Vitamin D in a nutshell:
Vitamin D is the sunshine vitamin, produced in our skin in response to sunlight. Deficiency of vitamin D can lead to rickets and it is thought that it may contribute to osteoporosis and even multiple sclerosis.Best source of Vitamin D for Juicers
Vitamin D is not really found in great quantities in fruits and vegetables. Cod liver oil, now that’s another matter, though it does make the juice taste strange. Cold water fish are also good sources. Chewing on sunflower seeds, or sprouting sunflower seeds can give you some vitamin D, and mushrooms are also a source. Not much luck for juicers then, so get out in the sun for your daily fix of vitamin D.
Australia has the highest rates of skin cancer in the world. Since excessive exposure to sunlight is a major predisposing factor for the deadly form of skin cancer called melanoma, in the early 1990's the Australian government launched a media campaign urging its people to spend more time indoors and to slather on sunblock whenever they ventured out into the sun.
Two years later, the ministry of health was shocked to learn that rates of skin cancer had gone up, not down. The reason this well-intentioned experiment in cancer prevention failed was due to the fact that fighting cancer requires vitamin D. Protecting the skin from the carcinogenic effects of sunlight came at the expense of depriving the body of the beneficial effects of sunlight, and without changes in diet, sun protection did not work.
But it is really not fair to be too harsh in judging the Australian health authorities. Vitamin D is a group of substances, not a single substance, and different people have very different vitamin D needs.
Vitamin D1, D2 & D3
Vitamin D consists of a group of chemicals including the nutrients commonly called vitamin D1, vitamin D2, and vitamin D3. Vitamin D1 is a combination of the chemicals ergocalciferol and lumisterol, vitamin D2 is the isolated ergocalciferol, and vitamin D3 is the chemical cholecalciferol.
The mixture of chemicals known as vitamin D1 occurs in plankton, certain kinds of invertebrate organisms, and mushrooms. They can “refine” it into vitamin D2. The human body can use vitamin D2, but it makes vitamin D3. And it cannot make vitamin D3 without cholesterol.
Cholesterol is the very basic building block of vitamin D3 in humans and vertebrate animals (animals that have a backbone, including the animals that provide the best food sources of vitamin D, cows and fish). Every cell in the human body has to use cholesterol for a variety of functions, especially the formation of a “rain coat” that protects the cell from dissolving into the bloodstream.
The lower, basal layers of the skin, the layer of the skin that generates new skin, contains an enzyme that converts cholesterol into a substance called 7-dehydrocholesterol. When certain wavelengths of ultraviolet light (which happen to be the same UV-B wavelengths of ultraviolet light that are involved in skin cancer) fall on 7-dehydrocholesterol, it is converted into a substance that is usually called “pre-vitamin D3.” This pre-vitamin only needs to “hook together” to form cholecalciferol, or vitamin D3.
We use vitamin D3 all over our bodies, but we make it in our skin. Since vitamin D3 is fat-soluble, it can't be dissolved in the bloodstream. It has to be carried through the bloodstream on a water-soluble protein. The vitamin D3 we get from supplements or digest from animal foods and the vitamin D2 we get from plant foods also has to be transported on this protein. Two different enzymes are involved in making the protein, and if our bodies don't have the ability to make these two enzymes, we are functionally deficient in vitamin D no matter how much the skin makes or how much we get from food and supplements.
Moreover, the conversion of vitamin D into its active form requires two more major steps. The vitamin D from our skin and from food at first travels through liver for further processing and into the bloodstream in the form of a compound called calcefidiol. It has to be carried into the kidneys on yet another protein to be converted into calcetriol. Only this fully activated form of vitamin D3 is useful in the human body.
Once vitamin D has been activated as vitamin D3, it is attached to a carrier protein that transports it all through the body. It attaches to at vitamin D3 receptor sites where it activates DNA to code the production of proteins that:
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- Transport calcium from the digestive tract into the bloodstream,
- Transport calcium out of the bloodstream into cells that use it, especially in bone,
- Regulates the processes of cell proliferation (multiplication into new cells, stopping the unchecked reproduction of cells in cancer) and differentiation (maturation into fully functioning cells, preventing them from becoming cancerous),
- Starts the chemical reactions that produce the stimulant hormones adrenaline (epinephrine) and noradrenaline (norepinephrine) in the adrenal glands,
- Modifies the hedgehog signaling pathway, a set of reactions that cause rapid growth in the embryo but potentially cause cancerous growth after birth,
- And activates certain kinds of white blood cells.
The important thing to understand about the complex chemistry of vitamin D3 is that getting enough vitamin D is not just about taking a supplement. It's also about getting enough protein and keeping the kidneys in good condition. Any interruption in the process of making, digesting, absorbing, or transporting vitamin D changes the amount of vitamin D our bodies need. Some people need more vitamin D than others.
