Dietary intervention trials

The reductionist approach of isolating dairy product components including calcium, CLA, and trans-fatty acids in dietary interventions trials often yields inconclusive results. It is therefore highly plausible that dairy products exert maximum health benefits when consumed in their natural form. Because individuals do not generally consume these individual dairy components in isolation, examining the effects of these foods in their whole forms should be encouraged. 

Tang, J.L et al., Systemic review of dietary intervention trials to lower blood total cholesterol in free living subjects, Br. Med. J., 316, 1213, 1998. 

Fattore, E., Bosetti, C., Brighenti, F., Agostoni, C., Fattore, G. (2014). Palm oil and blood lipid-related markers of cardiovascular disease a systematic review and meta-analysis of dietary intervention trials. Am J Clin Nutr, ajcn. 081190. 

Conversion of CLA Isomers in Conjugated Trienes. Plasma samples from adult male volunteers from the TransLinE study (31) as well as human milk samples were analyzed with particular attention to their conjugated fatty acid content The plasma samples were collected from volunteers before their inclusion in the dietary intervention trial. The milk samples were collected 4 and 45 d postpartum. (32). 

Panunzio MF, Pisano A, Telesfor P, and Tomaiuolo P (2003) Diet can increase 25-hydroxyvitamin-D3 plasma levels in the elderly a dietary intervention trial. Nutrition Research 23 1177-1181. 

More recently, large human intervention trials were undertaken with P-carotene alone, or in combination with non-dietary amounts of vitamin E. These trials were undertaken because of promising animal studies that suggested that these antioxidants could offer chemo-preventive action against oxidative stress. The results, which are summarised in Table 11.1, were disappointing. Although the study population in two of the studies (ATBC and CARET)... 

Data concerning gastric cancer are scarce. The prospective Netherlands Cohort Study found no correlation between lutein dietary intake and gastric cancer risk, whereas findings from the Physicians Health Study and the ATBC study reported no effect of P-carotene on gastric cancer incidence. Two case-control studies and three intervention trials (ATBC, CARET, and the Physicians Health Study ) showed no association of P-carotene, lycopene, lutein, zeaxanthin, and P-cryptoxanthin. 

In a 20-week multicenter intervention trial with lutein in healthy human subjects, no changes were noted in hematological or biochemical parameters after continuous daily lutein doses of 15 mg (0.25 mg/kg body weight, assuming a body weight of 60 kg). A relatively large number of human studies have examined correlations between macular degeneration and dietary intake of lutein or zeaxanthin, intakes via dietary supplements, and serum concentrations. 

Dolecek, T.A. 1992. Epidemiological evidence of relationships between dietary polyunsaturated fatty acids and mortality in the Multiple Risk Factor Intervention Trial. Proc. Soc. Exp. Biol. Med. 200, 177-182. 

There have been three primary and eight secondary prevention trials in which dietary change was the only variable. Dietary modification included reduction in total fat, substitution of saturated fat by polyunsaturated oils and reduction in cholesterol intake. These changes resulted in a reduction of saturated fat intake by 27 55% and reductions in plasma cholesterol of up to 18%. However, with the exception of one study, the Lyon Diet Heart Study (de Lorgeril et al., 1994), neither total or CHD mortality was lowered significantly by the dietary interventions (Ravnskov, 1998 Parodi, 2004). In the successful Lyon Diet Heart Study, a Mediterranean-type diet was compared with the usual post-infarct prudent diet. Throughout this trial, plasma cholesterol levels were similar in both the treatment and control groups. 

At tbe time that the U. K. and European Union reference intakes of folate shown in Table 10.3 were being discussed, the results of intervention trials for the prevention of neural tube defects (Section 10.9.4) were only just becoming available. At that time, there was no information concerning the effects of folate status onhyperhomocysteinemia (Section 10.3.4.2). TheU.S./Canadianreport (Institute of Medicine, 1998) notes specifically that protective effects with respect to neural tube defects were not considered relevant to the determination of the Dietary Reference Intake of folate, and there was insufficient evidence to associate higher intakes of folate (and lower plasma concentrations of homocysteine) with reduced risk of cardiovascular disease. 

Coenzyme QIO is a powerful antioxidant naturally occurring in the mitochondria of myocardium, and it is an electron carrier in the mitochondrial synthesis of ATP. Patients with heart failure have lower myocardial levels of coenzyme QIO, but supplementation has been demonstrated to have variable benefits in randomized controlled trials. One meta-analysis on the use in congestive heart failure showed improvements in stroke volume, ejection fraction, cardiac output, cardiac index, and end diastolic volume index. " Another antioxidant associated with beneficial effects in cardiac patients is lycopene, a natural constituent of tomatoes. Lycopene is the major carotenoid found in human serum, and epidemiological studies have indicated an effect of dietary supplementation in reducing heart disease. Few dietary interventions have been reported one study showed a mild but significant hypocholesterolemic effect, and another showed a significant reduction in LDL oxidation. " Animal studies show an antiatherogenic effect of DHEA, and a review of the clinical trials and studies on DHEA in males with coronary heart disease reported a favorable or neutral effect. Plasma levels of DHEA are decreased in patients with chronic heart failure in proportion to its severity. ... 

Mansel RE, Harrison B J, Melhuish J, et al. A randomized trial of dietary intervention with essential fatty acids in patients with categorized cysts. Ann NY Acad Sci 1990 586 288-294. 

Hebert, J.R., Barone, J., Reddy, M.M., and Backlund, J.Y. 1990. Natural killer cell activity in a longitudinal dietary fat intervention trial. Clin. Immunol. Immunopathol. 54, 103-116. 

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