I’ve received this question twice in the past week, so thought I’d turn it into a post in case other people are wondering the same thing:
“Do you have any view on whether calcium and Vitamin D supplements should be taken at the same time to ensure they are absorbed properly? This seems to be the reason that calcium and Vitamin D are often sold in the same pill. Alternatively, if you aim to get Vitamin D from sunshine, should you wait to take the calcium supplement at that point of the day?”
There is no need to take vitamin D (or get sun) at the same time as you eat calcium. The vitamin D that you eat needs to be absorbed into your blood and then taken to the liver to be modified into a circulating, storage form of vitamin D known as 25(OH)D. Then, when your body senses that you need to absorb more calcium, the kidney further modifies the 25(OH)D into the hormone calcitriol. Calcitriol then increases calcium absorption. Vitamin D ingestion at a single meal will not have an effect on calcium absorption at that meal.
1. On p. 8 of the Executive Summary for their 2010 Dietary Reference Intakes for Calcium and Vitamin D, the Institute of Medicine says that they are basing their recommendations on a vitamin D level of 16 to 20 ng/ml of 25(OH)D. I have been using that as the level to indicate adequate vitamin D. But later in the document (p. 14), they talk about ideal levels some more and conclude that less than 20 ng/dl might be potentially too low for some people and therefore they recommend at least 20 ng/ml.
I have changed the levels in my calcium and vitamin D articles to reflect this. (Thanks, Brandon!)
2. In the table of calcium in plant foods, I had listed the wrong amount of calcium in a 1/2 cup serving of “Mustard greens – frozen, cooked, boiled, drained, chopped” as 107 mg. It is actually 76 mg.
This is an abridged version of Calcium and Vitamin D, which includes references and more details on just about every paragraph below. This should conclude my calcium-vitamin D barrage of the past few weeks!
Americans are regularly being urged to consume more calcium in order to prevent osteoporosis. It is practically impossible to meet the recommendations without large amounts of cows’ milk, calcium-fortified foods, or supplements.
Because vegans do not eat dairy products, without fortified foods or supplements their calcium intakes tend to be low (about 400-600 mg per day compared to the U.S. recommended intake of 1,000 mg per day).
Traditionally, the vegan community has responded to this by saying osteoporosis is a disease of calcium loss from the bones, not a lack of calcium in the diet. This was based on two ideas.
The first idea is that ecological studies have shown that the countries with the highest intake of dairy products (northern Europe and the USA) have higher rates of hip fractures than do Asian and African countries where much less milk is consumed. This in turn, can be explained by the second idea, which is that studies show that after ingesting animal protein, people urinate large amounts of calcium.
Therefore, the thinking goes, calcium intake isn’t important for preventing osteoporosis and vegans are protected due to the lack of animal protein in their diets.
Unfortunately, there is a lot of evidence to suggest that this is not correct. It turns out that hip fractures are more indicative of the risk of falling than of osteoporosis in some countries, with a recent study from Hong Kong showing that while men and women in Hong Kong had lower rates of hip fractures, they had higher rates of vertebral factures, and the women had higher rates of osteoporosis than Caucasian women.
As for protein leaching calcium from bones into the urine – it’s a lot more complicated than that. The studies that showed calcium to be urinated out were done using protein isolates whereas eating protein from whole foods does not result in a calcium imbalance. Population studies and clinical trials show that protein, including animal protein, does not have a negative effect on bones (more details here).
So where does that leave vegans?
Vegans’ bone mineral density, a measure of osteoporosis, has been shown in many studies to be slightly lower than non-vegans. More importantly, the one study on Western vegans measuring fracture rates over time found that vegans in the group who got less than 525 mg of calcium per day had a higher fracture rate than vegans in the group getting more than 525 mg. The vegans in the lower calcium group also had higher fracture rates than the meat-eaters and lacto-ovo vegetarians.
Although it is possible to meet the calcium recommendations by eating greens alone, the average vegan probably will not meet recommendations without drinking a glass of fortified drink each day, eating calcium-set tofu, or taking a 250 – 300 mg supplement (in addition to eating an otherwise balanced diet).
The greens highest in absorbable calcium are kale, mustard greens, bok choy, turnip greens, collards, and watercress (more info). In addition to calcium, greens also contain vitamin K, potassium, and magnesium, which also contribute to better bone health.
While spinach, Swiss chard, and beet greens are high in calcium, it is not well absorbed due to their also high content of oxalates, which bind calcium and prevent absorption from the digestive tract.
Research is mixed about whether calcium intakes above 1,400 mg per day can put people at risk for chronic disease. If you take a calcium supplement, it’s best not to go overboard. Most vegans taking 250-300 mg per day would not come close to 1,400 mg.
