We all know that vitamin D is added to milk because it helps the body absorb and metabolize calcium for strong healthy bones, but a new study published this year from the National Institutes of Health (NIH) has also found some important information specifically for women.
NIH researchers found that, “Women who had sufficient amounts of vitamin D were 32 percent less likely to develop fibroids than women with insufficient vitamin D.”
Fibroids are non-cancerous tumors of the uterus. Fibroids often result in pain and bleeding in premenopausal women and are the leading cause of hysterectomy in the United States, according to the NIH.
Donna Baird, a researcher with the National Institute of Environmental Health Sciences (part of NIH), led the study of 1,036 women, ages 35-49, living in the Washington, D.C. area from 1996 to 1999, which completed questionnaires on sun exposure, as well as received ultrasounds to check for fibroids, and gave blood samples to check vitamin D levels.
The body can make vitamin D when skin is exposed to the sun or get it from food and supplements. The study found that, “Those who reported spending more than one hour outside per day also had a decreased risk of fibroids.”
Baird said that, “It would be wonderful if something as simple and inexpensive as getting some natural sunshine on their skin each day could help women reduce their chances of getting fibroids, but though the findings are consistent with laboratory studies, more studies in women are needed.”
Baird is currently conducting a study in Detroit to see if the findings from the Washington, D.C. study can be replicated.
Besides sunlight, among the best sources of vitamin D come from foods. The NIH finds that:
- Fatty fish such as salmon, tuna, and mackerel are among the best sources.
- Beef liver, cheese, and egg yolks provide small amounts.
- Mushrooms provide some vitamin D. In some mushrooms that are newly available in stores, the vitamin D content is being boosted by exposing these mushrooms to ultraviolet light.
- Almost all of the U.S. milk supply is fortified with 400 IU vitamin D per quart, but foods made from milk like cheese and ice cream are usually not fortified.
- Vitamin D is also added to many breakfast cereals and to some brands of orange juice, yogurt, margarine, soy beverages. Check the labels.
Having an insufficient level of vitamin D can cause a number of health problems. In children, vitamin D deficiency can cause rickets, a disease characterized by a failure of bone tissues to properly mineralize, resulting in soft bones and skeletal deformities.
Breastfed babies are also at risk of vitamin D deficiency. The NIH has found that, “Prolonged exclusive breastfeeding without the American Academy of Pediatrics recommended vitamin D supplementation is a significant cause of rickets, particularly in dark-skinned infants.”
“Human milk is a poor source of the nutrient,” adds the NIH, which recommends that breastfeeding mothers either “supplement with high doses of vitamin D” which can correspondingly increase the levels in their milk, or “breastfed infants should be given a supplement of 400 IU of vitamin D each day.”
The NIH says the recommended daily supplement amount for pregnant and breastfeeding women is 600 IU.
Those at highest risk of vitamin D deficiency include:
- Breastfed infants, since human milk is a poor source of the nutrient.
- Obese people, because their body fat binds to some vitamin D and prevents it from getting into the blood.
- People with disorders such as Crohn’s disease or celiac disease who don’t handle fat properly, because vitamin D needs fat to be absorbed.
- People with dark skin, because their skin has less ability to produce vitamin D from the sun.
- Older adults, since their skin doesn’t make vitamin D when exposed to sunlight as efficiently as when they were young and their kidneys are less able to convert vitamin D from its active form.
External factors that diminish the absorption of vitamin D, according to the Study of Environment, Lifestyles, & Fibroids, include:
- Sunscreen – The use of sunscreen blocks the production of vitamin D in the skin, though you can still get your necessary amount of vitamin D if at least some part of your skin is exposed to the sun without sunblock.
- Time of day – Only ultraviolet B (UVB) sunlight produces vitamin D on your skin. These light rays only reach the skin layer that produces vitamin D when the sun is fairly high in the sky.
- Location, climate, and air pollution – The further you are from the equator, the less UVB exposure you get. For example, Detroit is further away from the equator than Florida, so people who live in Detroit tend to get less sun exposure. In addition, factors such as pollution and cloud coverage can reduce UVB exposure by as much as 60 percent.
- Seasons– During the months from November to February, the sun stays low in the sky in many areas all day long, making it impossible to get enough skin exposure to make adequate vitamin D.
