By Atli Arnarson, PhD Authority Nutrition
Animal foods and plant foods have many differences.
This is especially true for their nutritional value, as many nutrients are specific to either plants or animal foods.
For optimal nutrition, it makes sense to follow a balanced diet that includes both.
This article lists 10 common nutrients that are difficult or impossible to get from animal foods.
1. Vitamin C
Vitamin C is the only essential vitamin not found in useful amounts in cooked animal foods.
It is a powerful antioxidant that is important for the maintenance of connective tissue. It also functions as a co-factor for many enzymes in the body.
Additionally, vitamin C deficiency may cause scurvy, a condition initially characterized by spotty skin and fatigue. Advanced scurvy can cause yellow skin, loss of teeth, bleeding and eventually death.
A diet of only animal foods usually doesn’t contain enough vitamin C. For this reason, people need to get it from fruit, vegetables, fortified food or supplements.
However, sufficient amounts of vitamin C can be acquired from raw liver, fish roe and eggs. Lower amounts are also present in raw meat and fish (1).
Since most people are already getting enough vitamin C from their diet, supplementation is usually unnecessary (2).
Nevertheless, several studies indicate that high vitamin C intake may:
- Protect against age-related mental decline (3).
- Reduce blood pressure (4).
- Improve the health of blood vessels, possibly cutting the risk of clogged arteries (5, 6).
- Some of these effects may only apply to those who are low in vitamin C to begin with.
Taking vitamin C can also enhance iron absorption from a meal. This can reduce the risk of anemia in people who are prone to iron deficiency (7).
Vitamin C is found in most plant foods, especially raw fruits and vegetables. The richest food sources include bell peppers, kale, kiwifruit, citrus fruits and various berries.
Bottom Line: Vitamin C is an antioxidant that is essential for optimal health. However, it is not found at useful levels in cooked animal foods. The richest sources of vitamin C are fresh fruits and vegetables.
Flavonoids are the most common group of antioxidants in plants. They are found in virtually all plant foods.
Many of the benefits of eating fruits and vegetables may be due to their flavonoid content. In fact, studies indicate that flavonoid-rich diets may have health benefits, such as:
- Reduced risk of heart disease (8, 9, 10).
- Improved brain health and function (11, 12).
- Better colon health (13, 14).
- Below is an overview of 4 common flavonoids, including their food sources and health benefits.
Quercetin is one of the most common flavonoids.
High intake of quercetin has been linked with lower blood pressure and a reduced risk of heart disease (15, 16, 17).
Quercetin is found in most plant foods, but rich dietary sources include capers, onions, cocoa, cranberries and apples. It is also available as a supplement (18, 19).
Catechins are a family of flavanols, the most abundant of which are (+)-catechin and epicatechin.
The health benefits of green tea catechins have been widely studied.
They have been linked to reduced blood pressure, improved blood vessel function and lower blood cholesterol (20, 21, 22).
Catechins are found in many fruits and beverages. Major sources include apricots, apples, pears, grapes, peaches, tea, cocoa and red wine (18, 23, 24).
Hesperidin is one the most common flavanones.
Studies indicate that hesperidin may help prevent heart disease and cancer. However, the evidence is mostly limited to studies in laboratory animals (19, 25).
Hesperidin is present almost exclusively in citrus fruits, especially oranges and lemons (26).
Cyanidin is the most widely distributed anthocyanin.
Anthocyanins are antioxidant pigments that are responsible for the bright colors of many fruits and vegetables.
Studies indicate that anthocyanins may reduce the risk of heart disease, but the evidence is still very limited (27).
Cyanidin is found in colorful fruits and vegetables. The richest food sources are dark-colored berries such as blackberries, black currants and black raspberries (28).
Bottom Line: Plant foods are rich in a diverse group of antioxidants called flavonoids. Common flavonoids include quercetin, catechins, hesperidin and cyanidin. Their intake has been associated with a variety of health benefits.
6-10: Dietary Fiber
The fiber found in plant foods is believed to be responsible for many of their health benefits.
Generally speaking, dietary fiber is defined as parts of plants that cannot be digested in the upper digestive system.
A high intake of fiber has been linked with many beneficial effects on health (29).
- Lower cholesterol (30).
- Reduced risk of heart disease (31).
- Decreased risk of constipation (32).
- Lower risk of colon cancer (33, 34).
- Increased feeling of fullness after a meal, promoting weight loss (35).
- Many kinds of fiber are also prebiotics, meaning that they are able to improve colon health by promoting the growth of beneficial bacteria (36, 37).
Below are 5 types of dietary fiber that have been shown to have health benefits in humans.
Beta-glucan is one of the most widely studied types of fiber.
It is a viscous fiber that has been linked with numerous health benefits.
As an effective prebiotic, beta-glucan ferments in the colon where it stimulates the growth of beneficial bifidobacteria. This can lead to improved colon health.
It may also lower blood pressure, reduce cholesterol and moderate the levels of blood sugar after meals (30, 38, 39, 40).
The richest sources of beta-glucan are the bran in oats and barley. Lower amounts of beta-glucan are found in other whole-grain cereals like sorghum, rye, wheat and rice.
Pectins are a family of prebiotic fibers found in fruits.
They come in various forms with different health effects (41).
Pectins may promote the growth of beneficial bacteria in the colon. They may also help ease chronic diarrhea and moderate blood sugar levels after meals (42, 43, 44).
Additionally, studies suggest that pectins may help prevent colon cancer (45, 46).
The main dietary sources of pectins are fruits, such as oranges, apples, plums, guavas, bananas and various berries.
Inulin belongs to a group of fibers known as fructans.
As prebiotic fibers, inulin and other fructans promote colon health by stimulating the growth of beneficial bifidobacteria (47, 48).
Studies indicate that diets high in inulin may relieve constipation (49, 50, 51).
However, some people experience side effects like flatulence and bloating (52, 53).
Inulin is found in various fruits and vegetables, including bananas, artichokes, asparagus, onions, garlic, leeks and chicory (54).
Unlike other dietary fibers, lignans are polyphenols rather than carbohydrates.
When they arrive in the colon, they are fermented by intestinal bacteria. This fermentation process turns them into phytoestrogens, which are subsequently absorbed into the bloodstream (55).
Phytoestrogens have been linked with several health benefits, including a reduced risk of heart disease and breast cancer (56, 57).
Lignans are found in most plant foods. The richest dietary sources are seeds (especially flaxseeds) and cereal grains (18, 58).
10. Resistant Starch
Starch is the most common carbohydrate in plants.
It is usually well-digested, but some of it may be resistant to digestion. This type of starch is called resistant starch.
Resistant starch promotes the growth of beneficial bacteria in the colon, improving colon health (59, 60).
Studies also indicate that resistant starch may increase the feeling of fullness and moderate the rise in blood sugar after meals (61, 62).
Resistant starch is found in various high-carb foods, including whole-grain cereals, pasta, legumes, unripe bananas, and potatoes that have been cooled down after cooking.
Bottom Line: Fiber may be responsible for many of the health benefits of plant foods. Important types of fiber include beta-glucan, pectin, inulin and resistant starch.
Take Home Message
A balanced diet rich in both plants and animal foods has many advantages.
Although a carnivorous diet can be healthy, it lacks many important nutrients that are specific to plants.