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Popeye's Spinach Trick Proves Plausible
2/7/2011
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by Craig Weatherby



Whenever he needs to fight a big guy, Popeye the Sailor Man downs a can of spinach… and sprouts bulging muscles in a flash.
 
Incredibly, it’s looking like the classic cartoon character’s veggie-fueled strength boost has a basis in reality.
 
In November of 2010 we summarized a study showing that drinking juice from a nitrate-rich vegetable increased blood flow to key areas of the brain (see “Can Beets & Co. Boost Aging Brains?”).

Vegetables by nitrate content 
(mg/100 g) < = less than, 
> = greater than
  • Very high, >250 – Celery, cress, chervil, lettuce, red beetroot, spinach, rocket (arugula)
  • High, 100 to <250 –Celeriac, Chinese cabbage, endive, fennel, kohlrabi, leek, parsley
  • Middle, 50 to <100 –Cabbage, dill, turnip, savoy cabbage
  • Low, 20 to <50 – Broccoli, carrot, cauliflower, cucumber, pumpkin, chicory
  • Very low, <20 – Artichoke, asparagus, broad bean, eggplant, garlic, onion, green bean, mushroom, pea, pepper, potato, summer squash, sweet potato, tomato, watermelon 
More recently, we reported on a British clinical trial, in which participants who drank nitrate-rich beet juice enjoyed reduced oxygen requirements while exercising (see “Beet-Borne Nitrates Seen to Aid Exercise”).
 
Now a clinical trial from Sweden confirms the Brits’ observation that dietary nitrates can boost muscle efficiency during exercise.
 
And the new study also detected one explanation for nitrates’ ability to temporarily enhance muscle endurance.
 
Namely, eating nitrates seemed to boost the efficiency of the cellular energy factories called mitochondria.
 
The mitochondria use oxygen in the process of turning sugar into the cellular fuel called ATP (adenosine triphosphate).
 
Swedish trial tests nitrate pills and examines participants’ tissues
Last year, scientists from Stockholm’s famed Karolinska Institute published a trial similar to the British one, which produced similarly positive muscle-endurance outcomes.
 
As they wrote, “We conclude that dietary nitrate supplementation, in an amount achievable through a diet rich in vegetables, results in a lower oxygen demand… This highly surprising effect occurred without an accompanying increase in lactate concentration, indicating that the energy production had become more efficient” (Larsen FJ et al. 2010).
 
The same Stockholm-based team conducted the new double-blind crossover trial in 14 healthy volunteers (11 men, five women) aged about 25 years.
 
The goal was to gauge the effects of a nitrate supplement, if any, on the participants’ endurance, mitochondrial efficiency, and whole-body oxygen consumption (Larsen FJ et al. 2011).
 
The nitrate supplement contained an amount equivalent to the nitrate found in 200-300g (seven to 10 ounces) of spinach or other leafy greens. Greens, beets, broccoli, and most vegetables are rich in nitrates.
 
After taking a small dose of nitrates for three days, the volunteers consumed less oxygen while riding an exercise bike.
 
Probing deeper than any prior study, the Swedes biopsied bits of tissue from the participant’s thigh muscles.
 
Following three days of taking nitrate pills, the subjects’ mitochondria showed a 19 percent rise in efficiency (P/O ratio), which was strongly linked to the reduction in “oxygen cost” during exercise.
 
Hope for prevention as well as power
The researchers also observed increases in another measure of mitochondrial efficiency, called thermodynamic coupling.
 
These effects were accompanied by a reduction in a protein that’s key to mitochondrial energy production, called ATN.
 
Professor Weitzberg noted that studies are needed to identify all of the mechanisms and pathways by which nitrate affects mitochondrial efficiency. 
 
As the Swedish team wrote, “The fact that the relatively short term dietary regimen can influence expression of important mitochondrial proteins may have profound impact on exercise physiology. Moreover, it may also have implications for metabolic and cardiovascular diseases in which dysfunctional mitochondria play a central role” (Larsen FJ et al. 2010).
 
 
Sources
  • Larsen FJ, Schiffer TA, Borniquel S, Sahlin K, Ekblom B, Lundberg JO, Weitzberg E. Dietary inorganic nitrate improves mitochondrial efficiency in humans. Cell Metab. 2011 Feb 2;13(2):149-59.
  • Nair KS, Irving BA, Lanza IR. Can dietary nitrates enhance the efficiency of mitochondria? Cell Metab. 2011 Feb 2;13(2):117-8.
  • Larsen FJ, Weitzberg E, Lundberg JO, Ekblom B. Effects of dietary nitrate on oxygen cost during exercise. Acta Physiol (Oxf). 2007 Sep;191(1):59-66. Epub 2007 Jul 17.
  • Larsen FJ, Weitzberg E, Lundberg JO, Ekblom B. Dietary nitrate reduces maximal oxygen consumption while maintaining work performance in maximal exercise. Free Radic Biol Med. 2010 Jan 15;48(2):342-7. Epub 2009 Nov 12.
  • Bailey SJ, Winyard P, Vanhatalo A, Blackwell JR, Dimenna FJ, Wilkerson DP, Tarr J, Benjamin N, Jones AM. Dietary nitrate supplementation reduces the O2 cost of low-intensity exercise and enhances tolerance to high-intensity exercise in humans. J Appl Physiol. 2009 Oct;107(4):1144-55. Epub 2009 Aug 6.
  • Karolinska Institute (KI). Nitrate improves mitochondrial function. Feb. 2, 2011. Accessed at http://ki.se/ki/jsp/polopoly.jsp?d=2637&a=115412&l=en&newsdep=2637

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