We discussed vitamin D in a past post which I recommend you review. In this post I'm joined by my wife, pediatrician Shally Sinha, to focus on vitamin D deficiency in children. However, we are also going to provide some very important additional information and updates that are applicable to adults as well.
There's an epidemic of vitamin D deficiency in children around the world and certain ethnic groups are particularly at risk due to the lifestyle factors discussed in my prior post and which we'll review here, with a focus on kids.
Before we discuss these risk factors, it's important to understand that vitamin D's metabolic and physiological functions makes it much more than just a vitamin.
Vitamin D is actually a hormone, like your thyroid or adrenal hormones, since it controls multiple key physiological and metabolic processes that affect the process of aging, growth, and inflammation which means a deficiency may be associated with conditions like heart disease, cancer, and autoimmune disorders to name a few.
Why Vitamin D is Key in Children at Every Stage
The effect of vitamin D deficiency on children starts in the womb. Vitamin D deficiency during pregnancy has direct effects on fetal growth and development, and may be linked to an increased risk of health conditions during childhood (asthma, allergies, etc.) and adulthood (multiple sclerosis, type 1 diabetes, inflammatory bowel disease, etc.) since vitamin D plays such a key role in proper immune system function.
In fact, if you are an adult who is suffering with asthma, allergies or an autoimmune disorder and no obvious cause could be found, a possibility is vitamin D deficiency in your mother during pregnancy, especially if you were not adequately supplemented after birth.
Poor skeletal growth in infants and children may also be caused by vitamin D deficiency which started during pregnancy. Recall vitamin D's more commonly known role, which is to allow your body to absorb calcium from your digestive tract, which is then deposited into your bones. Vitamin D deficient mothers are not able to supply adequate vitamin D to the fetus, which means fetal bone growth is impaired.
Risk Factors for Vitamin D Deficiency in Children (and Adults)
Before we review the risk factors for vitamin D deficiency in kids and adults (with some kid-specific advice), I want to provide a quick science lesson on Vitamin D.
UVB (ultraviolet B) rays from the sun first penetrate your skin and convert 7-dehydrocholesterol (7-DHC) into a vitamin D precursor (pre-vitamin D3).
Why did I underline and boldface “cholesterol” in this chemical name? To remind you that this is one of the many essential roles cholesterol plays in the body and how healthy dietary sources of cholesterol have been wrongfully vilified for years. Sorry, but I had to vent for a moment!
The pre-vitamin D3 from your skin then undergoes a 2-step activation process, first in your liver and then in your kidneys, to form the biologically active form of vitamin D known as 1,25-dihydroxyvitmain D3.
Sun-driven vitamin D production is the most effective way for your body to get sufficient vitamin D doses. In contrast, your diet only provides 10 percent of your vitamin D needs at best. The typical nutrient-deficient diets we see in clinic provide far less vitamin D, which leads us to a major point:
You cannot fix vitamin D deficiency in most children and adults through diet alone, especially if you have one or more of the risk factors listed below.
Risk Factor #1-Skin
Since skin is a primary site for the process of vitamin D synthesis, there are certain factors that prevent your skin from being an effective vitamin D producer.
- Skin pigment: Darker skin color is due the presence of the pigment melanin, which partially interferes with vitamin D synthesis. A dark-skinned person requires a significantly longer duration in the sun to get the same dose of vitamin D as someone who is fair-skinned.
- Sunscreen: Typical sunscreen use can significantly reduce but not completely eliminate vitamin D production in the body.
- Clothing: Keep in mind that even though you may have fairer skin that allows greater vitamin D production, covering major body surfaces up with clothing will completely negate that effect. For example, many individuals from India and East Asia prefer to keep most skin surfaces covered, due to concerns about darker skin, which is unfortunately still a social stigma. Cultural attire like the Muslim burqa, which covers all major body surfaces, would virtually eliminate skin-driven vitamin D production. Many parents from different parts of the world often tend to overdress or over bundle children due to fears about cold weather exposure causing infections, which would limit vitamin D production as well. We by no means suggest overturning cultural traditions and habits in these instances, but just to recognize these as red flag signs that vitamin D production in the body is being impaired.
Risk Factor #2-Too much body fat and too little dietary fat
Vitamin D is a fat-soluble vitamin, meaning it has an affinity for fat and requires fat to properly become dissolved into your blood, so it has its its intended effect upon your body's cells. This has two important implications.
First, if you have excess body fat, it acts like a magnet or a trap that takes up vitamin D and makes it less available to your bloodstream and thus body's cells. In other words, an overweight child or adult requires a higher dose of vitamin D than someone with lesser body fat.
Second, if you are eating a typical “low-fat” diet lacking healthy sources of dietary fat (discussed in prior posts), then your body absorbs less vitamin D from food and supplements. So be sure to stir-fry those mushrooms in some healthy fat to enhance vitamin D absorption!
Risk Factor #3-Eating a nutrient-deficient diet
This is related to the prior risk factor. Although we mentioned that diet is a much weaker source of vitamin D than sunshine, we still want to make sure we maximize the vitamin D we get through foods.
