Food vs. Capsule

Reference

Elemental magnesium and zinc: how much is actually in each form

The amount of the mineral itself, the elemental amount, is a fraction of the compound's weight. US Supplement Facts panels already state the elemental amount; the number on the front of the bottle or in a product name may be the weight of the whole compound. Calculated from molecular weight; hydrated forms are named where it matters.

Magnesium

Zinc

Calcium carbonate is about 40% calcium and calcium citrate about 21%. Ferrous fumarate is about 33% iron, ferrous sulfate (heptahydrate) about 20% and ferrous gluconate about 12%. The calculator above converts any of these for you.

The short version

What common doses look like on a plate

Calculated from the same USDA data as the tool, ranked by fewest calories. One serving is the amount named.

• 400 mg magnesium: 2.7 × 1 cup of Swiss chard, cooked (465 g, about 93 kcal); 2.6 × 1 cup of spinach, cooked (460 g, about 106 kcal); 4.1 × 1 cup of beet greens, cooked (588 g, about 159 kcal). Magnesium entry →
• 15 mg zinc: 0.22 × 3 oz of oysters, eastern wild, cooked (19 g, about 19 kcal); 1.7 × 4 oz of king crab, cooked (197 g, about 191 kcal); 1.5 × 6 oz cooked of top sirloin steak, broiled (261 g, about 490 kcal). Zinc entry →
• 18 mg iron: 2.8 × 1 cup of spinach, cooked (504 g, about 116 kcal); 4.6 × 1 cup of Swiss chard, cooked (796 g, about 159 kcal); 2.3 × 3 oz of oysters, eastern wild, cooked (195 g, about 199 kcal).
• 500 mg calcium: 4.7 × 2 cups of kale, raw (197 g, about 69 kcal); 0.58 × 1/2 cup of tofu, firm (calcium-set) (73 g, about 105 kcal); 1.9 × 1 cup of collard greens, cooked (355 g, about 117 kcal).
• 200 mcg selenium: 2.1 × 1 nut of Brazil nuts (10 g, about 69 kcal); 2 × 1 can (5 oz) drained of tuna, light, canned in water (283 g, about 244 kcal); 2.6 × 3 oz of mussels, blue, cooked (223 g, about 384 kcal). Selenium entry →
• 2 mg copper: 0.16 × 3 oz of beef liver, pan-fried (14 g, about 24 kcal); 0.41 × 3 oz of oysters, eastern wild, cooked (35 g, about 36 kcal); 4.7 × 1 tbsp of spirulina, dried (33 g, about 95 kcal).
• 900 mcg RAE vitamin A: 0.14 × 3 oz of beef liver, pan-fried (12 g, about 20 kcal); 0.67 × 1 tsp of cod liver oil (3 g, about 27 kcal); 0.27 × 3 oz of chicken liver, simmered (23 g, about 38 kcal). Vitamin A entry →
• 500 mcg vitamin B12: 5.9 × 3 oz of clams, cooked (506 g, about 748 kcal); 7.1 × 3 oz of beef liver, pan-fried (601 g, about 1,053 kcal). B-Complex entry →
• 500 mg vitamin C: 3.3 × 1 medium of red bell pepper, raw (392 g, about 102 kcal); 4 × 1 fruit of guava (219 g, about 149 kcal); 6.2 × 1 cup chopped of broccoli, raw (561 g, about 191 kcal). Vitamin C entry →
• 2,000 IU vitamin D: 2.7 × 1 cup sliced of white mushrooms, UV-exposed (191 g, about 42 kcal); 2.5 × 1 cup diced of maitake mushrooms, raw (178 g, about 55 kcal); 4.4 × 1 tsp of cod liver oil (20 g, about 180 kcal). Vitamin D3 + K2 entry →
• 1,000 mg omega-3 (EPA + DHA): 1.2 × 1 tsp of cod liver oil (6 g, about 50 kcal); 0.27 × 6 oz cooked of salmon, Atlantic farmed, cooked (47 g, about 96 kcal); 0.44 × 4 oz cooked of herring, Atlantic, cooked (50 g, about 101 kcal). Omega-3 Fatty Acids entry →
• 10 mg lutein + zeaxanthin: 0.52 × 1 cup of Swiss chard, cooked (91 g, about 18 kcal); 1.4 × 2 cups of spinach, raw (82 g, about 19 kcal); 0.49 × 1 cup of spinach, cooked (88 g, about 20 kcal).
• 10 mg lycopene: 1.1 × 2 tbsp of tomato paste (35 g, about 29 kcal); 0.63 × 1/2 cup of marinara sauce (79 g, about 39 kcal); 1.4 × 1 cup of tomatoes, cooked (329 g, about 59 kcal).
• 3 g glycine: 2.2 × 1 envelope (7 g) of gelatin powder, unsweetened (16 g, about 53 kcal); 0.9 × 1 oz of pork rinds, plain (25 g, about 137 kcal); 2.3 × 4 oz of king crab, cooked (257 g, about 249 kcal). Glycine entry →
• 500 mg tyrosine: 2.8 × 1 tbsp of spirulina, dried (19 g, about 56 kcal); 3.3 × 1 large white of egg white, raw (109 g, about 57 kcal); 0.43 × 1 cup of Greek yogurt, plain nonfat (97 g, about 57 kcal). L-Tyrosine entry →
• 500 mg betaine (TMG): 3.1 × 1 cup of spinach, cooked (562 g, about 129 kcal); 5.3 × 1 cup of pasta, cooked (735 g, about 1,162 kcal). TMG (Trimethylglycine) entry →

