A little knowledge is a dangerous thing. You clearly have more insight into things than the average person, but there is this: Vit. D3 is available from countless over the counter sources in the 5,000IU strength, and even 10,000IU is not hard to find. If commercial retailers large and small are confident enough in the non-lethality of the D3 form being safe enough for general consumption, why are you concerned? It isn't simply because of anonymity why I can generalize, my position is informed by the very wide availability of the product in question. That said, there is a very simple way to know for sure, and it does not involve avoiding fat soluble vitamin supplementation: get periodic blood analysis. Even if you don't have health insurance, and maybe even if you do, since lots of people with insurance still avoid routine health care because they have $5,000 deductibles... every year or two it is worth the $500 to find out what key markers of systemic health are doing. FWIW.

My doctor, has me taking Drisdol 50,000 IU of D2 once weekly plus some over-the-counter D3. But if I skip a few weeks then re-start, I don't notice any difference.

Many health plans today have a preventative slant with a free (other than copay) full physical once a year. Just specify that you want D as part of the blood work. And of course one doesn't notice the difference. Which doesn't mean that long term vitamin deficiencies are just fine. If there were no difference, our docs wouldn't have prescribed.

Keep in mind too that Vit. D overdose that comes from exposure to sunlight is impossible and that concerns about melanoma may be misplaced--e.g., rather than due to increased exposure to sunlight, reported increases in melanoma may as likely be due to decreased exposure.

In addition, it is reported that increased reporting of melanoma skin cancer may actually be due to, "an artifact caused by diagnostic drift" --

https://www.ncbi.nlm.nih.gov/pubmed/19519827

In addition to skewing disease rates as a result of the misdiagnosis on non-cancerous lesions, there also is evidence that the sites and distributions of lesions diagnosed as melanoma many times do not correspond to exposure to sunlight being the primary cause.

I believe this to be dangerous advice, given on the basis of one small study. If you want facts, try this: Skin Cancer Facts & Statistics - SkinCancer.org
Cover up, use sun block and minimize your sun exposure. Dermatologists think you should use sun block for your walk between house and car. Take vitamin D if determined to be a good idea by your doctor. Low blood levels of vitamin D are indicative of fracture risk and many other ailments and health risks.

If you want information about vitamin D, its uses and toxicity, try: https://www.direct-ms.org/pdf/VitDVie...APTER%2061.pdf

If you are interested in the difference between vitamin D2 and D3, see: https://www.medscape.com/viewarticle/746941

Don't have a functioning hypothyroid anymore so I get to do my calcium balance on my own. The metallic taste in the mouth let's me know when I'm low.

0.5 mcg of Calcetrol (what D3 metabolizes to) 2000 IU of D3 and 2g of Calcium Carbonate a day. If I know I'm going to go out and hammer 60 mi+ I'll put a 1G Tums in the Gatorade bottle. Blood tests every 6 mo for Thyroid and D levels among other things.

Why someone with a functioning Hypothyroid would get carried away with D3 doesn't make any sense.

you are just spending money on expensive pee.

There is no such organ as a hypothyroid. Calcetrol? Do you mean Calcitriol? Why are you taking that AND calcium carbonate? Vitamin D3 is fat soluble, it is not excreted in urine. You've got a lot of reading to do, if you get there you may also find out why it is a good idea to supplement D3 (and just about everything else) even if your Thyroid (and other things) is just fine.

An underactive thyroid gland (hypothyroidism) is commonly caused by Hashimoto's disease, an autoimmune condition that does occur in men as well as women. Persons with thyroid disorders may experience Vitamin D deficiency and supplementation may be required but the amount of supplementation can be difficult to determine, especially since studies have shown that too much Vit. D can increase the risk of heart disease.

e.g., see: https://www.ncbi.nlm.nih.gov/pubmed/17145139

No functioning parathyroid or thyroid at all.


Thyroid was removed and the parathyroid didn't survive the insult. Was told that's not that uncommon.


Regular blood testing for thyroid, Calcium and D levels. Monthly till things stabilized and now every 6 months.


There are medical reasons for supplement's, but unless you have one it's a waste of money and has the potential to do more harm than good. If you are outdoors cycling in the sun, you probably are making plenty of D.

I reference the "fad's" fueled by the medical community that once said that high doses of Vitamin A (also a fat soluble vitamin) and Vitamin E (another fat soluble vitamin) were once in vogue and people came to drugstores and bought it in droves. Years later they started seeing negative effects of longer term hyper-vitamin supplementation.

I'm being cautious because the good Lord gave us one liver and for full disclosure I have to put the brakes on such high doses until I can see that it is safe.

You reference high doses of D being widely available. I am skeptical because vitamins are not under the guidance of the FDA or any other governing body - hence all the bad diet supplements that have had to be taken off the market as well as the aforementioned A and E dosing regimen. Also, vitamins have no one company to be liable so there are no corporate lawyer or actuary warning with strong wording in the package insert.

I have no axe to grind with the Vitamin D community. I know very well people who believe that every headache is a "migraine".

