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Is low vitamin-D associated with glaucoma?
Is low vitamin-D associated with glaucoma?
What is vitamin D and what does it do?
Vitamin D is a nutrient found in some foods that is needed for health, to maintain strong bones and much more. Muscles need it to move, for example. Nerves need it to carry messages between the brain and every body part, and the immune system needs vitamin D to fight off invading bacteria and viruses.
Vitamin D maintains strong bones by helping the body absorb calcium (one of bone’s main building blocks) from food and supplements. People who get too little vitamin D may develop soft, thin, and brittle bones, a condition known as rickets in children and osteomalacia in adults. Vitamin D helps protect older adults from osteoporosis.
Vitamin D is found in cells throughout the body. Chemically, it is a group of fat-soluble secosteroids responsible for enhancing intestinal absorption of calcium, iron, magnesium, phosphate and zinc. In humans, the most important compounds in this group are vitamin D3 (also known as cholecalciferol) and vitamin D2 (ergocalciferol). Cholecalciferol and ergocalciferol can be ingested from the diet and from supplements. The body can also synthesize vitamin D (specifically cholecalciferol) in the skin, from cholesterol, when sun exposure is adequate (hence its nickname, the "sunshine vitamin").
Is vitamin D status associated with open-angle glaucoma?
Research research published in the journal article Public Health Nutr. (2014 Apr;17(4):833-43) suggests that vitamin D deficiency should be considered as a potential risk factor for the development of open angle glaucoma. The article is entitled "Is vitamin D status associated with open-angle glaucoma? A cross-sectional study from South Korea" and I will paste it below.
The May 2014 issue of the American Journal of Clinical Nutrition published the results of a trial of vitamin D supplementation in women which found that correction of vitamin D insufficiency resulted in weight loss and a significant reduction in C-reactive protein (CRP), a marker of inflammation.
How much vitamin D do I need?
Many nutrition researchers are convinced the Food and Nutrition Board's recommendations for adequate vitamin D intake are far below what your body really needs. Those guidelines call for 200 IU a day up to the age of 50, 400 IU from 51 to 70, and 600 IU over age 70.
Michael F. Holick, PhD, MD, who heads the Vitamin D, Skin, and Bone Research Laboratory at Boston University School of Medicine. says studies show that to achieve blood levels of vitamin D that can protect you against chronic diseases, you need an optimal dose of 1,000 IU of vitamin D a day.
Supplemental vitamin D is available in 2 distinct forms: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3).
Most foods aren't filled to the brim with vitamin D -- far from it. And the food situation is starker for those on a plant-based diet. I am not personally a fan of the type of vitamin D used to fortify foods such as milk, which is ergocalciferol (vitamin D2). In an article in American Society for Clinical Nutrition, Lisa A Houghton and Reinhold Vieth make the strong statement that "Vitamin D2, or ergocalciferol, should not be regarded as a nutrient suitable for supplementation or fortification."
And since sufficient sun exposure is a complex subject with many potential pitfalls, it looks like vitamin D3 supplementation is a wise decision.
Public Health Nutr. 2014 Apr;17(4):833-43
Is vitamin D status associated with open-angle glaucoma? A cross-sectional study from South Korea.
OBJECTIVE: Open angle glaucoma (OAG) is one of the major chronic diseases involving the optic nerve. However, little is known about the association between vitamin D and open angle glaucoma. The present study was conducted to test the hypothesis that lower vitamin D status is associated with greater prevalence of open angle glaucoma.
DESIGN: Cross-sectional study. Multivariable logistic regression was performed to examine the relationship between serum 25-hydroxyvitamin D (25(OH)D) and open angle glaucoma after adjusting for traditional potential confounders. OAG was defined by the criteria of the International Society for Geographical and Epidemiological Ophthalmology.
SETTING: The Fifth Korean National Health and Nutrition Examination Survey conducted in 2010-2011.
SUBJECTS: Six thousand and ninety-four adult participants randomly selected from 192 surveys in 131 locations in South Korea.
RESULTS: Multivariable-adjusted odds ratios of open angle glaucoma across quintiles of decreasing 25(OH)D were 1.26, 1.00 (reference), 1.31, 1.36 and 1.69 (P for quadratic trend <0.01). The odds ratio for the lowest 25(OH)D quintile was significantly higher than that for the second quintile (P < 0.01). In addition, we discovered that the predictors for worsening of open angle glaucoma, such as intraocular pressure or vertical and horizontal cup-to-disc ratios, had a significant relationship with 25(OH)D level.
CONCLUSIONS: There was a reverse J-shaped association between 25(OH)D levels and the risk of open angle glaucoma, with significantly elevated risk at lower 25(OH)D. The findings of this research suggest that vitamin D deficiency should be considered as a potential risk factor for the development of open angle glaucoma. To our knowledge, the present study is the first one that shows an association between vitamin D status and open angle glaucoma.
