Did you ever wonder if the food you eat has a direct effect on your health, well-being – and longevity? Well, I’m here to end that mystery. You ARE the foods you eat. Welcome to the Nutrition Facts podcast – I’m your host, Dr. Michael Greger.
Today, it’s all about the nitrates and nitrites. And if you’re wondering what the difference is, you’ve come to the right place. We start with a story about the effect of processed meat on lung function.
Recently, the World Health Organization classified processed meat, also known as cured meat—bacon, ham, hot dogs, lunch meat, and sausage—as definitively cancer-causing in humans. As if that’s not enough, high processed meat consumption has also been associated with increased risk of dying prematurely from all causes put together, and is a risk factor for several major chronic diseases, such as type 2 diabetes, coronary heart disease, and stroke. But what about lung issues like asthma?
Nitrites are added to processed meats as preservatives to preserve their pink (so they don’t turn gray), keeping them less rancid-tasting, and to prevent the growth of diseases like botulism. But put that same sodium nitrite in the drinking water of lab animals, and they develop emphysema. They nearly all developed emphysema. But that’s all the scientific knowledge we had on the subject coming into 2007, until this study, which found that frequent cured meat consumption is associated with increased risk for developing diseases like emphysema in people, too––chronic obstructive pulmonary disease (COPD). Eating it like every other day appeared to triple the odds of severe COPD. But it was just a snapshot-in-time study, so, we don’t know which came first––the sausage or the COPD. For that, we need prospective studies that follow people over time, and the big twin Harvard studies in both women and men both found that the risk of newly-diagnosed COPD increased with a greater consumption of cured meats.
Currently, we now have studies involving hundreds of thousands of people, showing that higher intakes of processed meat were associated with a 40 percent increased risk of COPD. It comes out to like an 8 percent higher risk of COPD for each hot dog you eat a week, or each weekly breakfast link sausage. What is going on?
Yes, there are advanced glycation end-products, so-called glycotoxins, that may be proinflammatory; there’s the saturated fat that can also trigger inﬂammation in the airways; the high salt content can present a potential risk for lung inflammation; or the increase in systemic inflammation in general. But the reason attention has focused on the nitrites is because nitrites may actually be one of the mechanisms by which tobacco smoke causes diseases like emphysema. Yes, cured meats are the principal source of dietary nitrites, but nitrites are also byproducts of tobacco smoke. One of the main constituents, besides the carbon monoxide and nicotine, are nitrogen oxides that are converted in the lung to nitrites.
The way nitrites appear to cause lung damage is by affecting connective tissue proteins like collagen and elastin. That’s what helps keep the airspaces in your lungs open, but nitrite can modify these proteins in a way that mimics age-related damage, including the fragmentation of elastin.
With that much lung injury, it’s logical to assume processed meat consumption could also exacerbate the disease of those who already have it. And indeed, cured meat consumption increases risk of COPD patients ending up back in the hospital, about twice the risk for those eating more than average, and it appears the more you eat, the worse it is.
Regarding lung health, processed meat intake has been associated with a likely increased risk of lung cancer, a decline in lung function, and chronic obstructive pulmonary diseases. But what about asthma? High processed meat consumption has been associated with higher asthma symptoms as well.
We knew about higher maternal intake of meat before pregnancy, potentially increasing the risk of wheezing in her children later on (based on a study of more than a thousand mother-child pairs). And we’re not talking about aspirating meat into your lungs and being misdiagnosed with asthma. Those who ate the most cured meats were 76 percent more likely to experience worsening asthma than those who ate the least. Since obesity is a likely risk factor for asthma, though, maybe the influence of the meat is just indirect, by contributing to weight gain? That might be a small part of it, but the main effect appears to be direct, suggesting a deleterious role of cured meat independent of weight. Put all the studies together, and processed meat intake appears to be an important target for the prevention of adult asthma in the first place.
Even if you don’t have any lung issues, processed meat consumption was negatively associated with measures of normal lung function, while fruit and vegetable consumption and dietary total antioxidant capacity was associated with better lung function.
But wait, you say. I just eat all natural, uncured hot dogs, with NO NITRATES OR NITRITES ADDED, in all caps. But if you magnifying glass the small print, it says “except those naturally occurring in… cultured celery juice.” See, to avoid saying they added nitrites, what they do is add something that has a lot of nitrates, like celery, and bacteria that convert the nitrates to nitrites. So, they are adding nitrites. They’re just straight-up duping consumers. We didn’t add any nitrites except, of course…for all the nitrites we added. We care about your health; so, no nitrites added. Who wants pepperoni with nitrites? So, we just added lots of nitrites. We would never add any nitrites. Now, just let the piggy picture distract you from the fact that we just lied to your face. Hormel was my favorite. “Except for those naturally occurring in seasoning”—pretty slick.
Europe doesn’t allow this kind of consumer fraud, demanding manufacturers explicitly label it as containing nitrites. You can’t even call it natural.
