Canned food can also be nutritious. Scientific comparison subverts cognition.

Canned food can be preserved for a long time without spoiling, leading some to believe it is inferior to fresh food and lacks nutritional value. However, this perception may be inaccurate. Over the same storage period, canned food may retain more nutrients and experience less nutrient loss compared to fresh food stored at room temperature.

1. Fruit and Vegetable Cans - Better Nutrient Retention Than Room Temperature Storage

Fresh fruits and vegetables have the highest nutritional value when they are ripe but unharvested. Once harvested and subjected to prolonged storage and transportation, their nutritional content gradually diminishes. For example, green peas lose 51% of their vitamin C within 24-48 hours of harvesting.

Canned goods are mostly made directly from fresh ingredients. During processing, the potassium, calcium, and magnesium content of fruits and vegetables does not decrease due to sterilization, and dietary fiber is also retained. While heat-sensitive vitamins C and B vitamins are lost to some extent, nutrient loss during transportation and storage is minimal, with vitamin C loss generally not exceeding 15%.

The University of Illinois conducted a comprehensive comparison of the nutritional content of fresh and canned fruits and vegetables. Although high-temperature heating during canning causes some loss of vitamins C and B, the vacuum seal of cans prevents oxygen exposure, resulting in significantly less nutrient loss than fresh fruits stored at room temperature or frozen vegetables.

Furthermore, canned goods typically undergo minimal further processing, resulting in less nutrient loss. Fresh vegetables, however, often require additional cooking, which can lead to a further 15%-55% loss of vitamin C and 11%-66% loss of vitamin B1.

Tests show that canned citrus fruits contain 10-47 mg/100g of vitamin C, while fresh citrus fruits typically contain 20-40 mg/100g. The difference is not significant.

Studies on canned sweet corn show that after heating at 15℃ for 25 minutes, while vitamin C is lost by 25% compared to fresh sweet corn, the total antioxidant activity increases significantly by 44%. Even more surprisingly, ferulic acid (an antioxidant) increases by 550%, and total phenolic substances increase by 54%.

Research also indicates that canned foods often contain more carotenoids than fresh foods, potentially increasing their bioavailability. Carotenoids are an important source of vitamin A for the human body. Compared to fresh tomatoes, canned tomatoes have increased lycopene and higher β-carotene content, potentially exceeding fresh tomatoes by 50%. The USDA Nutrient Database shows that canned pumpkin also has higher β-carotene and vitamin A than fresh pumpkin.

The canning process has also been shown to increase the protein (＞7%) and dietary fiber (＞5%) content of various beans, while also reducing the amount of lectins.

Additionally, some fruit cans add vitamin C to prevent oxidation and extend shelf life. For example, the vitamin C content of canned peaches may be higher than that of fresh peaches.

2. Canned Meat

While the high-temperature sterilization process for canned meat causes some loss of heat-sensitive B vitamins, it does not significantly affect protein and n-3 polyunsaturated fatty acids. The table below shows a nutritional comparison between fresh tuna and canned tuna. Most canned tuna on the market is yellowfin tuna and skipjack tuna.

In addition, canned fish retains a significant amount of vitamin D. Foods rich in vitamin D are rare, but mackerel is relatively rich in vitamin D among common foods, containing 16.1 μg/100g. Even canned mackerel contains 7.3 μg/100g, meaning 100g (about one palmful) can meet 73% of the daily vitamin D requirement for the average adult.

A US study showed that people who frequently eat canned food (≥6 cans/week) have a more diverse diet than those who rarely eat canned food (≤2 cans/week), including more fruits, vegetables, and protein-rich foods, and higher intakes of potassium, calcium, and dietary fiber. Therefore, in addition to fresh foods, nutritious canned foods can also improve nutrient intake and overall diet quality.

Therefore, canned food is not nutritionally deficient; don't misunderstand it. When fresh food is not readily available, canned food is a good alternative, helping to improve diet quality and enhance nutrition.