Bioavailability food matrix effect

The bioavailibility of quercetin-glycosides from onions, containing mainly quercetin-p-glucosides, was superior to that of various quercetin glycosides from apples (containing a mixture of quercetin-(3-galactosides and P-xylosides) and of pure quercetin-3-mtinoside (major species in tea). The possible matrix effect of the foods remains unclear. 

Handelman et al., 1996). Alcohol consumption was also shown to alter serum lycopene levels (Brady et al., 1997). Other factors that influence the bioavailability of lycopene are its release from the food matrix due to processing, presence of dietary lipids, and heat-induced isomerization from the all-trans to cis conformation. They all enhance lycopene absorption into the body. Ingestion of cooked tomato juice in oil medium increased serum lycopene levels threefold whereas consumption of an equal amount of unprocessed juice did not have any effect (Stahl and Sies, 1992). 

Table 12.2. Effect of the food matrix (microstracture) on nutrient bioavailability.

Nutrient Food (matrix) Matrix state (processing effect) Bioavailability Reference... 

An extensive series of studies performed at the FDA Division of Nutrition established a wide range of bioavailabilities for the iron sources used in food enrichment (8-12). However, the rank in Table 11 was based on direct feeding of the iron source to test animals. The impact of food processing or of the food matrix on iron bioavailability is not apparent in these rankings. Large differences in bioavailability between iron sources will become smaller or change completely as a result of some types of processing, while other processes have little effect. 

Iron Profile. The studies reviewed in the section on the effect of processing on iron bioavailability suggest that bioavailability depends upon the iron source, the food matrix, and the nature of the food process. The question remains does the source, matrix or the process have an effect on the chemical form of iron, or iron profile. 

Iron bioavailability is affected by valence state, form, solubility, particle size, and com-plexation which in turn may be affected by the food matrix. Complexation of iron has been found to have either a positive or negative effect on availability, with such compounds as ascorbic acid and fructose increasing availability and oxalates, phytates, phosphates and food fibers perhaps decreasing availability. Availability has also been shown to be directly correlated to acid solubility. We have found that acidity tends to increase ionization as well as favoring the ferrous state which has greater solubility at... 

Before considering the bioavailability of phytochemicals in a food matrix and relating these to biological effects in humans, it is important and necessary to understand that phytochemicals are mostly minor plant constituents whose concentration varies considerably according to, for example, seasonal and agronomic factors, the variety, age, and part of the plant examined. Such variability can lead to serious problems of interpretation of results from epidemiologal studies or human intervention trials if the dose of the phytochemical applied is not determined. 

While effective doses of 1 to 2 mg seem small, the total body pool of /3C can be estimated at 15 to 20 mg, with a total plasma pool of ateut 0.5 to 1 mg. In comparison with these pool sizes, a 2-mg effective dose is relatively large. In addition, the average daily effective dose of jSC from food sources is likely to be less than 1 mg, since matrix effects probably impair bioavailability of /3C to a larger extent than with supplements such as that used by van Vliet et al (1995). The minimum effective dose required to yield a significant TGR fraction response, taking into account the error associated with measurement, has not been determined, but is not likely to be much less than 1 mg. Consequently, use of unlabeled jSC, even coupled with use of the TGR fraction, is probably not well suited to study /3C uptake and metabolism at effective doses typically derived from dietary sources. 

Considering flavonoids, food matrix is a very important issue because it can influence the availability of the compounds to be absorbed in several ways first, the flavonoid must be liberated from the food matrix where it is inserted, and the difficulty of this process is dependent on the type of matrix second, if the food matrix has a more lipophilic environment, it can facilitate flavonoids solubiUzation and absorption. Ethanol seems to exert crucial effects on anthocyanin intestinal bioavailability, favoring its transport across intestinal epithelia. Also, interaction between different compounds may occur and interfere with absorption as well, competition or interactions for specialized transport systems are likely to occur due to the variety of molecules present in GI tract after a meal. Another important concept should be the frequency of the consumption. For anthocyanins, it is known that intestinal epithelial cells chronically exposed to anthocyanins are more prone to their own transport [33]. This is an important finding, justifying dietary recommendations, highlighting chronic consumptions of fruits and vegetables as healthy food habits. 

Some other major issues limiting the elinical trials and dietary recommendations are the variant effects of dose (quantity) and type of tea, specifically green and black. Most studies show some effectiveness with the application of medium to extremely high quantities. However, small-scale studies looking at risk factors and mechanistic substitute endpoints have also provided clues to its effectiveness. The matter is further confused by the variable bioavailability of these compounds, which depends upon human gut absorption and one s food matrix. Thus, to date, it remains unclear how to formulate dietary recommendations regarding the quantity and type of tea to be consumed by the general and diseased populations. 

The bioavailability of lycopene in tomato-based foods vs. that in fresh tomatoes increases even further when lycopene is consumed with oil. In studies by Stahl and Sies (1992, 1996), ingestion of tomato juice cooked in an oil medium resulted in a two- to threefold increase in lycopene serum concentrations 1 day after ingestion. An equivalent consumption of unprocessed tomato juice caused no rise in lycopene plasma concentration. This indicates that thermal pretreatment and an oil medium were beneficial for extracting lycopene into the lipophilic phase. Solubilization of lycopene in a lipophilic matrix is expected to considerably enhance its availability and its bioactivity. This is likely to boost its effectiveness as an antioxidant. However, this higher reactivity also renders lycopene more vulnerable to the detrimental effects of factors such as air, temperature and interactions with other components of the food. 

Milling results in particle size reduction. Milling techniques have long been used for size reduction of pharmaceutical powders to improve body absorption (Bentham et al, 2004). An increased surface area of food materials will increase the rate of water absorption of materials, improve solubility of dry products, and increase accessibility of sites for chemical reactions (e.g., oxidation, digestion, flavor release, catalyst, and enzyme activity). The structure of food is also important as it dictates how, when, and where food nutrients and flavors may be released. The effectiveness of nutrient bioavailability in food is in part related to its size although other factors such as interactions of the component with a matrix also influence how the component is released. 

However, only a fraction of carotenoids absorbed by the human body can effectively contribute to human health, reaches up to 10 % when a natural food is consumed [21]. A number of factors can affect the bioaccessibUity and/or bioavailability, including the species of carotenoids, linkages at molecular level, amount of carotenoid, matrix, effectors, nutrient status, genetics, host-related factors, and interactions among these variables. In carrots, for example, p-carotene is located in the chromoplasts (surrounded by a double bUayer membrane) of the plant cells (surrounded by a cell membrane and a cell wall), where it is often associated with proteins and/or residual membranes. This fact results in several physical barriers that have to be broken to make p-carotene accessible for absorption. 

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