The Mortality Risk of Elevated Serum Transferrin Saturation and Consumption of Dietary Iron

Arch G. Mainous; Brian Wells; Peter J. Carek; James M. Gill; Mark E. Geesey

doi:10.1370/afm.82

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Figure 1.
Kaplan-Meier survival curves for normal vs elevated transferrin saturation (TS) and low vs high iron intake.
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Figure 2.
Kaplan-Meier survival curves for normal vs elevated transferrin saturation (TS) and low vs high red meat consumption.

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Table 1.

Population Characteristics of Adults Aged 30 Years and Older from the Combined NHANES II and NHANES II Mortality Study with Normal (≤55%) and Elevated (>55%) Transferrin Saturation (TS)

Characteristics	Percent With Normal TS (n = 95,284,772)	Percent With Elevated TS (n = 1,073,696)	PValue
Age group
30–50 y	54.3	69.1	.02
51–64 y	30.6	19.7
>64 y	15.1	11.2
Race
White	88.0	86.6	.88
Black	9.6	9.5
Other	2.4	3.9
Sex
Male	47.5	48.4	.87
Female	52.5	51.6
Poverty income ratio
<1.0	14.0	10.2	.27
≥1.0	86.0	89.8
Education level
Not hs graduate	35.8	26.4	.15
Hs graduate	33.8	35.5
Some college	30.4	38.1
Body mass index
<30 kg/m2	85.3	94.6	<.01
≥30 kg/m2	14.7	5.4
Current smoker
No	60.1	40.6	<.01
Yes	39.9	59.4
Health status
Excellent	23.3	22.4	.70
Very good	24.7	28.6
Good	30.3	26.1
Fair	15.1	18.6
Poor	6.6	4.3
Charlson comorbidity index
0	16.1	22.7	.54
1	16.1	18.2
2	17.2	13.5
>2	50.6	45.6

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Table 2.

Adjusted Survival Analysis of All-Cause Mortality by Serum Transferrin Saturation (TS) and Levels of Iron Intake and Red Meat Consumption or Iron Supplements

TS Saturation Status	Hazards Ratio	95% CI
Note: all-cause mortality controlled by age, race, sex, poverty, education, body mass index, smoking, health status, and comorbidities at baseline.
Saturation by iron intake
Normal saturation, ≤ 18 mg/d	1.00
Normal saturation, > 18 mg/d	1.03	0.87–1.23
Elevated saturation, ≤ 18 mg/d	0.94	0.59–1.48
Elevated saturation, > 18 mg/d	2.90	1.39–6.04
Saturation by red meat consumption or iron supplements
Normal saturation, < 7 times /wk	1.00
Normal saturation, ≥ 7 times /wk	1.02	0.91–1.15
Elevated saturation, < 7 times /wk	0.62	0.32–1.22
Elevated saturation, ≥ 7times /wk	2.26	1.45–3.52

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The Article in Brief

Serum transferrin saturation can indicate an overload of iron. Among people with elevated levels of serum transferrin saturation, eating large amounts of red meat and other iron-containing foods was associated with increased death rates. Specifically, people with elevated transferrin saturation who reported high dietary iron intake had a 2.9 times greater risk of death than those who had normal transferrin saturation levels and reported low dietary iron intake. People who had a high transferrin saturation and reported eating red meat seven or more times per week had a risk of death 2.26 times greater than those who had normal transferrin saturation and reported eating low amounts of red meat. Simple dietary restrictions may help to reduce the risk of death associated with high transferrin saturation.