Oily fish, especially salmon, are a relatively good source of vitamin D, providing 360 international units (IUs) per 3.5 oz serving. Milk or milk substitutes like coconut or almond milk provide 100 IUs per 8 oz serving. If you don't eat fish, mushrooms are a decent source, although they have much less vitamin D than oily fish. Vegans are especially at high risk since they do not consume fish or dairy, with vegetarians a close second. We still very commonly see vitamin D deficiency, even in meat eaters, since they still are lacking adequate sun-derived vitamin D and often carry excess body fat.
You also want to make sure you and your children are getting other essential minerals in the diet which enhance vitamin D absorption and function, such as magnesium found in leafy greens, nuts and seeds. Eating excess grains actually remove vitamin D and magnesium from the body due to a chemical called phytic acid which I discuss in this post.
You can see now why certain cultural risk factors and cuisines, like a low-fat Indian vegetarian diet in the presence of darker skin and excess body fat, can make already deficient vitamin D levels much worse.
Risk Factor #4-Location and season
Living in northern latitudes with more limited UVB exposure means lower available doses of sun-driven vitamin D during the day. The months of November to March in particular are when vitamin D levels drop like a rock, especially in northern latitude regions, where not enough sun rays reach the earth's surface to power human vitamin D production.
Risk Factor #5-Exclusive breast feeding
Breast feeding has myriad health benefits for baby and is the preferred food source for infants, but breast milk is relatively deficient in vitamin D when compared to formula. The AAP (American Academy of Pediatrics) recommends 400 IUs of vitamin D for children less than one who are exclusively breast fed or are receiving less than 32 oz of formula. For children above age 1, the AAP recommends 600 IUs daily. Keep in mind that many vitamin D experts around the world believe this is still an insufficient dose of vitamin D, so consult your health care provider and use vitamin D levels as a guide when indicated.
Improving Vitamin D
Based on the risk factors we just discussed, it should be fairly obvious why so many people worldwide are suffering from a growing epidemic of vitamin D. Global obesity, an indoor lifestyle that boycotts adequate sun exposure to sufficient body surfaces (especially in those with darker skin), and an increasingly nutrient deficient diet devoid of healthy fats, but abundant in anti-nutrients are the major factors.
The first step is to optimize as many natural lifestyle habits as possible to improve vitamin D levels. All the factors that influence vitamin D improve other parts of your life as well. More time outdoors in natural sunlight, eating a nutrient-dense diet, and increased physical activity, all work together to lower body fat (further improves vitamin D absorption), decrease inflammation, and reduce the risk of most chronic health conditions.
What about supplements and testing?
Most kids and adults will need help with vitamin D supplements if they are deficient, especially if getting adequate sun exposure is not feasible. Vitamin D3 is better absorbed than Vitamin D2 formulations, especially if you buy a formulation that is in an oil suspension such as olive oil. I personally use a vitamin D3 supplement capsule that's in an olive oil suspension.
What dose should you take? It really depends on how deficient you are. Talk to your pediatrician or adult physician to first get a level checked and then the dosage can be adjusted accordingly. The specific test is the 25(OH)D (“25 hydroxy vitamin D”) blood test. Generally for every 1,000 units of vitamin D-3, levels go up by 5 ng/mL. This rule varies among individuals.
The optimal range for vitamin D is highly debatable, but most experts suggest a range between 40-60 ng/mL while some others suggest even higher ranges. Keep in mind that when it comes to supplements (and medications), higher doses are not always better and can be unsafe, so we suggest being cautious about over-supplementing until we have further high quality studies to evaluate efficacy at various vitamin D levels.
Can you become vitamin D toxic?
Since vitamin D is a fat soluble vitamin, it gets stored inside your body's tissues. Excessive amounts can become toxic over time. However, you would have to be taking megadoses to become toxic and it is suggested you supplement wisely while getting vitamin D levels monitored after any dosage changes. If you are deficient in vitamin K2, you might be more susceptible to the adverse effects of vitamin D since vitamin K2 ensures that calcium is being deposited into bones and teeth instead of soft tissues and blood vessel walls. To learn more about vitamin K's effect on vitamin D, review my prior post.
Final words on Vitamin D
Normal vitamin D levels are essential at every stage of life. In a growing fetus, it optimizes development of the immune system and reduces the risk of multiple health conditions later in life. In adulthood, it can help lower the inflammation associated with common disorders like heart disease, cancer and autoimmune disease. In seniors it can preserve bone and even muscular health, while maintaining metabolic and immune system function to maintain quality of life in our later years.
For a family dealing with vitamin D deficiency this isn't rocket science. Vitamin D deficiency represents a human disconnect from nature and natural foods. Embracing the sun more often with outdoor play and activities, nourishing your body with nutrient dense foods, and adding reasonable amounts of supplementation to account for our modern lifestyles is a more holistic way to support our vitamin D levels and overall health.