Vitamin D For Dummies book cover

Vitamin D For Dummies

By: Alan L. Rubin Published: 06-07-2011

Your plain-English guide to the many benefits of Vitamin D

Vitamin D is in the news every day, as new tests and studies reveal encouraging information about its power in maintaining good health and preventing major illnesses. No longer thought to just play a role in calcium intake and bone growth, Vitamin D has a host of other functions in the body, playing a role in prevention of serious diseases, including cancer, diabetes, and heart disease, as well as boosting immunity, improving athletic performance, losing weight, and more.

This hands-on, plain-English guide is perfect for anyone looking for helpful advice and information on the "nutrient of the decade."

  • Coverage of how Vitamin D works, and how much is needed for disease prevention
  • How and where to get sufficient amounts of the right kind of Vitamin D – from both your diet and nutritional supplements
  • The best ways to maintain healthy levels of Vitamin D

If you're looking to learn more about the many benefits Vitamin D can have on you and your family, you'll find everything you need right here.

Articles From Vitamin D For Dummies

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54 results
54 results
The Role of Vitamin D in Preventing Ovarian Cancer

Article / Updated 02-07-2017

Ovarian cancer may arise in the ovaries, oval-shaped organs found in pairs in the female reproductive system. Studies suggest that vitamin D plays a role in preventing and treating ovarian carcinoma. In 2009, about 21,550 cases were diagnosed and 14,600 women died of ovarian cancer in the United States. Ovarian cancer is usually a cancer of women older than age 60. Within the ovaries, eggs are produced, along with estrogen and progesterone. The following diagram shows the location of the ovaries. Location of the ovaries and other female reproductive organs. Ovarian cancer risk factors and symptoms Several factors increase the risk for ovarian cancer: Infertility Endometriosis, in which cells of the uterus are found outside the uterus, such as on the ovaries, causing pain and bleeding, especially during menstruation Postmenopausal estrogen supplementation Factors that decrease the risk for ovarian cancer include use of combined estrogen/progesterone oral contraceptives and contraception by tubal ligation (tying off the fallopian tubes). Ovarian cancer is associated with a number of signs and symptoms, but none that are specific to ovarian cancer. Consider the most important: Back pain Bloating Digestive symptoms, including constipation and lack of appetite A feeling of being full early Irregular menstrual cycles Pain in the pelvis or abdomen Swollen abdomen Vaginal bleeding Vague lower abdominal pain Ovarian cancer diagnosis and treatment Ovarian cancer isn’t usually diagnosed in its early stages because it tends to cause symptoms that aren’t specific to the disease. When ovarian cancer is suspected, a pelvic examination and CT scan can diagnose it. A definitive diagnosis requires a biopsy of the mass in the ovary. Treatment of ovarian cancer starts by surgically removing the ovary and fallopian tube. If the cancer has spread, chemotherapy is added to the treatment. Radiation therapy isn’t usually used because the ovaries are located near other vital organs. The prognosis for ovarian cancer is poor because the diagnosis is generally made so late in the disease. Complications that may occur include fluid in the abdomen, intestinal obstruction, and spread to other organs. The five-year survival rate is 45 percent. Vitamin D’s role in ovarian cancer The evidence that a lack of vitamin D plays a role in the occurrence of ovarian cancer is interesting; however, this relationship isn’t secure yet. Evidence that vitamin D plays a role in preventing and treating ovarian carcinoma includes the following: Calcitriol slows the growth and increases apoptosis (death) of cultured ovarian cancer cells. Drugs designed to act like calcitriol inhibit the growth of ovarian cancer in animal models. Results from several smaller studies suggest that higher 25-hydroxyvitamin D levels might be protective against ovarian cancer; however, a recent study that combines several smaller studies shows this may be limited to overweight women.

