A semi-quantitative FFQ, previously validated with 136 food records, was used to evaluate dietary intake at both study inclusion and at 10-year of follow-up [25 (link),26 (link),27 (link)]. For each food item, 9 options of intake were provided in the FFQ (>6 times/day; 4–6 times/day; 2–3 times/day; once/day; 5–6 times/week; 2–4 times/week; once/week; 1–3 times/month and never or almost never). To calculate the daily intake of nutrients and energy, the standard servings were multiplied by the frequency of consumption of each food and by the nutritional content or kilocalories of energy specified in Spanish food composition tables [28 ,29 ]. Other eating habits such as snacking between meals or following a special diet were also gathered at baseline. Compliance with the Mediterranean diet was measured with the score (0–9) of Trichopoulou et al. [30 (link)].
The Phenol-Explorer database version 3.6 (www.phenol-explorer.eu (accessed on 15 December 2022), whose methodology has been published elsewhere, was used to calculate the PC content of each food [31 (link),32 (link)]. The most common extraction method used for estimating PC intake was high-performance liquid chromatography (HPLC), which simultaneously quantifies phenolic acid esters and phenol glycosides together with aglycones and free phenolic acids, and normal-phase HPLC to estimate the proanthocyanidins content. Data from HPLC after hydrolysis method were used, if available, to calculate the aglycone in phenolic acids and lignans in some foods such as olives, beans and grains, since this analytical method uses hydrolysis to release certain compounds which cannot be solubilized without hydrolysis. Foods with only traces of PC were excluded. A weighted average was calculated according to the average dietary consumption of the Spanish adult population when the FFQ items contained more than one food [33 ], and for processed foods and recipes PC content was calculated according to their ingredients. Finally, the PC intake from each food was calculated by multiplying the content of each PC by the daily consumption of each food. The total PC intake (milligrams per day) was determined as the sum of all PC of each food item reported in the FFQ, and was also calculated by class intake. Additionally, we calculated the contribution of each specific food or food group to the total PC intake and expressed it as percentage.
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