Or they got it because they live in a climate where part of the year
it's difficult and/or dangerous to be out, and little sun is out, too.
Or they did all those things with their skin covered by clothing and
SPF, and with sunglasses on.

Susan

That's logical, but I don't think that the observation of relatively
high prevalence of low vitamin D status among type 2 diabetes patients
was a main point of this study. IMHO it was the association of low
vitamin D status within this population with increased
atherosclerosis. An excerpt from the abstract:

   "In multivariate regression analysis, low 25(OH)D
   concentrations independently predicted carotid IMT (P <
   0.001) in people with type 2 diabetes after adjustment for
   classical risk factors, diabetes duration, HbA1c, calcium,
   renal function tests, inflammatory markers, use of
   medications, and presence of the metabolic syndrome"

As for the relation between low vitamin D status and type 2 diabetes,
I take a couple of IMHO interesting quotes from

Zittermann A.
Vitamin D in preventive medicine: are we ignoring the evidence?
Br J Nutr. 2003 May;89(5):552-72. Review.
PMID: 12720576 [PubMed - indexed for MEDLINE]
<http://www.ingentaconnect.com/content/cabi/bjn/2003/00000089/00000005/art00002?t
oken=00531a0783f6da2dd5264f65263a3d4f58762f467c405847447b23442f7b317b763b6b674c7
a2d1245d>
(full text available from that page)

   "Experimental studies have demonstrated that a reduction in
   vitamin D activity can result in both increased insulin
   resistance and reduced insulin secretion (Boucher, 1998).
   Epidemiological data have shown a four- to five-fold higher
   prevalence of non-insulin-dependent diabetes in dark-skinned
   Asian immigrants in comparison with British Caucasians
   indicating that low vitamin D status may contribute to the
   pathogenesis of diabetes (McKeigue et al. 1992). Moreover, in
   elderly subjects the subgroup with the lowest tertile of
   25(OH)D levels had a significantly higher blood glucose
   increase and higher blood insulin increase after an oral
   glucose-tolerance test in comparison with the subgroup with
   the highest tertile of 25(OH)D levels (Baynes et al. 1997).
   Data indicate that vitamin D insufficiency may result in
   insulin resistance. Results are in line with the suggestion
   that enhanced levels of TNF-alpha, a cytokine with is
   inversely related to 25(OH)D and calcitriol (see p. 560),
   promote insulin resistance (Hotamisligil & Spiegelman, 1994).

   [...]

   It should be mentioned that hypertension, cardiovascular
   diseases, and diabetes mellitus are often associated with
   obesity. Obese subjects have an increased risk for low
   circulating 25(OH)D levels (Bell et al. 1985; Wortsman et al.
   2000) due to the storage of vitamin D and 25(OH)D in adipose
   tissue (Wortsman et al. 2000). The alterations in vitamin D
   metabolism of obese subjects in comparison with lean subjects
   are also associated with functional alterations such as
   elevated PTH levels (Bell et al. 1985; Wortsman et al. 2000).
   Obesity might thus contribute to insufficient circulating
   25(OH)D levels."

References about the relation between vitamin D status and muscle
function and physical performance:

Gloth FM III, Smith CE, Hollis BW, Tobin JD.
Functional improvement with vitamin D replenishment in a cohort of
frail, vitamin D-deficient older people.
J Am Geriatr Soc 1995;43:1269-71.
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&list_uids=7
594162&dopt=Abstract>

   "CONCLUSIONS: In this cohort of homebound older people,
   improvement in vitamin D status was associated with functional
   improvement as measured by the FEFA questionnaire."

Verhaar HJ, Samson MM, Jansen PA, de Vreede PL, Manten JW, Duursma SA.
Muscle strength, functional mobility and vitamin D in older women.
Aging (Milano). 2000 Dec;12(6):455-60.
PMID: 11211956 [PubMed - indexed for MEDLINE]
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=Abstra
ctPlus&list_uids=11211956>

   "Six months of treatment with alphacalcidol led to
   significant improvements (compared to the controls) in values
   of isometric knee extensor strength (left leg: 14.6% +/-
   5.7%. p=0.03; right leg: 11.5% +/- 5.0%, p=0.02) (mean +/-
   SEM). The achievements in the timed "Up & Go" test and 2-
   minute walking test did not improve in the alphacalcidol
   group compared to the controls after 6 months. However,
   within the vitamin D-deficient group, 6 months of
   alphacalcidol treatment led to a significant increase in the
   walking distance over 2 minutes (increase from 137.6 +/- 12.6
   to 151.3 +/- 11.2 meters, p=0.03). The controls, with normal
   vitamin D levels, did not exhibit improvements in performance
   of any of the tests over a period of 6 months. Summarized,
   alphacalcidol seems to improve muscle strength and walking
   distance over 2 minutes in vitamin D-deficient older women."

