Andrew Coggan wrote:
ericmulk wrote:
Not a health researcher but as an environmental engineer with some experience with nitrate (NO3) compounds, if the NHLBI does decide to do this study, they might want to look at the levels of NO3 in the drinking water (DW) of the participants. The study designers can get this data from the local drinking water supplier, and also, since so many people drink bottled water now, they might want to look at NO3 levels in the various popular bottled waters. I say this b/c the EPA DW regulations allow up to 10 mg/L of NO3 in DW. Assuming a 2 L/day water intake and NO3 = 10 mg/L, that's 20 mg/day of NO3 which could be a significant contributor to total dietary intake of NO3.
Indeed, both the EPA and the WHO set limits for nitrate in drinking water, due to (unfounded?) historical concerns about possible carcinogenicity. Despite this, people routinely exceed the maximum recommended daily nitrate intake, due to its presence in vegetables. Here in the US, for example, average daily nitrate intake is estimated to be 0.6-1.5 mmol/d, or 39-98 mg/d.
It is also probably worth noting that, at least acutely, the effects of dietary nitrate on exercise performance seem to require ingesting amounts that would be difficult to achieve via a normal diet. For example, we started with a dose of 4.6 mmol, or 300 mg, but moved up to a dose of almost 11 mmol, or 700 mg, when we couldn't replicate some of Jones' findings in our initial studies (still can't replicate some of them at this higher dose, BTW). The reason that such a high dose is apparently required may be because, at least based on animal data, there is a significant gradient of nitrate from muscle to blood, such that you have to raise plasma nitrate concentrations quite high to actually drive it into muscle. (The dose we're using increases plasma nitrate concentrations approximately 20-fold, but the redox state is such that plasma nitrite only increases by ~30% on average. OTOH, breath NO - an accepted biomarker of whole-body NO production - typically increases by 50-60%.)
Interesting, I haven't had a conversation about redox states a a few years, but we used to talk about it all the time in grad school:) I have several thoughts I'll throw out for you consideration. Regarding NO3 regulation by EPA/WHO, my understanding has always been that NO3 is fairly well established to be the cause of, or perhaps a contributing factor in, methylglobinemia, e.g. "blue baby syndrome". Apparently, NO3 at levels of over 10 mg/L does not have any adverse effect on kids over X yrs old or on adults, which would appear to be consistent with your finding that NO3 is actually beneficial to heart health. In fact, i have read of some cities petitioning EPA for a variance from the 10 mg/L standard, providing that all persons with children under age X will be extensively counseled on the need to not let their kid drink the tap water; not sure if any of these petitions were approved or not though. This leads to my next thought which about the alleged "unhealthiness" of meats such as hot dogs and bologna, which i understand have relatively high levels of NO3 and/or NO2, although i've never looked at what these levels are, and NO3/NO2 does not typically show up on the standard nutrition labels. Doing a very quick google search, i see an alleged limit of 200 ppm for NaNO2 in processed meats; using meat at this limit, consuming 100 g of meat = 100 g x 200 mg/kg x 1kg/1000 g = 20 mg NaNO2. Getting out the old periodic table, Na = 23.0, N = 14.0, and O = 16.0, so NaNO2 = 23 + 14 + 32 = 69 and N = 14, therefore (14/69)(20) = 4.06 mg
as N. This reminds me of a somewhat crucial distinction in reporting, i.e., in the water chemistry/engineering world, we always report mg/L NO3
as N, mg/L NO2
as N, etc. Do your labs use this same protocol??? Obv it can make a significant diff in reporting and TBH, I have occasionally forgotten in my initial set of calculations to make that final conversion from NO3 to NO3 as N, but managed to find my error when checking my work and hence never submitted any incorrect reports to the best of my knowledge. The EPA/WHO DW standard for NO3 is 10 mg/L
as N.
Another interesting part of the NO3 issue is that, since circa 1995/96, EPA has also regulated NO3 compounds as a hazardous/toxic substance under the Toxic Release Inventory (TRI) reporting system. Any entity releasing 50,000 lbs or more of NO3 compounds, expressed as NO3, must submit an annual TRI report to EPA. Your average biological wastewater treatment plant (WWTP) actually produces NO3 during the treatment process and hence most WWTPs have to submit the TRI report by 1 July of each year. As an environmental engineering consultant, I've done many NO3 calculations in my time and became the local "expert" on NO3 reporting, dubbed "Dr. Nitrates" by my comrades:)
"Anyone can be who they want to be IF they have the HUNGER and the DRIVE."