Our bodies synthesize many important compounds that maintain our health and bodily functions. Other equally important compounds are not produced endogenously (inside the body) but must be obtained from the foods we eat.
Today we'll look at a class of compounds that are naturally synthesized by plants and are essential to our health: carotenoids. This group of polyphenolic phytochemicals consists of the more than 750 naturally occurring pigments that give plants their yellow, orange, and red colors.
When absorbed by our digestive system, these powerful antioxidants support bone health, eye health, and more. After a review of the science behind carotenoids' incredible abilities, you'll get a recipe designed to maximize their bioavailability.
Carotenoids: An Overview
The human diet contains about 40-50 carotenoids, all of which are found in fruits and vegetables. While carotenoids are pigments that give plants their red, orange, and yellow color, there are also green vegetables that contain carotenoids, such as kale and spinach. But carotenoids are most famously found in warm-colored foods like papaya, sweet potatoes, watermelon, and carrots. In fact, the word carotene comes from the Latin word for carrot.
The two major chemical groups of carotenoids are carotenes and xanthophylls. Xanthophylls contain oxygen and carotenes are hydrocarbons that do not contain oxygen. Because their chemical composition causes them to absorb different wavelengths of light, xanthophylls are more yellow, while carotenes are more orange.1
Nutritionally, carotenoids are grouped in provitamin A carotenoids (α-carotene, β-carotene, and β-cryptoxanthin) that the human body can use to synthesize Vitamin A, and non-provitamin A (lutein, zeaxanthin, and lycopene) which cannot be used to produce Vitamin A. Non-provitamin A carotenoids aren't any less important though; they offer other unique health benefits.
Beta-carotene (β-carotene) is the most well-known carotene, likely because it is the carotene that the body most effectively turns into Vitamin A. Studies have associated beta-carotene with a reduced risk of metabolic disease, lung cancer, and sunburn.2,3 Studies have also found that beta-carotene supplements can increase the risk of lung cancer in smokers.4 Cantaloupe, mangoes, sweet potatoes, spinach, kale, papaya, carrots, and pumpkin are good sources of beta-carotene.
Alpha-carotene (α-carotene) is less effective than beta-carotene for Vitamin A production, but research has linked this compound to longevity, specifically via reductions in cancer and cardiovascular disease.5 Good sources of alpha-carotene include pumpkin, collards, tangerines, carrots, tomatoes, winter squash, and peas.
Lycopene is most famously found in tomatoes and is responsible for their bright red color. Lycopene is a potent antioxidant, and research has linked high lycopene levels to reduced rates of hip fracture.6 Other studies have found that post-menopausal women who increased their lycopene intake reduced their rate of bone-resorption- helping them to maintain bone mass.7 Lycopene is also found in watermelons, guavas, grapefruit, papaya, red cabbage, red bell peppers, carrots, asparagus, and parsley.
Lutein and zeaxanthin are closely linked to eye health and good vision. Both carotenoids are found in the retina where they play a protective role. Research has uncovered that these compounds reduce the risk of age-related macular degeneration as well as cataracts and decrease light sensitivity.8 Good sources include kale, spinach, turnip greens, paprika, summer squash, pumpkin, yellow-fleshed fruits, and avocadoes.
Beta-cryptoxanthin (β-cryptoxanthin) is a provitamin A xanthophyll carotenoid that studies have linked to reductions in lung cancer incidence.9 The compound is also a powerful antioxidant that reduces chronic inflammation. Researchers found that people who developed inflammatory polyarthritis (which includes rheumatoid arthritis) had 40 percent less beta-cryptoxanthin than those who did not. Even a modest increase in beta-cryptoxanthin intake, the amount present in about half a papaya, can help reduce inflammation and prevent arthritis.10 Papaya, mango, watermelon, corn, bell peppers, and oranges are good sources of beta-cryptoxanthin.
Carotenoids, all of which are powerful antioxidants, are found in a variety of forms that have different effects on the body. Some are utilized to produce Vitamin A and others are not, but the major carotenoids all provide substantial health benefits and are found in a variety of fruits and vegetables.
