Epidemiology of Vitamin D (EpiVida)—A Study of Vitamin D Status Among Healthy Adults in Brazil

Victoria Zeghbi Cochenski Borba; Marise Lazaretti-Castro; Sandra da Silva Moreira; Maria Conceição Chagas de Almeida; Edson Duarte MoreiraJr

Disclosures

J Endo Soc. 2023;7(1)

Abstract and Introduction

Abstract

Context: There are few studies of 25-hydroxyvitamin D (25(OH)D) concentrations in healthy adults in Brazil.

Objective: This work aimed to estimate the prevalence of vitamin D status and its association with lifestyle, sociodemographic, and anthropometric data in 3 regions of Brazil.

Methods: A cross-sectional study was conducted among blood donors of both sexes, living in the cities of Salvador, São Paulo, and Curitiba during summer. Blood samples were collected during the procedure. Serum 25(OH)D and parathyroid hormone (PTH) were measured in the same laboratory using chemiluminescence immunoassays. Lifestyle, sociodemographic, and anthropometric data were gathered by an interview with a standardized questionnaire. Vitamin D deficiency and insufficiency was defined as 25(OH)D levels below 20 ng/mL and below 30 ng/mL, respectively.

Results: A total of 1004 healthy adults were evaluated with mean levels of 25(OH)D (28.7 ± 9.27 ng/mL) and PTH (34.4 ± 15.1 pg/mL). The standardized prevalence of vitamin D deficiency and insufficiency was in the study population 15.3% and 50.9%: in Salvador 12.1% and 47.6%, in São Paulo 20.5%, and 52.4% and in Curitiba 12.7% and 52.1%, (P = .0004). PTH levels were negatively correlated with 25(OH)D levels. Greater body mass index (BMI) and higher latitude were significant predictors of vitamin D deficiency, whereas skin color (White), longer duration of sun exposure, and current use of dietary supplement were protective.

Conclusion: This study confirmed the high prevalence of vitamin D deficiency and insufficiency even in the midsummer in a healthy population of Brazil. Vitamin D levels are associated with sun exposure, latitude, BMI, skin color, and use of supplements.

Introduction

Vitamin D is in fact a "prohormone" given it can be synthesized in the skin from ultraviolet B light on cutaneous sun exposure, and then converted to its active metabolite 1,25-dyhydroxyvitamin D (calcitriol) in the kidney stimulated by parathyroid hormone (PTH). Diet provides low quantities of this "vitamin," and sunlight exposure is its main source. The most abundant circulant form is 25-hydroxyvitamin D (25(OH)D), which is considered the biomarker to evaluate vitamin D status and is classically related to mineral homeostasis and PTH secretion. Low level of 25(OH)D is the most common etiology of secondary hyperparathyroidism.^[1]

Vitamin D status depends on the population studied, health status, skin color, age, genetic background, geographic characteristics, among other factors, which makes it a considerable challenge to establish their normal levels. Low concentrations of 25(OH)D have been associated with many detrimental health conditions, both skeletal and extraskeletal. Different end points were used to stablish the 25(OH)D ideal levels, including secondary hyperparathyroidism, osteomalacia or osteoporosis, muscle weakness, increased risk of falls or fractures among others, with no definitive consensus so far.^[2]

The Institute of Medicine defines vitamin D deficiency as 25(OH)D levels lower than 20 ng/mL (< 50 nmol/L) regardless of the population studied.^[3] Other institutions take into account age, risk factors for vitamin D deficiency, and health status, such as presence of metabolic bone diseases and other chronic diseases to define 30 ng/mL as the preferred level.^[2,4,5]

Vitamin D deficiency is highly prevalent worldwide, with levels below 30 ng/mL (75 nmol/L) being described globally. The lowest levels (< 10 ng/mL or 25 nmol/L) are associated with rickets and osteomalacia and, although more frequent in Asia and the Middle East, can be present all over the world.^[6] In Brazil, inadequate vitamin D status has been described in all regions. A metanalysis of 72 studies developed throughout the country found an average of 28.16% deficiency (25(OH)D < 20 ng/mL) and 45.26% insufficiency (< 30 ng/mL). The southern and southeastern regions had the highest concentration of vitamin D deficiency, while the insufficiency was concentrated in the southeastern and northeastern regions. This metanalysis included studies that used different vitamin D assays, and the majority of the sample size was from the southernmost regions of the country.^[7] Other studies of the Brazilian population also showed a high frequency of vitamin D deficiency and insufficiency in patients with chronic diseases such as osteoporosis, systemic lupus erythematosus, chronic obstructive pulmonary disease, and others.^[8–10] Nevertheless, data regarding vitamin D status in a health population of both sexes, with different ages, samples collected at the same time range, measured with the same method, and with sociodemographic information, are lacking for the Brazilian population.