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The Role of Vitamin D in Protecting against Pancreatic Cancer

Article / Updated 02-07-2017

Pancreatic cancer generally has a poor prognosis because of its location in relation to other critical organs. Studies suggest that vitamin D may play an important role in fending off pancreatic cancer. The pancreas has two major functions: Producing hormones, insulin, glucagon, and somatostatin to control the glucose (sugar) in the body Producing enzymes that go into the small intestine and help to break down food into particles that the body can absorb Most of the pancreas lies behind the stomach, as shown in the following diagram. Any tumors that grow can’t be felt until they’re so large that the cancer is very advanced. For this reason, pancreatic cancer has a high mortality rate. About 42,500 new cases occur in the United States every year, and 35,250 deaths occur from pancreatic cancer. The location of the pancreas. Pancreatic cancer risk factors and symptoms Pancreatic cancers usually arise from the tissue that makes the enzymes for the small intestine rather than the tissue that makes the hormones. This cancer is called a “silent killer” because of a lack of early symptoms and nonspecific later symptoms. Other pancreatic cancers arise from the hormone-producing cells of the pancreas, called the islets. These cancers can be silent or they may cause low blood sugar (hypoglycemia) due to an insulin-producing tumor (insulinoma). Pancreatic cancer has many risk factors, some of which can be avoided and others that can’t. The most important are listed here: African American background Diabetes mellitus Excessive red meat in the diet Lack of vegetables and fruits in the diet Family history of pancreatic cancer Male sex Obesity Older age (older than 60) Smoking (responsible for 30 percent of pancreatic cancers) The most common signs and symptoms include the following: Diabetes, as the tumor replaces the tissue that produces insulin Dark urine from jaundice Loss of appetite, with nausea and vomiting Loss of weight Pain in the upper abdomen and back Painless jaundice (yellow eyes and skin) Pancreatic cancer diagnosis and treatment The diagnosis of pancreatic cancer is usually made at a late stage, when a patient complains of pain in the abdomen, has experienced weight loss, and has jaundice. The patient then usually has a computed tomography (CT) scan to find the location of the cancer. If the tumor is still localized to the pancreas, the first line of treatment is surgical removal of the tumor. Next, chemotherapy is given, but this is usually just to give the patient a few more months to live. Because pancreatic cancer is usually diagnosed late and the recovery from the disease is rare, some think that prevention is more feasible than treatment. Up to 30 percent of pancreatic cancer may be prevented by stopping smoking. Vitamin D’s role in pancreatic cancer Some evidence suggests that vitamin D may play an important role in pancreatic cancer. Consider these points: The amount of ultraviolet B irradiation from sun is inversely associated with the occurrence of pancreatic cancer worldwide. Calcitriol and drugs designed to act like calcitriol can slow the growth of pancreatic cancer cells in culture and in animal models. In a few studies, pancreatic cancer risk was higher when vitamin D intake was lower than 150 IU per day. Protection due to vitamin D was maximized when intake was over 300 IU per day. Although these findings are promising, there are a number of studies showing that high blood levels of vitamin D might be harmful! One study pooled the results of seven other studies and found that serum 25-hydroxyvitamin D levels greater than 40 ng/ml [100 nmol/L] doubled pancreatic cancer risk. Another one saw an even higher risk in smokers. It’s studies like these that make some vitamin D experts cautious about blanket recommendations to raise vitamin D intake to high levels. If the cancer-preventing effects of calcitriol are real, it may be that the doses currently recommended for bone health are all that’s needed to achieve them. The evidence for pancreatic cancer is consistent with other studies that show it’s important to avoid becoming vitamin D deficient (serum 25-hydroxyvitamin D levels less than 10 ng/ml [25 nmol/L]).

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How Vitamin D May Protect Against Prostate Cancer

