Answers to your mushroom questions about our product details, ordering & shipping, taking medicinal mushroom extracts, and about the health benefits and effects by mushroom type.
Please check your order confirmation email which will have a link to your order’s status. This link will also contain the tracking info if your order has shipped. Orders will generally ship within 2 business days if all items are in stock.
Items that are out of stock will ship on a first come first serve basis once they are back in stock.
Please check the packing slip that was shipped with your order to see if all items were packed. If items are missing from the packing slip then most likely some part of your order was out of stock at the time your order was placed.
Our system will ship the items that are in stock and it will queue up a backorder for the items out of stock. When new stock arrives, the rest of your order will ship immediately.
If the packing slip indicates all items were shipped and you did not receive everything, please contact us.
Contact us immediately with your order# and send us photos.
All of our orders ship from Sparks, Nevada, USA.
We ship to USA, Canada, Europe, Australia, New Zealand, Hong Kong, Singapore and Japan.
If you are in Canada you can also order via our Amazon.ca Store. Look for the wording “Sold By Real Mushrooms and Fulfilled by Amazon.” This will ensure the order comes from Amazon’s Canadian warehouse.
If you are in Europe you can also order via our Amazon.co.uk Store and it will ship from the UK.
If you do not see your country listed at checkout, we recommend setting up a freight forwarding account with some like Shipito. These types of services give you a US address to ship to and then charge you a small fee to forward your shipment on to your destination country.
See more info on our Shipping Page.
The majority of our order originate in the U.S. and the majority of our expenses are in USD hence all our prices are in USD
If you live outside the US, there is potential that your order may be assessed for duties and/or taxes. This is entirely dependent on your country’s import regulations. Typically, the higher the order value, the more likely it will be assessed for duties and/or taxes.
If you live in Canada, you can order off Amazon.ca and avoid possible duties and/or taxes. If our Amazon.ca product listing says “Sold by Real Mushrooms and Fulfilled by Amazon” then this is inventory that Amazon holds for us in Canada so it will be shipped from within Canada and you will avoid any border charges. However, if the Amazon.ca listing says “Sold and Shipped by Real Mushrooms” then this inventory comes from our US warehouse and does have the potential for possible border charges.
If you live in the EU, you can order off Amazon.co.uk and avoid possible duties and/or taxes. This is inventory that Amazon holds for us in the UK so it will be shipped from within the UK.
If you’ve ordered Real Mushrooms through Amazon then it is most likely that Amazon has shipped out your order. We send inventory to Amazon and they ship it out for us when you order it. Because Amazon takes care of the shipping and handling, they do not give us access to any of the tracking information to help you in the event that there is an issue with your order. I wish we would help you but we do not have the information needed to do so.
You will need to contact Amazon support directly in regards to your order.
For contacting Amazon, please see these helpful Amazon resources:
Subscriptions make sure you never run out of mushrooms. All subscribers get 15% off and free USA shipping. You can add, edit, modify, cancel, skip your subscriptions at any time. Fully customizable.
Choose the “Subscribe and Save” option when adding to cart.
When on any subscription enabled product page, select the “Subscribe and Save” option and select the number of units and how often you want to receive the product (every 1 month or 2 months).
Once you complete the checkout, you will receive an email to complete the creation of our Real Mushrooms account where you will be able to access all your subscriptions details.
- Log into your Real Mushrooms account
- Select Manage Subscriptions on the left
- Under Subscription Orders select the cancel option next to the product you would like to cancel
If you just want to skip a shipment, see below.
- Log into your Real Mushrooms account
- Select Manage Subscriptions on the left
- Under Subscription Orders select the edit option
- Here you can change how often it is delivered, the # of units, the credit card on file and shipping address
If you’re still fully stocked with mushrooms, instead of just cancelling, you can decide to skip a shipment.
- Log into your Real Mushrooms account
- Select Manage Subscriptions on the left
- Select Delivery Schedule on the left
- This will show all your upcoming shipments
- Here you can choose to skip a shipment
Mushrooms - General
We take great pride in providing mushroom extract powders of the highest quality. One of the ways we do this is by using the mushroom (fruiting body) in all our products rather than using the mycelium (mushroom root system) which is commonly grown with grain. I’ll explain more about this further below.
