We often hear about vitamin A and visual health, and immediately think about carrots. But there’s a lot more about vitamin A we usually don’t know.
People usually don’t understand what a carotenoid is and how it relates to vitamin A. And even if you do, did you know about the role they have in reducing prostate cancer risk?
In this article, we’re exploring carotenoids, a type of molecule with impressive health potential.
What are Carotenoids?
Most plants and fruits have bright colors, and carotenoids are usually the cause. They are plant pigments that give a natural reddish or yellowish hue to fresh foods. For plants, carotenoids are essential to protect themselves against free radicals. We can say that these substances behave similarly to our immune system.
In the nutritional field, most carotenoids are not considered vitamins. However, some of them convert into vitamin A. They are phytonutrients or plant chemicals, and deactivate free radicals that naturally form during photosynthesis. They work against reactive oxygen species, which are single and uneven oxygen molecules.
This type of singlet oxygen (two oxygen atoms with a double bond) reacts against normal tissue and cause significant damage. But when they react against carotenoids, they prevent oxidative stress.
These substances have 9 or more conjugated double bonds. They are useful to share electrons and neutralize free radicals. This happens in plants and the human body. That’s why they are linked to strong anti-cancer effects.
By countering the effects of free radicals, it prevents oxidative damage to the DNA. Without DNA damage, the risk of cancer is significantly reduced. Moreover, carotenoids are powerful anti-inflammatories and contribute to the immune system.
We cannot create carotenoids. Thus, the only way to get their benefits is through the diet. These substances are fat-soluble, so it is better to consume them along with fats. Before they are absorbed, they need to separate from plant tissues and become a part of a fatty structure in the gut called micelle (1).
Types of Carotenoids
From what we know, there are around 600 different carotenoids. We have studied the most common: beta-carotene, alpha-carotene, lutein, lycopene, and zeaxanthin. They are divided as a group into two subgroups:
- Carotenes: These are hydrocarbons and give an orange color to our food. They contain mostly hydrogen and carbon atoms. No oxygen.
- Xanthophyll carotenoids: They contain oxygen in the chemical formula and have a yellowish color.
We can also divide carotenoids into two groups, depending on whether or not they convert into vitamin A. Provitamin A carotenoid convert into vitamin A in the liver or intestines. They are essential for the macular pigment inside the eye and contribute to our vision.
Additionally, they are useful in maintaining healthy mucosal membranes in many tissues. Provitamin A carotenoids include beta-carotene, alpha-carotene, and beta-cryptoxanthin.
Other popular carotenoids such as lycopene, lutein, and zeaxanthin do not convert into vitamin A.
Here’s an overview of the most important members of the carotenoid family:
- Lutein and zeaxanthin: These are perhaps the most important for eye health. They are found in the macula lutea, a part of the retina fundamental for clear sight. It also protects the retina from damage by blue light. That’s why it has been related to preventing age-related macular degeneration. Additionally, it lowers cholesterol levels and reduces the risk of heart attack (2). We can find lutein and zeaxanthin in green leafy vegetables, pumpkin, and enriched eggs. Lutein and zeaxanthin from enriched eggs are absorbed more rapidly than others (3).
- Beta-cryptoxanthin: This is a provitamin A found in mango, papaya, and orange. It is a yellow pigment in egg yolks and butter, too. It is a powerful antioxidant and has been found beneficial to prevent cancer. Most studies about beta-cryptoxanthin focus on lung cancer prevention (4). Others also suggest it is a potent anti-inflammatory for rheumatoid arthritis (5).
- Beta-carotene: One of the most popular provitamins, A carotenoids. It creates more vitamin A than beta-cryptoxanthin and is considered more powerful. But surprisingly, it sometimes increases lung cancer risk instead of reducing it. Thus, as a supplement, it is not recommended for smokers. In the diet, it won’t cause this effect, though. It is useful against sunburns and lowers the risk of metabolic syndrome (6,7).
- Alpha-carotene: It is also a provitamin A, but has around half the potential compared to beta-carotene. It apparently has a potential benefit for longevity. High levels in the blood are associated with a lower risk of death by cancer, cardiovascular disease, and others. It is found in tomatoes, carrots, turnips, and pumpkins (8).