The aim of this study was to evaluate 25(OH)D and parathyroid hormone (PTH) levels in healthy adults from urban areas of Brazil, according to age group, sex, and latitude of residence.

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Next Section

Abstract and Introduction
Materials and Methods
Results
Discussion
References

Table 1. Descriptive characteristics of study population
Variables	Salvador			São Paulo			Curitiba			Total			P
Variables	Men (168)	Women (168)	Total (336)	Men (167)	Women (167)	Total (334)	Men (167)	Women (167)	Total (334)	Men (502)	Women (502)	Total (1004)	P
Age, median	37	36	36	38	35	38	38	36	37	38	36	37	.944
(interquartile range), y	(26–49)	(28–47)	(28–48)	(27–48)	(26–49)	(27–48)	(27–48)	(26–47)	(27–48)	(27–48)	(27–48)	(27–48)
Race or ethnic group													< 10 ⁻⁵
White	20.8	20.2	20.5	42.5	44.9	43.7	74.3	74.3	74.3	45.8	46.4	46.1
Mixed	50.6	46.4	48.5	41.3	38.9	40.1	18.0	15.6	16.8	36.7	33.7	35.2
Black	26.2	31.5	28.9	13.2	13.2	13.2	4.8	6.6	5.7	14.7	17.1	15.9
Other	2.4	1.8	2.1	3.0	3.0	3.0	3.0	3.6	3.3	2.8	2.8	2.8
Fitzpatrick skin type ^a													< 10 ⁻⁴
Type I, 0–6	6.5	7.9	7.2	8.4	10.2	9.3	9.6	10.2	9.9	8.2	9.4	8.8
Type II, 7–12	10.1	17.6	13.8	24.0	22.8	23.4	31.7	29.9	30.8	21.9	23.4	22.7
Type III, 13–18	34.5	28.5	31.5	32.9	40.7	36.8	35.9	37.7	36.8	34.5	35.7	35.1
Type IV, 19–24	39.3	32.1	35.7	26.3	19.2	22.8	18.6	18.0	18.3	28.1	23.0	25.6
Type V, 25–30	7.7	12.1	9.9	7.2	5.4	6.3	3.6	4.2	3.9	6.2	7.2	6.7
Type VI, 31+	1.8	1.8	1.8	1.2	1.8	1.5	0.6	0.0	0.3	1.2	1.2	1.2
BMI													.353
Underweight, 17.0–18.4	0.0	1.8	0.9	0.6	0.6	0.6	1.2	1.2	1.2	0.6	1.2	0.9
Normal, 18.5–24.9	35.1	34.5	34.8	28.7	34.1	31.4	31.7	43.1	37.4	31.9	37.3	34.6
Overweight, 25.0–29.9	38.7	42.3	40.5	46.1	41.3	43.7	40.7	27.5	34.1	41.8	37.1	39.4
Obesity I, 30.0–34.9	23.2	12.5	17.9	15.6	15.6	15.6	21.6	17.4	19.5	20.1	15.1	17.6
Obesity II, 35.0–39.9	1.8	5.4	3.6	6.0	6.6	6.3	4.8	7.2	6.0	4.2	6.4	5.3
Obesity III, ≥ 40.0	1.2	3.6	2.4	3.0	1.8	2.4	0.0	3.6	1.8	1.4	3.0	2.2
Blood donation, ≥ 2×/y	12.5	14.3	13.4	50.3	44.9	47.6	68.3	67.7	68.0	43.6	42.2	42.9	10 ⁻⁵
Cigarette smoking													< 10 ⁻⁴
Never smoker	83.3	93.5	88.4	67.7	72.5	70.1	88.6	91.6	90.1	79.8	85.9	82.9
Former smoker	10.7	4.2	7.4	25.7	19.8	22.8	7.2	6.0	6.6	14.6	10.0	12.3
Current smoker	6.0	2.4	4.2	6.6	7.8	7.2	4.2	2.4	3.3	5.6	4.2	4.9

Abbreviation: BMI, body mass index.
^aType I (0–6): pale white skin; always burns, never tans; type II (7–12): white skin; almost always burn, rarely tans; type III (13–18): light brown skin; burns moderately, tans uniformly; type IV (19–24): moderate brown skin; burns minimally, tans easily; type V (25–30): dark brown skin; rarely burns, tans easily; type VI (31+): dark brown to black skin; never burns. Bold = statistically significant.

