Analysis of seven folates in food by LC–MS/MS to improve accuracy of total folate data

Several studies have observed high plasma levels of homocysteine among patients with coronary heart disease (CHD). The only prospective study was based on US physicians, and concluded that homocysteine was associated with subsequent myocardial infarction (MI). However, the association was limited to those above a threshold level of homocysteine. We conducted a nested case-control study among the 21,826 subjects, aged 12-61 years, who were surveyed in the municipality of Tromsø, Norway. Among those free from MI at the screening, 123 later developed CHD. Four controls were selected for each case. Level of homocysteine was higher in cases than in controls (12.7 +/- 4.7 versus 11.3 +/- 3.7 mumol/l (mean +/- SD); P = 0.002). The relative risk for a 4 mumol/l increase in serum homocysteine was 1.41 (95% confidence interval (CI): 1.16-1.71). Adjusting for possible confounders reduced the relative risk to 1.32 (95% CI: 1.05-1.65). There was no threshold level above which serum homocysteine is associated with CHD events. In the general population serum total homocysteine is an independent risk factor for CHD with no threshold level.

Determining folate intake is difficult because existing folate data in food-composition tables are scarce and unreliable. The purposes of this study were first to analyze 125 of the most important foods that contribute to folate intake in the Netherlands and second to estimate the folate intake of a representative sample of the population. We analyzed the folate content of foods by using a newly developed HPLC trienzyme method combined with an affinity chromatography cleanup step. These results were then used to estimate the folate intake of persons aged 1-92 y who participated in the second Dutch National Food Consumption Survey (DNFCS) in 1992 (n = 6218). For 35 important folate-containing foods, the mean relative folate contents measured by HPLC were 66%, 80%, and 77% of values for comparable foods included in the British food-composition table; the Ministry of Agriculture, Fisheries and Food table; and the US Department of Agriculture database, respectively. P values for comparison of relative values with 100% were 0.001, 0.171, and 0.144, respectively. The mean dietary folate intake of the DNFCS participants was 182 +/- 119 microg/d. Intake of supplement users (n = 86) was 344 microg/d, with 147 microg/d from supplements. On the basis of these findings, 42% of men and 54% of women do not meet current Dutch recommendations of 60 microg/d for children and 200 microg/d for adults. Total folate quantities in foods, analyzed by HPLC, are approximately 25% lower than amounts listed in recent food-composition tables estimated by use of the microbiological method. On the basis of these new data, approximately 50% of a representative Dutch population sample does not meet the current recommendations for folate intake.