I am a journalist and medical writer with extensive knowledge in eg. clinical nutrition, pharmacology, oncology and endocrinology, all relevant to the scope of this article. I decided to take some time off from working on my textbook about pharmaceuticals and write my response to $Moonbeam13's breast cancer campaign. Unless you already know everything about the disease-protective properties of vitamin D, I can assure you that this article is well worth a read.

Instead of abstract ways to fight cancer I'm providing concrete advice on how to significantly reduce your risk of getting breast cancer and many other cancers, as well as other common debilitating and deadly diseases. Everyone who is serious about campaigning against cancer should be supplementing with vitamin D as well as recommending it to others. Sadly most people in this field have the enthusiasm, but lack the medical knowledge about the subject they're rallying against. The only way to be a good activist is to have enough knowledge.

Vitamin D

Vitamin D is best known for its importance in bone strength, but it has a variety of functions in the body and is now considered a steroid hormone. It is particularly important for the immune system, for preventing autoimmunity and cancer. The skin can produce vitamin D in sufficient sunlight and some foods also contain it, either naturally or through fortification, but even a combination of these approaches usually doesn't yield a sufficient intake of vitamin D.

Current recommendations of vitamin D intake are considered to be way too low by the leading vitamin D researchers. Usually the recommendation is 5-10 mcg (micrograms, one millionth of a gram) a day, while vitamin D researchers recommend 50-100 mcg a day. An intake of 25 mcg (1,000 IU) a day is enough to confer many benefits and offer protection from many illnesses, but even that is very difficult to acquire in the wintertime.

Margarine (and sometimes milk) is fortified in many countries, but the amounts contained are hardly ever sufficient - you'd have to eat very unhealthy amounts of margarine, or drink 5-20 liters of milk every day to get enough vitamin D. Eggs are another source, but you'd need to eat dozens of eggs a day. The only significant food sources of vitamin D are some wild mushrooms and fatty fish (such as herring, zander/pike-perch, whitefish and eel - eg. salmon contains lower levels) but still you'd need to eat them every day (or at least every other day), something that most people don't do.

Just 20 minutes in sunlight is enough for a light-skinned person to produce 250 mcg (10,000 IU) of vitamin D, which shows how insufficient the current recommendations really are and how non-toxic vitamin D really is. So why isn't sunlight enough? Because in many countries sunlight only produces vitamin D for a part of the year, sometimes only for a few months. Even in the summertime covering your skin with clothes or sunscreen greatly reduces the rate of vitamin D production.

People with a dark skin produce vitamin D at a much slower rate, so especially those black people who live in the north are at significant risk, and studies show that they are usually deficient in vitamin D. However, according to studies even some light-skinned people that get plenty of sun exposure are often deficient, which likely means that some people don't produce vitamin D as effectively as others.

So what are the benefits of supplementing with vitamin D?

It reduces the risk of cancer.^[1]

It reduces the risk of cardiovascular disease.^[2]

It reduces the risk of multiple sclerosis^[3],[4] and likely other autoimmune diseases^[5],[6] as well.

It reduces the risk of osteoporosis.^[7]

It reduces the risk of catching influenza and other respiratory infections.^[8]

It reduces the risk of both type I^[9] diabetes and likely type II as well.^[10]

It appears to be be neuroprotective ^[11] and slow down physical and cognitive aging.^[12],[13]

It may reduce the risk of schizophrenia^[14] and may have a role in regulating mood.^[12],[15] Vitamin D deficiency has been suspected of being the cause or one of the causes of seasonal depression (SAD). It has been implicated in autism as well, but there are no studies examining this theory yet, so we have to take it as a compelling hypothesis for the time being.

The first study there is a review of over 50 different studies looking at vitamin D and cancer risk. There are also many studies that show that sunlight reduces cancer incidence and/or mortality. That doesn't prove that vitamin D is the factor behind this observation, but considering that there are many studies showing the inverse association between cancer and high vitamin D intake and/or blood levels it seems very likely.

Vitamin D has been associated with a lowered risk of at least the following cancers: prostate, breast, stomach, colorectal, liver, gallbladder, pancreas, lung, bladder and kidney. The association is particularly strong with colon, breast and prostate cancers - the latter two being the most common cancers (excluding the very benign forms of skin cancer that are normally not included in cancer statistics) in women and men, respectively. Cancer of the pancreas can occur in people in their 30s and sometimes even in their 20s and it currently has an extremely high mortality, more than 95%. Lung cancer is more an illness of older people (not exclusively of smokers!), but it also comes with a pretty grim prognosis. Only about 10-15% of patients survive for more than five years.

If you think that the reductions in risk are small and insignificant, think again. Some studies have shown that supplementation may reduce cancer risk by up to 60% - which isn't anything to shrug off, considering that one in three people is estimated to get cancer in their lifetime. Getting inadequate amounts of vitamin D is a health hazard similar to smoking or obesity. And if you do smoke and don't get enough vitamin D, you have two serious risk factors already - and even more if you're significantly overweight. Quitting smoking and losing weight is easier said than done for many people, but luckily supplementing with vitamin D is very easy and inexpensive.

So, how should I acquire my vitamin D?

You should try to get 20 minutes of sun exposure three times a week in the summer, while not wearing sunscreen or having most of your body covered in clothes (you can apply sunscreen after that if needed). Longer periods of sunbathing do not provide additional benefit, as after the rate of vitamin D being produced is no bigger than the amount of it being destroyed. Of course, if you have any medical reasons that prevent you from being in the sun (such as lupus or photosensitizing medication) you should not take this advice, but supplement with vitamin D instead.