Article / Updated 02-07-2017

Prostate cancer is the most common cancer in men in the United States. Some scientists think vitamin D may help protect against prostate cancer. Prostate cancer generally occurs in men over the age of 50; however, it is slow growing in most men and takes a lifetime to develop. Prostate cancer has been found in the prostate gland of more than 80 percent of men over the age of 70 who died from an entirely unrelated disease. Some doctors are concerned that the major test for detecting prostate cancer, the prostate specific antigen or PSA test, is overused. Its major weakness is that it not only picks up prostate cancer, but it also detects another prostate condition that isn’t cancer called benign prostatic hypertrophy (BPH). Unfortunately, when men get a positive PSA test, many of them may have had radical prostatectomy (surgical removal of the prostate) and then suffered from problems with erections and urinary incontinence. Dr. Richard Ablin, who developed the PSA test, thinks that prostate cancer is a disease that many men can live with and that can be managed. They’re concerned that the side effects of prostate cancer removal (prostatectomy) aren’t worth it. Prostate cancer risk factors and symptoms Prostate cancer occurs in the prostate gland, a tiny gland that surrounds the urethra, the tube that carries urine and semen through the penis out of the body. The prostate is only 20 grams in size, and its function is to make seminal fluid to carry sperm from the testicles. The following figure shows the location of the prostate gland. The location of the prostate and other male reproductive organs. Prostate cancer is linked to many risk factors beyond gender, including the following: Age: The older you are, the more likely you are to be diagnosed with prostate cancer. Race: African Americans are 60 percent more likely to develop prostate cancer than Caucasians. Family history: Men whose fathers or brothers develop prostate cancer are more likely to develop it. Smoking: This bad habit is probably a risk factor for more aggressive prostate cancer. Most prostate cancers cause no symptoms, but when they’ve grown to become clinically important, they may cause these issues: Pain in the pelvic area Difficulty urinating (this is also seen in the non-cancer condition BPH) Difficulty having an erection Bone pain if the cancer has spread to bone Prostate cancer diagnosis and treatment Prostate cancer is diagnosed with a biopsy of the prostate gland. Finding cancer in the prostate doesn’t mean that the cancer is deadly, however. Because prostate cancer grows very slowly in most men, many men can live long, normal lives with prostate cancer. But for some men it can be a rapidly growing, deadly disease. Treatment of prostate cancer follows several paths: Active surveillance (sometimes called watchful waiting), in which the patient is monitored for symptoms or growth of the tumor but no treatment is performed until clear evidence of danger arises, such as rapid growth or obvious symptoms (the PSA test is useful during this time because it’s already understood that the person has cancer) Surgery, in which the prostate is entirely removed Radiation therapy Cryosurgery (freezing of the tissue, which leads to death of the prostate tissue, including the cancer) Chemotherapy with drugs that kill the cancer Hormone therapy to block the effect of testosterone to stimulate growth of normal and cancerous prostate cells Some combination of these treatments Vitamin D’s role in prostate cancer Although scientists think vitamin D affects prostate cancer, there are more gaps in the evidence. Here is evidence that makes scientists think vitamin D may be protective: The risk of prostate cancer appears to be higher in people who live in places where sunlight is limiting. Interestingly, if you have high sunlight exposure when you’re young, you may be protected from prostate cancer throughout your life, even if you move more north. African American men have the lowest levels of vitamin D in their blood and the highest levels of both prostate cancer and death from prostate cancer in the United States. In men with prostate cancer, PSA levels rise more slowly in the spring and summer, when vitamin D production in skin is normally highest. Calcitriol and drugs designed to function like it reduce the growth of prostate cancer cells and slow the growth of prostate tumors in animal models. Prostate cells can make active vitamin D from 25-hydroxyvitamin D. These studies suggest that higher intakes of vitamin D could protect men from prostate cancer. Unfortunately, when researchers have looked for a relationship between serum 25-hydroxyvitamin D and the risk of prostate cancer, the results have been confusing. Some studies show that near deficient levels of vitamin D status increase prostate cancer risk, some show that serum 25-hydroxyvitamin D levels don’t relate at all to prostate cancer risk, and others show that high serum 25-hydroxyvitamin D levels may lead to higher levels of prostate cancer.

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Diagnosing and Treating Osteoporosis

