Vitamin D and Cancer
I'd like to point readers to a couple of posts by Richard Nikoley over at Free the Animal, on the relationship between vitamin D status and various types of cancer. The epidemiology consistently shows an inverse relationship between vitamin D levels and cancer incidence. A few intervention trials also support a protective role of vitamin D against cancer. Increased sunscreen use has not reduced melanoma incidence, to the contrary. I've discussed this before as well. Richard got his graphs from the website GrassrootsHealth.Vitamin D deficiency and All CancerMelanoma, Sun and its Synthetic Defeat (sunscreen)Vitamin D is not just another vitamin. It's a hormone precursor that plays a fundamental role in the regulation of numerous bodily processes. Sunlight is an essential nutrient for physical and mental health.
Here are the best natural sources of vitamin D:
- Sunlight
- High-vitamin cold liver oil
- Summer blood from animals raised outdoors (for example, blood sausage)
- Fatty fish
Vitamin D is one of the few nutrients that may be worth supplementing during wintertime. Make sure to buy D3 and take at least 2,000 IU if you are going to bother.
21 comments:
Stephen,
From the links Richard gives in his blog entries, we're looking at about 20,000 iu of vitamin D being produced in just 20 MINUTES of direct exposure to sunlight.
Whether one believes in the african plains or the island-seaside dweller evolutionary model for homo sapiens, we are still very far today from acceptable daily levels of vitamin D. Even though the skin will curtail and stop producing vitamin D after a certain amount of time in the sun, we're looking at an estimate of around 100,000 iu a day for the average hunter gatherer, aren't we?
I myself take 10,000 iu a day a la Peter at Hyperlipid (as I get no sun). The enormously powerful ability the skin has evolved to make this hormone seems to be for an important reason, and I'm starting to think 10k may still be under the optimal HG range.
The only pre-agricultural people I know who rely primarily on dietary sources of vitamin D seem to be the Inuit. And even they have to eat fish morning, noon and night to do achieve this. There is a possibility that they're STILL D deficient too.
Any thoughts on what an optimal daily level of D for a typical equator-dwelling HG would be then? We need to take darkness of skin into account too of course, which would cut down the D production more under the hot sun.
Be careful in choosing a vitamin D supplement. Many of the gel caps have soybean oil as a filler (yuk!). Read the labels.
http://jcem.endojournals.org/cgi/content/full/87/11/4952
Effects of Above Average Summer Sun Exposure on Serum 25-Hydroxyvitamin D and Calcium Absorption
There is a tendency to overstate the amount of Vitamin D3 people get from sunlight.
The above paper shows in practice Outdoor Workers in Omaha averaged only 2800iu/daily over the year.
Workmen usually wear clothes at work, cutting down the skin area exposed. Standing as opposed to lying down also reduces the area exposed. We also have to factor in that once D3 has been made the D3 near the surface of the skin will be processed on into lumisterol if it continues to rece1ve UVB So longer continuous exposure may not result is huge amounts of D3 actually being stored.
The areas usually exposed to sunlight will of course tan first and most and this also will tend to reduce the ability of that skin to produce the maximum amount of D3.
This website has good information on the process.
http://www.uvguide.co.uk/vitdpathway.htm
I don't have a reference at hand, but I think I've read maximal Vitamin D3 production is limited to < 20000IU/day (and more realistically, ~10000IU/day).
I suspect most readers of Stephan's blog are familiar with Dr. Davis, but here's a plug for him: The Heart Scan Blog is a very good source about practical D3 supplementation and other issues.
Also check out:
Vitamin D Home Test
Stephan,
Aren't you concerned of the excess vitamin in cod liver oil? The vitamin A to vitamin D ratio is not good; one easily gets too much of retinol. There are animal studies showing that retinol causes bone loss even when the vitamin D levels are sufficient.
In addition to that, in many countries vitamin A is added to cod liver oil in order to stabilize the vitamin A content. That makes cod liver oil even higher in vitamin A than it is naturally.
Personally I do not recommend cod liver oil but vitamin D3 supplements (+ fish oil).