Why this exists

A capsule is a shortcut, not a different substance

Most of what is sold in a capsule also comes on a plate. The useful question is not whether a supplement works but what it is standing in for. Sometimes the answer is a handful of seeds, and the capsule is a convenience. Sometimes the answer is two pounds of fish a day, and the capsule is doing something no reasonable diet can.

Both answers are worth knowing before you buy. The first tells you the food is the better deal, because it brings fiber, protein and everything else along with it. The second tells you the dose is pharmacological, and the evidence for it has to stand on its own.

Two limits apply. Absorption from food and from capsules is not identical, and it differs by nutrient and form. And cooking changes the numbers, which is why every food here is named in the form it was measured in.

Questions

Common questions

How much food equals a 400 mg magnesium supplement?

About 2.6 cups of cooked spinach (460 g, roughly 106 kcal) or 2.7 cups of cooked Swiss chard (465 g, roughly 93 kcal). That is a large side of greens rather than a day's eating, which makes magnesium one of the nutrients where food is a realistic alternative to a capsule. Figures are from USDA FoodData Central (SR Legacy), per the cooked form named.

Which supplement doses cannot realistically be reached from food?

A 500 mcg vitamin B12 dose would take around 5.9 servings of 3 oz cooked clams, about 748 kcal, or 7.1 servings of 3 oz pan-fried beef liver, about 1,053 kcal. When the food equivalent runs to that many calories, the capsule is delivering a pharmacological dose rather than replacing a meal, and the evidence for that dose has to stand on its own.

Is it better to get a nutrient from food or from a supplement?

It depends on how much food the dose represents. Where the equivalent is a handful of seeds or a cup of greens, food is the better deal, because it brings fiber, protein and everything else along with it. Where the equivalent is two pounds of fish a day, the capsule is doing something no reasonable diet can. Two limits apply either way: absorption from food and from capsules is not identical and differs by nutrient and form, and cooking changes the numbers.

Go further

The guide behind the calculator

Every nutrient here has an entry in The Complete Supplement Guide: the form that absorbs, the dose the research supports, and what to avoid stacking it with. 177 pages, 147 entries, graded against the clinical evidence.

Get The Complete Supplement Guide →

All 147 entries, graded → · Protein plate builder →

This page is information, not medical advice. Talk to your doctor before starting a supplement, particularly if you are pregnant, nursing, managing a health condition or taking medication.