- Lycopene: This pigment is bright red, typically found in tomatoes, but also watermelons and guavas. It is a powerful antioxidant, and one of the best at deactivating singlet oxygen. It is associated with a reduction in prostate cancer risk, as discussed below (9).
- Astaxanthin: Astaxanthin is a very special carotenoid with many commercial applications. This is a metabolite created by photosynthetic bacterium organisms, yeasts, and algae. The most common source is a microalga by the name Haematococcus Pluvialis. It is very useful for skin health, skin repair, cardiovascular disease, and much more (10).
Can Carotenoids Reduce the Risk of Prostate Cancer?
As mentioned above, lycopene is by far the most important carotenoid for prostate cancer. It can be found in a variety of tissues, including the eye and the prostate. The best source is tomato and tomato-based products. They should be cooked in order to improve absorption.
According to studies, men with higher levels of plasma carotenoid have a lower risk of prostate cancer. Treating high-risk men with supplements may also contribute to lower their risk.
However, it is not a good idea for smokers and patients with a high risk of lung cancer. In these patients, dietary sources work the same and will be safer for them.
A study made with tomato products found out that they do lower the risk impressively. The investigators reported that 10 servings a week or more decreased prostate cancer risk by 35%.
The authors made relations with olive oil, fruit, and vegetable intake and found out that the relationship is independent of any other dietary modification. In other words, it doesn’t matter if you eat anything else. Independently, you will experience a 35% risk reduction by eating plenty of tomato-based products.
Other studies report similar findings, which range somewhere between 25 and 80% of decreased risk. Even if you don’t consume 10 servings of tomatoes every week, you still have benefits.
However, you will have a 10-20% additional risk reduction by increasing your intake. In any case, it is great news for males who want to maintain excellent prostate health. As a general recommendation, we should eat more cooked tomatoes. Raw tomatoes do have a significant effect, too. But a stronger effect can be found with cooked sources (11).
However, if you look at the evidence very closely, you will realize it is a bit outdated. The majority of the studies mentioned above are dated before 2010. Current data still shows that consuming tomato products may contribute to a lower risk of prostate cancer. However, the numbers are not as bit as big as 35%.
These studies are made with robust epidemiologic tools. Others are pooled analysis of the scientific data. And they report that the effect is around 1% risk reduction for every 2mg of lycopene.
There is definitely an association between lycopene and prostate cancer. However, patients with ongoing prostate cancer won’t likely benefit as much. Lycopene does not protect against prostate cancer’s aggressiveness. According to studies, it won’t make prostate cancer less aggressive or cure prostate cancer (12).
Further Health benefits of Carotenoids?
Carotenoids are not only useful to prevent prostate cancer. They are applicable to many aspects of human health. We can highlight these additional benefits:
- Visual health: It is actually one of the major benefits of carotenoids. They reduce the risk of age-related macular degeneration. For this purpose, we can use dietary sources of carotenoid supplements. Appropriate carotenoids for visual health include lutein, beta-carotene, and zeaxanthin. They have powerful antioxidant properties and reduce the incidence of eye disease (13).
- Cardiovascular health: Carotenoids are excellent antioxidants. As such, they reduce the incidence of atherosclerosis. This is a slow buildup of solid plaques made out of fatty acids in the arterial walls. They narrow the blood vessels and compromise blood flow. Carotenoids apparently improve hypertension and glucose intolerance, which also contribute to cardiovascular health problems. The best moment to use carotenoids for cardiovascular disease is before experiencing symptoms. After heart disease is advanced and atherosclerosis progresses, carotenoids will not have the same protective features. It should be consumed over a long period of time to take effect. They are protective but do not have a therapeutic role for cardiovascular health (14).
- Skin aging and sunlight damage: Carotenoids protect plants from UV rays. Similarly, these carotenoid molecules can be stored in the skin and prevent skin damage. The best carotenoids for skincare include beta-carotene and lycopene. They provide the best rate of skin protection. It does not matter if they come from supplement of dietary sources; they will do the work. They are also very useful in preventing skin redness and other effects of sunlight damage. They reduce wrinkling and skin aging due to UV rays and work even better when combined with vitamin E (14).
- Cancer protection: Besides prostate cancer, carotenoids have been associated with protection against other types of cancer. For example, it has been shown to inhibit breast cancer and reduce breast cancer risk (15). It is also useful to prevent skin cancer and pre-cancer lesions. What it does in these cases is stimulating cell differentiation and modulating programmed cell death. They are actually very good at inducing apoptosis in skin melanoma cells (14).
