Dietary Nitrate and Health: Effects on Blood Pressure and the Brain

In the last blog, I discussed how dietary nitrate influences exercise performance in healthy people. If you haven’t read that post, I suggest you do so now, for it will help you understand what’s to come. In this blog I’ll focus on dietary nitrate and health, exploring other contexts in which it makes sense to increase dietary nitrate intake. I’ll also touch on nitrate concentrations in foods and whether you should be concerned about consuming a nitrate-rich diet.

I’ll pick up where I left off (dietary nitrate and exercise), concentrating now on effects of dietary nitrate on elderly people. Once again, if you want to dive deeper into this topic, you should check out this excellent review article.

Elderly people typically have lower levels of nitrate, nitrite, and NO at rest. This may help explain why the elderly have impaired function of the cells that line the interior of blood vessels, which predisposes to pathologies such as atherosclerosis (the clogging of arteries with plaques). The elderly also have diminished increases in activity in the nitrate/nitrite/NO pathway in response to exercise, which may contribute to their lower exercise capacity. Therefore, the elderly appear to be prime candidates for nitrate supplementation.

There hasn’t been much research on effects of dietary nitrate on exercise in elderly people. However, so far studies have shown few effects of nitrate supplementation. For example, nitrate supplementation didn’t affect how far elderly people could walk in 6 minutes or measures of physical function that are important to daily life (such as grip strength and the ability to repeatedly stand up from a chair).

Hmm, not so promising.

But what about elderly people with chronic diseases characterized by impaired blood flow and oxygen delivery to cells?

The results are again inconclusive. Some studies have looked at nitrate supplementation in people with chronic obstructive pulmonary disease (COPD, a collection of lung diseases that among other things impair oxygen delivery to cells). Whereas nitrate supplementation prolonged exercise time to exhaustion in one group of COPD patients, nitrate supplementation did not affect how far COPD patients could walk in 6 minutes in another study.

What about heart failure, a disease in which the heart can no longer pump enough blood to meet the needs of the patient’s body?

Once more, effects of nitrate supplementation on exercise in people with heart failure aren’t consistent. In one group of patients, a single dose of nitrate was enough to extend how long patients could cycle for. In another group of patients, a single dose of nitrate did not affect cycling endurance, but a week of nitrate supplementation increased time to exhaustion by 24%, suggesting that repeated supplementation may be necessary for some patients to benefit. This said, not all studies have found that repeated nitrate supplementation improves how well heart failure patients tolerate cycling.

Looking at the results of all of these studies, I think it’s important to recognize that nitrate supplementation didn’t negatively affect any outcomes and in some instances was beneficial. And collating all studies of elderly people to date shows that elderly people remain sensitive to the effects of nitrate supplementation, which routinely lowers systolic blood pressure, a critical determinant of risk of many diseases.

Let’s segue to the brain.

Nootropics are compounds that boost brain function and brain health, and I’ve written about some of my favourites (1, 2, 3). I believe nitrate-rich beetroot juice may be a true nootropic, bolstering brain health both acutely and chronically.

Previously, Dan interviewed Jonathan Burdette about work Jonathan did showing that after a 6-week exercise program, elderly people who supplemented with dietary nitrate had changes in patterns of communication in their brains such that their grey matter more closely resembled that of young people. This suggests that nitrate supplementation facilitates rewiring of the brain (neuroplasticity), which is so important to adapting to changes in one’s life.

These effects of nitrate may reflect improved blood flow to regions of the brain that are important to planning, carrying out, and monitoring activities, including one area (the dorsolateral prefrontal cortex) that is basically involved in doing the right thing when it’s the harder thing to do.

So, what about brain function?

Two weeks of nitrate supplementation seems to improve reaction time of elderly people with type 2 diabetes, which may also be true of healthy young people, both at rest and during prolonged, intermittent exercise. This said, other studies did not find any effects of nitrate supplementation on cognitive function during cycling or simulated trekking at high altitude.

In summary, there are probably some benefits of nitrate supplementation, and no adverse effects have been identified… right?

There’s been considerable hoopla about dietary nitrate and risk of cancer. Nitrates and nitrites are added to processed meats to preserve them, stabilize color, and enhance flavor. There is compelling evidence that even small intakes of these foods are associated with increased risk of chronic diseases such as colorectal cancer and even risk of death from any cause.

Some speculate that this relates to dietary nitrate and nitrite increasing formation of carcinogenic nitrogen oxides named N-nitroso compounds, and some studies of humans support this idea. Admittedly, this research is cross-sectional (meaning that you can’t really say that processed meat caused cancer), but the data are quite consistent. The evidence is strong enough that the International Agency for Research on Cancer lists processed meat as a carcinogen, and bodies such as the European Food Safety Agency are probably rightly wary of foods that have nitrites and nitrates added to them.

So, to be clear, I’m not suggesting you increase your nitrate intake by eating processed meats, even if some people still think that bacon is the solution to the world’s most pressing problems.

However, I have no reservations in sharing that I think you may benefit from increasing your nitrate intake by consuming more whole vegetables… after all, people with higher vegetable intakes are less likely to die from any cause.

So, you shouldn’t be wary of periodically exceeding the Acceptable Daily Intake for nitrate (3.7 mg / kg body mass per day) if the lion’s share of it comes from vegetables. A hefty serving of beetroot is bound to exceed the Acceptable Daily Intake for nitrate (I am face palming as I type this), but at least the European Food Safety Agency acknowledges that the benefits of consuming fruits and vegetables outweigh any purported risk of nitrate content.

Finally, know that vegetables vary dramatically in their concentrations of nitrate. So, two people adhering to the same dietary guidelines can have very different nitrate intakes. Even two identical-size portions of the same vegetable can have vastly divergent nitrate concentrations, depending on factors such as the genetics of the vegetable, the fertilizer used (organic vegetables are therefore typically lower in nitrates), soil conditions, handling of the food during transport, and food preparation (washing, peeling, and/or cooking). This is why beetroot products with known quantities of nitrate can be useful if you’re trying to consume a specific dose of nitrate.

Nevertheless, if you want a rough idea of the nitrate concentrations of raw vegetables, check out the table below, which I reproduced from this paper.

Increasing your intake of nitrate-rich vegetables such as beetroot may not only boost your exercise performance, it may help you ward off the perils of high blood pressure and even give your brain function a little boost. For specifics on nitrate dosing and timing, refer back to my previous article. If nothing else, if you’re not already in the habit of piling your plate with vegetables, I hope these blogs give you more impetus to do so!

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