Vitamin D may be important for more than simply building and maintaining strong bones. Researchers have analyzed whether sufficient?vitamin D?may help prevent serious health problems such as cancer,?heart disease, and diabetes, notes an article published in January 2019?and a randomized trial published in August 2019, both in The New England Journal of Medicine. (1,2)
And while there isn’t definitive research to back up many of the health claims surrounding vitamin D, there’s no denying that the scientific community and the general public are fascinated with this nutrient. In fact, the number of research titles with the phrase “vitamin D supplementation” on the database PubMed increased more than 15-fold from 2003 to 2017, note the authors of?an article published in May 2018 in?Nutrients. (3)
What we do know is that vitamin D aids the absorption of calcium in the gut, which helps you grow strong and healthy bones. The nutrient is also helpful for reducing inflammation and plays a vital role in cell growth and the immune system. You derive vitamin D from sunlight exposure, food, and dietary supplements, according to the National Institutes of Health. (4)
Considering what scientists know about what's nicknamed the Sunshine Vitamin, how much do you need to keep your body in proper working order? It turns out that vitamin D recommendations aren’t one size fits all: A number of factors — from your age and sex to your ethnicity and geographical location — can affect your recommended intake.
Read on to learn about the surprising factors that can influence how much vitamin D you need.
Age-Based Recommendations for Vitamin D
When it comes to vitamin D, age matters, and for different reasons than you might expect.
Vitamin D Recommendations for Infants
The recommended adequate intake of vitamin D for infants is 400 international units (IU), equal to 10 micrograms (mcg), per day, according to the Centers for Disease Control and Prevention (CDC). (5)?Because human milk contains 5 to 80 IU per liter, it’s important to ensure your little one is getting adequate sunlight exposure or getting enough vitamin D supplemented in their diet, according to an article published in October 2015 in?Pediatrics. (6) The?CDC points out that a vitamin D deficiency may lead to rickets, a rare condition in Western countries but one that can cause growth delays. (5)
Vitamin D Recommendations for Children and Teens
While the recommended daily allowance (RDA) for children and teenagers is 600 IU (15?mcg), (3)?observational research suggests that higher levels of vitamin D may help prevent the development of?type 1 diabetes?in children, according to the Harvard T.H. Chan School of Public Health. (7)?Talk to your family?doctor to see if your child or teen needs more vitamin D.
Vitamin D Recommendations for Adults
The?RDA?of vitamin D for adults is also 600 IU?per day, but a number of factors may affect your recommended intake. Talk to your doctor to see if your level is adequate. (3)
Vitamin D Recommendations for the Elderly
The?RDA?for people age 70 and older is 800 IU. As you age, your body is no longer as efficient at synthesizing, absorbing, and digesting vitamin D as it was when you were younger, says?Robin?Foroutan,?RDN, an integrative dietitian at the Morrison Center in New York City and a spokesperson for the Academy of Nutrition and Dietetics. (4) These issues can lead to an increased risk for?osteoporosis?(bone disease), among other potential health issues, according to the National Osteoporosis Foundation. (8)
Does Being a Man or a Woman Affect How Much Vitamin D You Need?
Yes and no. Body size is more influential than sex when it comes to vitamin D intake recommendations,?Foroutan?says. On average, men weigh more than women. However, the relative amount of body fat an individual has may be more pertinent, since vitamin D is stored in body fat. (3)
A study published online in November 2014 in PLoS?One?aimed to analyze the effect that?body mass index?may have on vitamin D dosing targets. Findings suggested that participants who were obese needed 2 to 3 times more vitamin D than their normal-weight counterparts. (9)
But men and women are at different risks for various chronic conditions, which means adjusting your vitamin D target may be helpful for managing symptoms or delaying disease progression.
For example, women may be more likely than men to develop both thyroid disease, per the Department of Health and Human Services Office on Women’s Health, and osteoporosis, and a vitamin D deficiency is associated with both, other research suggests.?(10,11,12)?If you live with a chronic disease that is associated with your sex, your doctor may factor in vitamin D as part of your personal management plan.
How Ethnicity May Affect Your Need for Vitamin D
People who live in colder climates generally need more vitamin D than those who live closer to the equator, but among all geographic locations, people with darker skin tones often need more of the vitamin than those with lighter skin. Indeed, people with highly pigmented skin who live in cold climates are considered to be at a particularly high risk of vitamin D deficiency, according to a study published in June 2017 in the Journal of the American Academy of Dermatology. (13)
“Observationally, we’ve seen that people of African descent and people of Middle Eastern descent also need more vitamin D to achieve optimum levels,”?Foroutan?says.
