Habitual intake

Vitamin C occurs as L-ascorbic acid and dihydroascorbic acid in fruits, vegetables and potatoes, as well as in processed foods to which it has been added as an antioxidant. The only wholly undisputed function of vitamin C is the prevention of scurvy. Although this is the physiological rationale for the currently recommended intake levels, there is growing evidence that vitamin C may provide additional protective effects against other diseases including cancer, and the recommended dietary allowance (RDA) may be increased in the near future. Scurvy develops in adults whose habitual intake of vitamin C falls below 1 mg/d, and under experimental conditions 10 mg/d is sufficient to prevent or alleviate symptoms (Bartley et al., 1953). The RDA is 60 mg per day in the USA, but plasma levels of ascorbate do not achieve saturation until daily intakes reach around 100 mg (Bates et al., 1979). Most of the ascorbate in human diets is derived from natural sources, and consumers who eat five portions, or about 400-500 g, of fruits and vegetables per day could obtain as much as 200 mg of ascorbate. 

The problem of bone mineral loss, which accompanies aging of both men and women, has recently received much attention of the scientific community because the proportion of the elderly in the population is increasing especially in Western Europe and North America (J, 2). Among the various factors which affect the integrity of the skeleton are habitual intakes of mineral nutrients such as calcium, phosphorus and fluoride. Here we report the results of our investigations on the interactions between these minerals in relation to bone and soft tissues. 

Urinary excretion of quercetin increased significantly with dose and time after the consumption of fruit juice (blackcurrant and apple juice in a 1 1 mixture) in humans [75]. Ranges from 0.29-0.47% of ingested quercetin were found in the urine. The presence of quercetin in urine shows that it was absorbed by the gut, but the urinary content does not necessarily reflect absolute absorptive efficiency because absorbed quercetin may be metabolized (conjugated), stored and excreted through other routes such as the biliary tract. However, since quercetin is present in a variety of fruit and vegetables, plasma concentrations or urinary excretion of quercetin may potentially be useful as biomarkers of habitual intake of these foods. 

Consequently, a more objective way to measure the habitual intake of milk fat would be the fatty acid composition of adipose tissue. However, this is not routinely performed in larger cohort studies, due to cost and that the procedure is invasive and less tolerated by study participants. Analysis of plasma fatty acid composition is thus a more feasible option for examination to determine dairy intake in the study population. While some groups have separated plasma into its constituent phospholipids and cholesterol esters to analyze serum 15 0 and 17 0 as markers of dairy intake (Smedman et al., 1999), Baylin et al. (2005) found that plasma that was not separated into its constituent cholesteryl ester, phospholipids, and triacylglycerols was still able to reflect habitual dairy intakes comparably to adipose tissue. Thus, whole plasma is an acceptable alternative to fractionated plasma in the absence of adipose tissue for analysis to reflect habitual dairy intakes and may be a cost effective option for consideration when conducting future intervention studies to assess the affect of dairy products on health outcomes. 

Table 2.5 Prudent Upper Levels of Habitual Intake (jjug of preformed vitamin A/day)...

Prudent upper levels of habitual intake of retinol are shown in Table 2.5. 

Vitamin E seems to have very low toxicity, and habitual intake of supplements of 200 to 600 mg per day (compared with an average dietary intake of 8 to 12 mg) seems to be without untoward effect there are no consistent reports of adverse effects up to 3,200 mg per day, suggesting that an acceptable daily intake is in the very wide range between 0.15 to 2 mg per kg of body weight the European Health Food Manufacturers Association suggests an upper limit of 800 mg per day from supplements (Shrimpton, 1997). 

On the basis of depletion/repletion studies, the minimum adult requirement for riboflavin is 0.5 to 0.8 mg per day. In population studies, values of the EGR activation coefficient <1.3 are seen in subjects whose habitual intake of riboflavin is 1.2 to 1.5 mg per day. At intakes between 1.1 to 1.6 mg per day urinary excretion rises sharply, suggesting that tissue reserves are saturated. On the basis of such studies, reference intakes (see Table 7.6) are in the range of 1.2 to 1.6 mg per day (Bates, 1987a, 1987b). 

Studies on the tumor-inducing effects of heavy use of analgesics, especially those that contain phenacetin, have given contrasting results (SEDA-21, 100) (56,57). Two case-control studies have been published on the role of habitual intake of analgesics on the occurrence of urothelial cancer and renal cell carcinoma. 

Pommer W, Bronder E, Klimpel A, Helmert U, Greiser E, Molzahn M. Urothelial cancer at different tumour sites role of smoking and habitual intake of analgesics and laxatives. Results of the Berlin Urothelial Cancer Study. Nephrol Dial Transplant 1999 14(12) 2892-7. 

Matthew, J.A., Fellows, I.W., Prior, A., Kennedy, H.J., Bobbin, R., and Johnson, I.T., Habitual intake of fruits and vegetables amongst patients at increased risk of colorectal neoplasia. Cancer Lett., 114,255-258,1997. 

Three distinct facets of product use are commonly measured in food choice research purchase intent, acute intake, and habitual intake. The first construct, purchase intent. 

Studies on habitual intake of alcohol and vegetables have demonstrated relationships between sensation and intake that are mediated via liking (e.g. References [85,105]), which potentially explain studies that directly link taste gene variation to differential intake without measuring the intermediary variables. " " Other studies find relationships between food preferences and diet-related health outcomes, even in the absence of observed relationships with intake. For example, liking for spicy food is strongly correlated with habitual spicy food intake, and liking for spicy food associates with favorable blood pressure profiles and reduced adiposity. ... 

Table 1 1.6 Recommended upper limits of habitual intakes ofpreformed retinol...

A more generous estimate of requirements, and the basis of reference intakes, is the intake at which there is normalization of the activity of the red cell enzyme glutathione reductase, a flavoprotein whose activity is especially sensitive to riboflavin nutritional status. Normal values of the activation coefficient (section 11.7.4.1) are seen in subjects whose habitual intake of riboflavin is between 1.2 and 1.5 mg/day. 

An intake of 40 mg/day is more than adequate to maintain a total body content of 900 mg of vitamin C - the same as the British RNI. At a higher level of habitual intake, 60 mg/day is adequate to maintain a total body content of 1500 mg (the 1989 US RDA). Making allowances for changes in the rate of metabolism with different levels of intake, and allowing for incomplete absorption of the vitamin gives the Netherlands RDA of 80 mg/day. 

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