Loading…
Story
food source · 11
One medium orange supplies close to an adult's vitamin C for a day. Eaten whole, with its fiber intact, it does not pour sugar in all at once the way juice does.
Mechanism · Two jobs of vitamin C
The enzymes that build collagen need vitamin C to keep working; without it, collagen fibers cannot be twisted tight, which is where the bleeding gums and slow-healing wounds of scurvy come from. In the gut, vitamin C also converts the hard-to-absorb ferric iron in plants into the easier-to-absorb ferrous form, but only when it is eaten in the same meal as the iron-containing food.
Numbers · Who holds the vitamin C crown
Raw orange has about 53 mg of vitamin C per 100 g, and one medium orange comes close to a day's amount. By weight, raw red bell pepper has 2.4 times as much and green kiwi 1.7 times, so the title of vitamin C champion almost always falls to a single food table. Cut fruit left standing loses some of its vitamin C, and juicing throws away the fiber.
Raw red bell pepper has about 128 mg of vitamin C per 100 g, roughly 2.4 times as much as the same weight of orange. The idea that vitamin C comes only from fruit is a common misunderstanding.
Mechanism · Vegetables carry vitamin C too
Vitamin C dissolves in water and suffers from long cooking. Bell peppers are often eaten raw, in salads or quickly stir-fried, with little long heating to wear it down. Cruciferous vegetables and the tomato and pepper family are underrated sources of vitamin C, and bell peppers and kale rank ahead of many fruits.
In practice · Raw or quickly stir-fried
Raw red bell pepper has about 128 mg of vitamin C per 100 g, roughly 2.4 times the same weight of orange, so a small bowl of raw red pepper easily covers an adult's daily need. Long stir-frying or boiling wears this down; to keep the vitamin C, eat some raw or cook it quickly. The carotenoids in peppers, on the other hand, are absorbed better when cooked with oil, so having both raw and cooked peppers in a meal works best.
A 150 g serving of strawberries, about 8–10 berries, has about 87–134 mg of vitamin C against an adult need of 75–90 mg a day, so one serving covers it; and strawberries are almost always eaten raw, with no cooking step to wear it down.
Mechanism · Three jobs for vitamin C
Vitamin C helps the body twist collagen into strong fibers, converts plant iron in the small intestine into a form that is easier to absorb, and guards against oxidation in the fluid outside cells. It dissolves in water and is damaged by heat, but strawberries are almost always eaten raw, so little of their vitamin C is lost in the kitchen.
Numbers · The vitamin C in a serving
Raw strawberries have about 58–89 mg of vitamin C per 100 g; a 150 g serving has about 87–134 mg, against an adult need of 75–90 mg a day. Strawberries have about 32 kcal and 4.9–7 g of sugar per 100 g, and a glycemic index (GI) of about 40, low for a fruit.
←Kiwi
A medium green kiwi has about 70–92 mg of vitamin C, while the same weight of orange has only about 40 mg, so one kiwi usually comes close to an adult's need for the day.
Mechanism · Eating it raw keeps the vitamin C
Vitamin C dissolves in water and is damaged by heat. Kiwi is almost always eaten raw, with no cooking step, so you get nearly all of the vitamin C in the fruit. One kiwi comes close to a day's need; there is no reason to pile it on in superfood portions.
Numbers · Green kiwi and gold kiwi
Depending on its size, one green kiwi has about 70–92 mg of vitamin C; a medium one weighs about 75 g, and the same weight of orange has only about 40 mg. Gold kiwi is higher still, at about 105 mg per 100 g, and one usually covers a day.
Weight for weight, raw broccoli has about as much vitamin C as citrus fruit, or more. Many people think only fruit supplies vitamin C, but cruciferous vegetables are an underrated source.
Mechanism · It dissolves in water and fears heat
Vitamin C dissolves in water and is damaged by heat. When broccoli is boiled for a long time, the vitamin C is poured away with the cooking water; stir-frying, steaming or a quick blanch keeps more of it.
Numbers · Several nutrients on one plant
Raw broccoli has only about 30–35 kcal per 100 g and is about 90% water. Its vitamin C sits on the same plant as vitamin K1 and folate, and one long boil strips both of the heat-sensitive, water-soluble ones, vitamin C and folate, together.
Potato with its skin has about 13–20 mg of vitamin C per 100 g. That is not citrus territory, but it stands out among staple foods, and because potatoes are eaten in quantity, they are a real source of vitamin C wherever people eat a lot of them.
Mechanism · Vitamin C, rare in a staple
People assume only citrus has vitamin C, but potatoes stand out among staple foods. Vitamin C dissolves in water and is damaged by heat, so long boiling loses some of it, and like potassium it is concentrated in the skin and the layer just beneath it.
Numbers · The lever is portion size
Potato with its skin has about 13–20 mg of vitamin C per 100 g, not citrus territory; what makes it count is how much of it people eat. Peeling throws away the potassium, the fiber and this vitamin C together.
←Kale
Raw kale has about 93–120 mg of vitamin C per 100 g, more than citrus fruit. Vitamin C is damaged by heat, so quick cooking with little water, or eating kale raw, keeps more of it.
Mechanism · Two rules on one leaf
K1 needs fat, while vitamin C dissolves in water and is damaged by heat, so the same leaf follows two sets of rules. Quick cooking with little water and a little oil keeps a good share of both; eaten raw, kale keeps the most vitamin C.
Numbers · Vitamin C for very few calories
Raw kale has about 93–120 mg of vitamin C per 100 g, more than citrus fruit, at very few calories: about 35 kcal per 100 g, with about 2–3 g of fiber.
Tomatoes carry some vitamin C: one medium tomato supplies one to two tenths of the daily reference amount. Vitamin C is damaged by heat, so raw tomatoes have the edge here.