Vitamin D is also important for bones, as it can increase calcium absorption when the body signals that it needs calcium. Research has shown that in populations with calcium intakes similar to omnivores in the United States, vitamin D is more important than calcium for preventing osteoporosis.
In recent years, vitamin D has also been linked to many other diseases and some researchers have suggested that the recommended vitamin D levels are too low. However, the Institute of Medicine has reviewed the research and concluded that is not the case. The controversy has resulted in many people thinking they are deficient in vitamin D when they are not.
The only significant, natural, dietary sources of vitamin D are fatty fish, eggs (if chickens have been fed vitamin D), and mushrooms (if treated with UV rays). Most Americans get their dietary vitamin D through fortified milk and fortified margarine. The vegan diet contains little, if any, vitamin D without fortified foods or supplements. On average, vegans’ vitamin D levels are adequate, but somewhat lower than non-vegans.
Most people get a significant amount of their vitamin D from the action of UV rays on their skin. While the body can store vitamin D made in the sunnier months for use during less sunny times, this does not work for everyone. In fact, some people, even those living in sunny climates, develop extremely low levels of vitamin D. This can manifest itself through fatigue and bone pain.
If your arms and face (or the equivalent amount of skin or more) is exposed to the following amounts of midday sun (10 am to 2 pm), without sunscreen, on a day when sunburn is possible (i.e., not winter or cloudy), then you should not need any dietary vitamin D that day:
On all other days, people older than one year should get 600 to 1,000 IU of vitamin D.
Due to skin cancer concerns, some dermatologists recommend getting all your vitamin D from supplements rather than the sun. The amounts of sun above for light and dark-skinned people should be safe, but I have not seen research on how much sun is safe for elderly people and recommend talking to your doctor about how to get vitamin D if you believe you are at risk for skin cancer.
600 to 1,000 IU of vitamin D is only available in supplemental form or specially treated mushrooms.
There are two forms of supplemental vitamin D: D2 and D3. Vitamin D2 is always vegan, made from exposing fungi to UV rays. Vitamin D3 normally comes from fish oil or sheep’s wool, but there is a vegan version made by Vitashine.
A great deal of research has been conducted on vitamin D2 and D3. Vitamin D2 is effective at increasing bone mineral density (when given to people who are deficient). Vitamin D2 can also increase vitamin D levels temporarily, but is not as effective as vitamin D3 at keeping vitamin D levels raised when taken only weekly. If you take vitamin D on a regular basis, D2 should be fine, whereas if you are only going to take it sporadically, without getting sun in the interim, or find that your vitamin D levels will not increase on D2, then you should opt for D3.
If you are trying to raise your vitamin D levels with D2, make sure the laboratory can detect vitamin D2, and not just vitamin D3. Also make sure that you are not trying to raise your levels beyond what the Institute of Medicine says is adequate (50 nmol/l or 20 ng/ml) as there’s no sense in worrying if you cannot seem to get your vitamin D levels twice as high as necessary!
Food manufacturers are now creating large amounts of vitamin D2 in mushrooms by exposing them to commercial ultraviolet light or direct sunlight (55, 56). The vitamin D is well-retained in the mushrooms over the course of the typical storage life of fresh mushrooms, up to two weeks (55, 57). This vitamin D is effective in improving vitamin D status and no different from a vitamin D2 supplement (2).
2. Urbain P, Singler F, Ihorst G, Biesalski HK, Bertz H. Bioavailability of
vitamin D₂ from UV-B-irradiated button mushrooms in healthy adults deficient in
serum 25-hydroxyvitamin D: a randomized controlled trial. Eur J Clin Nutr. 2011
Aug;65(8):965-71. doi: 10.1038/ejcn.2011.53. Epub 2011 May 4. | link
55. Kalaras MD, Beelman RB, Elias RJ. Effects of postharvest pulsed UV light treatment of white button mushrooms (Agaricus bisporus) on vitamin D2 content and quality attributes. J Agric Food Chem. 2012 Jan 11;60(1):220-5. | link
56. Simon RR, Phillips KM, Horst RL, Munro IC. Vitamin D mushrooms: comparison of the composition of button mushrooms (Agaricus bisporus) treated postharvest with UVB light or sunlight. J Agric Food Chem. 2011 Aug 24;59(16):8724-32. | link
57. Roberts JS, Teichert A, McHugh TH. Vitamin D2 formation from post-harvest UV-B treatment of mushrooms (Agaricus bisporus) and retention during storage. J Agric Food Chem. 2008 Jun 25;56(12):4541-4. | link
1. Vesanto Melina, author of Becoming Vegan, kindly passed on a study about vitamin D2 in UV-irradiated mushrooms. 28,000 IU of vitamin D2 was fed to subjects either in the form of a supplement or from mushrooms, one time per week for four weeks. Vitamin D levels increased from 34 to 57 nmol/l in the mushroom group, and from 29 to 58 nmol/l in the supplement group (recommended levels are 40 – 50 nmol/l). The placebo group’s vitamin D2 levels decreased over the course of the study (1).