Article / Updated 02-07-2017

Doctors diagnose osteoporosis by performing a bone densitometry test, which measures the amount of mineral per square centimeter of bone. The areas studied in a bone densitometry study are usually the lumbar spine and the upper part of the hip. The test takes about ten minutes to complete. The bone density correlates fairly well with the tendency of a bone to fracture. Measurements at the hip and spine can predict fractures at other sites. The following diagram shows dense, healthy bones on the left; bones weakened by osteoporosis appear on the right. Healthy bones (a) are denser than bones affected by osteoporosis (b). Diagnosing osteoporosis Dual-energy X-ray absorptiometry (DXA) is the most common method for studying the density of your bones. In this study, you lie on a table; then two X-ray beams — one of high energy and one of low energy — are aimed at your bones. The amount of radiation that passes through the bone is measured for each beam. This amount is determined by the thickness of the bone. The bone density is measured by a formula using the difference between the two beams. This procedure is painless and safe; the amount of radiation is very small — about one-tenth the amount a patient receives during a routine chest X-ray. The test is limited by differences in testing methods and technicians. Results are also affected by curvature of the spine, calcium in the abdominal aorta and blood vessels, arthritic changes in the spine, and multiple previous fractures. The test doesn’t identify the cause of low bone density. Bone densitometry is recommended for the following groups: Women age 65 or older Men age 70 or older Women age 60 to 64 if they’re at increased risk — mainly low in weight, but also smokers and heavy drinkers (more than five drinks a week) Men between ages 50 and 70 who haven’t had sufficient testosterone Anyone older than 50 who’s had a broken bone Treating osteoporosis When osteoporosis is in full swing, a person will need medical help in the form of drugs. Several drugs treat osteoporosis by slowing or stopping the bone loss. They don’t affect vitamin D. The current drugs of choice are the bisphosphonate class of drugs. These drugs work by binding to calcium in bone, thereby blocking the ability of osteoclasts to break down any more bone. The most popular bisphosphonates currently are: Alendronate (Fosamax), taken once a day Risedronate (Actonel), taken once a week Ibandronate (Boniva), taken once a month Zoledronic Acid (Reclast or Aclasta), taken intravenously once yearly Bisphosphonates aren’t completely free of side effects. Some of the more serious ones include the following: Atrial fibrillation: The atria of the heart lose their regular motion and develop rapid disorganized movement. Inflammation of the stomach and erosion of the esophagus: The patient needs to be able to stand or sit upright for at least 30 minutes after taking a bisphosphonate. Because all bisphosphonates are poorly absorbed, the patient must avoid food, drink, and all medications for 30 minutes. (Some bisphosphonates can be administered intravenously, and this doesn’t happen with that route of delivery.) Osteonecrosis of the jaw: In osteonecrosis, one of the jaw bones is exposed through the gums, and infection and pain occurs. This condition generally occurs after a dental extraction in patients treated with the intravenous forms (ibandronate and zoledronic acid). Severe pain: The pain occurs in bones, joints, or muscles. Physicians monitor the effect of the bisphosphonates by repeating the bone densitometry study every year or two. If the bone densitometry remains stable or improves, the patient may stop the bisphosphonates after five years. Doctors continue to monitor bone density. Lack of estrogen has been shown to be the reason women lose bone at an accelerated pace at menopause; so, naturally, estrogen replacement had previously been the mainstay of osteoporosis therapy. It is quite effective at preventing spine and hip fractures. But estrogen also has been associated with cancer, especially breast cancer, as well as heart disease, so it’s not currently recommended as a primary treatment for osteoporosis.

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How Vitamin D Levels Affect Teeth

Article / Updated 02-07-2017

Teeth aren’t exactly bones, but they’re made up of similar tissues and are subject to the same problems bones may have. Vitamin D deficiency, including the conditions of rickets and osteomalacia, also can affect teeth. Exploring the normal development of teeth Humans develop two different sets of teeth: The baby, or primary, teeth begin to erupt from the gums at six months of age, which any parent knows is a painful time called teething. Primary teeth begin to develop between the sixth and eighth weeks of pregnancy. Permanent teeth form in the twentieth week of pregnancy. These times are critical, and the teeth may not develop if they don’t start by then. If a mom’s vitamin D and calcium levels are deficient when this development is taking place, the teeth don’t form normally. A tooth consists of a top part called a crown, made of enamel. Enamel is made up of calcium phosphate and is the hardest substance in the body. Under the crown is supporting dentin, which is mineralized tissue that isn’t as hard as the enamel. Within the dentin is the pulp of the tooth, which contains the nerves and blood vessels for the tooth. The tooth continues down into its bony support of the jaw and skull as one or more roots, which are covered by cementum. Cementum is another mineralized tissue that is softer than dentin or enamel. Cementum permits the tooth to attach strongly to the bone. Where the crown of the tooth meets its supporting bone, it’s surrounded by soft tissue called gingiva, or gums. The parts of a tooth. Knowing how rickets affects teeth Rickets, a condition resulting from inadequate mineralization of all the bones, can have a negative effect at every stage of the development of teeth. The primary effects of rickets include the following: Delayed formation: The baby teeth may not erupt until after one year. When they erupt, they may be smaller than normal. Periodontal disease: Periodontal disease can affect many different parts of the tooth, the bone, the cementum, or the gingiva. All of these weaken the anchoring of the teeth into bone. In the absence of sufficient vitamin D, the bone that forms in the jaw or skull isn’t sufficiently mineralized. Periodontal disease is also commonly caused by infection of the gums. When a gum infection occurs and the gingiva become inflamed, normal chewing or pressure on the gums makes them bleed easily. This condition is called gingivitis. Calcitriol helps regulate the immune system and protect against inflammation so some have suggested that low vitamin D status increases periodontal disease by increasing gingivitis. Regardless of the cause, when the teeth become loose in the mouth they may fall out. Dental caries: Dental caries, or cavities, are holes in the enamel of the tooth and can also result from inadequate vitamin D status. Because the teeth don’t mineralize sufficiently in rickets caused by low vitamin D status, this may increase a person’s chances of getting cavities. In the absence of vitamin D, infection is established on the tooth, leading to further loss of enamel and cavitation (holes in the teeth). Symptoms of dental caries include the following: Bad breath Chills Fever Foul taste Increasing infection Pain Tooth loss The caries can involve the enamel, the dentin, or the cementum. Pain occurs when the cavity reaches the dentin, which is connected to the nerves in the root of the tooth. Osteomalacia, a severe vitamin D deficiency that develops after the bones have been formed (in adults), can result in all these abnormalities as well. The teeth are painful, deformed, and subject to increased cavities and periodontal disease. They may be lost early.