All our mushroom extracts are from the leading supplier of organic mushroom extracts: Nammex. They have over 40 years of mushroom growing experience and were one of the first companies to bring organic medicinal mushroom extracts to North America. Their ingredients go through rigorous quality control and are tested twice for heavy metals, agricultural chemicals and microbial contamination to ensure they meet all standards for dietary supplements of this nature. All of their extract are made from certified organic mushrooms (fruiting bodies), organically grown or wildcrafted from deep within mountain regions of China.
Mushrooms used for dietary supplements are seldom grown in North American since it’s too expensive. In fact, China is the leading supplier of mushrooms worldwide and supplies over 85% of the world’s mushrooms. It has a rich history of mushroom use as both food and medicine and is the birth place of mushroom cultivation with shiitake being farmed in the early 1200s. China is one of the only places in the world where you can get 100% organic mushroom (fruiting body) extracts that can be sold at an affordable price.
An important note is that any products made in the USA are typically not made from mushrooms but mycelium, the mushrooms root system, grown on grains.
The grain cannot be separated from the mycelium so it ends up being a significant portion of these types of products. Independent analysis has shown that due to this high amount of grain, they contain very little of the active compounds found in the research. Read your supplements panel very closely and look for the words “mycelium”, “myceliated brown rice”, “mycelial biomass”, “full spectrum”, “whole life cycle” or other derivatives of mycelium. Click here to see what it actually looks like. It is not mushrooms. See “What is mycelium on grain” for more details.
This is why we specifically test for beta-glucans and starch, to show the potency of our products and to show that we have no added fillers like grain. Just 100% mushrooms.
Of course. All products are screened for heavy metals twice. We follow the American Herbal Products Association (AHPA) guidelines for heavy metals.
All of our product specifications follow the following industry established limits:
- Lead: <2ppm*
- Arsenic: <2ppm*
- Cadmium: <2ppm*
- Mercury: <0.1ppm*
Based on our recommended dosage (1g), our heavy metal limits are even stricter than the limits set by AHPA.
As we, the Real Mushrooms team, are also consuming our products on a daily basis, we are always concerned about the health and safety of our products.
*ppm = parts per million
Beta-glucans, which are a polysaccharide, are the most well researched medically active compound in mushrooms. For this reason, we specifically measure beta-glucan levels on our products. We do not believe in using polysaccharides as a measure of quality as it can be easily doctored using starch. Starch is an alpha-glucan, which is also a polysaccharide.
As an example, mycelium on grain products have been shown to have high levels of starch, which allows them to tout high polysaccharide numbers when in reality they have very low amounts of beta-glucans as the bulk of these polysaccharides are made up of starch. The starch comes from the grain that ends up in the final product.
Read our full article on why polysaccharides are a poor measurement of quality.
We list starch as a way to prove that our product is 100% mushroom.
Mushrooms generally do not contain starch. They do, however, contain small amounts of glycogen. Typically less than 5%.
As per the Nammex report, mushrooms have very low levels of alpha-glucans.
When we do our beta-glucan testing and verify the beta-glucans in the product, that same test also measures alpha-glucans. We use this alpha-glucan number as our starch basis though we know is it primarily glycogen because mushrooms do not contain starch. This saves us from additional testing costs to measure starch specifically when we already know that it is less than the alpha-glucan number.
Starch is a common carrier material that can be found in many medicinal mushroom supplements. It is often used as a carrier in mushroom extracts in the form of dextrose or maltodextrin.
In the case of myceliated grain products, high amounts of starch are present due to the grain that ends up in the final product.
This is why it is so important to measure starch so that you’re not wasting your money on carrier materials or grain. This is also why polysaccharides are a poor measure of quality. A simple iodine starch test can be done at home for under $5 to verify if any fillers are added.
All of our products have less than 5% alpha-glucans as they are made purely from mushrooms without any added of fillers or carriers.
Mycelium is the vegetative state (think root system) of the fungal life cycle. The fungal lifecycle consists of spore, mycelium and mushroom. Mycelium is the stage that produces a mushroom but it is not a mushroom. Just look at some images in Google.
Myceliated grain or grain spawn or mycelium biomass is a method for producing the seed for growing fresh mushrooms. It has now been adopted by many “mushroom” ingredient suppliers as an inexpensive way to produce a “mushroom” supplement, yet in reality it is not a mushroom product. It is a grain based mycelium product similar to tempeh.
