Monday, August 15, 2011
Nitrates – Nitrites: Health Promoting OR Dietary Disaster?
It is surprising to most people that nitrates and nitrites are a normal constituent of the human diet, with the average daily intake from all sources estimated at 75 milligrams. Nitrates and nitrites are found in many fruits and vegetables, drinking water as well as processed meats with the later contributing less than 5% of our daily intake.
Nitrates and nitrites differ only in how many oxygen atoms are attached to them. Nearly 100 percent of our intake of nitrate is converted to nitrite by beneficial bacteria in our saliva and gastrointestinal tract. Nitrites inhibit growth of harmful bacteria, which may help prevent overgrowth of less desirable bacteria in our GI tract. Additionally, nitrites are converted to nitric oxide and other metabolic products that have well-established beneficial actions on our vascular and immune system.
If it is surprising for people to learn that the vast majority of nitrates they consume come from eating healthy fruits and veggies it is even more surprising for them to learn that they appear to enhance mitochondrial function within cells, lower blood pressure, and potentially reduce risk of cardiovascular disease and diabetes (1). The nitric oxide produced by the conversion of nitrites has long been known to support heart and blood vessel function by relaxing vessel walls as well as decreasing blood pressure, preventing injury from heart attack and promoting wound healing.
For all the health benefits discussed so far there are a few detractors. One being the formation of cancer-causing nitrosamines, a class of chemical compounds easily formed when nitrites and amines in meat proteins (both contained in cured products) are heated to high temperatures. It was later discovered that ascorbic acid or sodium ascorbate (forms of vitamin C prevent formation of nitrosamines so now most cured meats contain this as well.
A recent study published online in the American Journal of Clinical Nutrition, August 10, 2011 (print version due Oct 2011) showed that 50 grams of cured meat daily, which is equivalent to 2 slices of bacon or one hot dog, increases risk of type 2 diabetes by 51%. They also found a 19% increase with daily intake of 3 ounces of red meat (a portion the size of a deck of cards) (2).
Risk of cancer and type 2 diabetes are a concern and many consumers are staying away from nitrates and nitrites in processed meats looking for products touting “no nitrates added” on the labels. Choosing “natural” and “certified organic” processed meat products which do not allow direct addition of nitrite or nitrate and are labeled as uncured is no guarantee you are not getting nitrates/nitrites. Since over 80 percent of the nitrates in our diets come from fruits and vegetables we have to dig a little deeper in the ingredient list to be safe. Many companies add nitrate-containing plant ingredients instead of sodium nitrite to produce a product that looks good, has an extended shelf life and can be marketed as “nitrate-free” or “no nitrate added”. This is no doubt a big surprise to consumers hoping to avoid nitrates/nitrites in their meats. These “natural” products may contain much higher levels of nitrites than the standard cured products according to some sources (3) but other reports indicate comparable or even slightly lower levels of nitrites (4).
So what is the bottom line on nitrates and nitrites? Since cured meats contribute only a fraction of the nitrates and nitrites we eat should we even worry about it? Clearly the health benefits of consuming more fruits and vegetables are not disputed so we are not going to stop consuming nitrates contained in them. In fact some of the healthiest vegetables such as kale, chard, spinach and beets contain the highest amounts of nitrates.
My advice: eat more fruits and vegetables, limit red meat to 18 ounces cooked weight per week (about 25 ounces raw weight) and rarely or occasionally consume processed meats instead substituting nuts, low fat dairy and whole grains.
1. Larsen, Schiffer, et. al. Dietary Inorganic Nitrate Improves Mitochondrial Efficiency in Humans. Cell Metabolism, 2011; 13 (2): 149-159
2. A. Pan, Q. Sun, et. al. Red meat consumption and risk of type 2 diabetes: 3 cohorts of US adults and an updated meta-analysis. Am J Clin Nutr Published online August 10, 2011
3. Nitrate-Free Bacon, Cook’s Illustrated, July 01, 2010.
4. “Issues and Alternatives Associated with Natural and Organic Processed Meats” Seminar, UW-Madison, May 4, 2010, Joe Sebranek, Professor, Animal Science Dept., Iowa State University
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