If you are you might want to reconsider ... Looks like an ancestral way of eating is already protective with magnesium supplementation.
There are some limitations - it's epidemiology and food questionnaires, but still interesting. Normal tension glaucoma is normal pressure glaucoma (optic nerve damage), and harder to diagnose. Most glaucomas are of high ocular pressure (tension), but NTG is different. Iron and calcium supplementation (the higher the greater) are correlated with NTG. Magnesium is being used in Switzerland to improve NTG patients' visual fields (test of peripheral vision).
March 20, 2012 (New York, New York) — An investigation into the effects of calcium and iron supplementation on ocular health has found that consuming high amounts of these supplements leads to an elevated risk for the development of normal-tension glaucoma (NTG), according to a study presented here at the American Glaucoma Society 22nd Annual Meeting.
"The aim of our study was to investigate the epidemiologic relationship between the supplementary consumption of the oxidants calcium and iron and the presence of glaucoma," said Dr. Wang.
The study population was derived from the 2007/08 National Health and Nutrition Examination Survey. Eligible participants were 40 years or older, had undergone an interview and eye exam, and had the ability to self-report glaucoma (n = 3848).
Average daily calcium and iron intake was determined from the amount of supplemental calcium/iron intake (including antacids, multivitamins, and prescription and nonprescription supplements) reported during a 30-day period. "These data were then divided into quintiles for logistic regression models," Dr. Wang explained.
Models accounted for the confounders of age, sex, ethnicity, education, income, health-related behaviors, general health condition, and comorbidities. The main outcome was the association between self-reported glaucoma and iron and calcium supplementation.
Of the 3848 subjects enrolled, 248 were subsequently found to have NTG. Associations between glaucoma incidence and dietary supplements were observed for the highest quartile of calcium intake (at least 800 mg/day). "These individuals have a 2.4 times greater risk of developing glaucoma than those who do not take supplements" (95% confidence interval [CI], 1.25 to 4.76), reported Dr. Wang.
Elevated risk for disease was also seen for iron supplementation, with the top quartile (at least 18 mg iron/day) demonstrating a statistically significant association between high supplement intake and NTG, compared with control subjects (odds ratio [OR], 3.80; 95% CI, 1.79 to 8.06).
"Most striking was the relationship for the concurrent use of calcium and iron in the top quartiles," said Dr. Wang, with high amounts of both supplements taken together demonstrating the greatest risk (OR, 7.24; 95% CI, 2.42 to 21.62).
She noted that the study had several limitations, one being that dietary sources of calcium and iron (e.g., kale, spinach) were not explored. However, given these results, confirmatory studies are being considered.
Interplay of Supplements: What About Magnesium?
Commenting on the study, Robert Ritch, MD, chief of glaucoma service and surgeon director at the New York Eye and Ear Infirmary in New York City, said that "in middle-aged people or older individuals, magnesium deficiency is not uncommon."
"There are some groups now — Dr. Josef Flammer's group at the University of Basel [Switzerland] for one — that are using magnesium supplementation in normal-tension glaucoma; I've started to use it in some patients as well," he noted.
One recent study that looked at a 300 mg oral dose of magnesium citrate in patients with NTG found a statistically significant improvement in mean deviation on visual field after 1 month of use, compared with patients who did not receive any magnesium (Eur J Ophthalmol. 2010;20:131-135). However, those study results revealed nothing about the mechanism of action of magnesium in improving vision scores.
Dr. Ritch suggested that if the data exist, associations between calcium, iron, and magnesium should be investigated, particularly with an eye toward [determining] the effect of magnesium on calcium metabolism.
The study was supported by the National Eye Institute, That Man May See, Research to Prevent Blindness, and a grant from the National Institutes of Health to the Clinical and Translational Science Institute at the University of California San Francisco. The study authors and Dr. Ritch have disclosed no relevant financial relationships.
American Glaucoma Society 22nd Annual Meeting Abstract 22. Presented March 3, 2012.
My mom still cannot donate blood because of chronically low iron levels. I tell her she's going to outlive us all, but I would not encourage her to stop her iron supplement because she get fatigued VERY fast and looks like she has two black eyes after a few days of not supplementing. She eats 1 bunch of kale per day, liver once a week, and oysters twice a week, but she had surgery last year after losing an enormous amount of blood (over half the volume in her body), and for some reason is just having a really hard time retaining iron stores now. They're looking into a possible infection that could be stealing all her vitamin C and impeding iron absorption from all the high-iron food she eats.
The point being: I think there are exceptions which may require temporary supplementation for reasons of quality of life, which is why there are no blanket statements.
Yes I still supplement iron as I have chronic low ferritin levels. I also supplement magnesium with good reason. I have no signs of glaucoma. My concern for low ferritin and the problems caused by too little magnesium outweigh any fear of glaucoma. I certainly think this is another good example of why its important to question your supplementation regime but for some of us taking iron and/or calcium supplementation is a good and even necessary thing. It is for me.
I a little embarrassed to admit that I am taking some mineral supplements. Just 3 different caps a day. A Calcium-Magnesium-Zinc combination, a Multi-Mineral Cap and a "Total Mins" capsule. Once a day. In each case my single capsule dosage is well below the recommended daily dosages on the respective labels. In effect I'm trying to capture enough to provide small trace amounts (minimal dosage) and hoping that my metabolism will recognize them, grab them and use them. Supplements are usually best taken WITH food. Especially something like cod liver oil caps. I have no usable empirical data with respect to supplements. I guess its just something I've fallen into over the years. Obviously its not strictly paleo or primal to take supplements. For decades we've heard of the benefit of various supplements for various conditions. Iron and folic acid for post-menapausalwomen or pregnant women. Calcium supplements to help against bone thinning. Saw palmetto recommended to help with male prostrate problems. Aspirin as a blood thinner for those at risk of stroke. Its a complex subject very problematic with respect to things like precisely optimal individual dosages and needs.
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