If you haven't read the rest of the series yet, here is your chance to catch up:
We already know that we can get our vitamin D from the sun, food (especially fish), and supplementation. We also know that a combination of sources is most likely to meet your vitamin D needs, which (according to the Vitamin D Council and a growing consensus) are much higher than prescribed by the government's Adequate Intake levels. Since vitamin D is a hormone, it plays mega-important roles in our bodies, like maintaining calcium levels so you don't go leaching it out of your bones. In our previous discussions, we've established the source for sunlight vitamin D (UVB rays) and food (fortified ones are out since they are processed, but fish and seafood are definitely in), so let's take a closer look at where supplemental vitamin D comes from.
Why You Should NOT Take Vitamin D2
In previous installments, we discussed that there are two different types of vitamin D (D2 and D3) and they are NOT equivalent. Here's why:
Vitamin D supplementation was first used back in the 1930s with rickets, a softening of the bones that leads to bowing (at this point most sources would show you some really gross pictures of deformed legs, but I think your imagination and mad Google skillz will suffice). While both D3 (animal-derived, called cholecaliciferol) and D2 (plant-derived, called ergocalciferol) are effective at treating rickets, the same cannot be said for raising serum 25(OH)D concentrations, the vitamin D you need in your body to perform its tasks.
Vitamin D3 is derived from animal sources (we'll discuss those in the next sections) while vitamin D2 is obtained from plants. Vitamin D2 is made when sterols (fat-like substances) in yeast are irradiated with UVB rays. While similar to our own process of making vitamin D from our own fatty substances (i.e. cholesterol) in our skin, plant "cholesterol" is not the same as ours, so it produces a different type of vitamin D that behaves differently in our bodies.
According to the Vitamin D Council vitamin D2 is NOT naturally found at high levels in our bodies. Even though we eat plants, we do NOT take in appreciable amounts of vitamin D2 (it is only a small quantity in a plant), so when we use D2 as a supplement, such high quantity of a novel substance can be toxic. In fact, there is evidence that D2 is more toxic in overdose than D3, despite D2 being only half as potent in the body and metabolized more quickly. D2 also goes through a different metabolic process than D3, creating different end products that aren't natural to our bodies either. Suffice it to say, if you can get D3, why use D2 and take these risks? Not convinced yet? There's more!
In "The case against ergocalciferol (vitamin D2) as a supplement" published in 2006 in the American Journal of Clinical Nutrition, the authors make their argument against using vitamin D2 to fortify foods or to take as a supplement. They bring up some important points:
- The differences between the two are present at a metabolic level; they go through different metabolic processes in the body that use vitamin D3 more efficiently than D2.
- Studies have found that vitamin D3 is two to three times (perhaps even more) as effective as D2 at raising 25(OH)D levels.
- Whereas vitamin D3 is used to prevent bone fractures, vitamin D2 has not been effective.
- Vitamin D2 isn't as stable as vitamin D3, so shelf life and storage are a concern.
If you take ergocalciferol, or "vegetarian vitamin D", be warned. Ergocalciferol is not vitamin D, but a vitamin D-like patent drug whose patent has expired. It does not normally occur in the human body and is probably a weak agonist at the receptor site, meaning it may actually partially block vitamin D actions. Ergocalciferol is the villain in most of the reported cases of toxicity in the world's literature. All bets are off in terms of measuring blood levels if you take ergocalciferol. Some of the labs can pick it up and some cannot. Do not take ergocalciferol—it is not vitamin D.Bottom line: You can NOT meet your supplemental vitamin D needs through vitamin D2, so only use vitamin D3!
Now we know why we need vitamin D3. So what is the best source of D3 for supplementation? Let's look at our options:
The Fish Source
Fish, especially oily fish like mackerel, salmon, anchovies, and sardines, naturally have high levels of vitamin D and omega-3 fatty acids. The same applies to their "oil" or refined, distilled form used for supplementation. Fish are a good source of vitamin D compared to terrestrial creatures because they consume so much plankton (or the fish that eat the plankton), which are producing loads of vitamin D from the sun. They also make some in their skin when they get near the water's surface, but much more is produced from eating plankton. Fish oil can be a good source of vitamin D, if it still has its D. However, most fish oil is stripped of its vitamin D during purification and it has to be added back in to be a source for both.
Last time we discussed how multitasking our vitamin D and omega-3 needs can spell trouble. Since we need such high dosage of omega-3 (see the brilliant Whole 9 fish oil calculator), even if our diet is pretty damn sound, we tend to OD on the vitamin D and on vitamin A if we use cod liver oil. It's just so high in vitamins A and D and so low in the precious EPA and DHA for omega-3s that we either OD and get the omega-3s we need, or we short change our omega-3 needs to meet our vitamin D requirements. And whether or not we even need any supplemental vitamin A is another can of worms...
Last time we discussed how multitasking our vitamin D and omega-3 needs can spell trouble. Since we need such high dosage of omega-3 (see the brilliant Whole 9 fish oil calculator), even if our diet is pretty damn sound, we tend to OD on the vitamin D and on vitamin A if we use cod liver oil. It's just so high in vitamins A and D and so low in the precious EPA and DHA for omega-3s that we either OD and get the omega-3s we need, or we short change our omega-3 needs to meet our vitamin D requirements. And whether or not we even need any supplemental vitamin A is another can of worms...