Health Benefits of Carotenoids
Clearly, carotenoids offer a whole lot of health benefits. The most well-documented health perks are:
- Fracture prevention
- Reduced bone-loss
- Improved eyesight
- Reduced light sensitivity
- Preventing macular degeneration
- Preventing arthritis
- Reduced inflammation
- Cancer prevention
- Preventing cardiovascular disease
- Reduced oxidative damage (antioxidant)
Bone Health Benefits of Carotenoids
The substantial bone-building benefits of carotenoids are attributed to the fact that they are powerful antioxidants that protect bone and the cells responsible for bone remodeling from oxidative damage. 11
Beta-cryptoxanthin has been shown to reduce bone-damaging inflammation.10
Lycopene was found to reduce hip fracture rates in a 17-year study that included 576 women, while other carotenoids were not associated with a change in fracture risk.6 This study supports the finding that lycopene reduces bone-loss and oxidative stress while it increases antioxidant levels.7
The improvements in eyesight and prevention of age-related macular degeneration found with lutein and zeaxanthin consumption protect bone health by preventing falls and accidents.8 Reduced eyesight directly correlates with an increase in falls and fracture, so anything that protects your vision also protects your bones.12
By reducing inflammation, decreasing oxidative damage and bone loss, and protecting eyesight, carotenoids strengthen your bones.
Increasing Bioavailability Of Carotenoids
Bioavailability describes the extent to which your body is able to absorb and use the nutritional content of the food you eat. While many fruits and vegetables are rich in carotenoids, that doesn't mean that your digestive system is able to absorb them well.
By using different food preparation techniques, or by combining certain foods, you can increase the bioavailability of many compounds. Studies have shown that there are easy ways to increase the bioavailability of carotenoids:13
- Food processing (cutting, chopping, dicing, blending) makes carotenoids more bioavailable
- Heat (cooking, grilling, baking) similarly releases carotenoids for better absorption
- The body requires fats to absorb carotenoids (as little as 3 to 5 grams is enough)
- Olive oil has been found to be optimally effective among vegetable oils at enhancing intestinal accessibility of carotenoids1
Increase your body's ability to absorb the carotenoids found in fruits and vegetables through food processing, cooking, and pairing with fats. Olive oil is a particularly effective vehicle for the absorption of carotenoids.
A Bioavailable Carotenoid-Packed Summer Treat
This recipe is perfect for any summer BBQ or cookout. Not only does it provide a bone-healthy, alkalizing vegetarian option that’s delicious, but it has been designed to maximize the bioavailability of the carotenoids contained in its colorful ingredients.
Servings: 6 skewers
- 1 large sweet potato, peeled and cut into large pieces
- 6 carrots, peeled and sliced thick
- 1 medium red bell pepper, chopped into large pieces
- 3 summer squash, sliced thick
- 2 cups cherry tomatoes
- 1 cup whole mushrooms
- 1 to 2 tablespoons olive oil
- Pinch of sea salt and black pepper
- Preheat oven to medium/high broil or turn grill on.
- Place the sweet potato and carrots in a large pot, cover with water, and boil for about 10 minutes or until almost tender and firm enough to stay on a skewer. Drain the water and allow to cool a bit.
- Add the vegetables in layers to the skewers, leaving enough space at both ends to allow for easy flipping. Brush with olive oil and sprinkle lightly with sea salt and black pepper.
- Broil or grill until vegetables are tender and grill marks are visible – about 10-15 minutes. Flip once halfway, and make sure they’re not overcooked.
Have A Bone-Building Summer (And Winter, And Fall, And Spring!)
Carotenoids are found in seasonal fruits and vegetables available year round. It's easy to tell whether your meal contains carotenoids because they announce themselves with a splash of warm color.
There's no need to count anything or take measurements. You can use the same method you use to ensure your meals are 80/20 pH-balanced: just look at your plate! Your eyes can tell you whether you're eating the colorful fruits and vegetables that are part of a carotenoid-rich, bone-building, life-giving diet.
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