When Consumer Reports put it to the test, they found the nitrite levels in all the products were essentially the same; so “no nitrites” doesn’t mean no nitrites. Consumer Reports and the Center for Science in the Public Interest have petitioned to stop this misleading practice. Nitrites are nitrites. “Their chemical composition is absolutely the same, and so are the health eﬀects.”
In our next story we look at how nitrites in processed meat form nitrosamines, a class of potent carcinogens.
Our story begins on a Norwegian fur farm in 1957. Mink were dropping dead left and right from a malignant new liver disease. The clue came when livestock starting dying from liver cancer as well. What tied all the cases together was the use of fish meal in their diets—fish meal that the country had just started preserving with sodium nitrite.
Subsequent research discovered nitrite, under certain circumstances, can form nitrosamines, which directly attack DNA, and are universally condemned as one of the key carcinogens in cigarette smoke. The occurrence in food was raised as a matter of gravest concern nearly a half century ago. Now, we know the nitrites added to processed meats can form these carcinogenic nitrosamines—now recognized as among the most potent chemical carcinogens.
For example, pregnant women who eat hot dogs risk having children with brain tumors—the #2 pediatric cancers. Then, children, who eat lots of hot dogs, have nearly ten times the odds of developing childhood leukemia—the #1 pediatric cancer.
Last year, in Meat Science, an article about the role of ham in a healthy diet breathed a sigh of relief: “[A]spects relating to health and wellbeing are increasingly important factors in consumer decisions, although the great palatability of ham largely outweighs such considerations.”
Finally today – we look at oxygenating blood with nitrate rich vegetables.
It’s great that we can improve athletic performance eating a few beets, but so what if you run 5% faster? It can be a fun experiment to eat a can of beets and maybe shave a minute off your 5K time, but these are the people who could really benefit from a more efficient use of oxygen: those suffering from emphysema. Yeah, young healthy adults eating greens and beets can swim, run, and cycle faster and farther, but what about those who get out of breath just walking up the stairs? Do nitrate-rich vegetables work where it counts? Yes, significantly extended time on the treadmill after two shots of beet juice.
It’s great that beet juice can decrease blood pressure in young healthy adults, but what about in those who really need it: older, overweight subjects? Just one shot of beet juice a day versus berry juice as a control, and in a few weeks, a significant drop in blood pressure; but within just a few days after stopping—after three weeks of beet-ing themselves up—blood pressure went back up. So, we have to eat our vegetables, and keep eating our vegetables.
Why did it take until 2015 to publish a study on lowering blood pressure in people with high blood pressure? You’d think that’d be the first group to try it on. Who’s going to fund it, though—Big Beet? Blood pressure medications rake in more than $10 billion a year. You can’t make billions on beets. But that’s why we have charities like the British Heart Foundation, which funded a study to give folks with high blood pressure a cup of beet juice a day for four weeks. After all, high blood pressure may be the #1 risk factor for premature death in the world. In ten years, it could affect nearly one in three adults on this planet. But put them on beet juice, and blood pressures drop and kept dropping, until it was stopped after a month. With so many people with high blood pressure even despite treatment, an additional strategy, based on the intake of nitrate-rich vegetables, may prove to be both cost-effective, affordable, and favorable for a public health approach to hypertension.
What about those with peripheral artery disease? Tens of millions with atherosclerotic clogs impairing blood flow to their legs, which can cause a cramping pain in the calves, called claudication, due to lack of blood flow through the blocked arteries, severely limiting one’s ability to even just walk around. But just drink some beet juice and walk 18% longer with just vegetables.
The nitric oxide from vegetable nitrates not only improves oxygen efficiency, but also oxygen delivery by vasodilating blood vessels, opening up arteries so there’s more blood flow. I’m surprised beet juice companies aren’t trying to position themselves as veggie Viagra; it could certainly explain why those eating more veggies have such improved sexual function, though this study was just a snapshot in time. So, you can’t tell which came first. However, it seems more reasonable that low fruit and vegetable consumption contributes to erectile dysfunction, rather than the other way around.
What about the most important organ, the brain? Poor cerebral perfusion—lack of blood flow and oxygen in the brain—is associated with cognitive decline and dementia, and they showed that the nitrate in vegetables may be beneficial in treating age-related cognitive decline. They showed a direct effect of dietary nitrate on cerebral blood flow within the frontal lobes, the areas particularly compromised by aging. This is a critical brain area for so-called executive function: basic tasks, and problem-solving important for day-to-day functioning. The nitrite from nitrate has been shown not only to increase blood flow to certain areas of the body, but also acts preferentially in low oxygen conditions, allowing it to increase blood flow precisely in the areas where it is needed most. And, that’s what they found in the brain: increased blood flow to the at-risk areas of the aging brain. And, the only side effects of beet-ing your brains out? A little extra color in your life.
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