Estimating diet

Bingham, S.A. et ah, Comparison of dietary assessment methods in nutritional epidemiology — weighed records v 24-h recalls, food frequency questionnaires and estimated diet records, Br. J. Nutr., 72, 619, 1994. 

While recognizing the limitations (discussed above) of such an approach to estimating diet composition and the intake of PPT, using the University of Surrey database in conjunction with diet diaries available from their other studies has produced interesting data... 

FIGURE 4 Relationship between the carbon isotope ratio values of estimated diet and measured tooth enamel for ungulate mammals adopted from Cerling and Harris (1999). 

For example, if an animal is given 10 g of chromic oxide per day and the concentration of indicator in the faeces is 4 g/kg DM, then faeces output would be calculated as 10/4 = 2.5 kg DM/day. If food intake is known, then dry matter digestibility could be calculated as (dry matter intake — faecal DM output)/DM intake. Alternatively, if DM digestibility is known, then dry matter intake could be calculated as faecal DM output/DM digestibility. The n-alkane technique is very useful in this context. As plants contain mainly odd-chain n-alkanes in their waxy cuticle, even-chain (C32) n-alkanes can be used as an external indicator to determine faecal output. At the same time, the odd-chain n-alkanes (C35) can be used to estimate diet digestibility. Dry matter intake can then be estimated in group-fed or grazing animals. 

Figure 4. Human diets at Maya sites in Belize based on bone apatite carbon and bone collagen nitrogen isotope ratios. Human bone apatite carbon corrected -9.5, and collagen nitrogen -3.0 to reflect estimated diet. Faunal bone collagen carbon corrected -2.0 to simulate flesh modem samples corrected +7.5 for industrial effect.

Massive studies of the health problems associated with fats have included the Anti-Coronary Club study in New York City (2), the Framingham study (3) in Massachusetts, and the Chicago study (4). These studies were financed by the United States federal government and supported by the Surgeon General s office, which issued a statement recommending that the fat component of the diet be reduced from an estimated 40% of calories to 30% (5). 

Pubhc concerns about pesticides in the diet of infants and children resulted in an expert committee convened by the U.S. National Academy of Sciences which devoted four years to the review of all available data. A consensus report was issued in 1993 (80). A number of recommendations for further work to more precisely define what constitutes the diet of infants and children were made. No risk could be estimated. The residue data reviewed by the panel were mainly from monitoring studies conducted by the PDA using multiresidue methods to analyze fresh produce and market basket samples collected from various geographic areas (81,82). These and other rehable scientific studies have demonstrated that relatively few food samples contain detectable residues. Most residues are far below estabhshed tolerances which are set above the maximum residue found in treated raw agricultural... 

A commercially interesting low calorie fat has been produced from sucrose. Proctor Gamble has patented a mixture of penta- to octafatty acid ester derivatives of sucrose under the brand name Olestra. It was approved by the FDA in January 1996 for use as up to 100% replacement for the oil used in preparing savory snacks and biscuits. Olestra, a viscous, bland-tasting Hquid insoluble in water, has an appearance and color similar to refined edible vegetable oils. It is basically inert from a toxicity point of view as it is not metabolized or absorbed. It absorbs cholesterol (low density Hpoprotein) and removes certain fat-soluble vitamins (A, D, E, and K). Hence, Olestra has to be supplemented with these vitamins. No standard LD q tests have been performed on Olestra however, several chronic and subchronic studies were performed at levels of 15% in the diet, and no evidence of toxicity was found. No threshold limit value (TLV), expressed as a maximum exposure per m of air, has been estabhshed, but it is estimated to be similar to that of an inert hpid material at 5 mg/m. ... 

Relatively Httie is known about the bioavailabiUty of pantothenic acid in human beings, and only approximately 50% of pantothenic acid present in the diet is actually absorbed (10). Liver, adrenal glands, kidneys, brain, and testes contain high concentrations of pantothenic acid. In healthy adults, the total amount of pantothenic acid present in whole blood is estimated to be 1 mg/L. A significant (2—7 mg/d) difference is observed among different age-group individuals with respect to pantothenic acid intake and urinary excretion, indicating differences in the rate of metaboHsm of pantothenic acid. 

Boron in the form of borate is an essential micronutrient for the healthy growth of plants and is present in the normal daily human diet at an estimated level of 3—40 mg as boron. It is not a proven essential micronutrient for animals (119). 

Figure 1.2. Estimated 8 C of Belleville diet based on the percent contribution of baked goods (20%), meat (10%) and vegetables (70%) to the whole diet. Experimentally determined 5 C for each food group is indicated.

The diet of the 19 century residents of Upper Canada was determined from historical sources and was reproduced in order to carry out chemical analysis. Stable carbon isotope analysis of food and human bone demonstrates that the spacing between the food eaten and the bone collagen is around 5.6%o. The value may vary slightly from this estimate since the latter is based on a reconstructed diet and a large number of bone samples, which exhibit a small amount of variation. Nevertheless, this empirically derived result agrees well with estimates from field (Vogel 1978), and laboratory studies (reviewed in Ambrose 1993). 

Table 3.2 shows the 5 Cu and 5 Cc values of herbivores, omnivores, carnivores and humans. The (climate-corrected) trophic level effect between herbivores and carnivores is 0.90%o. Human values are closer to carnivore and omnivore values than to herbivore 5 Cc values. The human 5 Cc values are on average 0.66%o more positive than the herbivore 5 Cc values, a good estimate for a carnivore effect in humans (see section on trophic level effects, below). The average human 5 Cc value is -19.92 1.28%o,which would indicate that Holocene humans in Europe had a diet that consisted of C3 terrestrial foods, whieh is as might be expected. By looking at the humans separate from the total bone data set, we notice potential human food selection (Fig. 3.3) we can see a non-climatic pattern, which is much less uniform than in the total bone data set (Fig. 3.2b). Italy (6 Cc = -21.3%o) has a much more negative 8 Cc value than the Czech Republic (8 Cc =-18.7%o), Spain (8 Cc = -19.3%o) and Greece (-18.9%o but the 8 N of 9.0%odoes not indicate marine food), while the northern European coimtries are closer to a 5 Cc value of-20%o. What the actual causes are for this pattern in the human samples is not clear to better understand these variations it is best to consider, where possible, the 8 N values with the 8 Cc values. 

Ambrose and Norr (1993) and Tieszen and Fagre (1993) have shown that 5 C of carbonate in bone apatite (6 C,p) is the most accurate measure of the whole-diet composition (Ambrose and Norr 1993 28). The actual 5 C of total diet is related to that of apatite by an isotopic offset (fractionation) which Ambrose and Norr estimate to be 9.5 0.6%o. Other estimates range from 9.6 0.1%o for small mammals on controlled diets (DeNiro and Epstein 1978) to 12%o for large herbivores on natural diets (Lee-Thorp et al., 1989). The origin of this offset is of some concern to us here. We can only use 5 Cap as a measure of total diet if we know A,p.j,e, and also know that this fractionation is a constant, at least for a given species, and does not itself depend on the quality of the diet. 

The task of reconstructing the diet can be defined as that of finding D and F, by first evaluating or estimating the matrix com-ponents dij and f,j(), and applying these values to measurements of B. 

---