One of the reasons that red meat intake could be associated with higher levels or mortality (and cancer) could because of the heme iron content (via oxidative damage)? That's unfortunate for me.. I have hemochromatosis and my transferrin saturation is almost constantly elevated (85% or higher) even if my ferritin levels are within a healthful range. I've already had problems with a adrenal adenoma, although I cannot say for certain it is linked to iron intake.
A little background reading:
When measuring the body's potential to store iron, transferrin saturation is a common laboratory test. It is usually calculated as a percentage and is the ratio of serum iron and total iron-binding capacity, multiplied by 100. Of the transferrin that is available to bind iron, this value tells a clinician how much serum iron is actually bound. For instance, a value of 15 % means that 15 % of free iron is being carried by transferrin.
Some relevant research:
Moderate elevation of body iron level and increased risk of cancer occurrence and death
"Men and women were divided into 5 groups on the basis of baseline transferrin saturation: 0 to 30%, 30–40%, 40–50%, 50–60%, and 60% and higher. Nineteen percent of men had a baseline transferrin saturation above 40% (the last 3 groups), whereas only 10 percent of women had transferrin saturation above 40%. For men and women combined, risk of cancer occurrence in each group relative to the first was 1.0, 0.95, 1.16, 1.38 and 1.81; for mortality the relative risks were 1.0, 0.96, 1.22, 1.29 and 1.73. There is evidence, in this cohort, of elevated cancer risk in those with moderately elevated iron level. This pattern was seen in women as well as in men."
Transferrin Saturation and Risk of Cancer
"In women, a positive association was observed between transferrin saturation and risk of stomach carcinoma (≥34.5% compared with ≤20.3%: relative risk (RR) = 3.5, 95% confidence interval (Cl) 0.98–12). In men, transferrin saturation was inversely associated with risk of colon and rectal carcinoma (≥40.7% compared with ≤26.0%: colon, RR = 0.62, 95% Cl 0.35–1.1; rectum, RR = 0.30, 95% Cl 0.08–1.1) and with non-Hodgkin's lymphoma (32.1–40.6% compared with ≤26.0%: RR = 0.31, 95% Cl 0.11–0.88; no cases observed with transferrin saturation ≥40.7%)."
The Mortality Risk of Elevated Serum Transferrin Saturation and Consumption of Dietary Iron
"Ingestion of large quantities of dietary iron and red meat in persons with high transferrin saturation is associated with an increase in mortality. Simple dietary restrictions may reduce the mortality risk associated with high transferrin saturation."
Transferrin Saturation in vegetarians versus omnivores:
The impact of vegetarianism on some haematological parameters
"Vitamin B12 and iron status were compromised by a vegetarian diet. Variations in mean corpuscular volume were determined by iron and vitamin B12 status. Lower lymphocyte and platelet count were accompanied by metabolic evidence that indicated vitamin B12 deficiency." Specifically, this study found lower transferrin saturation (almost pathologically low) in vegetarians.
Iron status of predominantly lacto-ovo vegetarian East Indian immigrants to Canada: a model approach
"Iron deficiency was higher among females than males: 33% vs 5%, respectively, via the TI model (serum ferritin, serum-transferrin saturation, and mean corpuscular- hemoglobin concentration) and 18-42% vs 2-22%, respectively, via individual biochemical-iron indices."
The bottom line:
You may not have hemochromatosis, but significant meat intake will raise transferrin saturation and predispose you to higher rates of cancer. High levels of alcohol intake and high levels of vitamin C intake will increase iron absorption regardless of whether the source is animal or plant. Tannins and phytates will block iron availability. Taking supplemental inositol-hexaphosphate with iron rich meals may be beneficial to those chronically high transferrin saturation.