Table 2. Unadjusted mean serum 25-hydroxyvitamin D level and prevalence of vitamin D deficiency (< 20 ng/mL) by selected characteristics
	25(OH)D, ng/mL			Vitamin D deficiency, < 20 ng/mL
	No.	Mean ± SD	P	N (%)	95% CI	P
Sex			.002			.004
Male	502	29.6 ± 10.3		65 (12.9)	6.8–23.2
Female	502	27.8 ± 8.1		87 (17.3)	10.8–26.6
Age, y			.354			.685
18–29	336	29.4 ± 9.1		43 (12.8)	5.8–25.9
30–39	236	28.1 ± 8.6		42 (17.8)	9.1–31.9
40–49	217	28.2 ± 9.1		31 (14.3)	6.0–30.5
50–59	166	28.4 ± 8.3		29 (17.5)	7.8–34.8
60–69	49	29.8 ± 15.3		7 (14.3)	2.6–51.3
City			< 10 ⁻⁴			< 10 ⁻³
Salvador	336	30.2 ± 10.4		39 (11.6)	4.8–25.2
São Paulo	334	27.1 ± 8.3		69 (20.7)	12.8–31.7
Curitiba	334	28.8 ± 8.8		44 (13.2)	6.1–26.2
Race			.317			.329
White	463	29.3 ± 8.9		58 (12.5)	6.3–23.4
Mixed	353	28.1 ± 9.2		64 (18.1)	10.6–29.2
Black	160	28.4 ± 10.6		27 (16.9)	7.2–34.9
Other	28	27.8 ± 7.2		3 (10.7)	0.8–64.8
BMI						< 10 ⁻⁹
Normal or underweight	356	30.9 ± 10.1	< 10 ⁻¹⁰	38 (10.7)	4.3–24.3
Overweight	396	28.5 ± 9.0		56 (14.1)	7.3–25.5
Obesity class I	177	26.5 ± 7.8		33 (18.6)	8.9–34.9
Obesity class II/III	75	24.2 ± 6.3		25 (33.3)	18.2–52.9
Smoking			0.111			0.377
Never smoker	831	28.8 ± 8.9		123 (14.8)	9.6–22.1
Former smoker	123	27.3 ± 8.5		22 (17.9)	7.1–38.2
Current smoker	49	30.4 ± 15.6		7 (14.3)	2.6–51.3
Fitzpatrick score ^a			.785			.925
Type I, 0–6	88	29.6 ± 9.4		10 (11.4)	2.2–42.0
Type II, 7–12	227	28.8 ± 9.3		34 (15.0)	6.6–30.5
Type III, 13–18	351	28.4 ± 8.4		52 (14.8)	7.6–26.8
Type IV, 19–24	256	28.4 ± 8.9		43 (16.8)	8.5–30.6
Type V, 25–30	67	29.6 ± 13.7		11 (16.4)	4.4–45.8
Type VI, 31+	12	27.2 ± 7.4		2 (16.7)	1.3–75.9
Multivitamins			< 10 ⁻⁹			< 10 ⁻⁵
No/past	791	27.8 ± 8.1		131 (16.6)	11.2–23.9
Current	209	32.1 ± 12.1		21 (10.0)	2.9–29.5
Use of supplements			< 10 ⁻⁵			< 10 ⁻⁵
No/past	909	28.0 ± 8.7		147 (16.2)	11.1–23.0
Current	92	31.8 ± 11.2		5 (5.4)	0.3–49.2

Abbreviations: 25(OH)D, 25-hydroxyvitamin D; BMI, body mass index.
^aType I (0–6): pale white skin; always burns, never tans; type II (7–12): white skin; almost always burn, rarely tans; type III (13–18): light brown skin; burns moderately, tans uniformly; type IV (19–24): moderate brown skin; burns minimally, tans easily; type V (25–30): dark brown skin; rarely burns, tans easily; type VI (31+): dark brown to black skin; never burns. Bold = statistically significant.

Table 3. Association between variables and serum 25-hydroxyvitamin D concentration (ng/mL) analyzed by stepwise multiple linear regression analyses ^a
Variables	Men		Women		Total
Variables	β (95% CI)	P	β (95% CI)	P	Regression coefficient β (95% CI)	P
Female sex	−	−	−	−	−
Age, y	0.027 (−0.042 to 0.096)	.444	−0.023 (−0.080 to 0.034)	.431	−0.969 (−2.130 to 0.191)	.102
Race or ethnic group, White vs other	0.982 (−0.908 to 2.872)	.308	2.791 (1.310 to 4.273)	.011	−0.002 (−0.047 to 0.043)	.933
Body mass index	−0.496 (−0.686 to −0.306)	< 10 ⁻⁶	−0.260 (−0.393 to −0.128)	< 10 ⁻³	1.856 (0.651 to 3.062)	< 10 ⁻³
Latitude	−0.221 (−0.380 to −0.063)	.006	−0.140 (−0.284 to 0.004)	.056	−0.357 (−0.472 to −0.243)	< 10 ⁻⁸
Average time under sun on weekday, min	0.008 (−0.003 to 0.019)	.151	0.021 (0.008 to 0.034)	.002	−0.096 (−0.284 to −0.044)	.007
Part of body exposed to sun					0.012 (0.003 to 0.020)	.006
Whole body (with bathing suit) vs less	2.390 (−1.190 to 4.969)	.069	2.426 (0.203 to 4.649)	.033	2.243 (0.524 to 3.962)	.011
Leisure time physical activity
Regular sports and exercise/athletic training vs less	3.950 (2.191 to 5.710)	< 10 ⁻⁴	0.586 (−0.801 to 1.974)	.407	2.292 (1.163 to 3.422)	< 10 ⁻⁴
Regular use of dietary supplements
(current vs no/past)	0.672 (−1.554 to 2.899)	.553	4.761 (2.698 to 6.824)	< 10 ⁻⁵	2.393 (0.861 to 3.925)	.002