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What is Vitamin D and How Does It Work?

Article / Updated 02-07-2017

Many people don’t have enough vitamin D, and are unaware of its many benefits. Scientists are discovering new possible roles for this important nutrient almost daily. If you think you have enough vitamin D in your body, you may be in for a surprise. What is vitamin D? A vitamin is defined as an essential nutrient that a living being must acquire in tiny amounts from the diet. A vitamin is a chemical that’s essential for your body but that your body can’t make; it must be ingested. By this definition, vitamin D isn’t a vitamin at all. Consider this — your skin can make vitamin D when it’s exposed to sunlight, so your body doesn’t have to acquire it from food. If vitamin D isn’t really a vitamin, what is it? It becomes a hormone called calcitriol (active vitamin D) after your body metabolizes it. A hormone is a chemical in your body that regulates your physiology. Vitamin D comes in two forms: Vitamin D2: The form found in plants (also called ergocalciferol) Vitamin D3: The form found in animals (also called cholecalciferol) Both forms of vitamin D are created when the ultraviolet rays of the sun act upon a form of cholesterol. In certain plants, the ultraviolet rays convert a molecule called ergosterol into vitamin D2. In humans, vitamin D starts as a substance in the skin called 7-dehydrocholesterol. The ultraviolet B (UVB) rays from the sun convert 7-dehydrocholesterol into vitamin D3. However, neither vitamin D nor vitamin D3 are active yet. In fact, vitamin D does nothing by itself; it’s completely inactive, and that may make you wonder what all the fuss is about. But it’s what vitamin D turns into that becomes important. How vitamin D forms in the body Vitamin D travels through the bloodstream to the liver, where it’s turned into 25-hydroxycholecalciferol (25(OH)D or calcidiol). This is a prohormone or precursor for the vitamin D hormone. The vitamin D prohormone travels through the bloodstream to the kidneys, where it’s turned into the active form, 1,25-dihydroxycholecalciferol (1,25(OH)2 D3 or calcitriol). 1,25(OH)2 D3 is the active vitamin D hormone. It is released back into the bloodstream where it then regulates how your body uses calcium and phosphorus. The following figure shows the conversion process in the body. Some controversy has arisen over whether vitamin D2 is as active as vitamin D3 when it’s ingested, but the consensus is that D3 is two or three times as potent in raising the level of 25-hydroxycholecalciferol. How the body creates vitamin D. Because the liver and the kidneys are involved in the production of calcitriol, diseases of these organs may affect your ability to make this hormone. Although the kidneys produce most of the calcitriol that ends up in the blood, there is some evidence that the conversion of 25(OH)D3 into 1,25(OH)2D3 may occur in other tissues in the human body. The production of calcitriol in these tissues is low in comparison to the kidney, and calcitriol made in these tissues is probably not released back into the serum. This calcitriol acts within the tissue where it’s made: Cells of the immune system (macrophages, dendritic cells) Brain Breast Colon (large intestine) Endothelial cells (inner lining of blood vessels) Pancreas Parathyroid glands Placenta Prostate Skin How vitamin D works The best understood role for calcitriol is in the control of how your body uses calcium and phosphorus to make strong bones. However, research is showing that many organs and systems in your body may also need active vitamin D. The intestine and bones rely on the kidneys to make and ship calcitriol to them. Other organs may be able to make small amounts of calcitriol on their own. Active vitamin D works by entering cells and attaching to a protein called the vitamin D receptor, located in the nucleus of cells, where the genetic material is located. This combination of calcitriol and its receptor stimulates the cell to make proteins that regulate the way the body works. For example, some of the proteins produced in response to calcitriol in the intestine help transport calcium across the intestine and into the bloodstream, greatly increasing the absorption of calcium from the diet. The vitamin D receptor is found in several cells that are critical for controlling the metabolism of calcium, phosphorus, and bone: intestinal cells, bone cells, kidney cells, and parathyroid gland cells. Vitamin D receptors also are present in most other tissues, including the brain, heart, skin, ovary and testicle, prostate gland, and breast, as well as the cells of the immune system, including white blood cells and other key immune cells.