Hey Stephen
I read at the westone price website that we only get about 4000 iu for the sun.
"The current suggested exposure of hands, face and arms for 10-20 minutes, three times a week, provides only 200-400 IU of vitamin D each time or an average of 100-200 IU per day during the summer months. In order to achieve optimal levels of vitamin D, 85 percent of body surface needs exposure to prime midday sun. (About 100-200 IU of vitamin D is produced for each 5 percent of body surface exposed, we want 4,000 iu.) Light skinned people need 10-20 minutes of exposure while dark skinned people need 90-120 minutes."
http://www.westonaprice.org/basicnutrition/vitamindmiracle.html
Is this info incorrect? Do we get much more if we are shirtless in the midday sun?
Sam mentioned Dr. Davis' HeartScan blog, which I follow daily as well. It is interesting that his position is that the ability of the skin to make Vitamin D drops off after age 40, making supplementation necessary all year long. I have not heard this elsewhere but it certainly could be true. Not sure of the source of his position. Could be based on anecdotal evidence from treating tanned individuals with osteoporis.
As to how much D to take, Dr. Davis would say the surest method would be to do a reliable test (as pointed out by others, there are home tests) throughout the year to determine blood levels given your normal activities, diet and supplementation. Then adjust your supplementation regimin accordingly and re-test. This approach would replace the input-based guestimating with output-based individual testing.
Of course, you have to be comforatble with what the appropriate blood level is. Dr. Davis has thoughts on that as well.
I take 6,000 IU per day based on input from various blogs; could be low. I have not done a home test. Sometimes I take extra if I feel a cold coming on.
I take Carlson brand, which is suspended in sunflower oil, but the amount in the tiny capsules is miniscule. I figure my fish oil capsules more than offset this amount since I eat no other sources of PUFA. I like the convenience over a bottle of cod-liver oil.
I separately supplment A (Carlson capsules, derived from fish livers) and K, which I first learned about on this excellent blog
Scott W
Stephan,
You sent me an email concerning a study comparing n-3 and n-6 pufa a month or two ago, and for some reason I can't find it -- sorry to contact you this way but consequently I couldn't find your email address either. Could you resend that email? Thanks!
Chris
Here you can find 2 excellent presentations on Vitamin D that will clear many doubts:
http://wildhorse.insinc.com/directms13oct2005/ - very informative
http://www.uvadvantage.org/portals/0/pres/ - this is the best lectures I've seen in my life (very funny and very informative)
Also, I sugest the following paper by Michael Holick:
http://www.ajcn.org/cgi/content/full/87/4/1080S
To know how much one should take, here's a good article:
http://www.thorne.com/altmedrev/.fulltext/13/1/6.pdf
Hi Stephen,
I am still a little bit concerned about what Dr. Mercola continues to say, (after his first "warning" against COL, although he knows about what you and Price have said about it.
What is your comment on:
http://articles.mercola.com/sites/articles/archive/2009/01/03/why-vitamin-a-may-not-be-as-useful-or-harmless-as-you-thought.aspx
and:http://articles.mercola.com/sites/articles/archive/2008/12/23/important-cod-liver-oil-update.aspx
Would appreciate that a lot, just to be sure that I don't get too mu ch Vitamin A. In other supplements there is also Vitamin A, so that adds up, so if I take good COL with butter oil, like you advise AND I take vitamins, is there then some danger?
Regards,
George.
Zazu,
I'm personally puzzled by Mercola's comments on cod liver oil as well. He says he's never seen a ratio of less than 10 to 1 A to D. Yet my HVCLO from Green Pasture's has around 6 to 1, which is substantially lower.
Stephan,
I know we're all hitting you with comments here all at once, but I'd be interested in your previous statement on fermentation of cod liver oil. Does this increase the amount of K? K2? My Green pasture's fermented CLO actually says it contains K AND K2 -- though it doesn't list the amounts of the vitamins (E, K, K2) besides A and D. In that instance, do you think another source of K2 would be necessary in the diet?