β, regression coefficient β.
^aPredictors included in the model were sex, age, race/ethnicity, BMI, latitude, time of sun exposure, part of body exposed to the sun, leisure time physical activity, and regular use of dietary supplements. No significant effects of education levels, income, work location, skin phototype, leisure outdoor, physical activity at work, or house type were found in the adjusted models. Bold = statistically significant.

Table 4. Odds ratios for vitamin D deficiency (serum levels < 20 ng/mL) according to levels of predictor variables in men and women
	Men			Women			Total
	Adjusted^a OR	(95% CI)	P	Adjusted^a OR	(95% CI)	P	Adjusted^a OR	(95% CI)	P
Female vs male	–			–			1.09	(0.74–1.62)	.664
Age, y	1.01	(0.99–1.03)	.212	1.01	(1.00–1.03)	.174	1.01	(0.99–1.03)	.209
Race or ethnic group, White vs other	0.56	(0.38–0.84)	.006	0.56	(0.37–0.83)	.005	0.56	(0.38–0.85)	.006
Body mass index
Normal or underweight, < 25.0	1 (ref)			1 (ref)			1 (ref)
Above normal, 25.0–29.9	1.40	(0.88–2.24)	.155	1.41	(0.88–2.26)	.150	1.41	(0.88–2.26)	.150
Obesity I, 30.0–34.9	1.76	(1.02–3.04)	.042	1.76	(1.02–3.03)	.043	1.78	(1.03–3.08)	.039
Obesity II and III, ≥ 35.0	2.92	(1.54–5.55)	.001	2.97	(1.56–5.65)	.001	2.91	(1.53–5.53)	.001
Latitude	1.06	(1.01–1.10)	.014	1.06	(1.01–1.10)	.009	1.06	(1.01–1.10)	.015
Time spent under sun on weekday, min
≤ 5	1 (ref)				1 (ref)				1 (ref)
5–15	0.56	(0.31–0.99)	.046	0.56	(0.32–1.00)	.049	0.55	(0.31–0.99)	.045
16–30	0.46	(0.25–0.86)	.014	0.48	(0.26–0.89)	.020	0.47	(0.25–0.87)	.017
> 30	0.29	(0.16–0.52)	.000	0.30	(0.17–0.54)	.000	0.30	(0.17–0.54)	.000
Part of body usually exposed to sun
Whole body (with bathing suit) vs less	0.60	(0.30–1.22)	.158	0.60	(0.30–1.21)	.154	0.48	(0.22–1.03)	.060
Engage in outdoor activities on leisure time
Rarely or a few times	1 (ref)			1 (ref)			1 (ref)
Very often or always vs	0.72	(0.49–1.06)	.100	0.76	(0.51–1.12)	.169	0.72	(0.49–1.07)	.103
Leisure time physical activity
Mainly sedentary/light to moderate activity	1 (ref)			1 (ref)			1 (ref)
Regular sport and exercise/athletic training	0.73	(0.50–1.07)	.105	0.73	(0.49–1.07)	.102	0.74	(0.50–1.08)	.118
Type of housing
Apartment or house without backyard	1 (ref)			1 (ref)			1 (ref)
House with backyard	0.72	(0.42–1.23)	.230	0.72	(0.42–1.23)	.230	0.72	(0.42–1.23)	.208
Regular use of supplements
No/past	1 (ref)			1 (ref)			1 (ref)
Current	0.42	(0.22–0.83)	.012	0.43	(0.22–0.84)	.013	0.43	(0.22–0.84)	.013

Abbreviations: OR, odds ratio; ref, reference.
^aAdjusted logistic regression model for all other predictor variables. Adjusted models included 979 (total), 491 (male), and 488 (female) participants with complete information on all considered variables. Bold = statistically significant.

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Epidemiology of Vitamin D (EpiVida)—A Study of Vitamin D Status Among Healthy Adults in Brazil

Abstract and Introduction

Abstract

Introduction

Tables

Tables

Tables

Tables

References

Authors and Disclosures

Authors and Disclosures

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