Correlation between vitamin D intake and serum 25 (OH) vitamin D3 levels in women of the St. Benedict Monastery ages 59-89

Purpose: to correlate vitamin D intake, diet plus supplements, with serum vitamin d levels in elderly women in central Minnesota.

Methods: IRB approved the study. Twenty-five women were recruited, ages ranged from 59-89 with an average age of 75.  The study was conducted in January, a time when vitamin D status is expected to be lowest. All subjects ate lunch and dinner meals in a common dining room. Meal observa5tions were conducted for five consecutive days (Tuesday through Saturday).  As subjects came through the meal line, food selections were documented with menu-tracking forms and the trays photographed to accurately assess food choices and portion sizes. Subjects recorded breakfasts and snacks individually. The diets were analyzed using Diet Analysis Plus version 10. The serum 25(OH)D3 levels were measured using an ELISA kit. 

Results: None of the subjects net the 2010 dietary guidelines for vitamin D intake from food sources (<70 years old: 600 IUY/day; ≥ 70 years old: 800 IU/day). The average dietary vitamin DS intake was 175 ± 112 IU/day and ranged from 32 - 464 IU/day. The participants on average only met 22% of the recommended daily value form food sources alone. Vitamin D supplements were used by 25 of the 26 participants. For those who took vitamin D supplements, the dosage ranged from 400-10,000 IU/day with an average of 2240 IU/day. Serum vitamin D values ranged from 30-186 nmol/L (12 ± 74 ng/mL) with an average serum value of 84 ± 34 nmol/L (34 ± 14 ng/dL).  The serum 25(OH)D3 value for the one individual who did not take supplements was in the insufficient range. Among supplement users, two were 25(OH)D3 deficient, 7 were insufficient, and 15 had optimal serum levels.  Vitamin D deficiency is a serum value < 50 nmol/L (20 ng/mL) and insufficiency is between 50-75 nmol/L (20-30 ng/mL).  Optimal serum value of vitamin D is ≥ 75 nmol/L (30 ng/mL).  On average, the vitamin D deficient subjects took 600 ± 283 IU/day of vitamin D supplements, the vitamin D insufficient subjects took 990 ± 737 IU/day, and the participant with optimal vitamin D levels took 2637 ± 2204 IU/day. The serum vitamin D of 42% of participants was either deficient or insufficient.

Conclusions: dietary intake of vitamin D did not correlate with serum levels: however, 25 of 26 participants took supplements. There is a strong correlation between supplemental vitamin d intake and serum 25(OH)D3 levels  (r = 0.79). Approximately 84% of the women taking ≥ 2000 IU/day had optimal serum 25(OH)D3 levels while 50% of those supplement with > 500 but < 2000 IU/day, and only 25% of those supplement with < 500 IU/day had optimal serum 25(OH)D3 levels. Elderly women living in central Minnesota appear to need 2000 IU of supplemental vitamin D daily to achieve optimal serum levels during winter months.

Research Advisor:Amy Olson, PhD, RDN, LD