Why Wearing Sunscreen Can Affect Vitamin D Absorption
While wearing sunscreen daily is key to help prevent sunburns, premature aging, and?skin cancer, this healthy habit can also affect how much vitamin D your skin synthesizes from the sun.
To get your fix, aim to spend 10 to 15 minutes outdoors without sunscreen,?Foroutan?says. “It can help get your levels where they need to be,” she says, echoing information from Harvard Health Publishing. (14)
The Possible Link Between Vitamin D and Chronic Conditions
Generally, research on the role vitamin D may play in disease prevention and management is murky. Particularly with regard to the benefits of taking supplements, most of the studies have been observational or done on small groups (or both). Until recent years, there has been a lack of large randomized, controlled trials, which are the gold standard for medical research because such studies point to cause-and-effect relationships between factors. The data now coming in from such trials?fails to back up previous claims about the benefits of vitamin D supplementation.
But one thing is for sure: The scientific community’s interest in vitamin D clearly isn’t waning. Here’s what some of the latest research suggests about how the vitamin may affect certain chronic conditions.
Bone Health As mentioned, vitamin D helps in the absorption of calcium in the gut. So it’s no surprise that vitamin D supplements have long been recommended for preserving bone health. However, recent research has found that they don’t live up to the hype. A review of more than 81 clinical trials published in November 2018 in The Lancet Diabetes and Endocrinology found that vitamin D supplements don’t prevent fractures or falls, or affect bone mineral density to a degree that is clinically meaningful. (15)
Type 2 Diabetes?Observational studies have associated?low vitamin D levels with a higher risk of developing type 2 diabetes. Yet the aforementioned randomized, controlled trial published in August 2019 in The New England Journal of Medicine concluded that supplements won’t lower that risk. A dose of 4,000 IU of vitamin D per day did not result in a significantly lower risk of developing type 2 diabetes compared with a placebo. (2)
Cardiovascular Disease Taking vitamin D supplements does not reduce the risk of heart attack, stroke, or death from heart disease, according to the findings of a randomized, controlled clinical trial involving more than 25,000 participants that was published in the aforementioned January 2019 in The New England Journal of Medicine. (1)
Cancer?In the same study, researchers found that vitamin D supplementation was not found to reduce the risk of cancer in participants overall. However, those who had developed cancer and were taking vitamin D were less likely to die early than those who took a placebo. Researchers also found a possible reduction in cancer risk for African Americans, and they called for further study to confirm those results. (1)
Rheumatoid arthritis (RA)?A small observational study of 44 people with?RA?and 25 controls found that vitamin D deficiency appeared to be more prevalent among people with RA, suggesting these people may benefit from taking a supplement. (16)?But a separate small randomized, controlled trial found that while a?vitamin D supplement helped people with RA?build stronger bones than the control group, the supplements didn’t result in other expected health improvements. (17)
Mood Disorders?Vitamin D is an established therapy for seasonal depression, also called?seasonal affective disorder, according to the National Institute of Mental Health. (18)?But more research is needed to determine whether a vitamin D supplement may benefit people with clinical?depression, according to a review and?meta-analysis published in April 2014 in Nutrients. (19)
Memory and Cognitive Function?Observational research suggests vitamin D deficiency is associated with cognitive impairment among older adults, but randomized, controlled research is needed to determine whether the vitamin plays a role in?dementia?risk and progression, according to a review published online in July 2016 in the Journal of Alzheimer’s Disease. (20) A large cohort study published online in October 2017 in Scientific Reports that studied participants’ genetics found no causal relationship between vitamin D levels and cognitive performance in mid- to late life. (21)
Thyroid Disease?The connection between vitamin D and people with?hypothyroidism?seems clearer, though larger-scale research is necessary. A small randomized, controlled trial found that the more severe a participant’s hypothyroidism (underactive?thyroid), the more severe their vitamin D deficiency. (12) “That encourages the advisability of [vitamin] D supplementation and recommends the screening for vitamin D deficiency and serum calcium levels for all hypothyroid patients,” the authors write.
Do You Need a Vitamin D Supplement?