Who Is at Risk for Vitamin D Deficiency?
At the beginning of the twentieth century, it was a lot easier to understand what caused vitamin D deficiency. Millions of children were locked into windowless sweatshops, forced to work long days doing industrial work as young as the age of four. Among the many deprivations of working in a sweatshop was a substantial risk of developing the vitamin D deficiency disease known as rickets.
Rickets is a condition in which bones don't form properly. They become brittle, and the skeleton does not grow to its mature strength and size. The bones can cause constant pain, and the failure to grow causes lifelong short stature. Children who developed rickets were plagued by knock knees, loose teeth, soft skulls, and swelling over the wrists as cartilage grew to support the wrists in ways that bone could not. And since vitamin D is essential for the absorption of calcium, children who developed rickets also develop low blood calcium levels which could cause painful and debilitating muscle spasms all over the body.
In our time, most people would be appalled by the way these children were treated and would do whatever they could to get the children off the work bench and into the sun. In the early 1900's, however, there was a different approach. Parents and taskmasters alike quickly learned that rickets could be prevented, in many cases, by giving children a daily dose of a nasty, unsanitary, literally rotten nutritional supplement called cod liver oil. The cod liver oil tasted putrid, because it was. But it gave children the vitamin D they needed to work even longer hours in the dark to earn their tiny salaries.
Modern cod liver oil, by the way, is almost always packed under sanitary conditions. It may be fermented, but it's no longer rotted.
Chances are that if you are reading this article, you don't work in a sweatshop. You may still be at risk for vitamin D deficiency. In the twenty-first century as in the past, some people become vitamin D deficient when they don't get enough sun. Obviously, if you live in some northerly nation such as Iceland or Russia, or if you live in Tasmania or the South Island of New Zealand or the tip of South America, you never get a lot of strong sunlight.
Summer sun closer to the poles, however, actually contains more UV-B rays than sunlight at the equator. If you get lots of sun during the summer, even if you live in a northerly or southerly location, your body can make the vitamin D you need to make it through the winter. If you don't get summer sun, however, you probably will suffer some degree of vitamin D deficiency during the winter months. Winter vitamin D deficiency can occur in locations as far south as Cairo, Tenerife, New Delhi, Tokyo, San Francisco, Atlanta, and Austin, Texas. In fact, there is no place in the United States that records more cases of modern-day rickets than the city of Atlanta, Georgia.
In the United States, summers tend to be hot. People flee to the air conditioned indoors and don't get the sun they need to make vitamin D. In some Southern states in the United States vitamin D deficiencies are worse in the summer than in the winter—although they can occur in the winter, too.
Another factor in getting enough vitamin D is skin color. The 7-oxycholesterol that the skin uses to make vitamin D lies in its basal layer. UV-B rays have to pass through about 25 layers of skin cells to reach the cholesterol they transform into pre-vitamin D.
The darker your skin, the more UV-B rays are absorbed before they can reach the basal layers. That is why people who have fair skin are less likely to be deficient in vitamin D than people who have dark skin. Wearing garments for sun protection or modesty, or using copious amounts of sunscreen, makes the problem worse.
Is vitamin D deficiency really as widespread as the experts (particularly those who want to sell vitamin D) tell us?
Vitamin D is actually a very common condition even when (1) people get plenty of sun and (2) people get plenty of vitamin D in the diet. The reason why making vitamin D and consuming vitamin is not enough is that the kidneys can't convert vitamin D into its active form if they are busy alkalizing the bloodstream. You don't really have a danger of “acidity” in your bloodstream as long as your kidneys are active. But the processes that keep your bloodstream pH in the safe range also keep the kidneys from making activated vitamin D. You can need vitamin D supplements even if you get lots of sun and you drink vitamin-D enriched milk and take a low dose of vitamin D supplements.
And because none of the clinical trials of vitamin D to date has taken into account the effects of alkalizing and acidifying diet, scientists have not been able to show the clear benefits of taking supplemental vitamin D. Some people will need more, and some people will need more. Most people, however, need more.
Ironically, both vegans (because they don't get enough dietary vitamin D) and heavy meat eaters (because their kidneys are busy with alkalization) are relatively high risk of vitamin D deficiency. People who spend all summer by the air conditioner are as at risk as those who are locked inside during the winter. And almost anyone who has a condition limiting mobility, such as arthritis or multiple sclerosis or osteoporosis, also develops a deficiency of vitamin D.
Vitamin D deficiencies can also occur in people who have celiac disease, Crohn's disease, ulcerative colitis, ischemic colitis, short bowel syndrome, and either chronic diarrhea or constipation, due to poor absorption of vitamin D from food. Infants who are exclusively breast fed are at risk of vitamin D deficiency because there is relatively little vitamin D in human breast milk.