The process involves taking a plastic bag of sterilized, cooked grain (rice, oats, sorghum, etc), injecting it with a fungal culture (reishi, chaga, shiitake etc.) and allowing the mycelium to grow out on the grain. Once the mycelium is fully grown out on the grain, it is harvested and the mycelium with the grain is dried and turned into a powder. This produces a product that does not contain any mushrooms, though the package may say “mushroom” on it, and it has a very high starch content (upwards of 70%) because of the residual grain ending up in the final product. Because of all this added grain, the amount of fungal material in the product is very low, leading to very low levels of active compounds like beta-glucans.
Myceliated grain is a cheap way to make “mushroom” supplements that are not actually mushrooms. In reality, when you compare the amount of active compounds in the product, it ends up being a very expensive product. To identify myceliated grain products, look for wording like “mycelium”, “myceliated brown rice”, “mycelial biomass”, “full spectrum”, “whole lifecycle” in the supplements panel and marketing materials. These are good indicators of grain based mycelium.
Products made entirely from mushrooms, like Real Mushrooms, typically have 5-10x more beta-glucans than mycelium on grain products.
Our extracts range from 1:1 to 16:1 but we do not list them specifically as we believe extract ratios have only limited value when not accompanied with active compound testing.
For example, without analytical testing there’s no way to know whether a 10:1 extract is more concentrated than a 4:1 extract. It is also possible to have two products with the same extract ratio yet with completely different levels of active compounds.
Also note that the higher the extract ratio, the more dense and sticky the final product gets so in order to keep it as a free flowing powder, a carrier is often added. This will dilute the potency. This is why measurement of active compounds and starch is so important.
Extract ratios can also be misrepresented. For example, fresh mushrooms are typically 90% water so the wet to dry ratio is 10:1. Some products use this ratio saying their products are a 10:1 extract (10lb of fresh mushrooms = 1lb of powder) when in reality it’s just a 1:1 (1lb of dried mushrooms = 1lb of powder). All extract ratios should be based off dry weight.
Without analytical testing of active compounds and starch measurements to show purity, extract ratios have limited value. Higher extract ratio does not equate to higher potency.
For these reasons, we do not specifically publish our extract ratios. If you’d like to know, just contact us.
The amount of active compounds in our products are some of the highest in the marketplace and the low levels of starch demonstrate the purity of our products.
All of our products have already been extracted with hot water and/or alcohol. Any further “extraction”, like adding them to hot water, will not effect the powder or the medicinal compounds.
When alcohol is used for extraction, it is precipitated out so it does not end up in the final product.
This indicates when the product was created. It is not an expiry date. The product is good for 2 years from the lot#.
Yes of course. A holistic vet who prescribes our products recommends 1/8 tsp twice daily for small dogs. Scale the dosage up or down accordingly to your pet’s size. If they do not like the taste, break the servings into smaller dosages more frequently over the day.
We use double extraction on our reishi and chaga ingredients in 5 Defenders and Reishi 415.
It is most important in reishi and chaga as much but not all of the beneficial triterpenes are non-water soluble. With other mushrooms it’s not as important as the main active component is the beta-glucans which are water soluble.
Typically with concentrated extracts, like in 5 Defenders and Reishi 415, you remove the mushroom fiber before concentration begins. This is why you would do separate hot water and alcohol extractions so you can obtain those beneficial triterpenes before the mushroom fiber gets removed.
On the other hand, our Chaga Extract, Lions Mane Extract, and Cordyceps-M products are 1:1 hot water extracts that still contain all of the mushroom fiber so nothing is lost in the extraction process and all of the non-water soluble components are still present even though it is a hot water extract.
For more information on this, please read our blog post.
Consumer brands typically don’t end up in the USDA Organic Integrity database because the brands themselves don’t apply to the certifying bodies for organic certification. It’s the facilities where the end products are produced that need to apply to be organically certified.
The facility producing the final product will add the brand’s products to their organic certificate annex which lists all the organic products for any brand that the facility produces. This means that the brand itself would not show up in the integrity database when you search for it, only the facility would.
In our case, we use North American Seasonings to produce our pouch products. They create the finished products and are certified by Washington State Department of Agriculture. You will find North American Seasonings in the USDA Organic Integrity database with our products listed.
