There is no clear evidence of a benefit to suggest vitamin D supplementation for weight loss.

For years, medical and nutrition experts have recommended Vitamin D to cure just about whatever ails you. I have seen it recommended for pain, weight loss, and bone health. Our side of bone health, there is limited research to suggest taking extra Vitamin D for just about anything else. That being said, there might be some benefit to taking extra if you have had a gastric bypass.

Vitamin D deficiency is common in obese individuals and during weight loss and especially those with a gastric bypass or other weight loss surgery. This is likely due to a decrease in food intake and absorption. For this reason, the recommended vitamin D doses in this specific population might be higher than for other healthy adults. A 2019 study looked at this very question and whether vitamin D supplementation might assist with weight loss​[1]​.

This study was conducted through a systematic search for relevant randomized controlled trials of oral vitamin D supplementation for at least 3 months in obese individuals without weight loss, and those on medical weight loss program, and following weight loss surgery. The researchers identified 26 relevant studies to review.

The researchers found that Vitamin D supplementation resulted in some positive results. One of three studies that looked at bone density found that supplementation increased bone density. None of the 26 studies showed any effect on weight loss or any protective effect against weight gain. The results for a positive effect on glycemic control and vascular protection were mixed.

The bottom line: Vitamin D does not appear to help with weight loss maintenance or loss. Vitamin D may assist with maintaining bone density but most can acquire this without supplementation. I recommend drinking milk. There is no clear evidence for a beneficial effect of vitamin D supplementation on cardio-metabolic parameters in obese individuals. More research is needed.