Assessment of Determinants of Dietary Vitamin D Intake in a Polish National Sample of Male Adolescents

Abstract

Background/objectives: Calcitriol, the active form of vitamin D, has a broad physiological effect, and its deficiency has been identified as a risk factor for many diseases. This study aimed to analyze the dietary intake of vitamin D and the factors determining its intake among Polish post-primary school students. The data obtained were then related to the dietary recommendations for the Polish population.

Methods: The study was conducted on a nationwide sample of 3257 male adolescents (aged 14-20 years) recruited from all macroregions of Poland. Dietary vitamin D intake (dVDi) was assessed using the Vitamin D Estimation Only-Food Frequency Questionnaire (VIDEO-FFQ).

Results: The median dietary intake of vitamin D was 4.36 µg daily. This value was below the recommended intake of 15 µg of vitamin D, according to Polish standards, in almost 80% of the study group. The observed dietary vitamin D intake bellow the recommended level ranged from 35.5% of students attending schools in the North-Western macroregion to 93.7% in the Central macroregion, from 45.4% of students attending schools located in the countryside to 92.7% in big cities, from 85.3% among underweight students to 76.7% of obese students, over 77% in both age groups (14-17 and 18-20 years old), and over 78% in both groups: supplementing and not supplementing vitamin D. Fish and fish products provided the highest vitamin D (38.7%), while cereal products and fats provided the lowest (4.49% and 4.35%, respectively). The highest amounts of vitamin D were provided by salmon, rainbow trout, herring, and eel (fish species containing 7-15 µg of vitamin D in 100 g of product), and halibut, mackerel, brook trout, sole, and tuna (fish species containing 1.05-4 µg of vitamin D in 100 g of product), and these fish were consumed in the largest quantities by male adolescents. Dietary vitamin D intake was notably higher in adolescents from the North-Western macroregion of Poland (median: 50.57 vs. 3.72-5.18 µg daily for other macroregions), those attending schools in the countryside (median: 49.49 vs. 3.97-4.39 µg daily for other locations of the school), those with a normal body weight (median: 4.59 vs. 3.38 µg daily for adolescents with underweight), and those who took vitamin D supplements (median: 4.71 vs. 4.06 µg daily for adolescents not supplemented with vitamin D). However, the results showed that dVDi was not dependent on age.

Conclusions: The study results indicate that low dVDi among Polish male adolescents can be attributed to the limited supply of vitamin D from dietary sources, especially fish and fish products. The necessity for interventions has been identified, including nutritional education on the role of vitamin D and its sources in the diet.

Keywords: Poland; calciferol; dietary sources; fish; male post-primary students.

Figure 1

The sampling and recruitment procedure for the study group.

Figure 2

Percentage of male adolescents with vitamin D dietary intake: 0 µg per day (a), (0, 2.5) µg per day (b), 〈2.5, 10) µg per day (c), 〈10, 15) µg per day (d) and ≥15 µg per day (e).

Figure 3

Dietary vitamin D sources in the subgroups of male adolescents. (T—total, C—Central, E—Eastern, M—Masovian Voivodeship, N—Northern, N-W—North-Western, S—Southern, S-W—South-Western; C-S—countryside, Sc—small city, Mc—medium city, Bc—big city; y—14 to 17 years old, o—18 to 20 years old; Uw—underweight, Nw—normal weight, Ow—overweight, Ob.—obesity; D(−)—not supplementing vitamin D, D(+)—supplementing vitamin D).

Figure 4

Percentage of male adolescents consuming: ≥2 (a), 〈1, 2) (b), and (0, 1) (c) servings or not consuming (d) fish (including salmon and herring) and fish products.