Also, why do you recommend supplementing with 2000 IUs of D3? Why not even higher?
Your thoughts would be much appreciated.
Gunther,
I'm skeptical of the 20,000 IU in 20 minutes figure. The skin adapts in the short and long term to UV exposure, reducing the vitamin D it synthesizes over time. A tan partially blocks D synthesis.
I don't know the D status of equatorial HGs, but I suspect it's close to what a young fair-skinned person will achieve after a summer of working outdoors. 60-70ng/mL 25(OH)D3 or so. The best way to know how much to take is to test yourself. I think it's worth noting that humans whose ancestors have spent a long time living at the equator are jet black! If your skin looks like that, you only make a fraction of the D a light-skinned person makes under the same conditions.
Juhana,
I'm not really concerned about vitamin A. Quality high-vitamin CLO can have a ratio of as low as 6:1 A to D, which won't cause problems. I agree that CLO with a ratio higher than 10:1 is problematic. Often D is removed during processing or extra A is added, as you mentioned. So you have to be picky if it's your only source of D. But I don't really recommend that CLO be the only source of D anyway. It should accompany sunlight when possible, foods rich in D such as fatty fish, and supplements if you choose.
Daiikon,
There is a lot of confusion surrounding this issue. Here's the problem. Some of the studies were done with people who are light-skinned, not tanned at all, and exposed to cloudless midday sun. Under optimal conditions, your skin makes D readily and in large amounts. But the conditions aren't usually optimal. I don't personally think 10-20 minutes on the hands and face 3X a week is even close to sufficient. It's nothing near the sun exposure our ancestors would have gotten.
Scott,
Dr. Davis is correct about D synthesis diminishing with age. I have a link to the data in my main D post (2nd to last paragraph), which takes you right to the figure.
Zazu,
I read Dr. Mercola's article. He has been influenced by Dr. Cannell, Willett etc who have recently published papers warning of vitamin A toxicity. I addressed this in a recent post "Is Vitamin A toxicity a concern?" Basically, the way to avoid vitamin A toxicity is to have a good vitamin D status.
If you are taking supplements that contain vitamin A on top of CLO and butter oil, you could be overdoing it.
Monica,
Yeah that's the same stuff I take. The K2 is probably from bacterial fermentation, which would be longer-chain menaquinones rather than MK-4. I don't think it's necessary to supplement K2 as long as you eat pastured butter and/or organ meats regularly.
The 2,000 IU number I threw out was a minimum. In one study, American men required 4,000-5,000 IU to maintain adequate D levels in winter. Another recent study in the UK came up with a lower figure, I think it was closer to 2,500 or 3,000. But some of that can be gotten from diet. I won't pretend to have "the answer", the only way to know for sure is to test. I've personally been supplementing with 4,000 IU on top of my CLO and other D-rich foods. I'm not going to bother testing but I'm not presenting myself as a role model either.
Hey Stephen
I fortunately live in San Diego(never a cloudy day) and I like to exercise for about an hour each day in the middle of the most intense sun with just swim trunks on. I am also taking 2500 iu of D3. I am fair skin of European descent but tan easily. Do you think this sufficient?
Thank You
Daiikkon,
It's more than sufficient, actually it's probably excessive unless you have dark skin. Our ancestors got nearly all the D they needed from the sun, and if you have the option like in San Diego, there's no need to supplement unless you are very dark-skinned or elderly.
Thanks Stephan, Another great post.
Thanks JMC great links.
This is a good Weston Price link I found whilst tracking down some of the issues raised.
I had long wondered if Vit d was an antioxidant but had no got down to tracking it down. It seems it is.
Robert Brown
Author
Omega Six The Devils Fat
www.Omegasixthedevilsfat.com
I think geographic location and sunny weather is just part of the Vit D variables. Even in mild climates there are lifestyle variables that play a significant factor, such as age and time of day spent outdoors, etc.