In the winter everyone should get at least 25 mcg, preferably 50-75 mcg, of vitamin D a day. Unless you eat wild mushrooms and/or fatty fish almost every day, you'll most likely need to supplement with vitamin D in pill or drop form. Try to choose a source that says it contains vitamin D3, as this form of vitamin D is more effectively absorbed than D2. Supplementation (with a smaller amount) during the summer is also a good idea, since you might be one of the folks who don't produce enough vitamin D even given sunlight.

Do not take cod liver oil to get your vitamin D! The reason for this is that cod liver oil, like all liver products, contains massive quantities of vitamin A. While vitamin A is of course important as well, hardly anyone in the Western world eating even remotely normally is deficient in it. If you take enough cod liver oil to get an ample dose of vitamin D, you can get vitamin A poisoning. And unlike with most vitamins, even doses slightly larger than the RDA can be harmful. Taking too much vitamin A can adversely affect your bone strength.

Do I have to take it every day?

Vitamin D is a fat soluble vitamin and stored in the body, so you don't have to take it every day. Eg. if you can get drops that contain 5 mcg of vitamin D per two drops (and thus the minimum recommended dose you should be taking is ten drops), you can take 70 drops once a week. One milliliter is approximately 30 drops, so that's about two milliliters. If you want to ensure better illness protection, you could take one teaspoonful (5 ml) of this supplement once a week, yielding about 375 mcg of vitamin D (about 54 mcg a day). It should be taken with a meal that contains at least some fat for best absorption.

How do I know I have enough of vitamin D/How do I know I'm not taking too much?

The best way to know if you have adequate levels of vitamin D is to have it tested (with bloodwork). This is an important test, but most doctors rarely ever do it. It costs about $50 if you have to pay for it out of pocket. However, even if you don't have it tested, it is completely safe to take these doses, as the human body can produce up to 250 mcg (10,000 IU) in just 20 minutes.

Does vitamin D supplementation help if I already have one of those diseases? Can it help in other conditions?

There isn't clear evidence for all of these conditions, but for many it seems to. And even if you have one of those diseases, you can still get another one (eg. if you have multiple sclerosis you can still get cancer - and may be even more likely to get cancer). According to one study the administration of vitamin D blocks the disease progression in an animal model of multiple sclerosis.^[16] Vitamin D seems to be an effective treatment for prostate cancer.^[17] There is some evidence that it might work for colorectal cancer as well.^[18]

While you can't prevent HIV infection with vitamin D (or even if you can, condoms and other measures are a much more important way), it seems like supplementing with vitamin D is probably a good idea in HIV/AIDS as well.^[19] The same is probably true for other immune system illnesses as well, such as CFS/ME (and I strongly suspect that vitamin D reduces the risk of getting this debilitating illness). It may be a culprit in fibromyalgia as well -

My next news article will tell you more effective ways of treating an already existent condition (with the exception of type I diabetes, since once you get it, the damage is quickly done).

Since sunlight makes the body produce vitamin D, does solarium have the same effect?

Vitamin D production requires UVB rays. Some solarium equipment only produces UVA spectrum rays, which doesn't promote production of vitamin D. So, it depends entirely on your solarium (I assume this is written on the actual machine, or the papers that come with the solarium have the information). I'd still recommend supplementation instead of using solarium during the winter. But if you're going to frequently use a solarium that produces UVB radiation for other reasons anyway, you can probably reduce the amount you're supplementing, but it's not necessary.

Other ways to reduce the risk of cancer or other illnesses

Of course, vitamin D supplementation isn't the only way to reduce cancer risk. If you smoke, quitting smoking is the best thing you can do - but you certainly knew it already. Consuming large quantities of alcohol is a cancer risk - and not just for liver cancer. Even lung cancer risk goes up with alcohol use, and so do the risks of eg. breast and colorectal cancer.^[20] Exercise, besides being healthy in general, can reduce the risk of eg. breast cancer. If you're obese, losing weight is a good way to lower your risk of some cancers, eg. one of the very deadliest, the pancreatic cancer.^[21]

There is another fairly easy way too - supplementing with selenium. It appears to decrease the risk of several cancers and slow down the spread of already existing tumors.^[22],[23] It probably isn't as good as vitamin D for reducing the risk of cancer and other illnesses, but as it is an antoxidant and beneficial to the immune system it may also prevent other conditions and/or reduce the damage they cause, particularly viral infections and cardiovascular disease.^[24]

In the next "issue"

My next article will be on a similar subject, but in it I will be shedding light on an effective but poorly known strategy for those who already have eg. cancer, HIV/AIDS, an autoimmune condition or a neurodegenerative illness (which can also be utilized as a preventive measure in high-risk cases).

References

For the references you'll have to see http://maija.irtie.org/vitamindrefs.html - I spent a lot of time formatting them to include them here, but you can thank DA's extremely inefficient admins who still haven't fixed the URL parser that has been severely broken for some four years or more now.

_{Disclaimer: This article is written by me (Maija Haavisto). It only provides links to a small fraction of the research done on the subject, as I don't have infinite resources and otherwise it would far exceed the maximum size of news articles. I am not a medical professional and I take no responsibility of any other possible errors in this information. Medicine is a constantly evolving science. This information is not intended to treat, cure or diagnose any illness. You use it at your own risk. If you are worried you are suffering from a chronic illness or may be at an increased risk for getting one, you should discuss it with your doctor. However, don't assume your doctor knows anything about vitamin D. Most doctors have very little information about nutrition and the little they have is outdated. Sadly, only a small minority of doctors follow scientific research - according to a study I'm unable to locate right now as few as five per cent.}