Reply #20: "Air pollution in Mexico varies among cities". Mexico City is unique, geographically, but the issue

[tiptoe]

of Vitamin D sufficiency would not be reducible merely to "plenty of sunshine in Cancun". A visitor/tourist's serum 25(OH)D level may be low to begin with, prior to "immersion" in sunny Cancun, and, moreover, if photochemical UVB-blocking sunscreens are used while there, no amount of daily sun exposure would yield significant Vitamin D stimulus benefit.

First

Air Pollution in Mexico

On a worldwide level, across the border from California, the air quality in Mexico is some of the worst this world has seen. Air pollution in Mexico is mainly caused by automobile traffic, the result of overcrowded roads, and automobiles that are often old and environmentally unsound. Air pollution in Mexico varies among cities as well. For example, in Mexico City, where pollution levels are at their worst, the city’s geography, which places it below sea level and surrounded on three sides by mountains, causes the pollution to stay trapped in the atmosphere. In other Mexican cities that border the United States, the causes of poor air quality are primarily from the factories that have sprung up along the borders.

source: http://www.encyclomedia.com/air_pollution.html

Second

Do you know your cousin's serum Vitamin D level? (Has she ever been tested?)

Low vitamin D increases flu risk"

If you want to make sure you are covering all your bases when it comes to flu prevention, there is more you can do than follow the typically-spouted recommendations. In fact, for sun-starved Seattleites, it is especially important to make sure you’re not deficient in Vitamin D, a crucial vitamin for immune system functioning linked to seasonal, epidemic flu.
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Vitamin D deficiency, common among Seattleites, is linked to influenza and respiratory tract infections. Studies have shown that children with vitamin D deficiency are predisposed to respiratory infections, especially viral infections rather that bacterial (Walker, 2009). In adults, studies show that higher vitamin D levels in the blood are associated with lower levels of upper respiratory infections (Ginde, 2009).

Vitamin D supplementation has been shown to reduce the incidence of respiratory infections in children, while studies using vitamin D supplementation in adults to prevent infections have been mixed (Cannell, 2006). For example, daily supplementation with 800 IU vitamin D3 for 12 weeks in older people living in the UK and Scotland was associated with fewer self-reported infections and antibiotics, but the estimated 10–15% reduction was not statistically significant (Avenell, 2007). It could be that higher dosages for a longer treatment time would have resulted in statistically significant reductions in infections and antibiotic use in this older, northern-latitude-based population.

Sunlight is an important source of vitamin D, but don’t be fooled into thinking that getting out in the Seattle sun this spring and summer will be sufficient, especially if your Vitamin D levels are already too low. A recent study of 93 people living in Hawaii with high amounts of sun exposure (participants spent an average 22.4 hours per week outside without sunscreen) found that 51% of the subjects had serum 25-hydroxyvitamin D concentrations below 30 ng/mL, defined as "low vitamin D status”. These results implied that the common clinical recommendation to allow sun exposure to the hands and face for 15 minutes may not ensure vitamin D sufficiency, according to the investigators (Binkely, 2007).
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References

Avenell A, Cook JA, Maclennan GS, Macpherson GC. Vitamin D supplementation to prevent infections: a sub-study of a randomised placebo-controlled trial in older people (RECORD trial, ISRCTN 51647438). Age Ageing. 2007 Sep;36(5):574-7.

Binkley N, Novotny R, Krueger D, Kawahara T, Daida YG, Lensmeyer G, Hollis BW, Drezner MK. Low vitamin D status despite abundant sun exposure. J Clin Endocrinol Metab. 2007 Jun;92(6):2130-5.

Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S, Garland CF, Giovannucci E. Epidemic influenza and vitamin D. Epidemiol Infect. 2006 Dec;134(6):1129-40.

Ginde AA, Mansbach JM, Camargo CA. Association Between Serum 25-Hydroxyvitamin D Level and Upper Respiratory Tract Infection in the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2009;169(4):384-390.

Walker VP, Modlin RL. The Vitamin D Connection to Pediatric Infections and Immune Function. Pediatr Res. 2009 Jan 28.

Wike Malone R, Kessenich C. Vitamin D Deficiency: Implications Across the Lifespan. The Journal for Nurse Practitioners. 2008 June;4(6): 448-454.

NOTE: The writer doesn't mention anything about the "constitutive pigmentation" of the "93 people living in Hawaii with high amounts of sun exposure...without sunscreen", but that, too, is a factor in ability to absorb UVB radiation. (See 18:40 Skin Cancer/Sunscreen -- The Dilemma and Your Health: Skin color matters in the vitamin D debate "Though someone in Boston with pale skin can get adequate vitamin D by exposing their arms and legs to the sun for 10 to 15 minutes twice a week in the summer, someone with the darkest skin might need two hours of exposure each time," Holick says. "It's impractical,"...)

Gauging your Vitamin D Status - Chart
What is the best serum 25(OH) Vitamin D concentration?

People living in sunny places with minimal clothing that doesn't limit vitamin D photosynthesis have serum 25(OH) D levels of 54 to 90 ng/ml (1)

A good target is 60ng/ml == 150 nMol/L (level of lifeguards in LA Jolla.)

A useful rule of thumb is that for every 100 IU of vitamin D3 ingested, you'll gain 1 ng/ml in serum 25(OH)D, so if your current level is 40 ng/ml you should take 2,000 IU to get up to 60 ng/ml. If your current level is 20 ng/ml, 4000 IU/day would raise it to 60 ng/ml. (2)

The Risk of Additional Vitamin D – Reinhold Vieth, PhD
Ann. Epidemiology, April 11, 2009 (Epub ahead of schedule)

”…Evidence from clinical trials shows, with a wide margin of confidence, that a prolonged intake of 10,000 IU/d of vitamin D(3) poses no risk of adverse effects for adults, even if this is added to a rather high physiologic background level of vitamin D.”

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A study by Dr. Cannell* from California also showed that vitamin D can help prevent influenza infections by strengthening the immune system. A daily intake of 2,000 IU should be taken — at minimum. A dose of up to 10,000 IU of vitamin D daily for a few days may also be helpful. Whether vitamin D will help with the swine flu is yet to be seen — however, I personally took a higher than usual dose of vitamin D last night after watching news reports on the infection. Better safe than sorry!

Dr. Eric Madrid
http://vitamind-prescription.com/2009/04/25/swine-flu-infection-and-vitamin-d-can-it-help/