After visiting your ailing grandmother with a hip fracture, you find yourself staring at a packed drugstore shelf of calcium and vitamin D supplements. Though you know vitamin D can help keep bones strong, which type do you choose? Do you really need it? At what dose? What is safe — and what is effective?
Not only does vitamin D enhance calcium absorption from food to support healthy bones, many health professionals, like ourselves, use vitamin D to prevent and support other conditions associated with vitamin D deficiency:
- Autoimmune disorders
- Tooth decay
- Bone loss
- Digestive challenges
- Cardiovascular disease
Look at that list! Would you risk being deficient?
A Boston University study on vitamin D revealed that women without adequate vitamin D had a 253% increased risk of colorectal cancer and a 222% increased risk of breast cancer. Additionally, studies out of Mt. Sinai Hospital in Toronto, Canada, showed that women with low levels of vitamin D at diagnosis are 94 percent more likely to have the cancer metastasize and 73 percent more likely to die within ten years of diagnosis. Similarly, a study in the journal Neurology showed that vitamin D deficiency doubled Alzheimer’s risk. Moreover, in a study in the American Journal of Clinical Nutrition, 800 IU of supplemental vitamin D daily reduced heart failure risk by 25%. And in first book Naked Calories, we revealed that a study from Children’s Hospital in Los Angeles found that women who were deficient in vitamin D were, on average, 16.3 pounds heavier than women who were not vitamin D deficient. Whether you focus on health today or in 20 years, vitamin D sufficiency is critical!
Are You D-ficient?
According to the Centers for Disease Control and Prevention, over half of the US population is vitamin D deficient regardless of age. A 2009 study found US children to be 70% deficient! Because sunlight drives vitamin D production in skin, most must supplement to meet our needs while living indoor lives.
Who is likely to be vitamin D deficient?
- People with limited sun exposure or who live north of ~33 degrees (Atlanta)
- Breastfed infants
- Older adults
- Obese individuals
- People with
- Darker skin
- Low fat diets
- Pancreatic insufficiency / Low lipase production
- Celiac disease
- Poor gallbladder function / Gallbladder removal
- Liver disease
- Cystic fibrosis
- Recent gastric bypass surgery
Obesity is associated with lower vitamin D levels because fat sequesters this vitamin. Sadly, low vitamin D drives down levels of the hormone leptin, which are correlated with metabolic disease and obesity.
Food, lifestyle, supplements, and medications may lower vitamin D status.
- FOOD: Some foods can actually reduce your vitamin D absorption. High phytate intake from a diet high in minimally processed plant proteins can speed vitamin D metabolism. But, the antinutrients don’t stop there—There are numerous naturally occurring compunds in foods that can be reduce your chances of reaching sufficiency,
- LIFESTYLE: Living a vegan or dairy-free vegetarian lifestyle can easily increase the risk of deficiency. An EPIC-Oxford study comparing the intake of 33,883 meat-eaters to 31,546 vegans revealed 75% more vitamin D in the meat-friendly diets.
- SUPPLEMENTATION: Excessive supplementation of vitamin A can reduce absoprtion of and negate the beneficial effects of vitamin D.
- MEDICATION: Medications that deplete vitamin D include thiazide diuretics, estrogen-containing oral contraceptives, calcium channel blockers, H2 blockers, and antacids. Furthermore, corticosteroids, cholestyramine, lipase inhibitors, phenobarbital, and phenytoin can impair vitamin D metabolism.
So What Does This Vitamin Do?
Vitamin D is both a vitamin (we have to consume it to live) and a hormone: a chemical messenger that moves around the body and tells cells what to do. Vitamin D is bossy. It tells the gut to make calbindin to help absorb calcium and helps keep calcium and phosphate levels in a tight range so bones form and muscles contract properly. It alters the behavior of cells that regulate growth, development, and planned death of other cells. Vitamin D even reduces inflammation and modulates neuromuscular and immune function. This is possible because the receptor where vitamin D talks to the cell is found all over the body— intestine, pancreas, kidney, skin, lungs, bone, immune cells, some endocrine glands, and even reproductive tissues!
What’s the D-fference Between the Forms Of Vitamin D In The Store?
Choose vitamin D3. Vitamin D3, also known as cholecalciferol, will help raise overall vitamin D levels and is considered safe at low to moderate doses. Do not supplement vitamin D2, also known as ergocalciferol, as recent research has shown it to be half as effective in women at raising D levels. Despite previous belief that both forms were safe and effective, in a study from the American Journal of Clinical Nutrition, vitamin D2 supplementation reduced overall vitamin D levels in just 28 days! Many practitioners still prescribe megadoses of D2 for deficiency, so be aware.
So How Do You Get Enough Vitamin D?
Get outside. If you live north of Atlanta, you will likely need more support than the great outdoors. Those with fair skin need to have arms, legs, and face exposed to sunlight at midday for at least 10 minutes without sunscreen to meet the RDI, and that time increases for those who are older or have darker skin.
Very few foods contain Vitamin D. The flesh of fatty fish (like salmon, tuna, or mackerel) and fish liver oils are the best natural food sources of vitamin D3. Small amounts are also found in beef liver, cheese, egg yolks from chickens that roamed outdoors, and mushrooms exposed to UV light. Most Americans get their vitamin D from fortified dairy and dairy-alternative products. Check out our guide to non-dairy milks for some d-licious options!
In a modern world, most of us must supplement. The RDI for vitamin D is currently up to 600 IU per day for children/adults and 800 IU for those over 70. In 2019, the RDI for adults and children will be raised to 800 IU.
Many Popular Multivitamins Fall Short in Vitamin D3 and others only supply D2
- Megafood Women’s One Daily offers 400 IU
- Kirkland Signature Daily Multivitamin and Minerals offers 400 IU
- Rainbow Light Kids One Food-Based Multivitamin offers 400 IU
- Garden of Life Multivitamin for Men (Vegan) offers 1000 IU
- Many multivitamin supplements use vitamin D2 (or don’t specify as to whether they include D2 or D3), so you’ll have to pay close attention. Examples of a few popular multivitamin brands that use D2 include BioCare, Green Source and Solgar, among others.
What Do We Recommend?
We recommend 2000 IU daily of vitamin D3 as a safe and effective dose for most people. In 2011, the Endocrine Society issued clinical practice guidelines stating that vitamin D levels must be at least 30 ng/ml (75 nmol/l) to get its beneficial effects. According to this report, we need at least 1500 to 2000 IU per day of supplemental vitamin D in adults (1000 IU per day for children) to achieve this level. This is why we put 2000 IU of Vitamin D3 in our multivitamin called Nutreince – so you can reap the benefits without worrying about taking too much– or too little!
Regardless of supplementation, get outside. Consider that our ancestors were outside. A lot. And we are not. Factors that affect vitamin D production in the skin include season, time of day, length of day, cloud cover, smog, skin melanin content, and sunscreen. For easy guidance on safe and effective sunscreens, check out our article on the science of suntan lotion — and go get that vitamin D!
- Articles cited above with links
- Micronutrient Miracle
- Naked Calories
- NHANES 2003–2006