Ziambaras K, Dagogo-Jack S.
Reversible muscle weakness in patients with vitamin D deficiency.
West J Med 1997;167:435?9.
<http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9426489>
<http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1304730&blobtype=pdf>

   "We report on two patients who presented with significant
   proximal muscle weakness, one with vitamin D malabsorption
   and one with dietary vitamin D deficiency. A search for
   inflammation or other causes of myopathy was negative. Muscle
   biopsy in one patient revealed type IIB fiber atrophy. Once
   normal serum 25-hydroxyvitamin D3 levels were restored, both
   patients experienced gradual muscle strength improvement and
   reversal of proximal myopathy within 6 months.

   [...]
   
   The ultimate proof of the diagnosis of vitamin D-deficient
   muscle weakness rests on the response to therapy. Improvement
   in muscle strength has been observed as early as after a
   week,5 but usually within one to two months,14,15 of
   treatment with pharmacologic doses of vitamin D. Treatment is
   required for several months, however, for complete recovery
   of muscle strength.13,15"

Glerup H, Mikkelsen K, Poulsen L, et al.
Hypovitaminosis D myopathy without biochemical signs of osteomalacic
bone involvement.
Calcif Tissue Int 2000;66:419?24.
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&list_uids=1
0821877&dopt=Abstract>

   "Hypovitaminosis D myopathy is a prominent symptom of vitamin
   D deficiency, and severely impaired muscle function may be
   present even before biochemical signs of bone disease
   develop. Full normalization of hypovitaminosis D myopathy
   demands high-dose vitamin D treatment for 6 months or more.
   Our findings indicate that serum levels of ALP cannot be used
   in the screening for hypovitaminosis D myopathy. Assessment
   of s-25OHD is the only reliable test."

Prabhala A, Garg R, Dandona P.
Severe myopathy associated with vitamin D deficiency in western New
York.
Arch Intern Med 2000; 160:1199-203
<http://archinte.ama-assn.org/cgi/content/abstract/160/8/1199>

   "Five cases of severe myopathy associated with vitamin D
   deficiency are described. Each patient was confined to a
   wheelchair because of weakness and immobility. Two were
   elderly, 1 was a 37-year-old African American with type 1
   diabetes mellitus, 1 was being treated for carcinoid
   syndrome, and 1 was severely malnourished due to poor oral
   intake. In each, weakness had previously been attributed to
   other causes, including old age, concomitant diabetic
   neuropathy, or general debility. Correct diagnosis was made
   initially by a high index of suspicion, following the
   demonstration of clinical proximal myopathy; confirmation was
   made by the demonstration of low 25-hydroxyvitamin D and
   elevated parathyroid hormone concentrations. Treatment with
   vitamin D caused a resolution of body aches and pains and a
   restoration of normal muscle strength in 4 to 6 weeks. Four
   patients became fully mobile and had normal 25-hydroxyvitamin
   D concentrations, and the fifth also became mobile. In the 4
   fully recovered cases, parathyroid hormone levels on follow-
   up were lower but still elevated. This finding suggests a
   degree of autonomy of parathyroid secretion known to occur in
   cases of long-standing vitamin D deficiency. Myopathy, due to
   chronic vitamin D deficiency, probably contributes to
   immobility and ill health in a significant number of patients
   in the northern United States. An awareness of this condition
   may significantly improve mobility and quality of life in
   patient populations vulnerable to vitamin D deficiency."

Endo I, Inoue D, Mitsui T, Umaki Y, Akaike M, Yoshizawa T, Kato S,
Matsumoto T.
Deletion of vitamin D receptor gene in mice results in abnormal
skeletal muscle development with deregulated expression of
myoregulatory transcription factors.
Endocrinology. 2003 Dec;144(12):5138-44. Epub 2003 Aug 13.
PMID: 12959989 [PubMed - indexed for MEDLINE]
<http://endo.endojournals.org/cgi/content/full/144/12/5138>

   "These results suggest that VDR plays a physiological role in
   skeletal muscle development, participating in temporally
   strict down-regulation of myoregulatory transcription
   factors. The present study can form a molecular basis of VDR
   actions on muscle and should help further establish the
   physiological roles of VDR in muscle development as well as
   pharmacological effects of vitamin D on muscle functions."

