3 ms·

That study is in rats. Non-heme iron (i.e. the iron in spinach) has repeatedly been shown to be absorbed poorly in humans. https://pubmed.ncbi.nlm.nih.gov/8207

by rcme 4y ago

That study is in rats. Non-heme iron (i.e. the iron in spinach) has repeatedly been shown to be absorbed poorly in humans. https://pubmed.ncbi.nlm.nih.gov/8207546/ https://pubmed.ncbi.nlm.nih.gov/8207546/ > ... studies have shown that the absorption of dietary nonheme iron in rats is much higher and less responsive to dietary variables than in human subjects.

Retric 4y ago
“(Bezwoda, Bothwell, Charlton et al.) the bioavailability of heme iron was measured to be about 20%, while the availability of non-heme iron varied between 6% and 18% depending on the amount of iron present in the meal.” Spinach has dramatically more Iron than Beef does so being absorbed at a lower ratio is offset by a much larger quantity of Iron being in the food.
- rcme 4y ago
  2.5X per unit weight… so the get the amount of iron in a 1/4 cheeseburger you’d need to eat 0.5-1 pounds of spinach. Possible, but hard.
  - Retric 4y ago
    How did you calculate that? If it’s got 2.5x as much and Bioavailability of iron in beef is ~20% and non beef ranges from 6% to 18% then… Worse case 2.5x * 0.06 / 0.20 = 75% as much per unit weight so you need 1/3 of a pound of Spinach. Best case was 2.5x * 0.18 / 0.2 = 225% so you need 1/9th of a pound. I am not saying your wrong, I just don’t get how you did that calculation.
    - deleted 4y ago
      [deleted]
    - rcme 4y ago
      Imagine a 1 lb steak contains N milligrams of of iron. After eating you'd absorb 0.2N milligrams. In 1 lb of spinach, there would be 2.5N milligrams of iron, and you'd absorb 6%, meaning you'd absorb (2.5 * 0.06)N milligrams, i.e. 0.15N milligrams. So clearly you need to eat more spinach to get the same amount of iron in the worst case. So you need to eat 33% more spinach in this case to get the same amount of iron. But some places list absorption of non-heme iron as low as 2%.

by rcme 4y ago

Retric 4y ago

“(Bezwoda, Bothwell, Charlton et al.) the bioavailability of heme iron was measured to be about 20%, while the availability of non-heme iron varied between 6% and 18% depending on the amount of iron present in the meal.” Spinach has dramatically more Iron than Beef does so being absorbed at a lower ratio is offset by a much larger quantity of Iron being in the food.

rcme 4y ago
2.5X per unit weight… so the get the amount of iron in a 1/4 cheeseburger you’d need to eat 0.5-1 pounds of spinach. Possible, but hard.
- Retric 4y ago
  How did you calculate that? If it’s got 2.5x as much and Bioavailability of iron in beef is ~20% and non beef ranges from 6% to 18% then… Worse case 2.5x * 0.06 / 0.20 = 75% as much per unit weight so you need 1/3 of a pound of Spinach. Best case was 2.5x * 0.18 / 0.2 = 225% so you need 1/9th of a pound. I am not saying your wrong, I just don’t get how you did that calculation.
  - deleted 4y ago
    [deleted]
  - rcme 4y ago
    Imagine a 1 lb steak contains N milligrams of of iron. After eating you'd absorb 0.2N milligrams. In 1 lb of spinach, there would be 2.5N milligrams of iron, and you'd absorb 6%, meaning you'd absorb (2.5 * 0.06)N milligrams, i.e. 0.15N milligrams. So clearly you need to eat more spinach to get the same amount of iron in the worst case. So you need to eat 33% more spinach in this case to get the same amount of iron. But some places list absorption of non-heme iron as low as 2%.