2. Dole is now making a Portobello Mushroom Powder with the RDA of 600 IU per teaspoon. (Link)
1. Urbain P, Singler F, Ihorst G, Biesalski HK, Bertz H. Bioavailability of vitamin D₂ from UV-B-irradiated button mushrooms in healthy adults deficient in serum 25-hydroxyvitamin D: a randomized controlled trial. Eur J Clin Nutr. 2011 Aug;65(8):965-71. doi: 10.1038/ejcn.2011.53. Epub 2011 May 4. | link
Dr. Michael Greger’s Latest in Clinical Nutrition 6 is now available! In it, he mentions a study about taking vitamin D with meals. I’ve wondered if doing this would help people whose vitamin D levels seem to be resistant to supplementation and so I tracked down the study and updated the VeganHealth.org article, Bones, Vitamin D, and Calcium:
Because vitamin D is a fat soluble vitamin, taking vitamin D supplements with foods that contain fat might increase absorption.
A 2010 study explored this (1). A group of people diagnosed with vitamin D deficiency had been prescribed supplements (some D2 and some D3) and were being monitored by the Cleveland Clinic Foundation Bone Clinic. Some of these patients’ vitamin D levels had not increased to desired levels. Patients with stubborn vitamin D levels were then instructed to take the vitamin D with meals. After 2 to 3 months of taking with meals, the average vitamin D level went from 30 to 47 ng/ml (75 to 117 nmol/l).
This study had no control group, so it is not clear that the vitamin D levels increased due to taking with meals. It could have been simply because their levels took longer to respond to supplements or because they were exposed to more sunlight during the meal period (the time of year studied was not reported). It should also be noted that even though these subjects’ vitamin D levels were more stubborn than other patients, their levels at the beginning of the study were well above those recommended by the Institute of Medicine (16-20 ng/ml or 40-50 nmol/l) the stubborn levels might have been a result of the body regulating vitamin D once it had reached an ideal level rather than an inability to absorb it.
1. Mulligan GB, Licata A. Taking vitamin D with the largest meal improves absorption and results in higher serum levels of 25-hydroxyvitamin D. J Bone Miner Res. 2010 Apr;25(4):928-30. Link
As promised in my post of July 29, Update: Vegan D3, I corresponded with Stephen Walsh, PhD of the UK Vegan Society about giving their seal of approval to the company Vitashine for vitamin D3.
Dr. Walsh said that they met with the company and that they were satisfied that the D3 in their product is vegan. Vitashine claims to get the D3 from lichen.
I then found a study that confirmed that at least some species of lichen grown in some locations contain vitamin D3:
Wang T, Bengtsson G, Kärnefelt I, Björn LO. Provitamins and vitamins D2 and D3 in Cladina spp. over a latitudinal gradient: possible correlation with UV levels. J Photochem Photobiol B. 2001 Sep 1;62(1-2):118-22. Abstract | PDF
The next logical question is whether vegans should go to the trouble of getting vitamin D3 instead of using vitamin D2. I would suggest that unless you are having problems raising your levels of vitamin D using D2, it is unnecessary.
One bit of advice I have is to take vitamin D with some fat to help increase absorption. I base this only on the fact that vitamin D is fat soluble – I do not know of any trials studying this.
As many of you know, the form of vitamin D made from plants is vitamin D2 (ergocalciferol), whereas the vitamin D from animals foods is vitamin D3. Some research has indicated that, especially in very large doses, D3 is more effective than D2.
Today, a reader (thanks again, Ivan!) pointed me to a company, Vitashine, that is selling a Vegan Society (UK) approved vitamin D3:
I’m going to look into this more with the Vegan Society to hopefully get some details.
In the meantime, Vitashine’s website does not instill confidence with this statement:
“Vitamin D3 (cholecalciferol) is the form of Vitamin D produced by the body after sun exposure. Vitamin D2 (ergocalciferol) supplements are widely sold on the market, but D2 needs to be further converted by the body to become active.”
Vitamin D3 also needs to be further converted by the body to become active. Whether it’s D2 or D3, both the liver and the kidney need to act upon it to convert it, respectively, to calcidiol and then calcitriol. Calcitriol is the active form of the vitamin.