OK, are you up for some
biochemistry? Simple biochemistry, I mean. It will help explain why vegetables
are good for your blood pressure and why beetroot juice has become the new
sports performance darling. The magic of nitrates in your diet seem to be part
of the solution, working beyond the benefits of just being fit and training
hard if you are an athlete.
Nitrates – the new training tool
It is only been in the
last five years or so that nitrates have gained recognition as compounds that
benefit our physiology. A series of studies have now shown that one very good
source of nitrates, beetroot juice, has dramatically reduced times in running
trials. One study showed a 30
second improvement in time over 5km in fit female runners, and you can’t
complain about that. Another study in men revealed that less oxygen was required to exercise at a set level
and they could cycle 12-14% longer before exhaustion.
However, it seems that
you need to take beetroot juice for six days rather than expect a result from just a single dose. It has even improved exercise capability in people with
peripheral artery disease (poor blood flow to the extremities of the body).
Beyond exercise
performance, nitrates also help keep blood pressure down and arteries healthy,
as we shall see.
How does nitrate work?
Let me take you on a
weird journey. Let’s say you eat nitrate-containing foods. They go through the
stomach and into the small intestine where the nitrate is absorbed into the
blood. The nitrate then circulates and becomes concentrated in the saliva which
is released into the mouth. Now oral bacteria convert the nitrate (NO3) in your
saliva to nitrite (NO2). These bacteria are not the ones that cause tooth
decay. Then you swallow the saliva. In the stomach the nitrites are converted
to nitric oxide, the wonder molecule that dilates your blood vessels making
blood flow easier, lowering blood pressure and slicing a chunk of time off your
personal best.
If you’ve read that and
it seems that nitrates go around the body twice, first as nitrate, then as nitrite
before becoming nitric oxide, then you have pretty well got the idea. Saliva?
Who would have thought it was good for blood pressure and endurance?
Where do I find nitrate?
It is primarily in vegetables, especially the leaves, stems and roots of green vegetables. Foods high in nitrates are spinach, silverbeet, kale, parsley, celery, lettuce, rocket, beetroot and radish. Modest amounts are in banana, broccoli, cabbage, leek, capsicum/peppers, cucumber, pumpkin, strawberries and, get this, potato crisps and salami where the nitrate is added as a preservative. Nitrates and nitrites got a bad name by association because they are added to cured meats to stop bacterial spoilage.
There is not a lot of nitrate in other vegetables and fruits, but they can’t be dismissed because they provide polyphenols and vitamin C, critical in nitric oxide production in the stomach. Nitrate levels in food vary depending upon fertilisers (more nitrate), soil type and light exposure (less nitrate). Nevertheless, by far the majority of nitrate in the diet comes from vegetables with vegetables and fruit combined providing 90% of dietary nitrates. About 2% comes from processed meats and another 4% from pizza and savoury snacks.
Nitric oxide (NO)
Why the fascination
with nitric oxide? As I have mentioned, NO helps relax blood vessel walls so
that more blood flows through and with great ease. In addition, it stops
platelets from clumping together to form blood clots, and also stops them from
adhering to the sides of your arteries to slowly block them. You have all heard
of Viagra. That famous tablet elevates NO levels to increase blood flow, but
only in one part of the body. Just don’t expect the same effect from a bowl of
salad.
Beetroot juice
OK,
now you want to know how much beetroot juice you need to give you a PB in your
next run, cycle, or triathlon. Simply put, the volume that will give you 300 mg
nitrate. The nitrate amount will be on the label (0.3g = 300 mg). The research
studies use about 500 mL (17 fl oz) but you can now buy beetroot juice
concentrate. Quaff it about two hours before you get active. For more detail read the excellent fact sheet
from the Australian Institute of Sport on beetroot juice and sport.
What does it all mean?
We are now looking at
nitrates in a different light and appreciating their health value. Eat your
vegetables. They are helping keep your blood pressure healthy while helping
your endurance and getting you through the day. Simple enough. Not suggesting
that you eat more pizza, crisps and salami for nitrates and you should know why
because you are smart. But that spinach salad should be looking more attractive.
If you enjoy sport, and
especially if you are involved in endurance sport, then also eat your
vegetables. In addition, vegetable juice (home-made, without the added salt
might be best) and beetroot juice taken a couple of hours before exercise could
make it a more beautiful experience.
If you go the beetroot
juice route note three things:
1)
I haven’t met anyone
who says it has a wonderful taste, especially the concentrate. Expect the
spinal shivver when consuming;
2) Your pee may turn
pink for a while. It’s OK. It’s your favourite colour anyway;
3) Don’t use
antibacterial mouthwash before taking beetroot juice because you will kill the
very bacteria that produce the nitrites needed to form nitric oxide.
As we find out more about
the bacteria in your mouth keeping you healthy, I wonder what will happen to
the sales of those mouthwashes? Yes, you still need to clean and floss your
teeth. No residual food in the mouth means no decay. But should you continue
with that mouth wash?
For those who love 75
page reports here is one on nitrates and nitrites in the Australian diet.