Pfeifer M, Begerow B, Minne HW.
Vitamin D and muscle function.
Osteoporos Int. 2002 Mar;13(3):187-94. Review.
PMID: 11991436 [PubMed - indexed for MEDLINE]
DOI: 10.1007/s001980200012
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=Abstra
ctPlus&list_uids=11991436>

Staud R.
Vitamin D: more than just affecting calcium and bone.
Curr Rheumatol Rep. 2005 Oct;7(5):356-64. Review.
PMID: 16174483 [PubMed - indexed for MEDLINE]
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=Abstra
ctPlus&list_uids=16174483>

   "Clinical consequences related to low vitamin D levels
   include not only osteomalacia, osteoporosis, and rickets, but
   also neuro-muscular dysfunction and fractures. Falls related
   to neuromuscular dysfunction lead to 40% of all nursing home
   admissions and are the largest single cause of injury-related
   deaths in elderly people.
   
   [...]
   
   It is well established that vitamin D deficiency not only has
   serious consequences for bone health, but also for other
   organ systems. Previous studies have shown that vitamin D
   supplementation reduces the number of fractures and directly
   improves neuromuscular function, thus helping to prevent
   falls and subsequent fractures."

Boonen S, Bischoff-Ferrari HA, Cooper C, Lips P, Ljunggren O, Meunier
PJ, Reginster JY.
Addressing the musculoskeletal components of fracture risk with
calcium and vitamin D: a review of the evidence.
Calcif Tissue Int. 2006 May;78(5):257-70. Epub 2006 Apr 21. Review.
PMID: 16622587 [PubMed - indexed for MEDLINE]
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?itool=abstractplus&db=pubmed&cmd=R
etrieve&dopt=abstractplus&list_uids=16622587>
<http://www.springerlink.com/content/w786x2mjm3276ggk/>

   "Additionally, calcium and vitamin D supplementation
   significantly improves body sway and lower extremity
   strength, reducing the risk of falls."

Zittermann A.
Vitamin D in preventive medicine: are we ignoring the evidence?
Br J Nutr. 2003 May;89(5):552-72. Review.
PMID: 12720576 [PubMed - indexed for MEDLINE]
<http://tinyurl.com/249efc> (full text available from that page)

   "It has been assumed already at the beginning of the 20th
   century that severe vitamin D deficiency results in a
   disturbed muscle metabolism (Ritz et al. 1980). Animal
   studies have demonstrated that the aktinomyosin content of
   myofibrills is reduced during experimental rickets (Stroder &
   Arensmeyer, 1965). Moreover, vitamin D deficiency can impair
   intracellular Ca metabolism in muscle cells. The Ca content
   of mitochondria isolated from vitamin D-depleted chicks is
   low (Pleasure et al. 1979) and Ca uptake into the
   sarcoplasmic reticulum is reduced during vitamin D deficiency
   (Curry et al. 1983). Patients with osteomalacia suffer from
   muscle weakness and have low serum levels of muscle enzymes
   (Ritz et al. 1980; Rimaniol et al. 1994). Supplementation
   with 357 or 1250 mcg vitamin D/d or 50 mcg 25(OH)D/d for 1 to 2
   months was able to normalize muscle strength in patients with
   myopathy (Rimaniol et al. 1994; Ziambaras & Dagogo-Jack,
   1997). Sub-clinical myopathy may even occur at serum 25(OH)D
   levels of 10-50 nmol/l (Peacock, 1995). In line with this
   assumption, leg extension power was positively correlated
   with serum 25(OH)D levels in elderly males and with serum
   calcitriol levels in the whole group of males and females.
   The males had mean 25(OH)D levels of 90 (sd 87.5) nmol/l and
   the females had mean 25(OH)D levels of 68 (sd 53) nmol/l
   (Bischoff et al. 1999b) indicating that a large number of
   subjects had an insufficient vitamin D status. A recent study
   has brought forward evidence that a low vitamin D status also
   contributes to the pathogenesis of congestive heart failure,
   a disease resulting in cardiac muscle weakness due to
   impaired myocardial contractility. Circulating levels of NT-
   proANP, a biochemical indicator of congestive heart failure
   severity, were inversely correlated with serum 25(OH)D levels
   (r2 0.16, P>0.001; Zittermann et al. 2003).

   Supplemental studies have demonstrated that doses of 0.5 mcg
   calitriol/d or 10 mcg vitamin D/d had no effects on parameters
   of muscle function (Table 4). A daily supplement of very high
   doses of vitamin D and also doses of 20 mcg vitamin D/d could,
   however, significantly improve muscle function in subjects
   with low initial 25(OH)D levels (Table 4). It should also be
   mentioned that in both intervention trials the 20 mcg vitamin
   D/d was combined with a daily supplement of 1 200 mg Ca.
   Probably, the combined effect of 20 mcg vitamin D with high
   doses of oral Ca was responsible for the beneficial effects
   in these studies."
   
