Table 1.

A comparison in experimental design between recent human population studies related to copper, zinc and hypertension.

Year	Subject number	Inclusion criteria	Exclusion criteria	Detailed procedure to diagnosis hypertension	References
2009	Total 2233 (1106 males and 1127 female); hypertensives 731 (348 males and 383 females)	Age 15–65; urban and rural residents; 312 and 88 subjects on treatment with anti-hypertension and anti-diabetic medication, respectively; an overnight fast before biochemical measures	No past medical history of any major disease, no evidence of infectious disease	N/A	M. Ghayour-Mobarhan, et al.
2010	Hypertensives 78 (56 males, 22 females)	Age 27–59, never treated and newly diagnosed, 13% smoker	No hypercholesterolemia, diabetes mellitus, impaired renal function, coronary or cerebrovascular disease; exclude heavy drunker, chronic inflammatory disease, persistent atrial fibrillation or flutter, women with oral contraceptives or estrogen replacement therapy	When seated arterial blood pressure (after 10min of rest) measured by sphygmomanometer thrice at 1-week intervals was consistently >140/90 mm Hg. Secondary forms of hypertension were excluded by routine diagnostic procedures	de la Sierra A, et al.
2011	Normotensives 40 (18 males, 22 females); obese hypertensives 40 (13 males, 27 females)	Age 25–65; normal renal and liver function; an overnight fast before biochemical measures	No history of coronary artery disease, stroke, congestive heart failure or malignacy. Secondary obesity, diabetes, other chronic disease, current use of dietary supplements; clinically evident inflammatory process	Resting seated blood pressure was measured three times and an average value was calculated according to The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) guidelines	Suliburska, et al.
2009	Normotensives 114; hypertensives 90	Age normotensives 35–70, hypertensives 40–85. Part of subjects on treatment with anti-hypertension and anti-diabetic medication	The complete tooth without discoloration and deformity. No history of caries or any type of tooth filing	Blood pressure above 140/80 mmHg	Nagaraj, et al.
2007	Hypertensives 250 (all males); normotensives 250 (all males)	Mean age 49	Secondary hypertension	The blood pressures were measured regularly for 2 weeks before the samples of blood and urine were taken. The criteria for hypertension defined by the World Health Organization are systolic and diastolic blood pressures (SP and DP) greater than 140 and/or 90 mmHg, respectively. It was recorded in the seated position by the usual mercury sphygmomanometer	Taneja, et al.
2004	Hypertensives 109 (male 83, female 26), normotensive 115 (male 85, female 30); match age-gender-socio-economic status	Age 30–58, lacto-vegetarian, rural and urban communities. Around 70% of the subjects had a sedentary level of physical activity	Smokers and alcohol consumtion	diastolic blood pressure of 90 mmHg or higher or systolic blood pressure of 140 mmHg or higher	Chiplonkar, et al.