I also live in "Sunny" San Diego county, but only a about 4 miles from the coast, so the sun is often obscured by the marine layer clouds, sometimes all day in certain months (we call it "May Gray", "June Gloom" as the coastal marine layer is especially prominent those months, but sometimes other months, too). That lowers the temperatures, too, making skin exposure less tolerable (ok, there are some here who wear beach clothing and sandals all year out of principle, but not most of us). It's 51°F on my patio today and that's not shorts and sandals weather to me (I'm usually in lightweight wool layers during the winter months, actually). Just a few miles to the east, the inland locations in San Diego County have much more unobscured sun and higher temperatures, though the temps are cooler as one goes higher into the mountains even farther east. In other words, there's a lot of climate variability here that may play a role, too.
(Having just spent a week back in my upstate NY hometown winter weather, I know any weather in SD sounds good right now to those in colder climates, probably). :-)
I have tried just getting summer sun without Vit D supplementation and my Vit D level went down compared to my winter levels with supplementation (so either way, despite the mild climate, I need supplementation if I want to get my Vit D level raised above the high 30s-low 40s).
And I don't have youth on my side anymore (I'm 47 tomorrow!), have Irish-German skin that doesn't tan well, and I had a basal cell skin cancer 10+ years ago (higher PUFA intake then, though), and so I have to balance the sun exposure with some care to not overdue it. And I'm indoors a lot, though I have a flexible schedule that allows for time out in midday if I choose (my garden would be happier, too).
And every other middle aged woman I know locally who has tested Vit D levels was either near the bottom of the reference range or deficient, despite tans and a fair amount of outdoor leisure activities (but they do spend weekday indoors while working). Those who have doctors who test Vit D regularly say there are a surprisingly high number of deficient people in this locality, considering the climate and sunshine availability. That's probably due more to lifestyle factors than location, but it does show one can't just assume that living in San Diego means Vit D levels are adequate, especially for older people who spend midday hours indoors.
My son has great levels, though I did start 3000 iU in supplements for him for the school year (he tested at 72 ng/ml in early December). But he's young and spends a LOT of time outdoors when schools isn't in session (we won't give him supplements when school is out). My husband (46 ng/ml on 4000iU suppl in December) and I clearly don't either get as much sun and/or make enough Vit D in response to the sun anymore, so we need to test and supplement. I have no idea how low our Vit D levels were before we supplemented, but I'llb bet they were quite low.
As many have said, if age, indoor work during the day, and heritage (skin pigmentation) are issues that might limit Vit D production, it's a good idea to get tested to see if supplementation is needed, and how much to take. I'm trying to stick to a late summer, late winter schedule for testing and dose adjustments.
Anna,
Thanks for sharing your experience. I suspect there are factors other than sun exposure and dietary intake that affect D status. Studies from the UK and US at similar latitudes show that Americans and the English require different amounts of D to maintain a good D status in the winter, even when factoring in summer exposure.
I've posted before about that study showing that wheat fiber supplementation depletes D and celiac patients are often severely D deficient (normalizes on gluten-free diet). I suspect there's something going on in some people, maybe inflammation, that depletes D at an accelerated rate. Add to that a lack of sun exposure and you have a big problem.
The UV index is 3 for the part of San Diego I live in. Would this be enough to make Vitamin D in the middle of the day?
Daiikkon,
Yes.
Stephan,
I disagree with your comment that there is no need for vit. D supplementation for someone living in San Diego. I found a page with a nice chart of UV intensity by date as a fraction of maximum (the maximum UV intensity being 12 noon standard time on June 21). This chart is specific to San Diego County. As you can see, at 12 noon on the winter solstice, the UV intensity is only one tenth of the maximum summer solstice intensity (which admittedly is pretty high in San Diego). But I doubt that this is enough to ensure adequate vitamin D production in just about any case, since most people don't get full-body sun exposure during the noon hour every day.
http://home.znet.com/schester/calculations/sun_avoidance_times.html
Check out this article before taking any vitamin D supplements:
http://escholarship.org/uc/item/4m84d4fn
We don’t need to maintain the same serum levels all year round; fluctuations are normal. The stuff is stored in our bodies anyway and released as needed.
Post a Comment