The majority of medicinal mushrooms are grown on sawdust. This sawdust is a byproduct from local sawmills. Mushrooms are great at recycling waste materials and this is a perfect example. Sawdust that might normally be thrown away or burned, can be used to grow mushrooms.
One exception to this is reishi, which is grown on individual hardwood logs in the ground. These logs come from locally sourced beech wood. See here for more info on the logs used for growing reishi.
Mushrooms - Health
Generally speaking, mushrooms are roughly 25% protein, 58% carbohydrates and 3% fat. The rest is vitamins and minerals. 1 gram would be around 3-4 calories.
The optimal way to use our product is whatever way is the most convenient for you. This could be with hot water, coffee, tea, smoothie, shake, yogurt, bone broth, etc.
We have not seen any research to indicate one way over the other. We all respond differently to medicinal mushrooms so find the method that works best for you. Some might find they respond better mixing it with food where as others might respond better on an empty stomach.
You are more than welcome to mix 5 Defenders with Reishi 415, Chaga, Lions Mane and Cordyceps-M in your coffee, tea, juice, smoothie, yogurt etc. There are some studies that suggest a synergy when you consume various medicinal mushrooms at once making them even more potent and effective.
Our general recommendation is not to exceed 3-5 servings per day unless you have direction from a health practitioner.
During pregnancy, it is imperative to understand that every women responds differently to adaptogen use. It would be best to consult your healthcare physician and proceed with caution on this topic.
There are 3 to 4 calories in a serving of 1 gram or 1000 mg.
Natural ingredients don’t always smoothly flow through processing equipment and capsule manufacturers need to utilize other ingredients in order to fill capsules. It is common practise for encapsulation facilities to require the use of other ingredients.
We have worked closely with our encapsulation partners to make sure that only what is added is absolutely necessary to create the capsules.
None of the 500mg is other ingredients. Every capsule still has 500mg of organic mushroom extract powder. The other ingredients are in small amounts on top of that 500mg. Other ingredients are required to be listed from biggest amount to smallest. If you look at our labels, the capsule itself (Hypromellose) is the biggest component of the other ingredients with everything following in incrementally smaller amounts.
The capsules contain 500 mg per capsule of medicinal mushroom. 2 capsules = 1000 mg of medicinal mushroom extract, which is equivalent to 1/2 tsp serving of the mushroom powder. In terms of potency and efficacy, both the capsules and powders are equally effective at delivering.
The capsules are great for travel purposes, where as the powder can be great added to recipes or mixed in coffee, tea, bone broth to change up the flavor profile and lend more the full mushroom experience. In the end, you can’t go wrong here. It all depends on what you prefer.
The capsule is made from hypromellose, which is vegetable based cellulose.
Because the capsules themselves aren’t certified organic, we cannot get USDA Organic status. You will notice that the majority of capsule based supplements are not USDA Organic and this is the reason why. When certified organic capsules become more readily available, we will be looking into utilizing them.
All of our mushroom ingredients inside the capsule are still USDA Certified Organic and the ingredients are noted as organic in the Supplement Facts panel.
Magnesium Stearate is derived from vegetable based non-GMO stearic acid. It is used as a flow agent to ensure the powder flows into the capsules evenly and doesn’t stick to the machinery.
You can find more info about Magnesium Stearate and Stearic Acid here.
Stearic acid is a vegetable based non-GMO fatty acid. It is used as a flow agent to ensure the powder flows into the capsules evenly and doesn’t stick to the machinery.
You can find more info about Magnesium Stearate and Stearic Acid here.
The vegetable source of the stearic acid we use is derived from sustainable palm oil.
Health Practitioner Accounts
To give you further details about the bitterness of Reishi 415, the bitterness comes from the beneficial triterpene compounds. These compounds give reishi its bitter flavor. These compounds are found in the mushroom and our product is extracted exclusively from the mushroom (fruiting body).
You want a reishi product to be bitter. If a reishi product is not bitter, start asking questions.
Many so-called reishi products do not taste bitter and this is a perfect indicator of the product not containing any detectable amounts of the beneficial triterpene compounds. This is either due to inferior extraction or the product not being made from the mushroom.
We use an 8:1 dual extract, meaning 8 kilos of ground up reishi mushroom makes 1 kilo of our extract powder.
We strictly use the cap of the reishi mushroom for extraction.
Yes. This is made from Ganoderma lucidum, now known as Ganoderma lingzhi which is red reishi.