- Bone health: Carotenoids have a positive effect on your bone structure and health. This is particularly true with lycopene, which protects the structure of the bone and prevents musculoskeletal disease. Beta-cryptoxanthin and beta-carotenes are also associated with significant benefits. They strengthen bone tissue and to avoid mineralization problems, such as osteopenia (16).
- Brain health: According to studies, consuming beta-carotene sources over a long period of time may protect against certain brain health problems. Supplementation or dietary sources protect our cognitive function. They prevent mental health decline associated with aging (17).
- Immunity boost: Vitamin A and carotenoids are important for the immune function. A deficiency causes significant immune problems, especially in the elderly (14).
Foods containing carotenoids
We can always use a dietary supplement with carotenoids. However, they are not always as effective as natural carotenoids.
Dietary intake with a high carotenoid content has a higher chance of providing the benefits described above. And there are many sources you can use to increase your carotenoid intake.
Here’s a list of high-carotenoid foods for your next visit to the grocery store:
- Carrots: They deserve the number one on the list because most of us know carrots have vitamin A and carotenoids. Half a cup of carrots has around 3000 mcg of alpha-carotene and 6500 mcg of beta-carotene. In the form of carrot juice, you get up to 10,000 mcg of alpha-carotene, 22,000 mcg of beta-carotene, and 800 mcg of lutein and zeaxanthin for each cup. They taste great in salads, soups, or as a side dish in a stew with beans and meat.
- Pumpkins: Whenever available, consider adding pumpkins to your diet. Either smashed or boiled, pumpkins are excellent sources of carotenes. 1 cup has around 6500 mcg of alpha-carotene, 5000 mcg of beta-carotene, and 2500 mcg of lutein and zeaxanthin. In a pumpkin pie, you would be consuming near 7500 mcg of beta-carotene per slice.
- Green leafy vegetables are not yellow because they have too much chlorophyll, but are abundant in dietary carotenoids. Green leafy vegetables are an excellent source of lutein, especially spinach, collards, and kale. For example, half a cup of boiled spinach can give you around 15,000 mcg of lutein and zeaxanthin and almost 7,000 mcg of beta carotenes.
- Tomatoes: They are by far the best source of lycopene. This individual carotenoid is better absorbed in cooked and processed tomatoes. 1 cup of tomato puree contains 54,000 mcg of lycopene. Tomato juice can give you up to 22,000 mcg of lycopene for each cup. And even tomato ketchup has its share of lycopene (around 2,000 mcg per tablespoon).
- Sweet potatoes: They taste very good in curries or make chips or mashed sweet potatoes. Either way, you will get a lot of beta-carotene. One medium sweet potato is expected to have around 14,000 mcg of beta-carotene.
- Red peppers: These peppers have a vibrant orange or red color because they are filled with carotenoids. You can get up to 2,000 mcg of beta-carotene and 600 mcg of beta-cryptoxanthin for each cup of boiled red peppers.
- Watermelon: This fruit is very tasty and has a lot of water content, but also a lot of carotenoids. One cup of raw watermelon can give you around 7,000 mcg of lycopene and 467 mcg of beta-carotene. You can eat it as it is or adds it to your salad. It is a great choice if you’re also trying to lose some weight.
- Orange: Naturally, oranges and citrus fruits are also a good source of carotenoids. We can have a cup of orange juice, which delivers 400 mcg of beta-cryptoxanthin and 300 mcg of lutein and zeaxanthin. Or maybe a medium orange, which has a bit less carotenoid, but more fiber content.
Carotenoids are essential substances found in plants. They protect plants from environmental threats and UV rays. They also have powerful antioxidant properties and work the same way in the human body.
Circulating carotenoids have significant health benefits. For example, they are associated with a reduction in cardiovascular risk. They are also very important for eye health. But one of the most attractive features in men is a reduction in prostate cancer risk.
According to classic studies about carotenoids, prostate cancer risk reduction can be as high as 35%. More recent studies show that carotenoid supplements and dietary sources have a discreet benefit of 1% risk reduction for every 2 mg of carotenoids.
In any case, carotenoids can give us significant benefits and protection against prostate cancer. They are also related to significant improvements in visual function, immunity, bone health, and much more.