Drink your way thin

The two-year study, called DIRECT (Dietary Intervention Randomised Controlled Trial), involved 322 Israeli people who were overweight, or had type 2 diabetes or coronary heart disease. They were asked to follow a low-fat, Mediterranean, or low-carbohydrate diet, and to fill out food frequency questionnaires and give blood samples at a few points throughout the study.

At the beginning of the study, blood levels of vitamin D were inversely associated with BMI, meaning the higher the vitamin D levels, the less the person weighed.

Those people who got the most dairy calcium (an average 583 mg per day, the amount in about 2 portions of milk), and those with higher vitamin D levels at six months, lost significantly more weight (about 12 pounds) after two years than people who got less of these nutrients.

The study’s authors commented that while they’re not sure how calcium and vitamin D work to help with weight loss, it’s possible that the effects are due to hormonal influences. Dairy products can inhibit an enzyme that may limit fat cell growth, and they could also increase the amount of fat lost in the stool. Higher vitamin D concentrations might also promote metabolic pathways that favour weight loss or lean body mass.

What if I don’t tolerate dairy?

Since both vitamin D and dairy calcium were associated with weight loss in this study, those who are dairy-sensitive can focus on improving vitamin D status by eating foods rich in D—like egg yolks, fatty fish, and cod liver oil. There are many liquid fish oils on the market cleverly disguised as orange and other-flavoured treats. Some cod liver oil supplements contain as much as 400 IU of vitamin D in a single teaspoon. Consult with your doctor to decide on the amount of vitamin D that’s right for you, and perhaps get your levels tested if you do not each much dairy or live in a northern latitude that does not get much sun.

(Am J Clin Nutr 2010;doi:10.3945/ajcn.2010.29355)