Sunday, November 17, 2013


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.