Few health issues affect as many age groups and are potentially linked to as many health conditions across as many geographical regions as vitamin D deficiency. Indeed, poor?vitamin D?status is a world health concern, affecting up to 42 percent of adults in the United States alone, with black and Hispanic people being most affected. (1)
If you or a loved one is at risk, what might a lack of the so-called sunshine vitamin mean for your health?
Vitamin D Definition
Vitamin D is produced in the body when your skin is exposed to sunlight. You can also get it from food sources such as eggs; fortified milk and orange juice; and fatty fish such as salmon, halibut, and herring. The fat-soluble vitamin plays an important role in every cell of the human body. It works with genes to encode the proteins that grow cells and tell them what to do depending on where they are in the body. (2)
At a basic level, vitamin D?plays a part in every system in the body. We often think of vitamin D as being important in bone health, and that is true. Vitamin D helps in the absorption of calcium, maintaining a balance of phosphate, and the growth and maintenance of bone. (2)
Vitamin D Functions in the Body
Don’t discount the importance of vitamin D. It plays many roles in the body, including the following.
“When your body’s stored levels of?vitamin?D dip too low, this can have negative impacts on bone health, especially in women as they age,” says Amy Gorin, RDN, the owner of?Amy Gorin Nutrition?in Jersey City, New Jersey. Women who are past?menopause?are at the highest risk of osteoporosis, an age-related bone disease that results when more bone is lost than created in the body. It is one of the main causes of bone fractures and breaks in the elderly. (3)
“Getting enough?vitamin?D may help prevent hyperparathyroidism,” adds Gorin. “This is a condition in which excess of the parathyroid hormone in the bloodstream may lead to osteoporosis, joint pain, and other issues.” (6,7)
Some studies suggest that taking vitamin D supplements may help to protect against certain types of cancer in some populations, as well as against death from cancer. For example, a study published in January 2019 in the New England Journal of Medicine suggest that those who developed cancer had a 25 percent lower death rate when they were taking vitamin D. The results are from the VITAL study, a large, randomized clinical trial involving more than 25,000 participants. These researchers also reported a possible reduction in cancer risk for African Americans, though they said that further study was warranted. (8)
How Much Vitamin D Do You Need?
The Food and Nutrition Board (FNB) at the National Academy of Medicine recommends that most people ages 1 to 70 get 600 international units (IU) of vitamin D each day. (9)
Recommended Daily Doses of Vitamin D
Here is the specific breakdown by age and pregnancy status: (2)
Infants (birth to 12 months): 400 IU
Children (1 to 13 years): 600 IU
Teenagers (14 to 18 years): 600 IU
Adults (19 to 70 years): 600 IU
Seniors (71 years and older): 800 IU
Pregnant and breastfeeding women: 600 IU
Yet the truth is, “very few food sources of?vitamin?D exist,” Gorin says. Individuals rarely get more than 288 IU per day from food and drink, on average. Cow’s milk and plant-milk substitutes that are fortified with vitamin D will only bring you around 100 IU per 8-ounce glass in most instances. Other food sources include fatty fish, eggs, and fortified orange juice. (2) “So if you’re not regularly eating those sources, you may want to consider taking a daily supplement,” Gorin advises.
The Endocrine Society recommends that adults take 1,500–2,000 IU per day in supplements to avoid being vitamin D deficient, and that infants and children should take 1,000 IU. This is based on their standard of having blood serum levels of the vitamin at 30 ng/mL (75 nmol/liter) or higher.?(10)
Some people believe more is better, and they take higher doses. But there is a limit to how much you can take before vitamin D may start to damage your health. The FNB recommends that people over the age of 9 take no more 4,000 IU per day in supplements — and 1,000–3,000 IU for infants and children up to age 8. Higher-than-recommended doses increase the risk for death, cancer, and cardiovascular events, as well as falls and bone fractures in older people. (2)
Consult with your doctor about whether you should take a supplement, and what the dosage should be. “It’s a good idea to get a baseline idea of your?vitamin?D levels through a blood test and go from there in terms of supplementation,” says Gorin. “When you are taking a?vitamin?D supplement, I’d recommend?vitamin?D3.”
