Written by justis berg
24 February 2011
 

Dietary Nitrates: A New Way of Increasing Nitric Oxide Production

 

Nothing beats getting a good pump in the gym. Traditionally, bodybuilders have resorted to using nitric oxide (NO) products to enhance NO production. Many bodybuilders know that nitric oxide can be increased via the synthesis of nitric oxide synthase, through the amino acid arginine. What many bodybuilders may not know is that NO can be produced via an alternative pathway without NO synthase.

Diet is a major provider of nitrates in the body. Nitrates can enhance the production of nitric oxide, independent of the arginine-dependent NO synthase pathway.1 In 2004, it was demonstrated that inorganic nitrate from dietary sources could be a major source of circulating nitrite— which enhances nitric oxide production independent of the arginine-NOS pathway.2

In one experiment, healthy subjects who ingested a dietary nitrate experienced a four-to-fivefold increase in plasma nitrite. It turns out that much of the dietary nitrite from food entering the stomach from saliva survives intact and reaches the systemic circulation. This suggests that inorganic nitrate from food can be a substrate for NO formation in the body. Nevertheless, based on numerous studies, it seems clear that dietary nitrates are indeed bioactive in the body.

 

Sources of Dietary Nitrates

Incorporating some fruits and vegetables into the diet in place of high protein can help facilitate greater production of nitric oxide production. A diet rich in fruits and vegetables is associated with a lower blood pressure and reduced risk of cardiovascular events. Despite extensive research, the active ingredient(s) responsible for this effect has not been pinpointed, and trials with single nutrients have been largely unsuccessful.

Remarkably, in a recent study of healthy volunteers,3 the blood pressure-lowering effect of dietary nitrate supplementation was similar to what was seen in the healthy control group in the DASH project, a classic vegetable/fruit diet trial4— indicating that nitrate could be an important and active ingredient of this diet. This means taking a nitrate supplement could be just as effective as eating fruits and vegetables for increasing NO production.

It should be noted that the dosage of nitrate used in the study (0.1 mmol/kg/day) is readily achievable through a diet rich in vegetables. So for those guys who are not eating fruits and vegetables, you may be missing out on getting better pumps in the gym.

Beetroot Juice— A High Source of Nitrates

In a recent study, Webb and colleagues found that blood pressure decreases if healthy volunteers ingest a natural nitrate source (beetroot juice). Researchers demonstrated that it was the nitrate in the juice that had the effect, and it occurred via the nitrate’s chemical reduction to nitrite.5 In the study, 0.5 L of fresh beetroot juice decreased systolic blood pressure as much as 10 mmHg, and blood pressure was still significantly reduced 24 hours later.5 The researchers found that blood pressure was reduced within just one hour of ingesting beetroot juice, with a peak drop occurring three to four hours after ingestion. Some degree of reduction continued to be observed up to 24 hours after ingestion.

Researchers demonstrated that the decrease in blood pressure was due to the chemical formation of nitrite from the dietary nitrate in the juice. The nitrate in the juice is converted in saliva, by bacteria on the tongue, into nitrite. This nitrite-containing saliva is swallowed, and in the acidic environment of the stomach is either converted into nitric oxide or re-enters the circulation as nitrite. The peak time of reduction in blood pressure correlated with the appearance and peak levels of nitrite in the circulation— an effect that was absent in a second group of volunteers who refrained from swallowing their saliva during, and for three hours following, beetroot ingestion.

A reduction in blood pressure was also demonstrated in 2006, in healthy volunteers, after three days of dietary supplementation with inorganic nitrate.6 In 2007, it was shown that dietary nitrate decreases whole-body oxygen consumption in humans during submaximal exercise.7 This could be due to the vasodilatation of the blood vessel walls, causing less need for oxygen consumption by muscle. The nitrate-nitrite-NO pathway may be viewed as complementary to the classical arginine-NOS pathway. These pathways work partly parallel to each other, but when oxygen availability is reduced and NOS activity is decreased, nitrite reduction to NO becomes more pronounced.

In sum, consuming natural foods high in nitrates may enhance muscle pumps in the gym. Or you could try beetroot juice, which is naturally high in nitrates.

 

References:

1. Lundberg JO, Weitzberg E, Cole JA and Benjamin N. Nitrate, bacteria and human health. Nat Rev Microbiol, 2004 Jul;2(7):593-602.

2. Lundberg JO and Govoni M. Inorganic nitrate is a possible source for systemic generation of nitric oxide. Free Radic Biol Med, 37, 395-400 (2004).

3. Larsen FJ, Ekblom B, Sahlin K, Lundberg JO and Weitzberg E. Effects of dietary nitrate on blood pressure in healthy volunteers. N Engl J Med, 355, 2792-2793 (2006).

4. Appel LJ, Moore TJ, Obarzanek, E, Vollmer WM, Svetkey LP, Sacks FM, Bray GA, Vogt TM,

Cutler JA, Windhauser MM, Lin PH and Karanja N, A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group. N Engl J Med, 336, 1117-1124 (1997).

5. Webb AJ, Patel N, Loukogeorgakis S, Okorie M, Aboud Z, Misra S, Rashid R, Miall P, Deanfield J, Benjamin N, Macallister R, Hobbs AJ and Ahluwalia A. Acute blood pressure lowering, vasoprotective, and antiplatelet properties of dietary nitrate via bioconversion to nitrite. Hypertension, 51, 784-90 (2008).

6. Larsen FJ, Ekblom B, Sahlin K, Lundberg JO and Weitzberg, E. Effects of dietary nitrate on blood pressure in healthy volunteers. N Engl J Med, 355, 2792- 2793 (2006).

7. Larsen FJ, Weitzberg E, Lundberg JO and Ekblom B. Effects of dietary nitrate on oxygen cost during exercise. Acta Physiol (Oxf), 191, 59-66 (2007).