MALVY D., ROUSSEL A.M., FAVIER A., HERCBERG S., 1998. Determining factors in the iron status of adult women in

(9)

the SU.VI.MAX study. Eur. J. Clin. Nutr., 52, 383-388.

GIBSON R.S., HEATH A.L., LIMBAGA M.L., PROSSER N., SKEAFF C.M., 2001. Are changes in food consumption patterns associated with lower biochemical zinc status among women from Dunedi, New Zeland? Br. J. Nutr., 86, 71-80.

GUILLAND J.C., LEMOINE A., POTIER DE COURCY G., CHRISTIDÈS J.P., 2001.

Vitamine B6. In : Apports nutritionnels conseillés pour la population française (3^rd Edition). Co-ordinator : Ambroise Martin.

Editions Tec&Doc; pp 196-203.

HERMANN W. , SCHORR H., PURSCHWITZ K., RASSOUL F., RICHTER V., 2001.

Total homocysteine, vitamin B12, and total antioxidant status in vegetarians.

Clin. Chem., 47, 1094-1101.

HILL M., 2002. Meat, cancer and dietary advice to the public. Eur. J. Clin. Nutr., 56 (Suppl. 1), S36-41.

JALLA S., WESTCOTT J., STEIRN M., MILLER L.V., BELL M., KREBS N.F., 2002. Zinc absorption and exchangeable zinc pool sizes in breast-fed infants fed meat or cereal as first complementary food.

J. Pediatr. Gastroenterol. Nutr., 34, 35-41.

LALAU J.D. , PAWLAK S., VILFROY M., 1996.

Sources alimentaires, rôles physiologi- ques et besoins en minéraux. I. Sodium, potassium, calcium, magnésium. Cah.

Nutr. Diet., 31, 313-320.

MANN N.J., LI D., SINCLAIR A.J., DUDMAN N.P., GUO X.W., ELSWORTH G.R., WIL- SON A.K., KELLY F.D., 1999. The effect of diet on plasma homocysteine concentration in healthy male subjects. Eur. J. Clin.

Nutr., 53, 895-899.

O’BRIEN M.M. KIELY M., HARRINGTON K.E., ROBSON P.J., STRAIN J.J., FLYNN A., 2001. The North/South Ireland Food Con- sumption Durvey: vitamin intakes in 18- 64-year-old adults. Public health Nutr., 4, 1069-1079.

ORTEGA R.M., LOPEZ-SOBALER A.M., REQUEJO A.M., QUINTAS M.E., GASPAR M.J., ANDRES P., NAVIA B., 1998. The influence of meat consumption on dietary data, iron status and serum lipid parameters in young women. Int. J. Vitamin. Nutr.

Res., 68, 255-262.

PREZIOSI P., HERCBERG S., GALAN P., DEVANLAY M., CHEROUVRIER F., DUPIN H., 1994. Iron status of a healthy French population: factors determining biochemical markers. Ann. Nutr. Metab., 38, 192-202.

SAMUELSON G., LONNERDAL B., KEMPE B., ELVERBY J.E., BRATTEBY L.E., 2000.

A follow-up study of serum ferritin and transferrin receptor concentrations in Swedish adolescents at age 17. Acta Pae- diatr., 89, 1162-1168.

VOLATIER J.L., COLLERIE DE BORELY A., LEBRETON S., 1997. La diversité alimen- taire en France. Note n˚ 9710, CREDOC, Paris.