Also called cholecalciferol, D3 is generated by your body through sun exposure, and also found in animal-sourced foods. It is the form of vitamin D that is best absorbed in your body. Vitamin D2 (ergocalciferol) is plant-based, and a good choice if you avoid anything that is animal sourced, per past research. (11) “Take the supplement with your fattiest meal of the day.?Vitamin?D is a fat-soluble?vitamin, so you’ll absorb it best this way,” Gorin advises.
“As well, you can get?vitamin?D through [unprotected] sun exposure,” she says. But it’s important to limit unprotected time in the sun to a few minutes and apply sunscreen after that.
Signs and Symptoms of Vitamin D Deficiency
The signs and symptoms of vitamin D deficiency can be very subtle in the early stages. Fatigue and even sadness are very generalized symptoms, but bone pain and muscle weakness may give you more of a clue. (2)
The bone disorder rickets is uncommon in the United States, but healthcare providers have seen babies and children with vitamin D deficiency, with breastfed African American babies at greater risk. Because the disease affects the growing tissue at the end of a child’s bones, visible symptoms include bowing of the femurs (thigh bones) or ribcage. (2,4)
In adults, vitamin D deficiency can cause osteomalacia, which can result in falls, bone breaks, and poor healing following fractures. Symptoms can include a dull, aching pain affecting the ribs, lower back, pelvis, hips, and legs. The pain might worsen at night or when pressure is put on the affected bones. Muscle tone may decrease and your legs may weaken, making walking more difficult. (5)
Not having enough vitamin D can also contribute to osteoporosis in older adults, with back pain, fractured or collapsed vertebra, a gradual loss of height over time, a stooped posture, and fragile bones being among the symptoms. (3)
Risk Factors for Vitamin D Deficiency
The following groups of people are at a higher risk for vitamin D deficiency.
People of color?“People with darker skin are at an increased risk for?vitamin?D?deficiency?because they have more melanin in their skin,” Gorin explains. “This is a pigment that decreases the skin’s ability to procure?vitamin?D from sunlight.” (2) Only 5 percent of African Americans had sufficient vitamin D levels in their blood as of 2004, according to Endocrine Society. This compares with 30 percent of white people in the United States. (12)
People with kidney disease?Vitamin D is converted into its active form in the kidneys, so if your kidneys are not functioning well, you could be taking in enough and absorbing enough, but your body can’t use it in the way it is needed. (12)
Individuals with liver disease Vitamin D deficiency has been associated with nonalcoholic fatty liver disease (NAFLD), in which extra fat cells build up in the liver, causing damage to the organ. (13) People with the disease are 26 percent more likely to be deficient in the nutrient than those who do not have the disease, according to a 2013 study published in Alimentary Pharmacology and Therapeutics. (14)
Individuals with various digestive disorders?This includes inflammatory bowel disease (ulcerative colitis?or?Crohn’s disease),?celiac disease, other various inflammatory or malabsorption disorders, and even?cystic fibrosis. These conditions limit or even destroy the body’s ability to absorb vitamin D from the food that is eaten. (2)
Those with limited sunlight exposure The further away you are from the equator, the more at risk you are for vitamin D deficiency due to the angle of the sun’s rays. But the reality is that unless you are in an area where it is warm and sunny most of the year, you cannot count on the sun for your vitamin D year-round. More specifically, during the winter months, the sun’s rays are not at the right wavelength to cause vitamin D synthesis in the skin no matter how sunny it may be on a given day. (10)
Those who are obese?The current statistics from the Centers for Disease Control and Prevention reveal that about 40 percent of adults?and 18.5 percent of children in the United States are?obese. (15,16)?When you have excessive body fat, vitamin D gets trapped in your fat tissues instead of going into circulation for use. Obesity is defined as a?body mass index (BMI)?greater than 30, according to the National Heart, Lung, and Blood Institute. (17)
Exclusively breastfed infants?Breast milk contains 20–40 IU/L of vitamin D,?so exclusively breastfed infants need at least 400 IU of supplemental vitamin D. (18,19) Supplemental vitamin D can be found in liquid form at most grocers and pharmacies.