The NIH adds that, “Skin exposed to sunshine indoors through a window will not produce vitamin.”
Some other important information is that research over the last decade has found that vitamin D in adequate levels also has a strong correlation to the decreased prevalence of many neurodegenerative diseases such as Parkinson’s disease and cancers including: prostate, colon, and breast cancer.
In 2008, a team of researchers at Emory University School of Medicine reported that “a significant portion of Parkinson’s patients suffer from vitamin D insufficiency,” adding that, “23 percent of Parkinson’s patients exhibited vitamin D deficiency, compared to 10 percent in the control group.”
Parkinson’s disease is a neurodegenerative disorder which causes difficulty with muscle coordination and control. Approximately 1.5 million Americans are affected by this disease, according to the National Institute of Environmental Health Sciences (NIEHS).
The Parkinson’s study says that vitamin D – a fat soluble pro-hormone – has been linked to “maintaining physiologic function as well as preventing diseases such as bone, cardiovascular, autoimmune, and notably neurogenic disorders.
The study also says its findings add to the “growing body of evidence in support of the notion that vitamin D deficiency may contribute to pathogenesis (meaning development) of Parkinson’s. Vitamin D regulates multiple cellular processes known to be abnormal in Parkinson’s disease, including cellular differentiation, proliferation, and apoptosis (meaning programed cell death).”
In cancer research, in 1996, the NIEHS collaborated with the University of North Carolina at Chapel Hill in a study which found that, “Men with a particular vitamin D receptor gene [combination] appear to have only one third the risk of developing prostate cancer requiring surgery.”
The study of 200 men – published in the journal Cancer Research – suggested that vitamin D in combination with the body’s inherited ability to make use of the vitamin may play a role “in reducing prostate cancer risk.”
NIEHS study researcher Dr. Jack Taylor, explained that, “Different men have different risks of prostate cancer and this could be based in part on how their bodies utilize vitamin D.”
Dr. Taylor cautioned that a “body’s metabolism of vitamin D is complex and simply increasing vitamin D consumption or sunlight exposure may not affect levels of the active form in the blood. Vitamin D exerts its effects in the body by binding to the cell’s vitamin D receptor. The vitamin D receptor gene helps direct the activity.”
Dr. Taylor added, “We are very excited about the use of this information in attacking prostate cancer, but we are definitely not recommending that men take additional vitamin D based on the results of this study.”
Overdosing on vitamin D is a serious concern. The NIH says that when the amount of vitamin D is too high in the blood, signs of toxicity can include: nausea, vomiting, poor appetite, constipation, weakness, and weight loss.
The NIH adds that, “by raising blood levels of calcium, too much vitamin D can cause confusion, disorientation, and problems with heart rhythm. Excess vitamin D can also damage the kidneys.”
The safe upper limit for vitamin D is 1,000 to 1,500 IU/day for infants; 2,500 to 3,000 IU/day for children 1-8 years old; and 4,000 IU/day for children nine years or older, as well as adults, and pregnant and lactating women, according to the NIH.
“Vitamin D toxicity almost always occurs from overuse of supplements. Excessive sun exposure doesn’t cause vitamin D poisoning because the body limits the amount of this vitamin it produces,” says the NIH.
Also, be aware of potential medication interactions before starting a regiment of vitamin D supplements. The NIH warns that:
- Prednisone and other corticosteroid medicines –which reduce inflammation – can impair how the body handles vitamin D, which can lead to lower calcium absorption and loss of bones over time.
- Both the weight-loss drug orlistat (brand names Xenical and Alli) and the cholesterol-lowering drug cholestyramine (brand names Questran, LoCholest and Prevalite) can reduce the absorption of vitamin D and other fat-soluable vitamins (A, E, and K).
- Both phenobarbital and phenytoin (brand name Dilantin) – used to prevent and control epileptic seizures – can increase the breakdown of vitamin D and reduce calcium absorption.
The NIH also recommends that you “tell your doctor, pharmacist, and other health care providers about any dietary supplements and medicines you take.
“They can tell you if those dietary supplements might interact or interfere with your prescription or over the counter medicines, or if the medicines might interfere with how your body absorbs, uses, or breaks down nutrients.”
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