Vitamin D is a fat-soluble hormone with important roles including promoting an optimally functioning immune system, allowing calcium to be absorbed into your body and plays a role in promoting brain function and health. A new study adds another important reason to make sure that your body is receiving enough vitamin D as it may help to increase your insulin sensitivity.
Insulin is a hormone which is produced in your pancreas. Insulin is needed for your body to take the sugar from your blood and into your cells to use as energy or stored for later use as glycogen. Insulin resistance is when your body does not respond normally to the level of insulin excreted by your pancreas. The sugar is not taken up by the cells of your body remains in your blood. Over time this level of insulin resistance can worsen and lead to conditions such as diabetes. If your insulin sensitivity improves the amount of insulin needed for your body to take up glucose from the blood into your cells reduces, in other words this system is working more efficiently.
PCOS stands for polycystic ovary syndrome which is when the eggs in your ovaries do not become mature enough for ovulation. It can Include amenorrhea which is too infrequent or more than 35 days apart between your period or oligomenorrhea which means too frequent periods which are less than 21 days apart. It is a syndrome which can cause acne, hair loss or excess growth due to high androgens. Finally, the syndrome causes polycystic ovary or cystic appearance on your ovary. Insulin resistance is commonly seen with women who have PCOS.
A randomized, placebo-controlled, interventional, double-blind study of 50 women with PCOS investigated the potential link between vitamin D and insulin sensitivity. 25 women were supplemented with 60000 international units (IU) of vitamin D weekly for twelve weeks. The second group of 25 women revied a placebo supplement. Both groups of women were assessed before and after the twelve weeks.
It was found that 68% of the women were vitamin D deficient, and 29%t were severely deficient in vitamin D. After the twelve-weeks the women receiving the vitamin D supplementation showed a decrease in insulin resistance and an increase in insulin sensitivity. There was a decrease in the amount of insulin and sugar present in the blood during periods of not eating or fasting insulin and fasting blood sugar levels.
This study shows the potential link between vitamin D in maintaining an glucose homeostasis, the balance between insulin and glucose in your body. While this study used supplementation the first port of call to achieve your recommended vitamin D requirements should be from the sun and from foods. Always talk to your doctor before you consider taking any supplement.
The adequate intake (AI) for Australia and New Zealand is 0-50 years 5 µg/d, 51-70 years 10 µg/d, >70 years 15 µg/d. There is no RDI or recommended daily intake yet as there is not enough research to determine this. Note 1 µg is equal to 40IU.
Food sources of vitamin D include:
Seafood
- Sardines, canned, 2 sardines 1.2 µg
2. Tuna, canned, 85g 1.0 µg
Trout (rainbow), farmed, cooked, 85g 16.2 µg
3. Salmon (sockeye), cooked, 85g 14.2 µg
Fortified food products from cereal, breads, spreads like margarines and butter, and plant-based drinks like soy.
Cod liver oil 1 teaspoon 34 µg
Dairy
- Milk, 2% fat, Vit D fortified 1 cup 2.9 µg
2. Cheddar cheese, 28g 0.3 µg
Liver, beef, 85g 1.0 µg
Egg yolk. One large egg yolk 3.8 μg
Mushrooms exposed to UV light: This provides vitamin D in the form of vitamin D2. Mushrooms, exposed to UV light, ½ cup 9.2 µg
Take home message: Ensure you are achieving your needed vitamin D. It is a fat-soluble vitamin which plays many important roles in your body, one of which may include increasing your insulin sensitivity.
References:
- Understanding Insulin Resistance. American Diabetes Association. https://www.diabetes.org/healthy-living/medication-treatments/insulin-resistance
- Gupta, T., Rawat, M., Gupta, N. et al. Study of Effect of Vitamin D Supplementation on the Clinical, Hormonal and Metabolic Profile of the PCOS Women. J Obstet Gynecol India 67, 349–355 (2017). https://doi.org/10.1007/s13224-017-1008-1
- U.S. Department of Agriculture, Agricultural Research Service. Food Data Central 2019