Another problem with fish oil as our source for vitamin D is contamination with heavy metals (like mercury), PCBs, and dioxins. Predatory fish like mackerel and salmon accumulate toxins because they straddle a higher rung on the ladder of who eats whom. Another concern is for liver oils, like cod liver oil. While regular fish oil is usually derived from all/other parts of the fish, cod liver oil is derived from the liver and the liver's function is to detoxify the blood, so it's where toxins accumulate. It follows that your cod liver oil if not purified extremely well could be a source of toxic contaminants to your system. The Weston A Price Foundation counters that vitamin A (also in cod liver oil) protects against dioxins (at least in animal studies) and that mercury is not present in the liver, but in the protein.
Even if you jump through all the hoops to find the best, most purified source, you could still be in danger. The contaminants that are supposedly purified from fish oil might still be present, according to this lawsuit that surfaced in March. It is disconcerting when you trust those guarantees of purity on the labels only to find out they're lies. However, with this big lawsuit taking the major companies to task, you can bet on ALL the companies stepping up their game and improving their products. So I am not going to agonize over the brand I choose.
Another concern that is gnawing at me: the depletion of fisheries through our fish oil consumption (read this short article from Time Magazine and this one from the New York Times). Over-reliance breeds over-fishing. It is a troubling issue. I know I have to eat to survive, but when does the cost of meeting my needs overbalance the ecological scales to the point of no return? Although I am and will NEVER be a vegetarian, I still consider the cost of meeting my needs and try to minimize my impact as much as possible in my ever-evolving journey. While I still take my fish oil, I hope that alternative and more sustainable sources become viable. :)
To counterpoint, many of the fish used as sources of fish oil (like anchovies and mackerel) are fast-reproducers, so their numbers can bounce back as long as they are not over-fished beyond the limits of their natural replenishment. Here is more about cod liver oil processing from the Weston Price Foundation. For more than you would ever want to know about fish oil production, browse this page from the United Nations.
The Wooly Source
Most vitamin D3 (cholecalciferol) in supplements comes from sheep's wool, from which the oil or fat (called lanolin) in extracted. Animals that don't have their skin exposed to the sun make their vitamin D in their hair, fur, or wool. Glands in their skin secrete cholesterol that reacts with UVB rays to create vitamin D (a process very similar to our own production of vitamin D by cholesterol in our skin). Animals ingest that vitamin D in their hair, fur, or wool by grooming themselves. Isn't that cute? Doesn't that make you want to go and lick your dog, cat, or bunny to meet your vitamin D needs? No?
The lanolin used for supplements is obtained from shearing sheep of their wool. To extract the lanolin, wool is washed in hot water and cleaned with scouring detergents that separate out the dirt, salts, and lanolin by centrifuge. The lanolin is concentrated and then exposed to UVB radiation to create cholecalciferol, or vitamin D3. Since its source is wool, lanolin is a naturally renewable resource since sheep can be shorn once a year during their lifespan of 10-12 years (on average). As far as an animal product goes, this is pretty humane :)
Bottom line: If you want to find the best, most renewable source of vitamin D3 by supplement, choose a brand that uses lanolin or sheep's wool.
Stay tuned for more explorations into the wide world of vitamin D! I hope you are learning more than you thought you'd ever want to know about vitamin D right along with me. If you have more to add or different avenues you'd like me to explore, please let me know!
Coming Soon: Testing for Vitamin D (as soon as I get back my own results!)
Additional References Used
Wikipedia entries on vitamin D, lanolin, sheep shearing, and domestic sheep.
The World's Healthiest Foods: Vitamin D
The Wooly Source
Most vitamin D3 (cholecalciferol) in supplements comes from sheep's wool, from which the oil or fat (called lanolin) in extracted. Animals that don't have their skin exposed to the sun make their vitamin D in their hair, fur, or wool. Glands in their skin secrete cholesterol that reacts with UVB rays to create vitamin D (a process very similar to our own production of vitamin D by cholesterol in our skin). Animals ingest that vitamin D in their hair, fur, or wool by grooming themselves. Isn't that cute? Doesn't that make you want to go and lick your dog, cat, or bunny to meet your vitamin D needs? No?
The lanolin used for supplements is obtained from shearing sheep of their wool. To extract the lanolin, wool is washed in hot water and cleaned with scouring detergents that separate out the dirt, salts, and lanolin by centrifuge. The lanolin is concentrated and then exposed to UVB radiation to create cholecalciferol, or vitamin D3. Since its source is wool, lanolin is a naturally renewable resource since sheep can be shorn once a year during their lifespan of 10-12 years (on average). As far as an animal product goes, this is pretty humane :)
Bottom line: If you want to find the best, most renewable source of vitamin D3 by supplement, choose a brand that uses lanolin or sheep's wool.
Stay tuned for more explorations into the wide world of vitamin D! I hope you are learning more than you thought you'd ever want to know about vitamin D right along with me. If you have more to add or different avenues you'd like me to explore, please let me know!
Coming Soon: Testing for Vitamin D (as soon as I get back my own results!)
Additional References Used
Wikipedia entries on vitamin D, lanolin, sheep shearing, and domestic sheep.
The World's Healthiest Foods: Vitamin D
BIG MEDICAL NOTE:
This is NOT medical advice to take vitamin D or any other supplements. Consult your doctor (and try to educate him/her with this information), do some research, and formulate your OWN plan.
