Nitro Greens: How Spinach and Arugula Boost Blood Flow Naturally-The Hidden Chemistry in Your Salad Bowl

1. Nitrogen in Plants – Uptake and Assimilation

• Plants primarily take up nitrogen from the soil in two inorganic forms:

  • Nitrate (NO₃⁻)

  • Ammonium (NH₄⁺)

• In leafy vegetables, nitrate (NO₃⁻) is the dominant stored form.

• Once absorbed, part of it is reduced via the nitrate reductase pathway:

NO3−+2e−+2H+  →nitrate reductase NO₂⁻ + H₂O 

NO₂⁻ −+6e−+8H+  →nitrite reductase  ​NH4+​+2H2​O

• The resulting NH₄⁺ is incorporated into amino acids (via glutamine synthetase and glutamate synthase pathways).

• However, in leafy greens like spinach and arugula, a large fraction of NO₃⁻ is left unmetabolized and accumulates in vacuoles → hence their high nitrate levels.

2. Why Leafy Greens Accumulate More Nitrate

• Leaves are the main site of photosynthesis, and nitrogen is critical for chlorophyll and enzymes (RuBisCO).

• When light is low (less photosynthetic activity), nitrate reduction slows → more nitrate accumulates.

• Fast-growing leafy crops (spinach, arugula, lettuce) are particularly nitrate-accumulating plants.

3. Human Biochemistry of Dietary Nitrate

• When we eat spinach/arugula, nitrate (NO₃⁻) undergoes the nitrate–nitrite–nitric oxide pathway:

  1. Oral reduction: Bacteria in saliva reduce ~20% of NO₃⁻ to NO₂⁻.

  2. In stomach (acidic pH):

     2HNO2  →  NO+NO2+H2O2HNO₂ \;\to\; NO + NO₂ + H₂O2HNO2​→NO+NO2​+H2​O

     Nitric oxide (NO) is produced — a potent vasodilator.

  3. Systemically, NO₂⁻ can be further reduced to NO under hypoxic conditions (important for cardiovascular function).

• This is why dietary nitrates improve blood flow, lower blood pressure, and enhance exercise performance.

4. Average Nitrate Content in Leafy Greens (mg NO₃⁻ per kg fresh weight)

• Arugula (rocket): 4,800 – 7,200 mg/kg

• Spinach: 1,500 – 3,500 mg/kg

• Lettuce: 1,000 – 4,000 mg/kg (varies by type)

• Chard / Beet greens: ~2,000 – 3,000 mg/kg

(For reference, WHO acceptable daily intake (ADI) for nitrate = 3.7 mg/kg body weight ≈ 260 mg/day for a 70 kg adult — easily exceeded by a big salad, but from vegetables it’s considered safe and beneficial due to antioxidants.)

5. Chemical Engineering Perspective

• This nitrate accumulation can be modeled as a mass balance problem between:

  • Uptake rate from soil (depends on fertilizer & water availability)

  • Assimilation rate into amino acids (depends on light intensity, enzyme activity)

  • Storage rate in vacuoles (nitrate reservoir in leaves)

Where:

• Ruptake= transport from soil → root → xylem

• Rreduction= enzymatic conversion to NH₄⁺ in chloroplasts

• Rtranslocation​ = movement to non-leaf tissues

In spinach/arugula, R₍uptake₎ ≫ R₍reduction₎, especially under low light → nitrate buildup.

✅ So in chemical terms:

• Leafy greens are nitrate accumulators.

• Nitrate is stable, highly soluble, stored in vacuoles, and later becomes a precursor for nitric oxide (NO) in our body.

• That’s why arugula & spinach are both nutritionally valuable “nitrogen-rich” foods.