CYCLING PERFORMANCE TIPS
The duration of improvement in exercise performance is between 5 and 30 minutes. Specific studies:
It is not the nitrate molecule itself that provides this performance benefit, but a metabolic end product, nitric oxide. Nitrate is an inorganic anion which is particularly abundant in green leafy vegetables such as spinach, beetroot, rocket, or lettuce. It is converted into nitrite [NO2-] by bacteria in the mouth. The nitrite is absorbed into the systemic circulation and subsequently reduced to the active agent nitric oxide (NO). Nitric oxide is known to be an important "signaling molecule" at the cell level is assumed to be the active agent improving the nerve/muscle interaction. And it appears that this benefit is directly related to the ability of the diet or supplement to elevate the plasma [NO2-].
Before we address the question as to who might benefit from nitrate supplements, it is important to note that nitrates are not on the World Anti-Doping Agency's (WADA) Prohibited List. A recent review concluded that both acute and more chronic dietary nitrate supplementation improved cycle efficiency (and thus time trial performance) for events of 5 to 30 min duration in trained, but sub-elite, cyclists. But the same studies have not found an effect in the highly trained endurance athletes. The studies showing negligible benefits of nitrates in these elite athletes used acute (2 to 3 hours before the ride) and short-term (3 day before the ride) supplementation protocols which leaves open the possibility that longer-term supplementation, and/or higher nitrate doses, might improve performance in this group of elite athletes. Here is a bit more detail for those interested in teasing out the relationship between level of training versus the benefit of oral nitrates. To quote: "In conclusion, our study shows that the ergogenic effects of nitrate supplementation are significantly related to the individual aerobic fitness level, with no benefits observed on highly trained subjects (VO2peak > 60 mL/kg/min). These different effects on O2 cost of exercise and performance seem related to the relative changes in plasma [NO3-] and [NO2-]... provides further evidence to the notion that nitrate supplementation might be ergogenic if it results in an appreciable increase of plasma [NO2-]. The optimal nitrate-loading regimen required to elevate plasma [NO2-] and to enhance performance in elite athletes is different from that of low-fit subjects and requires further attention.
Bottom line - for all except the very top elite cyclists, both short term (single pre event dosing) as well as longer term (7 day) supplementation look provide equal performance enhancement.
How much nitrate is necessary to provide a performance benefit? For single dose, acute supplementation, most studies used 6 to 8 mmol of nitrate taken 2 hours before the activity. One paper looked at larger doses and found no benefit above 8.4 mmole nitrate. For chronic, multi day supplementation, the same dosages were used, only for longer periods of time.
Where do you get dietary nitrates (besides beets)? Celery, cress, chervil, lettuce, red beetroot, spinach, rocket (rucola) are all high in nitrate with > 250 mg nitrate per 100 gm of vegetable. But the preparation of the vegetable, beets for example, makes a difference. Home processed beets were found to be significantly higher in nitrate content than the commercially processed beets. This difference was attributed to differences in processing methods. Pickled and Harvard beets contained significantly lower amounts of nitrate/nitrite on a dry weight basis than the other types of processed beets.
How does 8.4 mmole of nitrate convert into beets (assuming 250 mg nitrate per 100 gram of vegetable as mentioned above).?
Finally there are various supplements on the market that might be considered. But if you are going to use a supplement, check on the nitrate content. It is not always indicated on the label. I had to send 2 emails to Beetelite to find that it had only 250 mg of nitrate per dose.
Beet (or other nitrate) supplement should be taken at least 2 to 2.5 hours before the event (if a single acute supplement is being used) or for 2 to 6 days if a chronic dietary change is planned.
Is this emphasis on nitrates worth it? To quote: "It should be emphasized that 5 to 9Êmmol of nitrate can readily be consumed within the normal diet and there is presently no evidence that additional nitrate intake produces greater benefits." So for the average cyclist, who is eating a balanced diet, supplements may be more than is needed. And if in doubt, eat an extra serving of greens and occasional beets. There is little to be lost, and for the elite athlete a definite potential for gain from a trial of beet juice as a supplement or a change to a high nitrate diet (spinach, beet root, rocket). For those interested in more information, this is a nice summary article.
How about safety? In 2015 there was a WHO report indicating a significant cancer risk with processed meats, and implicated nitrates as the culprit. How about nitrates in vegetables (beets, celery, spinach, etc.)? There have been several large meta-analyses (A, B) indicating a protective effect of vegetarian diets as far as cancer risk was concerned, and one Canadian investigation (referenced in this study) that specifically called out nitrate or nitrite and ascorbate-containing foods as having no risk and instead noted they were significantly protective (from the perspective of an associated cancer risk). The reason? Most likely due to the associated fiber and other natural organic molecules. I found this to be a nice but somewhat simplistic overview of the subject for those looking for more.
Until recently, the production of nitric oxide was thought to occur only via synthesis from arginine. But beet juice offered another pathway. Now Viagra offers a third pathway to increase the effects of NO by increasing the sensitivity to NO released from nerve endings and endothelial cells in the corpus cavernosum of the penis with sexual stimulation . This NO stimulates an enzyme to convert guanosine triphosphate (GTP) into cyclic guanosine monophosphate (cGMP). It is then the cGMP that causes the smooth muscle of the blood vessels in the penis to relax, which in turn causes an inflow of blood leading to an erection. cGMP is broken down and back to the inactive GMP by a second enzyme phosphodiesterase type 5 (PDE5). Men who suffer from erectile dysfunction often produce too little endogenous NO. This means that the small amount of cGMP they produce is broken down more quickly (the same rate, but less total cGMP to be metabolized) and therefore doesn't have the time to accumulate and cause the vasodilation effect. Sildenafil (Viagra) works by inhibiting the enzyme PDE5. This means that cGMP is not hydrolyzed as fast, accumulates, and this allows the blood vessel smooth muscles to relax. Sildenafil is a potent and highly selective inhibitor of PDE5. Thus Viagra, by its effect on metabolic breakdown, increases the effects of a set amount of NO to lead to vasodilation.
The obvious 2 questions are:
So what are my take aways from my review?