Myth: Our Needs for Vitamin D Can Be Met By Sunlight
Though not really a vegetarian myth per se, it is widely believed that one's vitamin D needs can be met simply by exposing one's skin to the sun's rays for 15-20 minutes a few times a week. Concerns about vitamin D deficiencies in vegetarians and vegans always exist as this nutrient, in its full-complex form, is only found in animal fats which vegans do not consume and more moderate vegetarians only consume in limited quantities due to their meatless diets.
It is true that a limited number of plant foods such as alfalfa, sunflower seeds, and avocado, contain the plant form of vitamin D (ergocalciferol, or vitamin D2). Although D2 can be used to prevent and treat the vitamin D deficiency disease, rickets, in humans, it is questionable, though, whether this form is as effective as animal-derived vitamin D3 (cholecalciferol). Some studies have shown that D2 is not utilized as well as D3 in animals and clinicians have reported disappointing results using vitamin D2 to treat vitamin D-related conditions.
Although vitamin D can be created by our bodies by the action of sunlight on our skin, it is very difficult to obtain an optimal amount of vitamin D by a brief foray into the sun. There are three ultraviolet bands of radiation that come from sunlight named A, B, and C. Only the "B" form is capable of catalyzing the conversion of cholesterol to vitamin D in our bodies and UV-B rays are only present at certain times of day, at certain latitudes, and at certain times of the year. Furthermore, depending on one's skin color, obtaining 200-400 IUs of vitamin D from the sun can take as long as two full hours of continual sunning. A dark-skinned vegan, therefore, will find it impossible to obtain optimal vitamin D intake by sunning himself for 20 minutes a few times a week, even if sunning occurs during those limited times of the day and year when UV-B rays are available.
The current RDA for vitamin D is 400 IUs, but Dr. Weston Price's seminal research into healthy native adult people's diets showed that their daily intake of vitamin D (from animal foods) was about 10 times that amount, or 4,000 IUs. Accordingly, Dr. Price placed a great emphasis on vitamin D in the diet. Without vitamin D, for example, it is impossible to utilize minerals like calcium, phosphorous, and magnesium. Recent research has confirmed Dr. Price's higher recommendations for vitamin D for adults.
Since rickets and/or low vitamin D levels has been well-documented in many vegetarians and vegans, since animal fats are either lacking or deficient in vegetarian diets (as well as those of the general Western public who routinely try to cut their animal fat intake), since sunlight is only a source of vitamin D at certain times and at certain latitudes, and since current dietary recommendations for vitamin D are too low, this emphasizes the need to have reliable and abundant sources of this nutrient in our daily diets. Good sources include cod liver oil, lard from pigs that were exposed to sunlight, shrimp, wild salmon, sardines, butter, full-fat dairy products, and eggs from properly fed chickens.
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Sunlight Sunlight is the best way to get Vitamin D. Twenty minutes for white people, up to 90 minutes a day for blacks produces between 10,000IU to 20,000 IU per day. There are also numerous other substances created in the skin in sunlight, that are believed to be beneficial, that researchers have not yet studied, in addition to vitamin D.
While it is true that people living above 35 degrees north of the equator cannot make vitamin D all year around, it is still important to make best use of the time available, when there is enough UVB.
Diet You can't get enough Vitamin D from diet. The required amounts of oily fish, cod liver oil, mushrooms, or fortified foods are impractical to consume daily.
The body needs 3,000IU - 8,000IU per day for optimal health. A multi-vitamin contains 400IU to 800IU. If sunlight is not an option, supplementation is the best alternative.
Cod liver oil is great, but does not contain sufficient Vitamin D in a 10 ml dose. Taking more than 2-3 times this is not recommended as the Vitamin A (retinol) it contains can build up to toxic levels in body fat if large doses are taken over an extended period.
Vitanin D2 This is as effective as Vitamin D3 in maintaining 25(OH) Vitamin D levels in the body. The problem is that vegans cannot eat enough foods that contain it to get an adequate dose.
In summary sunlight is the best way to get vitamin D. If it is not sunny where you live, then try to eat as much oil fish as possible. Take a daily supplement of vitamin D (aim for a total of 3,000 IU -5,000IU), and Cod lover oil.
It is not necessary for vegans to eat meat for Vitamin D. Bioavailable Vitamin B12 and good saturated fats are another issue.
