The science

For each meal, Timiya estimates what you ate and how much of it your body is likely to absorb. What you eat with a food, how you cook it, and when you drink your tea all change how much of it counts.

Scientists call the share your body takes in bioavailability. Here is what Timiya counts, and the studies behind it.

What changes how much you take in

Tea or coffee with the meal

Tea and coffee may get in the way of the iron in beans, greens, and grains. Timiya asks when you had your chai. In one study, tea an hour after a porridge meal had about half the effect of tea with it.

Sources: Disler 1975, Hurrell 1999, Ahmad Fuzi 2017

Vitamin C and a sour side

Vitamin C in the same meal may help your body take in the iron from plants. Kachumbari, cabbage, or an orange all add it, and a squeeze of lemon or some tomato helps a little too.

Sources: Hallberg 1986, Hallberg 1989, Teucher 2004

A little fat with your greens

Greens carry a form of vitamin A that the body uses better with some fat. Timiya asks how your greens were cooked and counts more when there was oil. Studies suggest 3–5 g of fat may be enough.

Sources: Ribaya-Mercado 2002

Soured or fermented grains

Souring uji is an old habit that works. Fermenting may break down some of what holds iron back in the grain, so Timiya counts more of the iron in soured uji.

Sources: Gibson 2006

Meat or fish with plant iron

Some meat, chicken, or fish, omena included, may help your body take in the plant iron in the rest of the meal. Egg and milk don’t have this effect, so Timiya doesn’t count them for it.

Sources: Cook 1976

Grains and beans

Maize, beans, and other grains and legumes hold a natural compound that may get in the way of iron and zinc. A big plate of ugali or githeri holds more of it, so Timiya counts less of its iron and zinc. WHO and FAO assume about 15% of zinc is absorbed from diets high in unrefined grains and legumes, against 30% from mixed diets.

Sources: Hallberg 1989, WHO/FAO 2004

Spinach and calcium

Spinach holds its calcium tightly, so little of it counts. Kale and its cousin sukuma wiki give theirs up much more easily. Timiya counts less of the calcium from spinach and some other greens.

Sources: Heaney 1988, Heaney 1990, Weaver 1999

Calcium with iron

A lot of calcium in one meal, such as a big glass of milk, gets in the way of iron. Timiya counts a little less iron from a meal high in calcium. Milky chai drunk an hour or more after the meal doesn’t count against it.

Sources: Hallberg 1991

Beans with maize

Grains and beans each run short of a different protein building block, and together they cover each other. So Timiya counts more of the protein in githeri than in maize or beans alone.

Sources: Young 1994

Where the numbers come from

Common foods such as ugali, sukuma wiki, beans, and omena use values from the Kenya Food Composition Tables (published with FAO) and USDA FoodData Central. For other foods, Timiya’s AI estimates the values, and the app labels them as estimates.

Your daily targets come from the Dietary Reference Intakes of the US National Academies, with the World Health Organization’s limits for salt and sugar.

Sources: Kenya Food Composition Tables 2018, USDA FoodData Central, IOM 2006, WHO 2012, WHO 2015

What Timiya doesn’t do

Timiya doesn’t measure anything in your body. It estimates from what you log, so a wrong portion or a missed side changes the result. If it gets something wrong, you fix it before it counts.

Soaking beans is an old habit, and Timiya doesn’t count it. Your clinic’s advice comes first.

What’s still in review

Every figure Timiya shows is an estimate, and some of the factors above are provisional. We’ve sent our values to a nutritionist and a clinician for review. While that runs, the app marks the notes still in review, such as its fasting notes and supplement cautions.

How we write about health

Every claim on this page about how the body works has a source, listed below. Journal articles list theirs at the end. Evalyne Njambi, a nutritionist, writes our journal.

If you spot a mistake, tell us and we’ll fix it.

Tell us about a mistake

Sources

  1. Disler PB et al. The effect of tea on iron absorption. Gut. 1975;16(3):193–200. doi.org/10.1136/gut.16.3.193
  2. Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. Br J Nutr. 1999;81(4):289–295. doi.org/10.1017/S0007114599000537
  3. Ahmad Fuzi SF et al. A 1-h time interval between a meal containing iron and consumption of tea attenuates the inhibitory effects on iron absorption. Am J Clin Nutr. 2017;106(6):1413–1421. doi.org/10.3945/ajcn.117.161364
  4. Hallberg L, Brune M, Rossander L. Effect of ascorbic acid on iron absorption from different types of meals. Hum Nutr Appl Nutr. 1986;40(2):97–113. pubmed.ncbi.nlm.nih.gov/3700141/
  5. Hallberg L, Brune M, Rossander L. Iron absorption in man: ascorbic acid and dose-dependent inhibition by phytate. Am J Clin Nutr. 1989;49(1):140–144. doi.org/10.1093/ajcn/49.1.140
  6. Teucher B, Olivares M, Cori H. Enhancers of iron absorption: ascorbic acid and other organic acids. Int J Vitam Nutr Res. 2004;74(6):403–419. doi.org/10.1024/0300-9831.74.6.403
  7. Ribaya-Mercado JD. Influence of dietary fat on beta-carotene absorption and bioconversion into vitamin A. Nutr Rev. 2002;60(4):104–110. doi.org/10.1301/00296640260085831
  8. Gibson RS, Perlas L, Hotz C. Improving the bioavailability of nutrients in plant foods at the household level. Proc Nutr Soc. 2006;65(2):160–168. doi.org/10.1079/PNS2006489
  9. Cook JD, Monsen ER. Food iron absorption in human subjects. III. Comparison of the effect of animal proteins on nonheme iron absorption. Am J Clin Nutr. 1976;29(8):859–867. doi.org/10.1093/ajcn/29.8.859
  10. WHO/FAO. Vitamin and Mineral Requirements in Human Nutrition. 2nd ed. 2004. www.who.int/publications/i/item/9241546123
  11. Heaney RP, Weaver CM, Recker RR. Calcium absorbability from spinach. Am J Clin Nutr. 1988;47(4):707–709. doi.org/10.1093/ajcn/47.4.707
  12. Heaney RP, Weaver CM. Calcium absorption from kale. Am J Clin Nutr. 1990;51(4):656–657. doi.org/10.1093/ajcn/51.4.656
  13. Weaver CM, Proulx WR, Heaney R. Choices for achieving adequate dietary calcium with a vegetarian diet. Am J Clin Nutr. 1999;70(3):543S–548S. doi.org/10.1093/ajcn/70.3.543s
  14. Hallberg L et al. Calcium: effect of different amounts on nonheme- and heme-iron absorption in humans. Am J Clin Nutr. 1991;53(1):112–119. doi.org/10.1093/ajcn/53.1.112
  15. Young VR, Pellett PL. Plant proteins in relation to human protein and amino acid nutrition. Am J Clin Nutr. 1994;59(5):1203S–1212S. doi.org/10.1093/ajcn/59.5.1203S
  16. FAO and Government of Kenya. Kenya Food Composition Tables. 2018. www.fao.org/3/I9120EN/i9120en.pdf
  17. US Department of Agriculture. FoodData Central. fdc.nal.usda.gov/
  18. Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. National Academies Press. 2006. doi.org/10.17226/11537
  19. WHO. Guideline: Sodium intake for adults and children. 2012. www.who.int/publications/i/item/9789241504836
  20. WHO. Guideline: Sugars intake for adults and children. 2015. www.who.int/publications/i/item/9789241549028