What Happens When We Don't Get Enough Vitamin D?
Rickets are the classic example of vitamin D deficiency. Due to a century of public education, rickets is now very rare, except in a few locations in Africa, and even there, it is a combination of vitamin D deficiency (having to eat refined grains for the bulk of the diet and sickness confining the child indoors) and calcium deficiency that causes the problem.
Osteomalacia is the modern example of vitamin D deficiency. Unlike rickets, osteomalacia usually strikes adults. There is not enough vitamin D for the body to make use of calcium to maintain bone, and tiny, painful fractures proliferate. Although extremely high-dose vitamin D therapy is not something you should attempt on your own (especially since other conditions can also cause bone pain), typically taking 50,000 IU or more of vitamin D reverses the underlying problem so that bones can begin to heal so that pain subsides.
Vitamin D deficiency is also believed to be a factor in osteoporosis. It's never enough just to get vitamin D to prevent osteoporosis. You also need calcium, phosphorus, and vitamin K, and it's important to avoid stressing your kidneys with an “acidifying” diet.
Vitamin D deficiency may be connected to certain kinds of cancers, especially colon and skin cancer. Black men and women who don't get enough vitamin D are often at especially elevated risk for colon cancer. White, Asian, Mediterranean, Middle Eastern, and Hispanic men and women who don't get enough vitamin D are at increased risk of melanoma.
Vitamin D deficiency has also been associated with hair loss, allergies, tremors, Parkinson's disease, and all the health conditions that can be caused by deficiencies of calcium or phosphorus, since vitamin D is involved in the absorption of calcium and phosphorus from food and supplements.
How Much Vitamin D Is Enough?
The Food and Nutrition Board of the Institute of Medicine in the United States raised the recommended dietary allowances for vitamin D in 2010. These are the levels of vitamin D intake that are adequate to help prevent rickets and osteomalacia.
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- Infants up to a year of age need 400 IU (10 micrograms) of vitamin D per day.
- Everyone else up to the age of 70 needs 600 IU (15 micrograms) of vitamin D per day.
- People 71 years of age and older need 800 IU (20 micrograms) of vitamin D per day.
If you use sunscreen, or if you never get out in the sun, or if you are always covered when you go outside for religious reasons, or if you have black skin, or if you have any of the predisposing factors for vitamin D deficiency mentioned earlier in this article, you will probably need at least 2,000 IU (50 micrograms) per day.
It's very easy to get 2,000 IU of vitamin D per day if you are able to get full-body sun exposure. Just 10 to 15 minutes of exposure of the whole body (or nearly the whole body) to sunlight will enable the skin to make 10,000 IU of vitamin D. Two sessions in the sun or in a tanning bed will take care of all your body's vitamin D needs, although it is very important to avoid sunburn to avoid skin cancer.
The best vitamin D supplements contain the kind of vitamin D the body actually uses, vitamin D3. This form of vitamin D may be labeled as cholecalciferol. It is available over-the-counter and over the Internet in 400 IU, 500 IU, 1000 IU, 5000 IU, and 10,000 IU doses.
If you already have healthy vitamin D levels, taking 2000 IU of vitamin D3 (it's important to check the label to make sure you are getting D3/cholecalciferol) will keep them healthy even when you don't get sun. If you don't have healthy vitamin D levels, however, taking just 2000 IU per day probably won't do you a lot of good.
That is because the body's ability to absorb vitamin D3 depends on vitamin D3. It has to have a certain “critical mass” of D3 in circulation to take more vitamin D3 into the bloodstream through the small intestine. For the first month, it's usually necessary to take 1,000 IU of vitamin D3 for every 15 kilos (33 pounds) of body weight. If you weigh 75 kilos (165 pounds), you will need 5,000 IU of vitamin D3 per day for a month to get back to normal (assuming you don't have any absorption issues). If you weigh 150 kilos (330 pounds), you will need 10,000 IU of vitamin D3 every day for a month.
In the United States, the FDA requires the 50,000 IU dosage to be in the form of vitamin D2. Essentially, the FDA only lets you get more vitamin D if you get it in a form your body can't use right away. For self-treatment you probably should avoid taking more than 10,000 IU per day anyway, because there are no reports of toxic overdose when adults take vitamin D3 at this level. Infants should never be given more than 2,000 IU per week.