What you fail to consider in your argument is balance. While it may be true that people who eat moderately (animal flesh and organs as well as plant matter) are healthier than those who don't, we live in a nation where people overeat, and they overeat cows, chickens, and pigs. By providing examples of vegetarians who overeat and omnivores who do not, you provide a weak analogy. In addition, you fail to note that plants do contain vitamin D; you fail to note that people do take multi-vitamins for Vitamin A and D; you fail to note that people can receive extra calcium through tablets.
I remain uncommitted on this issue because health factors do vary: I believe most people who choose a vegetarian diet for health reasons are healthier and evidence does show vegetarians live longer, but what makes a person healthy is moderation (and, yes, genetics).
This forum did not discuss the ethical issue of the way the United States raises and slaughters animals , which is a fact in why many people turn to vegetarianism . I would have liked this issue addressed.
The whole point is moot in regards to the main discussion of is a vegetarian diet healthier? Eating a diet of vegetables will provide plenty of vitamin D for you body which you acknowledge albeit saying they are possibly not utilized as well. So why are you listing a sunlight myth as evidence in proving a vegetarian diet is not optimal? I'm not sure it's even a well accepted myth, rather seems to just be one more bit of ammo Weston A Price misuses.
The latest and seemingly most comprehensive study comparing D2 and D3 concludes that in fact vitamin D2 is just as effective. Below I quote Dr Michael Holick who explains the latest study to date.
" To determine whether vitamin D2 was as effective as vitamin D3 in maintaining circulating blood levels of 25-hydroxyvitamin D, a study was conducted whereby healthy adults received either 1,000 IU of vitamin D2 or 1,000 IU of vitamin D3 in a capsule once a day in the winter for 11 weeks. In addition, one group received a placebo capsule and one group received a capsule that contained 500 IU of vitamin D2 and 500 IU of vitamin D3 daily for 11 weeks. Blood levels of both 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 were determined by state of the art method using liquid chromatography tandem mass spectroscopy. Holick et al, (Vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-hydroxyvitamin D, J Clin Endocrinol Metab 93:677-681, 2008;) reported that the blood levels of 25-hydroxvitamin D rose to the same degree in the healthy adults who took either 1,000 IU of vitamin D2 a day or 1,000 IU of vitamin D3 a day for 11 weeks. The group that received vitamin D2 also had their blood level of 25-hydroxyvitamin D3 measured. There was no significant drop in the blood level of 25-hydroxyvitamin D3. To determine whether the mixture of vitamin D2 with vitamin D3 would alter the blood levels of 25-hydroxyvitamin D, the adults who received 500 units of vitamin D2 with 500 units of vitamin D3 also raised their total blood levels of 25-hydroxyvitamin D3 in an almost an identical manner as the adults who received 1,000 IU of vitamin D2 or 1,000 IU of vitamin D3 a day for 11 weeks. The authors concluded that ingesting 1,000 IU of vitamin D2 or 1,000 IU of vitamin D3 a day during the winter (at a time when sun exposure had no influence on blood levels of 25-hydroxyvitamin D) that both vitamin D2 and vitamin D3 were equally effective in maintaining the blood levels of 25-hydroxyvitamin D. Furthermore, vitamin D2 did not have a negative influence on serum levels of 25-hydroxyvitamin D3. Adults who took 500 units of vitamin D2 with 500 units of vitamin D3 had similar increases in their blood levels of 25-hydroxyvitamin D suggesting that vitamin D2 taken with vitamin D3 does not have any negative influence on the metabolism of vitamin D3.
The authors reviewed in their Conclusion several studies that had previously reported that vitamin D2 was as biologically effective as vitamin D3 in both pregnant women and in healthy adults. This study confirms these observations and adds to the body of scientific literature demonstrating that at least when healthy adults take 1,000 IU of vitamin D2, they can be assured that it is as effective as taking 1,000 IU of vitamin D3 "
Plenty of vegan foods are fortified with vitamin D. You can buy fortified soy milk, orange juice, breakfast cereals... Or take a multi-vitamin. And/or spend time outdoors in the sunlight.
More resources:
http://www.vegansociety.com/food/nutrition/vitaminD.php
http://www.veganhealth.org/articles/bones
I've been vegan over two years and vegetarian 26 years prior and I've NEVER had a nutrient deficiency. Eat a wide variety of foods, learn about nutrition, and use common sense.