Mowe M, Haug E, Bohmer T.
Low serum calcidiol concentration in older adults with reduced
muscular function.
J Am Geriatr Soc 1999;47:220-6.
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&list_uids=9
988294&dopt=Abstract>

   "CONCLUSIONS: Older people with reduced muscle function often
   had reduced levels of calcidiol serum concentration. Low
   levels of calcidiol were not associated with signs of general
   undernutrition, such as low body mass, or with reduced arm-
   muscle circumference or triceps skinfold thickness. This
   finding may suggest a physiological role for calcidiol in
   muscle function. Reduced muscle strength increased disability
   in our older subjects, which may be improved by vitamin D
   supplementation in vitamin D-deficient subjects.

   [...]
   
   Our findings may be clinically relevant to the
   musculoskeletal health in the aged, because vitamin D
   insufficiency has been shown to be associated with lower
   muscle strength and increased falling tendency in adults.
   Conversely, supplement of native vitamin D or treatment with
   active vitamin D has been reported to improve muscle
   functions and protect from falling events and falling-
   associated fractures (29, 30, 31, 32, 33). Whether the
   beneficial effects of vitamin D treatment occur via direct
   VDR actions on skeletal muscle cells or indirect mechanisms
   remains unclear. Interestingly, however, abnormal expression
   of MyoD family members and MHC isoforms has been reported in
   various models of immobilization and denervation (34, 35, 36,
   37, 38). Considering the plasticity and highly adaptive
   nature of muscle fibers, it is conceivable that reprogramming
   and adaptations of muscle fibers may occur under various
   pathological conditions, particularly in elderly patients,
   and that these processes may be modulated by VDR-dependent
   vitamin D actions.
   
   In summary, we have shown that VDR gene deleted mice exhibit
   abnormal skeletal muscle development. These abnormalities
   occur independently of secondary metabolic changes such as
   hypocalcemia and hypophosphatemia and are accompanied by
   deregulated expression of myogenic transcription factors and
   MHC isoforms. These effects appear to involve direct vitamin
   D actions on muscle through VDR, because similar effects were
   reproduced by treatment of VDR-positive myoblastic cells with
   1,25(OH)2D in vitro. The present study can form a molecular
   basis of VDR actions on muscle and should help further
   establish the physiological roles of VDR in muscle
   development as well as pharmacological effects of vitamin D
   on muscle functions."
   
Solomon AM, Bouloux PM.
Modifying muscle mass - the endocrine perspective.
J Endocrinol. 2006 Nov;191(2):349-60. Review.
PMID: 17088404 [PubMed - indexed for MEDLINE]
<http://joe.endocrinology-journals.org/cgi/content/full/191/2/349>

   "Calcium, vitamin D and phosphate levels all impact on muscle
   function most notably in deficiency states such as the
   myopathy seen in osteomalacia. This has been confirmed as a
   histological atrophy of muscle, predominantly type II fibres
   and is exacerbated by ageing (Janssen et al. 2002).
   Polymorphisms of the vitamin D receptor and vitamin D
   knockout models have a significant muscle phenotype (Demay
   2003). Vitamin D null mice have smaller muscle fibres and
   raised levels of MRFs. These changes are reversed by
   treatment with vitamin D (Endo et al. 2003). Vitamin D-
   receptor polymorphisms associated with body composition and
   muscle strength have been reported in men and women. One
   study assessing older men showed variation in the vitamin D-
   receptor FokI polymorphism (Roth et al. 2004), with a
   different polymorphism linked with muscle strength in a
   further study of older women (Geusens et al. 1997). In a
   longitudinal study looking at sarcopenia in older men and
   women, low vitamin D was linked with increased risk (by
   approximately x2) of reduced muscle mass and strength. a
   similar relationship was found with raised parathyroid
   hormone levels (Visser et al. 2003). In functional terms,
   several trials have examined the relationship between vitamin
   D status and falls; these have been recently reviewed
   (Mosekilde 2005)."

Janssen HCJP, Samson MM, Verhaar HJJ.
Vitamin D deficiency, muscle function, and falls in elderly people.
Am J Clin Nutr 2002;75:611-5.
<http://www.ajcn.org/cgi/content/full/80/2/496>

   "In conclusion, vitamin D deficiency is a condition that may
   cause muscle weakness in elderly persons. Although only a few
   intervention studies with vitamin D have been conducted in
   elderly people, the available evidence indicates that vitamin
   D supplementation preserves muscle strength and functional
   ability in high-risk groups, eg, frail, mostly homebound
   elderly people. Additional research, preferably by means of
   controlled randomized trials, is needed to confirm these
   findings."