Recommended high quality vitamin D3 products:
Vitamin D Fact Sheet for Consumers
What foods provide vitamin D?
Very few foods naturally have vitamin D. Fortified foods provide most of the vitamin D in American diets, but as I said above, that source should not be regarded as suitable! Furthermore, few plant foods contain vitamin D and we already know that a plant-based diet is the healthiest overall diet. Mushrooms do provide some vitamin D. But often the vitamin D content of mushrooms is being boosted by exposing these mushrooms to ultraviolet light -- so I would choose to avoid such mushrooms!
Can I get vitamin D from the sun?
The body makes vitamin D when skin is directly exposed to the sun, and most people meet at least some of their vitamin D needs this way. Skin exposed to sunshine indoors through a window will not produce vitamin D. Cloudy days, shade, and having dark-colored skin also cut down on the amount of vitamin D the skin makes.
However, despite the importance of the sun to vitamin D synthesis, it is prudent to limit exposure of skin to sunlight in order to lower the risk for skin cancer. When out in the sun for more than a few minutes, wear protective clothing and apply sunscreen with an SPF (sun protection factor) of 8 or more. Tanning beds also cause the skin to make vitamin D, but pose similar risks for skin cancer.
People who avoid the sun or who cover their bodies with sunscreen or clothing should include good sources of vitamin D in their diets or take a supplement. Recommended intakes of vitamin D are set on the assumption of little sun exposure.
Am I deficient in vitamin D?
In general, levels below 30 nmol/L (12 ng/mL) are too low for bone or overall health, and levels above 125 nmol/L (50 ng/mL) are probably too high. Levels of 50 nmol/L or above (20 ng/mL or above) are sufficient for most people.
By these measures, some Americans are vitamin D deficient and almost no one has levels that are too high. In general, young people have higher blood levels of 25-hydroxyvitamin D than older people and males have higher levels than females. By race, non-Hispanic blacks tend to have the lowest levels and non-Hispanic whites the highest. The majority of Americans have blood levels lower than 75 nmol/L (30 ng/mL).
Certain other groups may not get enough vitamin D:
- Breastfed infants, since human milk is a poor source of the nutrient. Breastfed infants should be given an appropriate supplement of vitamin D each day.
- 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 to its active form.
- People with dark skin, because their skin has less ability to produce vitamin D from the sun.
- 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.
- Obese people, because their body fat binds to some vitamin D and prevents it from getting into the blood.
What happens if I don’t get enough vitamin D?
People can become deficient in vitamin D because they don’t consume enough or absorb enough from food, their exposure to sunlight is limited, or their kidneys cannot convert vitamin D to its active form in the body. In children, vitamin D deficiency causes rickets, where the bones become soft and bend. It’s a rare disease but still occurs, especially among African American infants and children. In adults, vitamin D deficiency leads to osteomalacia, causing bone pain and muscle weakness.
What are some effects of vitamin D on health?
Vitamin D is being studied for its possible connections to several diseases and medical problems, including diabetes, hypertension, and autoimmune conditions such as multiple sclerosis. Two of them discussed below are bone disorders and some types of cancer.
As they get older, millions of people (mostly women, but men too) develop, or are at risk of, osteoporosis, where bones become fragile and may fracture if one falls. It is one consequence of not getting enough calcium and vitamin D over the long term. Supplements of both vitamin D3 (at 700–800 IU/day) and calcium (500–1,200 mg/day) have been shown to reduce the risk of bone loss and fractures in elderly people aged 62–85 years. Men and women should talk with their health care providers about their needs for vitamin D (and calcium) as part of an overall plan to prevent or treat osteoporosis.
Some studies suggest that vitamin D may protect against colon cancer and perhaps even cancers of the prostate and breast. But higher levels of vitamin D in the blood have also been linked to higher rates of pancreatic cancer. At this time, it’s too early to say whether low vitamin D status increases cancer risk and whether higher levels protect or even increase risk in some people.
Can vitamin D be harmful?
Yes, when amounts in the blood become too high. Signs of toxicity include nausea, vomiting, poor appetite, constipation, weakness, and weight loss. And 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, and 4,000 IU/day for children 9 years and older, adults, and pregnant and lactating teens and women. 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.
Are there any interactions with vitamin D that I should know about?
Like most dietary supplements, vitamin D may interact or interfere with other medicines or supplements you might be taking. Here are several examples:
- Prednisone and other corticosteroid medicines to reduce inflammation impair how the body handles vitamin D, which leads to lower calcium absorption and loss of bone 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-soluble vitamins (A, E, and K).
- Both phenobarbital and phenytoin (brand name Dilantin®), used to prevent and control epileptic seizures, increase the breakdown of vitamin D and reduce calcium absorption.
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.