Mechanism · Raw wins here, heat wins elsewhere
Vitamin C and folate are both damaged by heat and partly lost in long cooking, so raw tomatoes have the edge for vitamin C. The lycopene in the same fruit is the opposite: it dissolves in fat and is absorbed better when the tomato is cooked with a little oil. For one tomato, the best way to eat it depends on which nutrient you are after.
Numbers · The vitamin C in one tomato
Raw tomato has about 18 kcal per 100 g and is more than 94% water. One medium tomato supplies one to two tenths of the daily reference amount for vitamin C. Tomato paste has had its water cooked off, so 100 g of it concentrates the calories, sugar and lycopene several times over, while some of the vitamin C is lost in the long heating.
Pineapple has about 47.8 mg of vitamin C per 100 g, in the same range as orange; a usual serving of 100–200 g supplies about 48–96 mg. Fresh-cut pineapple keeps more of it than canned.
Mechanism · Fresh fruit keeps it
Vitamin C dissolves in water and is damaged by heat. Fresh-cut pineapple keeps its share; canned pineapple is heated and packed in syrup, so it loses some vitamin C and gains sugar. The bromelain in pineapple can tenderize meat on the plate, but there is no reliable human evidence that eating it helps digestion, and that is a separate matter from its vitamin C.
Numbers · A usual serving
Pineapple has about 47.8 mg of vitamin C per 100 g and orange about 53 mg, so the two are in the same range. A usual serving of 100–200 g supplies about 48–96 mg, close to or at an adult's daily need of 75–90 mg. Dried pineapple concentrates the sugar 4–5 times and cannot be counted like fresh fruit.
Lychee has a simple nutrient profile: almost nothing but sugar, water and vitamin C. It has about 71.5 mg of vitamin C per 100 g, a little more than orange, and that is its clear strength.
Mechanism · No gel to slow the sugar
Lychee has very little fiber, so there is no gel to slow its sugar on the way into the blood. Vitamin C is its clear strength; claims that lychee polyphenols slow aging come mostly from test-tube experiments, and a strong effect in a test tube does not mean a benefit in the body.
Numbers · How much to eat at once
Lychee has about 71.5 mg of vitamin C per 100 g, a little more than orange (about 53 mg), with about 1.3 g of fiber, 0.8 g of protein and 0.4 g of fat. A usual sitting is 5–10 fruits (about 80–150 g), so the total sugar is not extreme. Dried lychee concentrates the sugar about 4–5 times, so portions have to be counted by dried weight.
Pomelo and grapefruit are citrus sources of vitamin C. Eating the segments with their membranes gives more fiber than drinking the juice, and the sugar reaches the blood more slowly.
Mechanism · Membranes are fiber, juice is sugar water
Eaten as whole segments with their membranes, the fiber stays and sugar enters the blood more slowly; juicing filters most of the fiber out. The vitamin C is still in the juice, but the quality of that meal's carbohydrate has changed.
Safety · On regular medicines, ask first
Grapefruit and some pomelos disable an enzyme in the gut that breaks down certain drugs, so those drugs reach higher levels in the blood. One whole grapefruit or about 200 mL of grapefruit juice is enough to have a clinically meaningful effect on a sensitive drug. If you take a statin, certain blood-pressure drugs, an immunosuppressant or an antiarrhythmic drug, ask your doctor or pharmacist before eating grapefruit or pomelo.
synergy · 3
Vitamin C works as an antioxidant in the watery fluid inside and outside cells, and vitamin E guards the fats of the cell membrane. After E stops a free radical it is oxidized itself, and C can restore it so it keeps working; this step comes mainly from laboratory studies.
↔Zinc
Zinc and vitamin C both take part in wound healing and immunity: vitamin C is used to build collagen, and zinc lets cells divide quickly. When both are short, healing is held back on two fronts.
↔Iron
Vitamin C helping non-heme iron into gut cells is one of the classic same-meal pairings in nutrition: eat fruit or vegetables with beans, leafy greens or fortified grains, and more of the iron is absorbed.
cofactor · 3
→Iron
Vitamin C converts the ferric iron in plants into ferrous iron, which is easier to absorb, and holds onto the iron so it does not turn into a deposit the gut cannot take up. With vitamin C in the same meal, non-heme iron absorption rises markedly.
Vitamin C is an essential cofactor for making collagen: both prolyl and lysyl hydroxylase depend on it, and without it hydroxyproline cannot be made, so collagen's triple helix will not hold together. The reopening wounds and fragile connective tissue of scurvy follow exactly this path.
→Bone
Prolyl hydroxylase needs vitamin C as its cofactor to twist the three strands of type I collagen into a stable triple helix. Collagen is roughly 30% of bone by weight and about 90% of its organic matrix. Mineral makes bone hard; collagen keeps it from being brittle.
depletes · 1
The steady stream of oxidants in smoke uses vitamin C up faster: an isotope study found faster turnover in men smoking more than 20 cigarettes a day, so the dietary reference intakes add 35 mg a day for smokers. In people regularly exposed to secondhand smoke, blood vitamin C fell between that of smokers and the unexposed (a small cross-sectional study). Vegetables and fruit can cover the gap.
regulates · 2
Part of a large dose of vitamin C is turned into oxalate in the body, raising urinary oxalate, and the risk of calcium-oxalate stones may rise with it. Thomas 2013 found that Swedish men who regularly took vitamin C supplements had a higher risk of kidney stones (an observational study). People who have had kidney stones should not take high-dose vitamin C supplements on their own; ask a doctor first.
Vitamin C against colds is a widely repeated claim, but in the trials pooled by a Cochrane systematic review, long-term supplements did not reduce colds in the general population; regular supplements shortened colds in adults by only about 8%, and starting once symptoms appear did essentially nothing.