Vitamin D is a vitamin that behaves like a hormone. In fact, cells throughout your body have receptors for this important vitamin/hormone. Why is the sunshine vitamin so important? Preliminary research shows a link between a low vitamin D level and inflammation linked to some autoimmune diseases. Plus, it may help to keep other age-related health problems in check including hypertension, diabetes and certain types of cancer. It’s also vital for healthy bones. In addition, there also appears to be a link between obesity and low levels of vitamin D. Does vitamin D play a role in regulating body weight?
Vitamin D Level and Obesity: What’s the Link?
Vitamin D deficiency is more common in people who are overweight and obese. What’s less clear is whether vitamin D deficiency directly contributes to weight gain and obesity or whether people who are obese simply have lower levels of vitamin D. Sub-optimal vitamin D levels are common, especially in older people and people who live in areas without direct sunlight during certain times of the year. One reason obese people have lower vitamin D levels is they don’t absorb vitamin D as well from through their skin or digestive tract. Plus, vitamin D that is absorbed is stored in fat tissue where it can’t be as readily used. The question is whether correcting a low vitamin D level through diet or supplements helps overweight and obese people lose weight.
There is some evidence that vitamin D helps with weight control even in people who are normal weight. A large study involving over 36,000 women showed that those who supplemented with vitamin D3 (400 I.U.) and calcium (1,000 milligrams) daily for three years were less likely to gain weight. With menopausal weight gain so common, it’s a good idea to make sure you’re not deficient in vitamin D as you approach the menopausal years.
One way vitamin D may help with weight control is by reducing the tendency of your fat cells to store fat. When vitamin D is low, levels of a hormone called parathyroid hormone goes up. Parathyroid hormone puts a brake on the breakdown of fat stores, leading to an increase in body fat. Low calcium levels also trigger a rise in parathyroid hormone. This may explain why some studies show a diet rich in calcium promotes weight loss. Vitamin D is also important for calcium absorption from the intestinal tract.
Vitamin D and Leptin
Vitamin D may help with weight control by regulating appetite too. When you’re deficient in vitamin D, fat cells produce less leptin. Why is this important? Leptin sends satiety signals to the brain to encourage you to stop eating. If your vitamin D levels are low, you may not get the same degree of leptin feedback and end up eating more. There’s also a link between vitamin D deficiency and insulin resistance. When your cells are resistant to insulin, there’s more insulin floating around, making it easier for fat cells to store fat.
Low Vitamin D Levels and Belly Fat
If your vitamin D level is low, you may also have a more difficult time controlling belly fat. A study published in the Journal of Clinical Nutrition showed that overweight and obese adults who supplemented with vitamin D lost more visceral abdominal fat than those that took a placebo. Visceral belly fat is linked with a number of health problems like heart disease and type 2 diabetes.
Are You Getting Enough Vitamin D?
With age, it becomes more difficult for your skin to make vitamin D when it’s exposed to sunlight, so even if you’re exposing your skin to sunlight, you may not be getting the same benefits you did when you were younger. People with darker skin pigment also require more sunlight exposure to produce vitamin D.
What about diet? Unfortunately, there aren’t a lot of foods that are naturally rich in vitamin D. Fatty fish is one of the best natural sources. A serving of wild salmon can have as much as 900 I.U. of vitamin D while farmed salmon has only about 25% of that amount. Dairy foods are also a decent source of vitamin D. Plus, they contain calcium that may have a synergistic effect on controlling weight and belly fat. Most milk is fortified with vitamin D, although the amount is modest. You can also find orange juice and yogurt that’s vitamin D fortified.
The best way to make sure you’re getting enough vitamin D is to ask your doctor to check a vitamin D level through a blood test. If your levels are low, you may need a vitamin D supplement to boost your D level. Even with a supplement, it can take months to get your level up.
The Bottom Line?
There’s growing evidence that vitamin D is important for weight control – and for your overall health. You may have a low vitamin D level and not know it, so ask your doctor to check a vitamin D level when you go to your next physical. Otherwise, make sure you’re exposing your skin to sunlight for at least fifteen minutes several times a week and add more fatty fish to your diet. You’ll benefit from the omega-3s in fatty fish as well.
References:
Nutr J. 2013 Jun 25;12(1):89.
Am J Clin Nutr. 2000 Sep;72(3):690-3.
Arch Intern Med. 2007 May 14;167(9):893-902.
Med Hypotheses. 2003 Nov-Dec;61(5-6):535-42.
The American Journal of Clinical Nutrition. 2012. 95(1).
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