Vitamin D, also known as the “sunshine vitamin,” has been under the spotlight recently due to its potential role in regulating insulin and blood sugar levels.
In a recent study, researchers explored the association of vitamin D, both in the diet and blood, with insulin resistance among Japanese women.
They studied 406 Japanese women who participated in a health examination.
None of these women were taking hormones or diabetes medications, and they had no history of cancer, heart disease, or stroke.
The team collected data on their medical history and lifestyle habits through questionnaires.
They asked them how much time they usually spend in the sun, as this can impact vitamin D levels. To understand their dietary vitamin D intake, they used a validated food frequency questionnaire.
The team also measured fasting plasma glucose and insulin concentrations in their blood, which allowed us to calculate their insulin resistance scores using the homeostasis model assessment (HOMA-IR).
The team found that women with vitamin D deficiency (defined as blood 25(OH)D levels less than 20 ng/mL) had higher fasting plasma insulin levels and HOMA-IR scores than women with adequate vitamin D levels.
This suggests they had higher insulin resistance.
After adjusting for various factors including age, season, menopausal status, BMI, smoking status, alcohol intake, physical exercise, and intake of fat and calcium, they found a significant inverse association between blood vitamin D levels and both fasting insulin levels and HOMA-IR.
In simpler terms, lower blood vitamin D levels were linked to higher insulin resistance.
Interestingly, they didn’t find any association between dietary vitamin D intake and insulin resistance when we adjusted for the same factors and hours of sun exposure.
The team also observed an inverse association between blood vitamin D levels and HOMA-IR in women with lower BMI, lower fat intake, or higher calcium intake.
However, the interaction terms weren’t statistically significant, suggesting that these factors didn’t significantly modify the association between vitamin D and insulin resistance.
These findings suggest that blood vitamin D levels, but not dietary vitamin D intake, are inversely associated with fasting insulin levels and insulin resistance in non-diabetic Japanese women.
This provides new insights into the potential role of vitamin D in blood sugar regulation and diabetes prevention.
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