Nitrates

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.

Sweetening agents 2

There is nothing quite like commenting on sweetening agents to generate a response, often quite emotional. A couple of comments that are suitable for publication are reproduced in the letters section below. If I say something positive about a sweetener, especially aspartame, then someone will want to disagree. Let’s be honest, there are far more negative than positive comments about “artificial sweeteners” on the internet.

  

One enduring concern is that sweeteners cause cancer. This has been refuted by the Cancer Council and the famous Mayo Clinic and others, but maybe they are all working in collusion.

500 year old advice still relevant

Last month I attended the International Union of Nutrition Science conference in Spain. There I met Sir Andrew Renwick, Professor of Medicine at the University of Southampton, UK who has spent all his professional life in toxicology. He said that in “the last 46 years in studying sweeteners I have not seen any scientifically reproducible evidence that any sweeteners cause any harm to humans in the amounts normally consumed.”

He referred to the famous quote by Paracelsus (1493-1541) that “all things are poison … only the dose which makes something a poison”. There are variations on the translation, but simply put, it is the dose that determines whether something is good, neutral or bad for you.

Aspartame

He singled out aspartame, now approved in over 90 countries, stating that it has a larger safety database that any other food additive. Aspartame is a methylated dipeptide, comprising two amino acids phenylalanine and aspartic acid. You will remember from biology that amino acids make up proteins.

Some methanol is produced when aspartame is consumed, and you will hear people tell you scary stories about methanol, only because they don’t understand what Paracelsus said 500 years ago. Yes, methanol is produced but only in very small, non-harmful, amounts. There is more methanol in the same volumes of orange juice, apple juice and tomato juice than in a soft drink sweetened with aspartame. In fact there is six times more methanol in tomato juice than a diet drink, but you don’t hear scary stories about tomato juice, and neither should you because it is all about dose.

“Nobody listens, no matter how many authoritative scientific reviews take place. Low-calorie sweeteners are among the most extensively studied of all food additives. Media stories about “health concerns” usually focus on a single recent observation and ignore the totality of the database available,” said Renwick.

Of course, because he says this, his words are quoted by agencies and companies that have a vested interest in sweeteners, so then people think that he has become a mouthpiece for sweeteners and can’t be trusted. That’s the way conspiracy theories work. One final comment he made was that the Wikipedia entry on the aspartame controversy was “surprising unbiased.”

Natvia

I was asked about Natvia, which is a mix of Stevia and erythritol. Stevia has been discussed in an earlier blog. It is quite safe.

Erythritol is not often found in foods, although it comes from a common family of sugar-alcohols, a bit like mannitol and sorbitol often used for its sweetness, mainly back in the 1980s in confectionery such as gum and mints. Some of you will remember Blizzard mints with sorbitol. I always remember them because, when lecturing at a university I mentioned Blizzard mints as an example of a product with sugar-alcohols. After a few minutes one quizzical student put up her hand and asked: “Where do you buy “lizard mince”?” A reminder to me to enunciate better. Yes, it was funny, and no, I don’t think lizard mince is legal either.

Anyway, erythritol is a sweetener with about two-thirds the sweetness of sugar. It has passed all the safety and toxicology tests thrown at it, even at high doses. It is absorbed from the gut and excreted through the kidneys unchanged. Its sweetness works well in combination with stevia.

What does it all mean?

If you eat sensibly, then there is a very good chance that you will eat somewhere between none and very little intense added sweetener, in which case it shouldn’t alarm you. If you are consuming two litres of diet soft drink, a litre of diet cordial, 1 kg of diet yogurt and 10 cups of tea with two tablets of sweetener per cup then I’m willing bet that your overall diet is pretty crap anyway. My blunt and unattractive view is that people focus way too much on minor issues of no consequence, distracting them from doing something useful like giving to charity, walking the dog and reducing the amount of the most dangerous food additive known to man. It’s called salt, but who cares?

And yes, I do enjoy a diet soft drink after a long bike ride (60+ km for me), so don’t think that I can be trusted to give you a balanced argument on sweeteners!