Those on self-imposed or medically restricted diets?Whether you are eliminating certain food groups because you want or need to, the result is the same — risk of various?nutrient deficiencies, including vitamin D deficiency, go up. (10)
People who are lactose intolerant This condition — an inability to digest the milk sugar lactose, leading to gas, bloating, and digestive issues — puts you at risk for vitamin D deficiency because you are less likely to consume fortified dairy products. The Mayo Clinic notes that with your doctor’s approval, you can safely drink lactose-free milk and you may be able to eat yogurt and cheese in small doses. There are dairy-free cheeses out there as well, or you can take a lactase enzyme supplement such as Lactaid before eating dairy to cover any digestive discomfort. Plant-based beverages that are fortified with vitamin D can also be beneficial. (2,21)
Those with an allergy to dairy When someone has a dairy allergy, they must eliminate all forms of dairy. The allergy involves an immune reaction to the protein in dairy — risks can range from skin rashes to life-threatening anaphylactic reactions. (22) Adults and children with a dairy allergy can benefit from taking a calcium and vitamin D supplement, as well as consuming plant-based beverages enriched or fortified with calcium and vitamin D.
Vegans Following a vegan diet, which involves eating only plant-based fare and no animal products, is linked to vitamin D deficiency. (2) That’s because it eliminates fortified dairy, eggs, and fatty fish as food sources for the nutrient. You may take vitamin D2 supplements (which are plant-based) or drink fortified nondairy beverages to make up the difference.
People on certain fad diets Some fad diets, such as?paleo and?Whole30, eliminate food groups that contain vitamin D. The paleo diet does not include dairy, though you can eat eggs and fish. Also, you can take supplements and plant-based beverages enriched and fortified with calcium and vitamin D. Meanwhile, Whole30 was created only to be a 30-day cleansing diet, but many people are doing it to lose and keep weight off beyond that period. Whole30 does not allow for any alternative version of dairy during the cleansing period because the diet calls for dairy-free, grain-free foods in their original form only. Consider taking a supplement while you are on Whole30.
And what about:
Pregnant and lactating women? Past studies suggested low vitamin D status in pregnancy can contribute to early deliveries and preeclampsia (or high blood pressure during pregnancy), pointing to possible benefits of supplementation. But in October 2019, the World Health Organization updated its guidelines to say that taking supplements is not recommended for pregnant women, noting that more research is needed about possible effects on preterm births. Moms-to-be are advised to get the nutrient from a balanced diet and sunlight exposure instead. For pregnant women who have been diagnosed with vitamin D deficiency only, taking no more than 200 IU in supplements is recommended. (23) As previously mentioned, the recommended daily allowance (RDA) is set at 600 IU overall — from all sources — for pregnant and lactating women.
Screening and Diagnosis of Vitamin D Deficiency
During screenings for vitamin D deficiency, a good healthcare provider will analyze your potential risk factors and your personal health history.
But keep in mind that most health insurance companies do not cover a vitamin D blood test unless your doctor documents symptoms or you have a disease that would put you in a high-risk category, such as kidney disease or various bone diseases.
Measures of vitamin D deficiency vary, generally ranging from 12–30 ng/mL. A blood level of less than 12 nanograms per milliliter (ng/mL) definitely will get you the vitamin D deficiency diagnosis. (2,9)
How to Increase Your Vitamin D Intake
Very few foods in our American diet contain decent amounts of vitamin D. Fatty fish, such as salmon and swordfish, contain 450 to 600 IU vitamin D per 3 ounces. Milk, some cheese, and certain yogurts contain 80 to 125 IU per serving.
