Association between a new dietary protein quality index and micronutrient intake adequacy: a cross-sectional study in a young adult Spanish Mediterranean cohort

PURPOSE: There is no evidence of a dietary index that measures not only the quantity but also the quality of protein. The aim is to investigate the association between a new dietary protein quality index (PQI) and micronutrient intake adequacy in a Mediterranean cohort. DESIGN: We assessed 17,535 participants’ diet at baseline using a semi-quantitative FFQ. The PQI was calculated according to the ratio of protein (g/d) sources: [fish, seafood, lean meat, pulses, eggs, nuts, low-fat dairy, and whole grains]/[red and ultra-processed meats, whole-fat or semi-skimmed dairy, potatoes and refined grains]. Participants were classified into quintiles of PQI. We evaluated the intakes of Fe, Cr, I, K, Mg, Ca, P, Na, Se, Zn and vitamins A, B1, B2, B3, B6, B12, C, E and folic acid. Micronutrient adequacy was evaluated using DRIs. Logistic regression analysis was used to assess the micronutrient adequacy according to quintiles of PQI. RESULTS: In this cross-sectional analysis, a total of 24.2% and 4.3% participants did not to meet DRIs in ≥ 4 and ≥ 8 micronutrients, respectively. The odds of failing to meet ≥ 4 and ≥ 8 DRI were lower in participants in the highest quintile of protein quality (OR = 0.22; IC 95% = 0.18, 0.26; P-trend < 0.001; and OR = 0.08; IC 95% = 0.05, 0.14; P-trend < 0.001, respectively) as compared to participants in the lowest quintile. CONCLUSION: Higher PQI was found to be strongly associated with better micronutrient intake adequacy in this Mediterranean cohort. The promotion of high-quality protein intake may be helpful for a more adequate intake of micronutrients. The odds of failing to meet certain numbers of DRIs were lower rather than saying lower risk. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00394-022-02991-z.