Because there are so many factors that can affect your vitamin D level, it’s important to talk to your doctor if you suspect you’re deficient. They can perform a blood test to see if you may benefit from upping your intake of?vitamin D–rich foods?like salmon, fortified milk, and eggs, or taking a vitamin D supplement, according to MedlinePlus. (22) Again, if you live in a place where winters are cool and dark, you may benefit from a supplement.
Talking with your doctor before supplementing is even more important if you’re managing a chronic condition. Not only are the benefits of vitamin D supplements unclear for certain health conditions but there’s a chance the supplement may do more harm than good if you’re taking a medication that?interacts poorly with it.
Another thing to keep in mind is that the Food and Drug Administration doesn’t regulate supplements like it does over-the-counter medication and prescription medication. (23) Have a conversation with your doctor about their recommended brand and dose to maintain or improve your health.
Editorial Sources and Fact-Checking
- Manson J, Cook N, Lee I-M, et al. Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease.?The New England Journal of Medicine. January 2019.
- Pittas?A, Dawson-Hughes B,?Sheehan?P, et al. Vitamin D Supplementation and Prevention of Type 2 Diabetes.?The New England Journal of Medicine. August 2019.
- Scragg?R. Emerging Evidence of Thresholds for Beneficial Effects From Vitamin D Supplementation.?Nutrients. May 2018.
- Vitamin D: Fact Sheet for Health Professionals.?National Institutes of Health Office of Dietary Supplements. March 24, 2020.
- Breastfeeding: Vitamin D.?Centers for Disease Control and Prevention. December 14, 2019.
- Hollis B, Wagner C, Howard C, et al. Maternal Versus Infant Vitamin D Supplementation During Lactation: A Randomized Controlled Trial.?Pediatrics. October 2015.
- The Nutrition Source: Vitamin D.?Harvard T.H. Chan School of Public Health. March 2020.
- Calcium and Vitamin D.?National Osteoporosis Foundation. February 26, 2018.
- Ekwaru?J,?Zwicker?J,?Holick?M, et al. The Importance of Body Weight for the Dose Response Relationship of Oral Vitamin D Supplementation and Serum 25-Hydroxyvitamin?D in Healthy Volunteers.?PLoS?One. November 2014.
- Thyroid Disease.?Department of Health and Human Services Office on Women’s Health. April 1, 2019.
- Cawthon?P. Gender Differences in Osteoporosis and Fractures.?Clinical Orthopaedics and Related Research. July 2011.
- Mackawy?A, Al-ayed?B, Al-rashidi?B. Vitamin D Deficiency and Its Association With Thyroid Disease.?International Journal of Health Sciences. November 2013.
- Kaufman B, Luna A,?Kaushik?S, et al. Skin Pigmentation and Vitamin D Status: A Single-Center, Cross-Sectional Study.?Journal of the American Academy of Dermatology. June 2017.
- Time for More Vitamin D.?Harvard Health Publishing. September 2008.
- Bolland?M, Grey A,?Avenell?A. Effects of Vitamin D Supplementation on?Musculoskeletal?Health: A Systematic Review, Meta-Analysis, and Trial Sequential Analysis.?The Lancet Diabetes and Endocrinology. November 2018.
- Kostoglou-Athanassiou?I,?Athanassiou?P,?Lyraki?A, et al. Vitamin D and Rheumatoid Arthritis.?Therapeutic?Advances in Endocrinology and Metabolism. December 2012.
- Hansen K,?Bartels?C,?Gangnon?R, et al. An Evaluation of High-Dose Vitamin D for Rheumatoid Arthritis.?Journal of Clinical?Rheumatology. March 2014.
- Seasonal Affective Disorder.?National Institute of Mental Health. March 2016.
- Spedding?S. Vitamin D and Depression: A Systematic Review and Meta-Analysis Comparing Studies With and Without Biological Flaws.?Nutrients. April 2014.
- Landel?V,?Annweiler?C, Millet P, et al. Vitamin D, Cognition, and Alzheimer’s Disease: The Therapeutic Benefit Is in the D-Tails.?Journal of Alzheimer’s Disease.?2016.
- Maddock?J,?Zhou?A,?Cavadino?A, et al. Vitamin D and Cognitive Function: A?Mendelian?Randomization Study.?Scientific Reports. 2017.
- Vitamin D Test.?MedlinePlus. February 26, 2020.
- Dietary Supplements.?Food and Drug Administration. August 16, 2019.