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Vitamin D For Dummies Cheat Sheet

Cheat Sheet / Updated 03-27-2016

Vitamin D is essential for good health; however, it is a required nutrient only when you don't get enough ultraviolet B (UVB) rays from the sun. Unfortunately, many people can't get enough sun exposure and need to get vitamin D from their diet or from supplements. When you have enough vitamin D in your body, you can protect the health of your bones and prevent osteoporosis. New evidence suggests vitamin D may also help prevent many other diseases.

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Key Points You Need to Know about Vitamin D

Article / Updated 03-26-2016

Even as researchers continue to discover how vitamin D can protect your health, a lot of misinformation still surrounds this amazing vitamin. Here are some of the key points you need to know to understand the role of vitamin D in your health. You can make vitamin D in your skin when you're exposed to UVB light from the sun. People who don't get enough sun exposure need vitamin D in their diet. Whether you get vitamin D from sun, diet, or supplements, your body turns vitamin D into a hormone called 1,25 dihydroxyvitamin D (or calcitriol). This is the form of vitamin D that directly affects your health. Many people don't get enough UVB light to make vitamin D in their skin. It's hard to get enough vitamin D from food alone. You can find out if you have enough vitamin D in your system by getting a blood test for a form of vitamin D called 25-hydroxyvitamin D. Vitamin D supplements are safer than people used to think. The recommendations for vitamin D intake were set to help you protect your bones. Breast milk generally doesn't provide enough vitamin D to babies. Vitamin D may be important for more than just bone health. New evidence suggests it may strengthen your immune system, prevent cancer, and stop other chronic diseases. The proposed new roles for vitamin D and health are still being tested.

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What Are the Benefits of Vitamin D?

Article / Updated 03-26-2016

New information about vitamin D's role in health is being published almost daily. Here are the key functions of vitamin D, divided into those that are firmly established, those for which there is growing evidence, and those that are proposed but not yet confirmed. It's firmly established that vitamin D Facilitates absorption of calcium from your diet; essential for normal healthy bones Prevents osteoporosis, osteomalacia, and rickets There is growing evidence that vitamin D may Contribute to a normal healthy immune system Prevent autoimmune diseases Protect the body from cancer, especially breast, colorectal, and prostate cancers Vitamin D is showing promise that it may Protect the heart from heart attacks and heart failure Prevent both type 1 and type 2 diabetes Prevent asthma Prevent Alzheimer's disease Prevent Parkinson's disease

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Recommendations for Vitamin D Intake

Article / Updated 03-26-2016

New recommendations for vitamin D were released by an expert panel in 2010. These recommendations for daily intake of vitamin D are based on the current literature on vitamin D and are set to protect the health of your bones. They're based on the assumption that you get no vitamin D from sun exposure. 2010 Recommendations for Intake of Vitamin D Age RDA or AI* UL** Birth to 6 months 400 IU*** 1000 IU 7–12 months 400 IU 1500 IU 1–3 years 600 IU 2500 IU 4–8 years 600 IU 3000 IU 9–70 years 600 IU 4000 IU More than 70 years 800 IU 4000 IU *RDA = recommended daily allowance; AI = adequate intake**UL = upper safe limit for daily intake***IU = International Units Some people believe that you may need even more vitamin D than these recommendations; however, the scientific evidence to support these claims is lacking. Still, as long as you stay under the recommended upper safe intake limit, you can choose to take more vitamin D.

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