By Dr. Mercola
Vitamin D is a fat-soluble, hormone-like vitamin, and many therefore believe that if you're obese you need more of it because body fat acts as a "sink" by collecting it.
However, muscle and fat may well act the same when it comes to storing vitamin D for future use.
New research using mathematical models has shown that a heavily muscled man and an obese man who weigh exactly the same would need the same amount of vitamin D.
The key to determining how much vitamin D is appropriate for an individual appears to be body weight rather than body fat.
This was not previously widely appreciated by most experts.
Your Body Weight May Dictate How Much Vitamin D You Need
If you're overweight or obese, you're therefore likely going to need more vitamin D than a slimmer person -- and the same holds true for people with higher body weights due to muscle mass.
Your best source for this vitamin is daily exposure to the sun, without sunblock on your skin, until your skin turns the lightest shade of pink.
While this isn't always possible due to the change of the seasons and your geographic location (and your skin color), this is the ideal to aim for as it will optimize your vitamin D levels naturally.
To use the sun to maximize your vitamin D production and minimize your risk of skin damage, the middle of the day (roughly between 10:00 a.m. and 2:00 p.m.) is the best and safest time. During this UVB-intense period you will need the shortest sun exposure time to produce the most vitamin D.
If sun exposure is not an option, using a safe tanning bed (one with electronic ballasts rather than magnetic ballasts, to avoid unnecessary exposure to EMF fields) is the next best option. Safe tanning beds have far less of the dangerous UVA than sunlight, while unsafe ones have more UVA than sunlight. If neither of these are feasible options, then you should take an oral vitamin D3 supplement – and this is where the dosage becomes of crucial importance.
What's the Correct Dose of Vitamin D?
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Based on research published by GrassrootsHealth from the D*Action study, the average adult needs to take 8,000 IU's of vitamin D per day in order to elevate his or her levels above 40 ng/ml -- the bare minimum requirement necessary for disease prevention. Ideally, you'll want your levels to be between 50-70 ng/ml. As Carole Baggerly, director and founder of GrassrootsHealth, noted:
"We just published our very first paper. We have about 10 people in this study now that are taking 50,000 IU a day and they're not reaching a potential toxicity level of 200 ng/ml. It should be noted, however, that this is not a recommended intake level. The study reported data on about over 3,500 people. … One very significant thing shown by this research was that even with taking the supplement, the curve for the increase in the vitamin D level is not linear. It is curvilinear and it flattens, which is why it's even hard to get toxic with a supplement."
This means that even if you do not regularly monitor your vitamin D levels, your risk of overdosing is going to be fairly slim -- even if you take as much as 8,000 IU's a day. (As an aside, there is evidence that the safety of vitamin D is dependent on vitamin K, and that vitamin D toxicity (although very rare with the D3 form) is actually aggravated by vitamin K2 deficiency. So if you take oral vitamin D, ideally you should take vitamin K2 as well or use organic fermented foods that are high in vitamin K2, as you need about 150 mcg per day.)
That said, 8,000 IU is only a ballpark estimate of what most people likely need -- it is simply impossible to make a general recommendation that will cover everyone's needs. For instance, the lighter your skin, the more vitamin D you will produce from sun exposure, and the closer you live to the equator, the more vitamin D the sun on your skin will produce. Similarly, the more you weigh, the more vitamin D you need.
So it is an inexact science trying to figure out how much vitamin D your body is able to produce naturally and balancing that with how much you need in supplement form. You really need to be your own vitamin D level sleuth, and I strongly suggest you do the necessary work, because this is truly one of the most powerful vitamins available for your health, and one that the majority of people currently are deficient in.
The only way to truly optimize your own vitamin D levels is to work with your doctor, take the 25 OH D blood test and then get sun exposure and/or supplement with a dose somewhere in the range of 5,000-40,000 IU, retesting your blood levels after a few months of supplementation.
For children below the age of 5 I recommend 35 IU per pound per day and for pregnant women I recommend anywhere from 5,000 to 10,000 IU per day. But again, there really is no "right" amount unless you take the time to have your blood levels checked, as the amount it takes to keep your levels within the below optimal range is the one that is right for you.
Is There a Link Between Low Vitamin D Levels and Obesity?
There is a connection, yes. Vitamin D levels tend to be low in obese individuals as well as in those who are physically inactive,i and one researcher even went so far as to state that vitamin D deficiency is the cause of common obesity and metabolic syndrome:ii
"There is evidence for a central control mechanism which maintains body-weight to a set-point by the regulation of energy intake and energy expenditure through homeostatic pathways. It is suggested … that common obesity occurs when the set-point is raised and that accumulation of fat mass functions to increase body size. Larger body size confers a survival advantage in the cold ambient temperatures and food scarcity of the winter climate by reducing surface area to volume ratio and by providing an energy store in the form of fat mass.
In addition, it is suggested that the phenotypic metabolic and physiological changes observed as the metabolic syndrome, including hypertension and insulin resistance, could result from a winter metabolism which increases thermogenic capacity. Common obesity and the metabolic syndrome may therefore result from an anomalous adaptive winter response. The stimulus for the winter response is proposed to be a fall in vitamin D.
… It is here proposed that a fall in vitamin D in the form of circulating calcidiol is the stimulus for the winter response, which consists of an accumulation of fat mass (obesity) and the induction of a winter metabolism (the metabolic syndrome) … It may be possible to reverse the increasing prevalence of obesity by improving vitamin D status."
Several studies have also confirmed a link between vitamin D deficiency, abdominal obesity and visceral fat, while research even shows that increasing your vitamin D levels may improve weight loss if you're following a reduced-calorie diet.iii Interestingly, new research also found that weight loss among overweight and obese women is associated with increased vitamin D levels,iv so there appear to be strong links between vitamin D status and your weight, through various mechanisms working on multiple levels.
Why is Vitamin D So Important, Anyway?
We've addressed ways to optimize your vitamin D levels … but you may be wondering why this is so important, especially if you're still under the impression that vitamin D is mostly a nutrient for your bones. Many people think that vitamin D is really a vitamin, but in reality, the active form of vitamin D is one of the most potent hormones in your body, and regulates more genes and bodily functions than any other hormone yet discovered. Vitamin D is produced as a pro-hormone in your skin after sunlight exposure, and is then converted to the potent hormone form.
Without adequate levels of this hormone, you could die, and indeed, many do die from vitamin D deficiency-related causes. Vitamin D could rightly be described as a "miracle nutrient" for your immune system, as it enables your body to produce well over 200 antimicrobial peptides, which are indispensable in fighting off a wide range of infections. Furthermore, when your organs convert the vitamin D in your bloodstream into calcitriol, which is the hormonal or activated version of vitamin D, they can then use it to repair cellular damage, including damage associated with cancer cells and tumors.
Theories linking vitamin D to certain cancers have been tested and confirmed in more than 200 epidemiological studies, and understanding of its physiological basis stems from more than 2,500 laboratory studies, according to epidemiologist Cedric Garland, DrPH, professor of family and preventive medicine at the UC San Diego School of Medicine. Other research has linked vitamin D to a number of chronic and acute health conditions including heart disease, infertility, influenza, colds, respiratory tract infections, depression and more.