Nitraten maken je sterk*
Nitraten in de voeding werden tot voor kort
beschouwd als gevaarlijk doch steeds meer studies laten zien dat nitraten ook
voordelig kunnen zijn. Zo blijkt uit deze Zweedse studie dat drie dagen een
kleine portie nitraten er bij gezonde mensen voor zorgt dat voor een inspanning
duidelijk minder zuurstof nodig is, omdat hun cellen efficiënter werken. De
nitraten zorgen ervoor dat de mitochondrieën (deze voorzien onze cellen van
energie) veel efficiënter gaan werken. Mitochondrieën zijn normaal gesproken
niet heel efficiënt, zegt onderzoeker Weitzberg. De nitraten veranderen dat. De
hoeveelheid nitraten die gebruikt werden in de studie zijn vergelijkbaar met de
hoeveelheid in 2-3 bietjes of 1 portie spinazie.
Of het langdurig eten van grotere hoeveelheden ook zo goed is, is onduidelijk,
zo zeggen de onderzoekers. Patiënten met diabetes of hart- en vaatziekten
hebben slecht functionerende mitochondrieën, mogelijk hebben zij baat bij een
regelmatige dosis spinazie. Dat willen de wetenschappers nu uit gaan zoeken. De
wetenschappers waarschuwen wel om na het eten van spinazie niet meteen de mond
te spoelen met mondwater of iets dergelijks. Daardoor verdwijnen namelijk de
bacteriën in de mond die nodig zijn om de bioactieve stoffen in spinazie om te
zetten.
Want More Efficient Muscles? Eat Your Spinach
After taking a small dose of inorganic nitrate for three days, healthy people
consume less oxygen while riding an exercise bike. A new study in Cell
Metabolism traces that improved performance to increased efficiency of the
mitochondria that power our cells.
The researchers aren't recommending anyone begin taking inorganic nitrate
supplements based on the new findings. Rather, they say that the results may
offer one explanation for the well-known health benefits of fruits and
vegetables, and leafy green vegetables in particular.
"We're talking about an amount of nitrate equivalent to what is found in
two or three red beets or a plate of spinach," said Eddie Weitzberg of the
Karolinska Institutet in Sweden. "We know that diets rich in fruits and
vegetables can help prevent cardiovascular disease and diabetes but the active
nutrients haven't been clear. This shows inorganic nitrate as a candidate to
explain those benefits."
In fact, up until recently nitrate wasn't thought to have any nutritional value
at all. It has even been suggested that this component of vegetables might be
toxic. But Weitzberg and his colleague Jon Lundberg earlier showed that dietary
nitrate feeds into a pathway that produces nitric oxide with the help of
friendly bacteria found in our mouths. Nitric oxide has been known for two
decades as a physiologically important molecule. It opens up our blood vessels
to lower blood pressure, for instance.
The new study offers yet another benefit of nitrate and the nitric oxides that
stem from them. It appears that the increased mitochondrial efficiency is owed
to lower levels of proteins that normally make the cellular powerhouses leaky.
"Mitochondria normally aren't fully efficient," Weitzberg explained.
"No machine is."
Questions do remain. The new results show that increased dietary nitrate can
have a rather immediate effect. But it's not yet clear what might happen in
people who consume higher levels of inorganic nitrate over longer periods of
time. Weitzberg says it will be a natural next step to repeat the experiment in
people with conditions linked to mitochondrial dysfunction, including diabetes
and cardiovascular disease, to see if they too enjoy the benefits of nitrates.
"Among the more consistent findings from nutritional research are the
beneficial effects of a high intake of fruit and vegetables in protection
against major disorders such as cardiovascular disease and diabetes," the
researchers concluded. "However, the underlying mechanism(s) responsible
for these effects is still unclear, and trials with single nutrients have
generally failed. It is tempting to speculate that boosting of the
nitrate-nitrite-NO pathway may be one mechanism by which vegetables exert their
protective effects."
As an interesting aside, Weitzberg says that the benefits of dietary nitrates
suggest that powerful mouthwashes may have a downside. "We need oral
bacteria for the first step in nitrate reduction," he says. "You could
block the effects of inorganic nitrate if you use a strong mouthwash or spit [instead
of swallowing your saliva]. In our view, strong mouthwashes are not good if you
want this system to work." (Februari 2011)
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