Dermatologists almost universally agree that the safe, healthy way to attain sufficient levels of vitamin D is through food and vitamin supplements. According to the National Institutes of Health (NIH) Office of Dietary Supplements, very few foods naturally contain vitamin D. However, many more are fortified with the vitamin,1 and if someone doesn’t take in enough D through food, supplements can more than make up for it.
In 2010, the Institute of Medicine (IOM) of the National Academies established these recommended dietary allowance (RDA) figures for daily vitamin D in international units (IU).2
Almost all scientists agree that low levels of vitamin D are associated with bone loss and osteoporosis. Some also believe they may be linked to other diseases from diabetes and heart disease to several cancers, but this link has not been substantiated. All agree more research is needed. Harvard Medical School and Brigham and Women’s Hospital in Boston are currently in the middle of a vitamin D and omega-3 fatty acids (VITAL) trial, tracking more than 20,000 men and women across the US to see whether daily dietary supplements of 2,000 IU vitamin D or omega-3 fatty acids reduce risk for developing cancer, heart disease and stroke in people who do not have a prior history of these illnesses.3 Though this study is still in progress, some groups already recommend taking in higher amounts of vitamin D than recommended by the IOM: for example, the Harvard School of Public Health recommends 1,000 to 2,000 IU per day, and the International Osteoporosis Foundation advises adults over age 60 to take in about 800-1,000 IU.
The Skin Cancer Foundation concurs with the IOM’s current recommendations, and advises everyone to attain these levels through a combination of food and supplements. For people who are specifically deficient in vitamin D, the Foundation considers it acceptable to take in 1,000 to 2,000 IU daily for limited periods. Most experts agree that taking in more than 2,000 IU a day is excessive and can lead to its own problems.
Remember to always EAT YOUR D’S
Is it really possible to attain enough vitamin D from food? If you’re shooting for the recommended dietary allowance (RDA) of 600 International Units (IU) daily set by the Institute of Medicine (with which The Skin Cancer Foundation agrees), let’s see what it would take:
- Fatty Fish: These are the Cadillacs of vitamin D foods. A three ounce serving of cooked swordfish will net you 566 IU of vitamin D, almost the entire RDA for the day. The same amount of cooked sockeye salmon, almost as D-lightful, will give you 447 IU. A 6-oz. can of tuna fish, drained of its water or oil, gives you about 3 ounces of tuna, containing about 154 IU of vitamin D, or about ¼ of the RDA. A can of sardines offers about 46 IU.1
- Liver and eggs: These are just about the only other foods that naturally have any appreciable vitamin D content, and even then, only about 42 IU and 41 IU (for a single jumbo egg) respectively.
- Fortified foods: In response to a rickets outbreak in the 1930s, food manufacturers began fortifying many foods, especially dairy foods and cereals, with vitamin D. Remember to read labels, because a food is only fortified if it says it is. A cup of fortified orange juice can net you a substantial 137 IU. A cup of fortified milk can have between 115 and 124 IU, and six ounces of fortified yogurt will have about 80; a tablespoon of fortified margarine, 60. About a cup of fortified dry cereal will give you 40. Even infant formula is often fortified with 40 IU or more of vitamin D.
- Cod liver oil: This was Aunt Polly’s nutritional panacea of choice, but she had to chase Tom Sawyer all around his white picket fence to give it to him, and he gagged it down holding his nose. You don’t hear about a lot of people taking cod liver oil today. But it is the single highest source of vitamin D in the American diet (if it is indeed in the American diet). With one tablespoon of cod liver oil, you take in 1,360 IU of vitamin D-- more than twice the daily RDA.
So, it is quite possible, though not easy, to take in 600 IU of vitamin D each day through food, even if you’re not a cod liver oil enthusiast. For example, have surf and turf for dinner– swordfish (566 IU) and liver (42 IU), and you’re over the top. Or, a three-egg omelette (123 IU), fortified orange juice (137 IU), and fortified milk (115 IU) for breakfast, with a can of tuna (154 IU) and some yogurt (80 IU) for lunch, and you’ve broken 600 again. It can be done. For most people, however, taking supplements is the most effective and efficient way of maintaining appropriate levels of vitamin D.
The best indicator of your vitamin D status is your serum concentration of 25(OH)D. The next time you have a blood test for vitamin D, check the numbers. In general, if your 25(OH)D level is less than 12 ng/mL, you have a vitamin D deficiency. If it is between 12 and 20 ng/mL, your level is still considered insufficient or inadequate for bone and overall health in otherwise healthy individuals. Levels above 20 ng/mL are generally considered adequate for bone and overall health in otherwise healthy individuals, and levels above 50 ng/mL may be excessive, with potential adverse effects.
Published on August 6, 2015
- Vitamin D—Health Professional Fact Sheet. National Institutes of Health Office of Dietary Supplements. http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/. Checked April 7, 2015.
- National Academies, Institute of Medicine, Food and Nutrition Board. Dietary reference intake for calcium and vitamin D. http://www.iom.edu/Reports/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D.aspx. Nov. 30, 2010. Accessed Feb. 2, 2012.
- The Nutrition Source. Vitamin D and health. Harvard School of Public Health. http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/vitamin-d/#iomvitamin-d. March 29, 2011. Accessed Feb. 2, 2012