There is some quantitative evidence that vitamin D deficiencies... like any other deficiency... happens over a long length of time... like a decade or more. I am weary of any hyper supplementation that corrects a 10+ year long deficiency with a few month push.

I understand our community's need to 'get back on the bike' after injury.. or 'have to get that ride in before the rain or darkness' --> I just don't think that it is pragmatic to supplement in this rushed fashion. I see people deficient in vitamin B12 that need monthly injections... I see people needing to supplement iron for months or even years to correct their deficiency.

I know of no other vitamin or co-factor that can be corrected so quickly. Since it is fat soluble, I don't want people to supplement without... to your point.... having the insurance to adequately access their kidney or liver clearance. A CBC includes many liver and kidney enzymes. How many people don't consider OTC products or vitamins when telling their doctor what they are taking. Again, human nature.

First do no harm. Since the consequences of low Vitamin D are moderate, what is the rush. I am well versed in clearance of medicines and as important... the mechanism of action of the uptake system. It is much safer (judged by other vitamins and other supplementation programs that have had to be rescinded or revoked) to moderate your supplementation--> that lower levels each day is safer as levels return to normal.

What's the rush? I also have to consider an arthritis medicine or blood modifier that people might be taking to delay the clearance of larger doses of vitamin D. After all... you have to know your audience....

and....

we are....

in the ....

Fifty Plus section.....


I'm using perspective and intuition and theory and first and last.....doing no harm.

Yes, you are doing harm if you discourage older people from getting the nutrients they need to preserve bone density. Adequate vitamin D levels are necessary for the bones to absorb calcium and thus stay strong and free of fractures. Fractures are a major risk for older cyclists because many have low bone density. In the past 2 years in my group of maybe 30 older cyclists we have had 8 crashes which resulted in serious fractures. This is serious business. See: https://www.bikeforums.net/training-n...n-improve.html

From what I've read as regards bone mass density in the elderly, walking (which involves more impact) may be better than cycling (which is less of an 'odd impact exercise'). Taking vitamins to increase calcium absorption may be a good idea but getting enough calcium the diet must come first so cycling probably helps there-- e.g., increasing the caloric requirement. The important thing to know about bones is that they will never get stronger than the body feels they need to be so... without the right kind of exercise, maintaining BMD can still be a problem no matter what you eat or how many vitamins you take.

I give up. CarbonFiberBoy... I am in no way suggesting that older people not get the nutrients they need. Discourage? no. Constant, every day inundated supplementation is prudent. I'm struggling to find evidence of discouragement. Thinking that one can reverse years and years of moderate Vitamin D deficiency with huge huge amounts of Vitamin D in short time...is...troublesome.
To say without question that the reason so many of the cyclists your group have had fractures is low bone density is fatally flawed. If you fall the wrong way, no matter your bone density, it will result in bones breaking.
You are right, this is serious business, but to rush through therapy and risk possible organ injury is not reasonable.
First do no harm = make sure therapy is safe. When in doubt, don't risk people's health, short term or long term.

If anyone visiting this thread is interested in the facts of Vitamin D supplementation and its benefits for the older athlete, such facts are presented in these studies and articles:
https://www.medscape.com/viewarticle/746941
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3725481/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3289217/
https://jissn.biomedcentral.com/arti...970-015-0093-8

I picked out one of the above studies at random -- second to last -- and, it really goes to show there really are no easy answers here... Did you see the Conclusion?

...multi-factorial... limited evidence to support the proposition that Vitamin D deficiency is performance limiting...

and, what about that callout to the lack of evidence concerning those, "supra-physiological levels," that the authors throw out in the last sentence of their study?

What does this mean...?
Does that mean too much of a good thing may be bad? Some studies say, "yes."

I doubt your choice was random. You have a nice strawman there. I suggest that no one should look to vitamin D as a performance-enhancing supplement. The whole idea is to maintain good health and good bone density. There is a lot of evidence in those articles and studies that appropriate vitamin D blood levels are important for both those things, and that the doctor-prescribed dosages mentioned in comments in this thread are in fact appropriate.

Also note that many doctors are still not up to speed on the difference between D3 and D2, the former being now preferred.

... a nice strawman?

I don't have a dog in this matter except that I wish we knew more than we actually do. And, we are right to be suspicious even of medical findings (e.g., see, Why Most Published Research Findings Are False by JPA Ioannidis - ‎https://robotics.cs.tamu.edu/RSS2015N...ed.0020124.pdf )

In the last article for example-- there is a lot of info and in summary we see results coming from studies subjecting animals to, supraphysiological dosages of vitamin D3, with findings of, multiple physiological enhancements, and also findings that, both deficiency (12.5 to 50 nmol/L) and high levels of vitamin D (>125 nmol/L) can have negative side effects, with the potential for an increased mortality.

So, what to do?

Pretty simple: knowing people who are treated for medical problems for whom receiving advice to take Vit. D (and calcium) supplements is common, these patients' blood is tested on a regular basis to measure, their plasma 25(OH)D levels so as to maintain optimum serum levels, in order to determine if supplementation is needed.

