Lipids carnivore diets

Figure 10.2. Schematic diagram showing how restricted conversion of fatty acids to amino acids influences the fractionation between collagen and CO3 of bone apatite LI = lipid component, PR = protein, T = total isotopic composition AP = COj component of apatite, a) Herbivorous diet (Cj plants only) b) Carnivorous diet, assuming rj = 1 (no barrier to fatty acid conversion to AAs) c) Carnivorous diet, assuming ri < 1 note that carbonate-collagen fractionation is smaller.

Lipids are a second major source of carbon in most animal diets, perhaps the major source in some carnivorous diets Lipids are metabolized for energy requirements, although somewhat more slowly than carbohydrates Lipids tend to be depleted in by about 2 0/00 or more relative to carbohydrates in any particular food (data in 6 7 9) Virtually all lipid carbon is ultimately... 

Most accounts of the larger A,p.,.o in carnivores have attributed this effect to higher proportion of lipids in the diet of carnivores. This arises because carnivores obtain all or most of their nutrition from the flesh of other animals, a significant part of which is composed of lipid. By contrast, lipids make up a much smaller fraction of the total carbon pool in the diet of herbivores, particularly mminants which get much of their energy from digestion of cellulose. Humans who selectively use seeds and grains as food sources obtain a... 

Herbivores typically eat diets with high carbohydrate and low protein and lipid. F is about 0.15, and the protein is mainly plant derived and not very different in S C from the non-protein (i.e., Dp is close to Dn). For carnivores, F is typically 0.5 or over, and carbohydrate is low. Animal protein is generally isotopically heavier, while the non-protein is much higher in lipid, so that Dp - Dn is generally quite large (>5%o). The spacing, Bcolla Bcarb. for the two diets is evaluated according to the equation above. 

Carnivores rely on a protein-rich diet and produce new biomass primarily from dietary amino acids, although the enzymes required for de novo amino acid synthesis are present (Garmes et al., 1998). Bone collagen, muscle (meat) and apatite were analyzed for a set of modern southern African herbivores and carnivores (Lee-Thorp et al., 1989). The isotopic analyses showed i C enrichment in bone collagen, apatite and muscle, and depletion in lipids. Difference in values between herbivores and carnivores indicates a trophic effect, which for carbon in bone collagen is 2.5-3%o (Fig. 2). 

Vitamin A is a fat-soluble micronutrient that is required by all vertebrates to maintain vision, epithelial tissues, immvme functions, reproduction, and for life itself. It was discovered in 1913 as a minor component in eggs, butter, whole milk, and fish liver oils. It soon became apparent that vitamin A exists in two chemically distinct yet structurally related forms. The first form to be characterized was retinol, a lipid alcohol that is present only in foods of animal origin. Retinol is also known as preformed vitamin A because it can be metabolized directly into compovmds that exert the biological effects of vitamin A. A second form of vitamin A, present in deep-yellow vegetables, was characterized as /3-carotene, which is synthesized only by plants but can be converted to retinol during absorption in the small intestines. These carotenoids are sometimes referred to as provitamin A. The nutritional requirement for vitamin A can be met by preformed retinol, provitamin A carotenoids, or a mixture, and therefore it is possible to obtain a sufficient intake of vitamin A from carnivorous, herbivorous, or omnivorous diets. 

Being at the end of the food chain, carnivorous marine mammals accumulate in their blubber chlorinated pesticides of anthropic origin, especially DDT, chlordanes, PCBs (polychlorinated biphenyls) and heptachlor, at concentrations that may be toxic to the animals. The lipid and chlorinated pesticide compositions are related to the diet the diet may be deduced, at least in part, from the detailed composition of the blubber. This approach to the biochemistry of marine mammals has produced a great number of publications, the most recent of which include the following Maruya and Lee (1998) Aguilar, Borrell, and Pastor (1999) Kannan et al. (2000) Ross et al. (2000) Watanabe et al. (2000) Kajiwara et al. (2001) Kubota, Kunito, andTanabe (2001) Le Boeuf et al. (2002) Hoekstra et al. (2003) Vetter, Jun, and Althoff (2003) Hansen et al. 

An outstanding feature of the composition of brain phospholipids is its remarkable consistency, irrespective of species or diet. The concentrations of the precursor EFA are extremely low (18 2, n-6,0.1-1.5% and 18 3, n-3, 0.1-1.0%) while arachidonic (20 4, n-6) and docosahexaenoic (22 6, n-3) acids predominate at 8-17% and 13-29% respectively in all species. This contrasts with the liver lipids where there is much greater variation between species. The precursor EFA are present in much greater concentrations than they are in brain and there are major differences in the product EFA. For example, 22 5 is the major n-3 fatty acid in the liver lipids of ruminants and other herbivores while 22 6 predominates in the carnivores and omnivores. Fatty acids of the n-6 family usually predominate in liver phosphoglycerides, even when the overwhelming dietary intake is in favour of the n-3 fatty acids. Thus, zebra and dolphin, both species that have an overwhelming excess of n-3 fatty acids in the diet, attain a preponderance of n-6 acids in the liver phosphoglycerides (Table 5.14). 

---