Papaya

Papaya (Carica papaya)

Papaya is a tropical fruit that originated in Central America and is now grown around the world. Nutritionally it stands out for three things: an unusually large amount of vitamin C (about 61 mg per 100 g, almost double an orange), a high concentration of carotenoids, and a unique enzyme called papain that breaks down protein.

Unlike other sweet tropical fruits, papaya is relatively low in sugar: 7.8 g per 100 g, less than mango (13.7) or banana (12.2).

Nutrition facts per 100 g (fresh papaya)

A whole medium papaya (about 300 g of flesh) provides about 130 calories and more than 180 mg of vitamin C, twice the recommended daily intake.

Papain: the enzyme that made the fruit famous

Papain is a proteolytic (protein-digesting) enzyme from the cysteine protease family. It is concentrated mainly in the milky sap (latex) of the unripe, green fruit, and its concentration drops considerably as the fruit ripens.

What it really does:

• Tenderizes meat. This is its best-proven and most common use: papain breaks down collagen fibers and softens tough cuts of meat. Commercial meat tenderizer powders are based on it.
• Helps digest protein. Papain supplements have been studied for bloating and discomfort after meals, with mixed results. A caveat: the ripe papaya that we eat contains far less of it than a supplement, and some of it is broken down by stomach acid.
• What it doesn’t do: papaya does not “burn fat”, does not cleanse the liver and does not replace pancreatic enzymes in pancreatic insufficiency. These claims are marketing and are not backed by evidence.

A practical extra: tenderizing meat with grated green papaya or its juice really works, but limit it to 15 to 30 minutes. Any longer and the meat turns mushy.

Papaya seeds: yes or no

The black papaya seeds are edible, have a sharp taste reminiscent of black pepper, and contain benzyl isothiocyanate and carpaine.

What there is: lab studies and very small human studies have looked at anti-parasitic activity (mainly against intestinal worms), antibacterial activity and a protective effect on the kidneys in animal models.

What’s missing: there is no high-quality clinical research in humans to establish these uses, and no established dose.

The important caveats:

• Studies in rats and monkeys found a reversible drop in sperm motility after high doses of papaya seed extract. The relevance to humans at food amounts has not been shown, but men trying to conceive shouldn’t eat large amounts.
• Pregnant women should avoid papaya seeds and green, unripe papaya. The latex contains compounds that have been linked to uterine contractions. Ordinary ripe papaya is considered safe.
• A reasonable amount to try: one teaspoon (about 5 to 7 ground seeds) a day, no more.

Benefits

• An exceptional amount of vitamin C: 68% of the daily value in 100 g. It supports immune function and collagen production, and significantly improves the absorption of plant iron when eaten in the same meal.
• Highly bioavailable carotenoids: the lycopene and beta-cryptoxanthin in papaya are absorbed better than those in tomatoes or carrots, as shown in bioavailability studies, probably because of the structure of the fruit’s chromoplasts.
• Relatively low in sugar for a tropical fruit: 7.8 g per 100 g, less than mango, pineapple or banana. It is a relatively good fit even for people watching their sugar intake.
• Fiber and bowel regularity: 1.7 g per 100 g, combined with a high water content. A small study found improvements in constipation and bloating after a papaya-based preparation.
• Folate: 9% of the daily value per 100 g.
• Skin health: a combination of vitamin C, vitamin A and beta-carotene.

Downsides and risks

• Allergy and latex cross-reactivity: papain is a known allergen. People with a latex allergy are at higher risk of a cross-reaction to papaya, avocado, banana and kiwi (“latex-fruit syndrome”).
• Pregnancy: avoid green papaya and the seeds. Ripe fruit is considered safe.
• Interaction with blood thinners: papain may increase the effect of warfarin. Anyone taking anticoagulants should consult a doctor before taking papain supplements.
• The “soapy” taste: some people find that ripe papaya has an unpleasant taste and smell, caused by isothiocyanate compounds. This is a genetic response, not a sign that the fruit has gone bad. A squeeze of lemon largely neutralizes it.
• Too much beta-carotene over time can cause carotenodermia, an orange tint to the skin. It is harmless and fully reversible.
• Still sugar: although it is relatively low in sugar, a large serving adds up. People with diabetes should count it within their daily total.

Practical use

• Spotting a ripe fruit: the skin is mostly yellow-orange and gives slightly to gentle pressure. A completely green fruit won’t ripen well after picking.
• A squeeze of lemon over the fruit neutralizes its typical smell and adds vitamin C.
• Green papaya is used as a vegetable, grated into Thai salad (som tam) or cooked. In this form it is very low in sugar.
• A smart pairing: with a plant source of iron, such as lentils or tahini, to use the vitamin C to improve absorption.
• Don’t add it to gelatin: papain breaks down the gelatin proteins and stops it from setting. The same rule applies to pineapple.

Summary

Papaya provides more vitamin C than an orange, carotenoids with especially high bioavailability, and less sugar than most tropical fruits, all for 43 calories per 100 g. The enzyme papain is real and works well for tenderizing meat, but most of the health claims around it are exaggerated. The seeds can be tried in moderation, and green fruit and seeds should be avoided during pregnancy.