I'm thinking supplementation during the winter may be a good idea but then, I eat milk and cheese and there may be other fortified foods in my diet that I do not know about so, I really don't have a clue what dose I'd take or how needed or safe it would be. It's enough to make you think about eating more salmon though and perhaps going to a pricey salad bar occasionally to mack-out on caviar and anchovies.

(OP here) It was not my intention to provoke any type of argument in this thread, looking back though I realize that some people are quite opinionated when it comes to nutritional supplements, so I apologize if I inadvertently created an inflammatory thread.

Bear in mind that I began this thread based on my doctor's readings of actual blood work, I've had two tests in the last 8 months,. So his advice at least had some basis, rather than just a vague notion that "more Vitamin D is good for people". I fully recognize there's people out there who will swear by mega-doses of all sorts of supplements in their search for the fountain of eternal youth (or whatever they seek) without lab results or any other diagnosis or medical justification. Me, I don't subscribe to that notion, but if the doctor tells me that the blood tests say I need a vitamin supplement, then I'm going to pay attention to what he says. Incidentally my thyroid isn't up to snuff, I've been on synthetic thyroid hormone (levothyroxine) for about 15 years and perhaps that's why normal diet and sunshine alone isn't enough to maintain a good blood serum level 25 (OH)D.

We do know that too little Vitamin D is associated with rickets, and we know that too much can cause toxicity. In between there's the middle ground. The researchers in the studies I've read don't always agree on what a "normal" 25 (OH)D reading should be, but it's quite plausible to me that if there's an insufficiency--not enough defiency to cause rickets, but well below "normal" level--then perhaps there could be other problems (less obvious than rickets). It's always plausible to me that very high 25 (OH)D readings could also cause problems though not quite as obvious as the problems evident at the toxicity level. In other words, way too little is very bad, way too much is also very bad. In between the spectrum would go from "low enough to cause some problems" then reaching up to "on the low end of normal but not causing problems" then "normal" then reaches up to "on the high end of normal but not causing problems" then eventually it reaches the "high enough to perhaps cause some problems" before eventually reaching the toxicity level. Make sense?

The couple of studies I found on toxicity seemed to indicate that the body tended to tolerate high levels quite well, though, so the "high enough to perhaps cause some problems" was way up there, way beyond normal levels. Perhaps equally as important, though, they didn't seem to observe any discernible benefit--no magic "fountain of youth" there.

All that to say: I believe I'll continue with the doctor's recommended supplement level until the next blood test in 3 months, since there does not appear to be any significant risk in taking that dosage level. If my measured blood levels then are higher-than-normal, I'll press the doctor on why he believes I should maintain that dosage level. I must admit though, since I've started taking the supplement, I do believe I am feeling just a little more peppy and less tired--though as an engineer I know that's hardly conclusive.

Those questions are why preventative-based health plans provide a free annual physical. The doctor makes recommendations for how one can improve one's health. That said, these days we all need to advocate for ourselves and examine more closely everything we hear or are told. Thus my doc recommended D2. I looked into it and saw that D3 is now recommended. I checked with him and he agreed with using D3 instead. We followed his dosage recommendations.

As discussed above the results, specific forms and optimal intake of vitamin D are inconclusive, not to mention the nutrient to nutrient interactions between vitamins which nonetheless apparently suggest that vitamin D should be taken with vitamin K --e.g., the sources you cited above talk about interactions that, affect arterial calcification and hypervitaminosis.

An alternative to Vitamin D supplements?

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Well that was an interesting read, but at the end, he says we should eat less and exercise more and get more stress to activate the natural autophage response, rather than take supplements.

I eat lightly, exercise regularly, and have enough stress in my life already, thank you. Yet my blood work shows low D. So I frankly think the article was almost completely useless.

Of course,other folks who eat too much and don't exercise will always benefit from a proper diet with regular exercise.

.

I think you have to read the article in the context of what is called, intermittent fasting...

I thought it might be interesting to see what Abbot Labs suggests based on the specs for its latest Ensure product that it is spending a lot of bucks on in advertising for the old folks (protein and 25 vitamins and minerals)-- the number is %RDI / %DV*


Vitamin A 15
Vitamin C 100
Calcium 50
Iron 25
Vitamin D 120
Vitamin E 100
Vitamin K 25
Thiamin 25
Riboflavin 25
Niacin 25
Vitamin B6 25
Folate 40
Vitamin B12 50
Biotin 25
Pantothenic Acid 25
Phosphorus 35
Iodine 25
Magnesium 25
Zinc 70
Selenium 80
Copper 25
Manganese 25
Chromium 25
Molybdenum 25

____________
Per 8 fl oz (237 mL) *Percent Daily Values (%DV) are based on a 2,000 Calorie diet.

As you can see from the above, vitamin D is cheap so they throw in 120% of the supposed daily requirement in an 8 oz bottle (350 calories out of a supposed 2000 calorie diet).

However, vitamin K obviously is an expensive vitamin. You only get 25% of your daily requirement.

According to Dr. Mercola's (from his website) Story at-a-glance: "Evidence shows that vitamin D is dependent on vitamin K, and that vitamin D toxicity is actually caused by vitamin K2 deficiency."