Study points to nutrient deficiency in clinical severe obesity
Clinically severe obese individuals may be prone to nutritional deficiencies, with a large number having suboptimal vitamin D levels, according to a study from Singapore. The deficiencies may also differ by ethnicity.
Participants of this prospective, observational study were 577 individuals with clinically severe obesity scheduled to undergo metabolic-bariatric surgery (primary sleeve gastrectomy or gastric bypass; mean age 40.6 years, 61.2 percent female, 40.6 percent Chinese, mean BMI 42.4 kg/m2) between September 2008 and November 2017.
Vitamin D deficiency was the most common nutritional deficiency observed, with 92.9 percent of the participants having suboptimal levels. Of these, 25.6 percent had vitamin D insufficiency (25(OH)D <30 mcg/L), 57.5 percent had vitamin D deficiency (25(OH)D <20 mcg/L), and 9.8 percent had severe vitamin D deficiency (25(OH)D <10 mcg/L). [Obes Surg 2018;doi:10.1007/s11695-018-3494-3]
Individuals with higher BMI appeared to have lower vitamin D levels, with significantly higher 25(OH)D levels among those in the lowest BMI quartile compared with those in the highest BMI quartile (19.8 vs 16.3 mcg/L; p<0.001 in those with BMI <37.2 vs >46.6 kg/m2).
About 35 percent of patients had secondary hyperparathyroidism, indicated by elevated intact parathyroid hormone levels, while 11.4 percent had elevated serum alkaline phosphatase levels.
“High prevalence of vitamin D deficiency associated with secondary hyperparathyroidism was observed in our multi-ethnic Asian cohort presenting for metabolic-bariatric surgery,” said the researchers.
“Almost all patients had vitamin D insufficiency, more than two-thirds had vitamin D deficiency, and one in ten had severe vitamin D deficiency, with parathyroid hormone elevation in 34.7 percent. This finding has important implications given that the detrimental effect on bone is compounded after bariatric surgery,” they said, highlighting the possible role of vitamin D supplementation pre-surgery as well as the need for pre-surgery measurements of 25(OH)D levels to guide dosing, duration, and response to supplementation.
Thirty-one and 9.5 percent of the participants had folate and vitamin B12 deficiency, respectively. Low serum ferritin levels were detected in 29.3 percent of the participants, while 32.7 percent had low iron levels and 27.9 percent had elevated total iron binding capacity.
Nutritional deficiencies also appeared to differ significantly according to ethnicity. With regard to 25(OH)D levels, participants of Chinese ethnicity had higher levels compared with Malay (mean, 20.4 vs 17.0 mcg/L; p=0.001) or Indian participants (mean, 16.7 mcg/L; p=0.002), with higher rates of vitamin D deficiency and severe vitamin D deficiency also more common among Malay and Indian participants compared with Chinese participants (p<0.001 and p=0.007, respectively).
Ferritin levels were also higher in Chinese compared with Malay or Indian participants (mean, 151.5, 97.5, and 67.7 mcg/L, respectively; p<0.001 vs Chinese participants), while iron levels were higher in Chinese compared with Malay participants (mean, 15.2 vs 12.6 μmol/L; p<0.012). Total iron binding capacity was higher in Indian compared with Chinese (mean, 71 vs 66 μmol/L; p=0.001) or Malay participants (mean, 67 μmol/L; p=0.005), haemoglobin levels were higher in Chinese compared with Indian women (mean, 13.4 vs 12.7 g/dL; p<0.001), and albumin levels higher in Chinese compared with Malay (mean, 40.6 vs 38.8 g/dL; p<0.001) or Indian participants (mean, 38.9 g/dL; p=0.002).
“Although the three different ethnic groups live within the same environment, they are culturally diverse, with different traditional diets,” said the researchers, acknowledging that they were unable to assess the impact of diet or supplementation on the nutritional deficiencies due to lack of data.
The researchers also pointed out that the findings are associative and as such, further research is necessary to identify causes of the nutritional deficiencies.
“Our data also suggest that the nutritional guidelines concerning metabolic-bariatric surgery may need to be adapted depending on the ethnic group,” they said.