by Leah Frankel, MS, RD | firstname.lastname@example.org
The sun is finally shining (at least in most of the country), but before you go outside you might want to reconsider your current sun protection routine. Hopefully you’re lathering up with sunscreen to prevent skin cancer but did you ever consider the idea that too much sunscreen could be detrimental to your health? Vitamin D, sometimes know as the sunshine vitamin, is the only vitamin that we can produce without eating anything since your body can create enough vitamin D by spending some time in the sun. The question remains: How can you get your vitamin D without increasing your risk of developing skin cancer?
The Sunshine Vitamin
Vitamin D is a fat-soluble vitamin (meaning it is absorbed when consumed with fat, as opposed to water-soluble vitamins which are absorbed when consumed with water). Vitamin D helps with the absorption of calcium while also helping to regulate the levels of phosphorus and calcium in your blood stream. Unlike any other vitamin or mineral, vitamin D can be consumed from food sources or produced with exposure to the sun. In line with the fact that there are two ways we can obtain vitamin D, there are two forms of the vitamin: the form that we consume in foods, ergocalciferol (vitamin D2), and the form that we produce with a little help from the sun, cholecalciferol (vitamin D3). Vitamin D2 or D3 are then converted into the active form of vitamin D3 by the liver and kidney.
How Much Sun Do You Need?
Most people can produce enough vitamin D with 10-15 min of sun exposure, 3-5 days a week. However, these recommendations are based on the assumption that the person is not wearing sunscreen and some of the body, typically the face and arms, are uncovered by clothing and therefore able to receive direct sunlight. It is important to remember that the amount of vitamin D produced in response to sun exposure can vary depending on clothing type, the amount of melanin in the skin and the use of sunscreen. It is believed that casual exposure to sunlight without sunscreen will typically provide sufficient vitamin D to last through the winter months. However, if you live in an area where there is little sun year round or you do not spend any time in the sun, it is important to consume adequate dietary sources of the vitamin or supplementation may be necessary.
Getting Vitamin D Without the Sun
As we discussed earlier there are two forms of vitamin D: vitamin D2 and vitamin D3. Vitamin D2 is derived from dietary sources, mainly fatty fish, dairy products (including fortified milk, cheese, butter, cream, and margarine), fortified cereal or other enriched foods and multivitamins.
While there has been some debate regarding the amount of vitamin D that should be consumed, the Adequate Intake (amount that is necessary to maintain adequate health) recommended by the U.S. Institute of Medicine of the National Academy of Sciences is 5 micrograms (200 IU or International Units) daily for all individuals (males, female, pregnant/lactating women) between the ages of 18-50 years. For anyone 50-70 years-old, 10 micrograms daily (400 IU) is recommended. For those who are over 70 years-old, 15 micrograms daily (600 IU) is suggested. For infants, children and teenagers under the age of 18, 5 micrograms (200 IU) is recommended daily, however, recent studies suggest 10 micrograms (400 IU) may be beneficial.
While those recommended intake numbers sounds spectacular, they aren’t much help if you don’t know how much vitamin D is actually in the foods you eat…so we’ve included a list of foods that are high in vitamin D below:
Herring, fresh, raw, 1 oz: 6.6 micrograms
Salmon, cooked, 1 oz: 3.5 micrograms
Cow’s Milk, fortified, 1 cup: 2.5 micrograms
Sardines, canned, 1 oz: 2.1 micrograms
Egg yolk: 0.6 micrograms
Looking at some of these foods, you might wonder how you can reach your daily intake. Do you really have to consume a can of sardines every day (which we do not recommend for social reasons alone)? If you look closely at the serving sizes you’ll notice that, for example, 1 oz. of salmon provides 3.5 micrograms of vitamin D…and most people consume significantly more than 1 oz of fish at any given time. The take home message: make sure to factor serving size into your calculation!
Consuming Too Much or Too Little?
Deficiencies in vitamin D result in rickets in children and osteomalacia or osteoporosis in adults; these diseases are characterized by defects in bone mineralization. Rickets is a condition in which the mineralization of growing bones is impaired as a result of insufficient vitamin D, calcium and phosphorus, all of which are important for normal bone growth. Osteomalacia, which means soft bones (you can see the change in bone density in the x-ray to the left), is seen in adults with inadequate dietary intake of vitamin D, insufficient sun exposure or chronic diseases including kidney and liver disease. On the other hand, osteoporosis is characterized by calcium loss from the bones leading to increased risk of bone fractures.
As with most things in life, too much is never a good thing. Too much vitamin D can cause your body to absorb too much calcium leading to calcium deposits in soft tissue. Since vitamin D is fat soluble, excess doses are stored in your body’s fat (as opposed to water-soluble vitamins which are excreted in urine when you consume too much).
Vitamin D and Aging:
As you age, your experiences a 75% reduction in its ability to produce vitamin D3 as a result of less efficient production in your skin as well as reduced sun exposure, making the elderly particularly at risk for vitamin D deficiency (1). Since the elderly are at a higher risk for bone fractures and osteoporosis (for a number of reasons, many of which we are sure you can imagine), multiple studies have looked at the effect of vitamin D supplementation on bone health. A study by Trivedi et al, examined the effect of vitamin D supplementation on risk of fracture in the elderly (2). The study provided the 2,686 male and female subjects ages 65-85 years, with 100,000 IU of vitamin D, or a placebo, every 4 months for a 5-year period. The study showed a reduction in fracture risk in the hip, wrist/forearm and vertebrae by 33% in the group receiving the vitamin D supplementation. However, the RECORD (Randomized Evaluation of Calcium and/or vitamin D) trial compared the effects of 1000 mg calcium carbonate, 800 IU vitamin D3, combined 800 IU vitamin D3 and 1000 mg calcium carbonate to a placebo on 5,292 men and women over the age of 70 years with previous a fracture, during a 2 year period (3). No significant differences were seen between the various groups in regards to bone fractures. Very confusing, we know. Science has a way of doing that to us.
So What Do I Do?
There are many ways to get your needed dose of vitamin D, whether through the sun, food or supplements. The best plan of attack depends on your lifestyle, age and a number of other factors. Most of the population meets their body’s vitamin D needs from sun exposure alone. If you are unable to spend 10-15 min in the sun without sunscreen, make sure you eat enough foods high in vitamin D. In the elderly or people living in areas with little sunlight, supplementation may be necessary to reach adequate levels. Remember that you only need a little sunlight to get all of the vitamin D your body needs. If you’re planning a day in the sun, don’t forget your sunblock!
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Palacios C. The role of nutrients in bone health, from A to Z. Critical reviews in food science and nutrition. 2006;46:621-8.
Trivedi DP, Doll R, Khaw KT. Effect of four monthly oral vitamin D3 (cholecalciferol) supplementation on fractures and mortality in men and women living in the community: randomised double blind controlled trial. BMJ. Clinical research ed. 2003 Mar 1;326:469.
Grant AM, Avenell A, Campbell MK, McDonald AM, MacLennan GS, McPherson GC, Anderson FH, Cooper C, Francis RM, et al. Oral vitamin D3 and calcium for secondary prevention of low-trauma fractures in elderly people (Randomised Evaluation of Calcium Or vitamin D, RECORD): a randomised placebo-controlled trial. Lancet. 2005 May 7-13;365:1621-8.