How much water is in your food?

It is already in the official numbers. NASEM and EFSA both define total water intake as drinking water plus beverages plus food moisture, and the CDC describes intake the same way, naming water-rich fruits and vegetables and giving no numeric target.^1,2,9

Total water 3.7 L/day (men) and 2.7 L/day (women). Fluids 3.0 L (101 fl oz, about 13 cups) for men and 2.2 L (74 fl oz, about 9 cups) for women. Food provided 19% (0.7 L for men, 0.5 L for women); elsewhere the chapter says about 20% from food and 80% from fluids.

Caveat: The adequate intake is set from median US intakes, not a physiological requirement. Cite NASEM directly: Maughan 2016's introduction misstates the women's figure.

The share swings with the cuisine. About 19–22% in US data, 20–30% assumed in Europe, and 38.0% measured by duplicate portion in young Chinese adults.^4,1,2,5

US about 22% from food; one in-depth US study found 20.7%. Water content bands: 90-99% for fat-free milk, cantaloupe, strawberries, watermelon, lettuce, cabbage, celery, spinach, pickles and cooked squash; 80-89% for fruit juice, yogurt, apples, grapes, oranges, carrots, cooked broccoli, pears and pineapple; 70-79% for bananas, avocados, cottage cheese and baked potato; 30-39% for cheddar, bagels and bread.

Caveat: The authors note the underlying intake measurements are poor.

Food brings sodium and potassium, which help you keep the fluid. After exercise, a meal eaten with plain water left people near balance at six hours; the same volume drunk as a sports drink left them in deficit.⁷

n=8, 2.1% body mass lost, water intake 150% of the loss. Meal 63 kJ/kg (53% carbohydrate, 28% fat, 19% protein). Urine: meal plus water median 665 mL (range 396-1190) vs 934 mL and 954 mL for the sports drink. Net balance at 6 h -29 mL vs -337 mL and -373 mL. Sodium intake 63 ± 4 vs 42 ± 2 mmol; potassium 21.3 vs 6.8 mmol.

Caveat: Abstract only.

Soup is the food that behaves like a drink. After 2.5% dehydration, chicken broth and chicken noodle soup restored plasma volume while water and a sports drink did not. USDA puts plain broth at 97.7% water — 234 mL in a cup.^8,3

n=30 (15 men, 15 women), 2.5% body weight lost, 2 h of rehydration. Chicken broth Na 109.5 and K 25.3 mmol/L; chicken noodle soup Na 333.8 and K 13.7 mmol/L; sports drink Na 16.0 mmol/L. Plasma volume vs before dehydration: broth -1.6 ± 1.1% and soup -1.4 ± 0.9%, against water -5.6 ± 1.1% and sports drink -4.2 ± 1.0% (P<0.01). Urine: sports drink 310 ± 30 mL vs broth 188 ± 20 mL.

Caveat: Abstract only. Only two 175 mL portions were the test drink; the rest was water, and the soup's sodium was very high.

In children, more fruit and veg tracks with better hydration. In 442 German children aged 4–10, each extra 100 g of solid fruit and vegetables predicted about 46 mL more free water reserve — observational, so association, not cause.⁶

n=442 children, 1286 records. Each extra 100 g of solid fruit and vegetables predicted about 46 mL more free water reserve; fruit and vegetable juice beta = 43 (P<0.0001). Solid fruit and vegetables supplied 12% of total water intake and juices 10%. 22% of the children had a negative free water reserve.

Caveat: Abstract only; observational.