Visser M, Deeg DJ, Lips P.
Low vitamin D and high parathyroid hormone levels as determinants of
loss of muscle strength and muscle mass (sarcopenia): the Longitudinal
Aging Study Amsterdam.
J Clin Endocrinol Metab 2003;88:5766?72.
<http://jcem.endojournals.org/cgi/content/abstract/88/12/5766>

   "After adjustment for physical activity level, season of data
   collection, serum creatinine concentration, chronic disease,
   smoking, and body mass index, persons with low (<25
   nmol/liter) baseline 25-OHD levels were 2.57 (95% confidence
   interval 1.40-4.70, based on grip strength) and 2.14
   (0.73-6.33, based on muscle mass) times more likely to
   experience sarcopenia, compared with those with high (>50
   nmol/liter) levels. High PTH levels (>=4.0 pmol/liter) were
   associated with an increased risk of sarcopenia, compared
   with low PTH (<3.0 pmol/liter): odds ratio = 1.71 (1.07-2.73)
   based on grip strength, odds ratio = 2.35 (1.05-5.28) based
   on muscle mass. The associations were similar in men and
   women. The results of this prospective, population-based
   study show that lower 25-OHD and higher PTH levels increase
   the risk of sarcopenia in older men and women."

Bishoff HA, Stahelin HB, Urscheler N, et al.
Muscle strength in the elderly: its relation to vitamin D metabolites.
Arch Phys Med Rehabil 1999;80:54?8.
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&list_uids=9
915372&dopt=Abstract>

   "CONCLUSION: Muscle strength declined with age in ambulatory
   elderly people and showed modest, but significant, positive
   correlation with 1,25(OH)2 vitamin D in both sexes and with
   25(OH)D in male subjects. Therefore vitamin D deficiency
   appears to contribute to the age-related loss of muscle
   strength, which might be more pronounced in institutionalized
   elderly people with a high prevalence of vitamin D
   deficiency."

Bischoff-Ferrari HA, Dietrich T, Orav EJ, Hu FB, Zhang Y, Karlson EW,
Dawson-Hughes B.
Higher 25-hydroxyvitamin D concentrations are associated with better
lower-extremity function in both active and inactive persons aged > or
=60 y.
Am J Clin Nutr. 2004 Sep;80(3):752-8.
PMID: 15321818 [PubMed - indexed for MEDLINE]
<http://www.ajcn.org/cgi/content/full/80/3/752>

   "BACKGROUND: Vitamin D may improve muscle strength through a
   highly specific nuclear receptor in muscle tissue.
   
   [...]
   
   CONCLUSION: In both active and inactive ambulatory persons
   aged > or =60 y, 25(OH)D concentrations between 40 and 94
   nmol/L are associated with better musculoskeletal function in
   the lower extremities than are concentrations < 40 nmol/L."

Szulc P, Duboeuf F, Marchand F, Delmas PD.
Hormonal and lifestyle determinants of appendicular skeletal muscle
mass in men: the MINOS study.
Am J Clin Nutr. 2004 Aug;80(2):496-503.
PMID: 15277176 [PubMed - indexed for MEDLINE]
<http://www.ajcn.org/cgi/content/full/80/2/496>

   "CONCLUSION: In elderly men, low physical activity, tobacco
   smoking, thinness, low testosterone (AFTC and FTI), and
   decreased 25(OH)D concentrations are risk factors for
   sarcopenia."

Zamboni M, Zoico E, Tosoni P, et al.
Relation between vitamin D, physical performance, and disability in
elderly persons.
J Gerontol A Biol Sci Med Sci 2002;57:M7?11
<http://biomed.gerontologyjournals.org/cgi/content/abstract/57/1/M7>

   "Conclusions. In community-dwelling elderly women, 25(OH)D is
   related to muscular function and reported disability. Because
   of the high prevalence of hypovitaminosis D in the elderly
   population, this association seems to be clinically
   relevant."

J. R Sharkey, C. Giuliani, P. S Haines, L. G Branch, J.
Busby-Whitehead, and N. Zohoori
Summary measure of dietary musculoskeletal nutrient (calcium, vitamin
D, magnesium, and phosphorus) intakes is associated with
lower-extremity physical performance in homebound elderly men and
women
Am. J. Clinical Nutrition, April 1, 2003; 77(4): 847 - 856.
<http://www.ajcn.org/cgi/content/full/77/4/847>

See also the link

<http://heartscanblog.blogspot.com/search?q=vitamin+d>

provided by RArmant for the references aboty the relation between
vitamin D status and physical performance.