“Duanwood” is not a specific type of wood but actually a trademarked term by Dragon Herbs. They have done a great job promoting “Duanwood Reishi” as being top quality.
But what does it really mean?
According to their website: “Duanwood means “original wood.” The Reishi is grown on logs cut wild from the forest. The logs are from the same trees that Reishi grows on in the wild, producing the most potent Reishi.”
So Duanwood actually means reishi grown on wood logs and the vast majority of reishi grown in China already is log grown. Reishi grows on different species of hardwood trees so the actual wood log used will vary.
Our reishi mushrooms are grown on locally sourced beech wood.
Deforestation is the conversion of forest land to non-forest land.
The wood used for growing reishi is coming from tree farms which are continuously harvested and replanted. This is not deforestation.
The thing to remember with China is that they’ve had civilizations there for thousands of years. Much of China has been harvested many times over. What might look like wild foliage over there is almost certainly planted.
In much of our travels through China we pass miles and miles of planted bamboo and hardwood lots. These areas are continuously harvested and replanted.
This is by no means similar to common contributors to deforestation like sugarcane, palm oil, rice, corn and meat where the forests are removed for the production of these crops.
- Mix the reishi w/raw honey or local maple syrup and top it off with spices like ceylon cinnamon, nutmeg, and/or ginger
- Consider taking less throughout the day
- Add the reishi with other foods/liquids to mask the intensity
- Consider opting for the capsule version instead
5 Defenders contains the following extracts:
- 8:1 Organic Chaga Sclerotium Extract (hot water / alcohol extract)
- 8:1 Organic Maitake Mushroom Extract (hot water extract)
- 15:1 Organic Reishi Mushroom Extract (hot water / alcohol extract)
- 8:1 Organic Shiitake Mushroom Extract (hot water extract)
- 8:1 Organic Turkey Tail Mushroom Extract (hot water extract)
Authentic Cordyceps (O. sinensis), the caterpillar fungus, the one everyone sees in pictures (the dead caterpillar with the blade-like fruiting body growing from it) is actually the most expensive mushroom in the world; upwards of $40,000/Kg. With such a price tag there is absolutely no way authentic cordyceps (O. sinensis) could be used in an affordable supplement product.
Cultivation of authentic fruiting bodies has previously been impossible and only recently has China figured out how to cultivate Cordyceps sinensis to produce a fruiting body. That being said, the price is still much too high for commercial supplements, leaving only mycelium available for commercial products.
Anything from China is typically a product called Cs-4 which is a 100% pure mycelium product made via liquid fermentation.
Anything produced in the U.S. is mycelium on grain, which ends up being very high in starch due to the nature of Cordyceps mycelium which grows very slowly leaving a high amount of residual grain in the final product.
At Real Mushrooms we take a different approach. We use Cordyceps militaris because fruiting bodies can be cultivated. This allows us to use 100% organically certified fruiting bodies for our Cordyceps-M extract powder. We do not deviate from our ethos of offering 100% fruiting body products with high beta-glucan levels and next to no starch.
If you’d like to learn more about how Cordyceps relates to supplements, read: Cordyceps and Supplements: Past and Present.
See the answer above and this product contains no bugs.
Lions Mane Extract
There is still a lot of conflicting data around the NGF compounds in lion’s mane.
The two groups of compounds commonly cited are hericenones and erinacines. Hericenones are in the mushroom and erinacines are in the mycelium.
The issue with focusing on hericenones and erinacines is that we know of no reliable lab that can measure these compounds. So regardless of what any product might say in their marketing there is no way to verify any claims for these compounds.
For erinacines in the mycelium, this is all based on pure mycelium research. Almost all lions mane mycelium products are myceliated grain. This is apples to oranges. Myceliated grain has shown very low levels of the primary actives like beta-glucans so more abstract compounds like erinacines will likely occur in undetectable amounts.
With our Lion’s Mane extract, nothing is removed during the extraction process so even though it is a hot water extract, it will still contain all the non-water soluble compounds.
It’s important to remember that the only three clinical trials are using the whole mushroom:
These used un-extracted lions mane mushroom powder. As our product is extracted and still contains the entire mushrooms, it would be consistent with these studies with added bioavailability from being extracted.
Until a reliable lab can measure hericenones and erinacines, we are confident with staying consistent with the existing clinical data.