Very few foods contain vitamin D. There's about 160 IU of vitamin D in a tablespoon (15 ml) of cod liver oil, but more than 1 tablespoon of cod liver oil contains too much vitamin A for an adult, and more than 1 teaspoon (5 ml) of cod liver oil contains too much vitamin A for an infant. There's about 600 IU of vitamin D in a 3-1/2 oz (100 gram) serving of cold-water fish such as salmon or herring. You get about 200 IU of vitamin D from a 3-1/2 oz (100 g) serving of either tofu of shellfish, and about 100 IU in a glass of milk. Mushrooms, potatoes, and spinach contain about 20 IU per serving—and who can eat 50 servings of mushrooms a day? It's a lot easier to get your vitamin D from supplements rather than from food.
FAQ About Vitamin D
Vitamin D is one of the hottest topics in nutritional supplementation and natural health. These frequently asked questions are organized in alphabetic order by topic for your convenience.
Q. Autism. Is there a relationship between vitamin D consumption and autism/Asperger's syndrome?
A. Many children stop drinking vitamin D-enriched formula and start drinking vitamin D-free fruit juice around the age of 18 months, which is when autism symptoms begin to develop. In the United States, the counties with the lowest rates of autism are also the counties where the greatest number of women participate in the WIC (Women, Infants, and Children) Program to ensure that mothers and children get enough thiamin, riboflavin, and vitamin D.
Q. Cancer. Can vitamin D treat cancer?
A. Vitamin D seems to be more important for preventing cancer than for treating it. The problem with vitamin D for treating cancer is that cancer that has spread to the bone increases calcium levels and vitamin D supplements have unpredictable effects in this situation. Discuss vitamin D supplements with your oncologist before taking them.
Q. Celiac disease. I have celiac disease. Should I be taking vitamin D?
A. Yes, and you will also need supplemental A, E, K, essential fatty acids, and minerals, but please talk with your physician before taking any type of supplement.
Q. Cod liver oil. Is cod liver oil a good source of vitamin D?
A. Depending on whether the cod liver oil is fermented, it can be, but sometimes won't be, a good source of vitamin D. It's very rich in vitamin A, however, and it's important to limit children's doses to 1 teaspoon (5 ml) and adult doses to 1 tablespoon (15 ml) to avoid overdosing vitamin A. Separate vitamin D supplements are a more reliable source of vitamin D.
Q. Colds and flu. Can taking vitamin D prevent colds and flu?
A. There is a natural antiviral compound that seems to require about 2000 IU of vitamin D for the body to make, but it's more important to preventing viral infections than treating them.
Q. Diabetes. I've heard that taking vitamin D is as effective as metformin (the world's second most often-prescribed diabetes medication after insulin) for lowering high blood sugar levels. Is that true?
A. Vitamin D for diabetes works by helping the beta cells in the pancreas absorb calcium, which releases insulin from its storage form. It is helpful for type 2 but not for type 1, in which the beta cells don't make insulin that calcium could release.
Q. High blood pressure. Will vitamin D lower blood pressure?
A. Usually a few points, by helping the linings of the arteries absorb calcium. It's not an alternative medication.
Q. Hyperparathyroidism. Is vitamin D the answer?
A. The parathyroid glands are tiny glands on either side of the thyroid gland that make the hormones for controlling the movement of calcium in and out of the bloodstream. Sometimes they “burn out” when the body receives too little calcium or too much lithium or phosphorus. Vitamin D is helpful for preventing the condition but not for treating it, although people who develop hyperparathyroidism continue to need the same amounts of vitamin D as anyone else.
Q. Kidney disease. Are there any restrictions on vitamin D supplements for people who have kidney disease?
A. Sometimes the kidneys process too much vitamin D3. Sometime chronic kidney failure makes it difficult for the kidneys to process vitamin D3 at all. If you have kidney disease, discuss vitamin D supplements with your doctor before taking them.
Q. Medications. Do medications have any affect on vitamin D status?
A. Statin drugs for cholesterol and most diuretics raise vitamin D levels. Anticonvulsants, medications for migraine, medications for asthma, and tuberculosis treatments lower vitamin D levels.
Q. Megadoses. I found a 50,000 IU vitamin D3 (not D2) product online. The instructions don't say how often to use it. Is this for everyday use?
A. No. It's too much for every day. It isn't enough to change your vitamin D levels if you take it just once a month, but it's OK for use once every 1 to 2 weeks.
Q. Multiple sclerosis (MS). Is vitamin D helpful in treating MS?
A. Since most people who get MS live in northerly, cloudy climates, researchers have long assumed that vitamin D deficiency played a role in the development of the disease.
Q. Sunscreen. Does it really make a difference in vitamin D production if I always use sunscreen all over my body before I go out into the sun?
A. A sunscreen with an SPF of 8 reduces vitamin D production by 95%. Higher SPF sun protection products essentially eliminate vitamin D production. You can't get the vitamin D you need from the sun if you use sun protection. It's still important to avoid sunburn when you don't use sunscreen, so get your sun in early morning.