Background: The healthy immigrant effect is a phrase that has been used for decades to describe better cardiometabolic health in African immigrants than African Americans. The recent global increase in cardiometabolic diseases raises the possibility that immigrant health may be changing. Therefore, a new assessment of cardiometabolic health in African immigrants is warranted. Methods: Glucose tolerance status, blood pressure, and visceral adipose tissue (VAT) volume were compared in 214 self-identified healthy men comprised of 138 African immigrants, 76 African Americans, mean age 36 -9 years [mean -standard deviation (SD); range 20-64 years]. Insulin resistance was defined by the lowest quartile of the insulin sensitivity index (S I £ 2.28 mU/L

OBJECTIVEAbnormal glucose tolerance is rising in sub-Saharan Africa. Hemoglobin A1c by itself and in combination with fasting plasma glucose (FPG) is used to diagnose abnormal glucose tolerance. The diagnostic ability of A1C in Africans with heterozygous variant hemoglobin, such as sickle cell trait or hemoglobin C trait, has not been rigorously evaluated. In U.S.-based Africans, we determined by hemoglobin status the sensitivities of 1) FPG ≥5.6 mmol/L, 2) A1C ≥ 5.7% (39 mmol/mol), and 3) FPG combined with A1C (FPG ≥5.6 mmol/L and/or A1C ≥5.7% [39 mmol/mol]) for the detection of abnormal glucose tolerance.RESEARCH DESIGN AND METHODSAn oral glucose tolerance test (OGTT) was performed in 216 African immigrants (68% male, age 37 ± 10 years [mean ± SD], range 20–64 years). Abnormal glucose tolerance was defined as 2-h glucose ≥7.8 mmol/L.RESULTSVariant hemoglobin was identified in 21% (46 of 216). Abnormal glucose tolerance occurred in 33% (72 of 216). When determining abnormal glucose tolerance from the OGTT (2-h glucose ≥7.8 mmol/L), sensitivities of FPG for the total, normal, and variant hemoglobin groups were 32%, 32%, and 33%, respectively. Sensitivities for A1C were 53%, 54%, and 47%. For FPG and A1C combined, sensitivities were 64%, 63%, and 67%. Sensitivities for FPG and A1C and the combination did not vary by hemoglobin status (all P > 0.6). For the entire cohort, sensitivity was higher for A1C than FPG and for both tests combined than for either test alone (all P values ≤ 0.01).CONCLUSIONSNo significant difference in sensitivity of A1C by variant hemoglobin status was detected. For the diagnosis of abnormal glucose tolerance in Africans, the sensitivity of A1C combined with FPG is significantly superior to either test alone.

Vitamin D levels in people of African descent are often described as inadequate or deficient. Whether low vitamin D levels in people of African descent lead to compromised bone or cardiometabolic health is unknown. Clarity on this issue is essential because if clinically significant vitamin D deficiency is present, vitamin D supplementation is necessary. However, if vitamin D is metabolically sufficient, vitamin D supplementation could be wasteful of scarce resources and even harmful. In this review vitamin D physiology is described with a focus on issues specific to populations of African descent such as the influence of melanin on endogenous vitamin D production and lactose intolerance on the willingness of people to ingest vitamin D fortified foods. Then data on the relationship of vitamin D to bone and cardiometabolic health in people of African descent are evaluated.