Currently it is not possible to measure these compounds but we are looking into ways to do so.
While Chaga is commonly referred to as a mushroom, the part of the chaga that is wild harvested is actually not a mushroom but a sclerotium. A sclerotium is a hardened, dense mass of mycelium. Chaga is unique in that it is not pure mycelium like other sclerotia’s (poria, polyporus) as much of the mass is actually wood fiber which comes from the tree is grows on.
While many claim otherwise, from the data that we’ve seen it definitely looks to be sustainable.
The only sustainability report that we’ve found was done in Russia, who is a large exporter of chaga. It showed that chaga could easily sustain existing demand for the foreseeable future.
It also estimated that 20% of all birch forest in Russia are infected with chaga.
The Finnish Forest Research Institute has said that anywhere from 6-30% of birch forests in Sweden and Finland are infected with chaga.
Our own personally take is that chaga is definitely sustainable as there are vast birch forests all across the northern hemisphere. The problem being that harvesters will have to go further and further into the woods to find chaga which will further increase the price of raw chaga. At some time, there may be a tipping point where chaga will become too expensive for supplements which will curb demand well before there is any worry about over-harvesting.
This is a common misconception.
Chaga is classified as a tree disease in British Columbia. It infects the host tree, typically birch, and slowly consumes it. At some point in the future, the tree will die due to chaga weakening it from the inside. This might be 5 years or 20 years but eventually it will happen.
This is similar to the majority of medicinal mushrooms as they consume organic matter for food.
There’s an internet myth that chaga is only found on 1 to every 10,000-20,000 birch trees (<0.01%). The source of this information seems to stem from an issue of Mycophile magazine from 2006 which stated: “according to one chaga product site, only one birch tree in 15,000 bears chaga”. Safe to say, this figure is purely anecdotal.
One report out of Russia stated that 20% of all birch trees are infected with chaga. The Finnish Forest Research Institute has said that anywhere from 6-30% of birch forests in Sweden and Finland are infected with chaga. Given this data, I would assume Canada to contain similar levels. This is a multiple magnitude difference than the estimates above and is based on actual data from reputable sources.
This often gets asked in reference to this paper. The women in this paper was taking around 10 grams per day which we do not recommend on any of our products without consulting your health practitioner. The paper does not say whether it was raw chaga or an extract powder and it is also the only reported case we’ve come across.
Research data that we’ve seen in regards to oxalates and chaga, shows anywhere from 2-10% oxalates. Extraction may lower oxalate levels like it does when cooking food.
There are also many foods which will have higher amounts of oxalates than chaga on a per serving basis. As an example, a bowl of cereal may have as much or more oxalates than a serving of chaga. Another example is if you are a big kale or spinach eater.
If you are on a low oxalate diet, you should discuss chaga with your health practitioner prior to consumption.
While there are many sources that suggest that Chaga contains a high ORAC score (oxygen radical absorbance capacity). This ORAC value is misleading and not backed by sound research. This is why we do not test our Chaga for its ORAC value. See this article from the US Department of Agriculture:
All of our chaga is harvested from the forests in Siberia.
Turkey Tail Extract
PSK stands for Polysaccharide-K. This is a medical grade product out of Japan that is derived from turkey tail. It is approved for use in Japan as an adjunct therapy with chemotherapy.
PSP stands for Polysaccharide-peptide. This is a medical grade product out of China that is derived from turkey tail. It is approved for use in China as an adjunct therapy with chemotherapy.
It is nature derived. We use organic Agaricus mushroom (button mushroom), which has been exposed to UV light bringing the vitamin D content up to over 40,000 IU per gram.
Mushrooms contain a fungal sterol called ergosterol. When mushrooms (agaricus, shiitake, oyster, etc) are exposed to UV light, they convert ergosterol (provitamin D2) to Vitamin D2.
The Agaricus mushroom powder doesn’t need to be extracted in order to increase the Vitamin D2 content.
Here are a few studies but we have more in our Mushroom Vitamin D article.
Holick, M. F., Biancuzzo, R. M., Chen, T. C., Klein, E. K., Young, A., Bibuld, D., … Tannenbaum, A. D. (2008). Vitamin D2 Is as Effective as Vitamin D3 in Maintaining Circulating Concentrations of 25-Hydroxyvitamin D. The Journal of Clinical Endocrinology & Metabolism, 93(3), 677–681.