Oxidation of blood lipids, particularly LDL, is increasingly being recognized as a very important risk factor in cardiovascular disease (41,42,43). So what is the role of meat in an oxidation resistant diet?
Generally speaking, meat fatty acids are much more stable less prone to oxidation than polyunsaturated fat and studies typically support this (9,12).
Two studies found that consuming monounsaturated fat produced LDL that was more resistant to oxidation in vitro than saturated fat (9,12). Since olive oil was used, the effect on LDL oxidation resistance may have been mediated by antioxidants in the olive oil. This is supported by studies in which virgin olive oil consumption was more beneficial to LDL oxidation resistance than refined olive oil (10) and high oleic sunflower oil (11). At this point it is unclear whether monounsaturated fat itself would produce more oxidation resistant LDL than saturated fat. Monounsaturated fat does, however, seem to result in more oxidation resistant LDL than eating carbohydrates (45,46,47,63).
Of the prior studies, one found that consuming saturated fat, on the other hand, produced lower TBARS levels compared to monounsaturated fat (12) and the other study noted no difference (9). Measuring TBARS (or thiobarbituric acid reactive substances) is a method of determining the amount of lipid peroxides, or damaged fats, in the blood and serves as a marker of oxidized LDL in the blood.
In 2000, Madeleine J. Ball et al. performed a study where subjects were fed diets with either lean red meat or tofu and various markers of health were examined after one month (44). By the end of the study, those consuming soy had LDL that was more resistance to LDL oxidation in vitro. Previous research suggests this was likely not due to a beneficial effect of soy’s fats (48) or isoflavones (49), so what was it? Other than the possibility that a copper 2+ induced in vitro LDL oxidation resistance test isn’t as predictive as a TBARS test (55,56), my suspicion is that iron was the important factor here.
You see, red meat is rich in iron and eating it often raises plasma ferritin levels, a marker of the amount of iron in the blood (50). On the beginning of the next page we see data on the ferritin levels of subjects in trial similar to the tofu v. red meat study, but instead of tofu it was carbohydrates (mostly grains):
The black bar represents the high carb group, the white bar the meat group. As you can see the ferritin levels jumped up in the meat group. So why is this important? Well, high blood iron is seen as a likely casual factor in LDL oxidation (51,52,53) and lowering ferritin levels increases LDL resistance to oxidation (54).
So should we avoid meat, or at least red meat, because it raises our iron levels? Not quite. First, not everyone will see elevated blood iron from eating red meat (I didn’t). Furthermore, we can control our iron levels pretty well. If you choose to eat a lot of red meat and should you risk raising it too high you can get your ferritin level measured and reduced via blood donation/phlebotomy, or you can eat your meat with compounds that reduce iron absorption. These compounds include:
• Phytic acid (57), found in seeds, nuts, and whole grains.
• Polyphenols (58), found in tea, coffee, wine, and chocolate.
Additionally, vitamin C taken with iron appears to increase its absorption (59,60,61), so one should avoid consider the hypothesis that concurrent consumption of red meat and vitamin C rich foods may increase blood iron levels.
I think too much iron is far and away the main negative thing that can be encountered from eating any significant quantity of red meat.