Pescatarians (vegetarians who eat fish) can take 1 tablespoon of cod liver oil and get about 1,400 IU vitamin D for about 135 calories. If you’re vegan, you can fall in love with UVB-treated mushrooms, as they are the only source of vitamin D in the produce aisle. Raw maitake mushrooms contain the highest amount of vitamin D, with 786 IU per cup, diced, according to Monterey Mushrooms. (24)?Some mushrooms are grown to soak an extra amount of vitamin D from UVB light for a short period of time, their website notes. (25) As previously mentioned, many plant-based beverages are fortified with 100 IU per 8-ounce glass, so that’s another way you can get to your recommended daily amount. (2)
How to Treat a Vitamin D Deficiency
If you are diagnosed with vitamin D deficiency, your doctor may prescribe a course of treatment that involves large doses to get you back up to sufficient levels. The Endocrine Society suggests that all adults who are vitamin D deficient be treated with 50,000 IU of vitamin D2?or vitamin D3?each week for 8 weeks (or 7,000 IU per day) to get to a blood level of 30 ng/mL, followed by maintenance therapy of 1,500–2,000 IU each day. (10)
A Final Word on Vitamin D Deficiency
Make sure you are getting adequate amounts of vitamin D in your diet. If you are not, a daily supplement may be required to make up the amount you are falling short. Most people will not be able to meet their vitamin D needs through food alone on a regular basis, so a supplement will be warranted.
If you are in an at-risk category, consider getting tested to see if you fall in the insufficient or deficient categories.
Additional reporting by?Angela Lemond, RDN.
Editorial Sources and Fact-Checking
- Forrest KY,?Stuhldreher?WL. Prevalence and Correlates of Vitamin D Deficiency in U.S. Adults.?Nutrition Research. 2011.
- Vitamin D: Fact Sheet for Health Professionals.?National Institutes of Health. August 7, 2019.
- Osteoporosis.?Mayo Clinic. June 19, 2019.
- Rickets.?Mayo Clinic. May 14, 2019.
- Osteomalacia.?Mayo Clinic. April 29, 2017.
- Parathyroid: Background: Incidence and Risk Factors. American Association of Endocrine Surgeons.
- Hyperparathyroidism. Cleveland Clinic. October 25, 2016.
- Manson J, Cook N, Lee I-M, et al. Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease. New England Journal of Medicine. January 3, 2019.
- Ross AC, Taylor C, Yaktine A, et al. "Chapter 5: Dietary Reference Intakes for Adequacy: Calcium and Vitamin D."?Dietary Reference Intakes for Calcium and Vitamin D. National Academies Press. 2011.
- Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, Treatment, and Prevention of Vitamin D Deficiency: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology and Metabolism. July 2011.
- Tripkovic L, Lambert H, et al. Comparison of Vitamin D2 and Vitamin D3 Supplementation in Raising Serum 25–Hydroxyvitamin D Status: A Systematic Review and Meta-Analysis.?American Journal of Clinical Nutrition. June 2012.
- Kennel K, Drake M, Hurley D. Vitamin D Deficiency in Adults.?Mayo Clinic Proceedings. August 2010.
- Nonalcoholic Fatty Liver Disease. American Liver Foundation.
- Eliades M, Spyrou E, Agrawal N, et al. Meta-Analysis: Vitamin D and Non-Alcoholic Fatty Liver Disease. Alimentary Pharmacology and Therapeutics. August 2013.
- Adult Obesity Facts.?Centers for Disease Control and Prevention. August 13, 2018.
- Childhood Obesity Facts.?Centers for Disease Control and Prevention. June 24, 2019.
- BMI?Categories: Calculate Your?BMI?Index.?National Heart, Lung, and Blood Institute.
- Greer FR, Marshall S. Bone Mineral Content, Serum Vitamin D Metabolite Concentrations, and Ultraviolet B Light Exposure in Infants Fed Human Milk With and Without Vitamin D2 Supplements. Journal of Pediatrics. February 1989.
- Vitamin D Supplementation.?Centers for Disease Control and Prevention. January 24, 2018.
- Calton JB. Prevalence of Micronutrient Deficiency in Popular Diet Plans. Journal of the International Society of Sports Nutrition. 2010.
- Lactose Intolerance. Mayo Clinic. April 21, 2018.
- Milk Allergy. Mayo Clinic. June 6, 2018.
- Vitamin D Supplementation During Pregnancy. World Health Organization.
- Basic Report: 11993, Mushrooms,?Maitake, Raw.?United States Department of Agriculture Agricultural Research Service. May 2016.
- Monterey?Mushrooms Have Vitamin D.?Monterey?Mushrooms.