Given the interest that my post on diet and cancer seemed to generate, I decided I’d go into a little more detail about the micronutrients in our foods and how they might reduce cancer risk. I use the word “might” because although the studies show a probable risk reduction, we still can’t confidently say “yes, it is THIS specific compound that makes this food lower cancer risk”. Apart from anything else, each food contains a complex myriad of different elements, which may all play their own part in risk reduction, either on their own or working together.
You can listen to the audio version here:
These are fat-soluble red/orange pigments, including beta-carotene and lycopene that I talked about recently here, that are important for our bodies in making vitamin A. There are more than 600 different carotenoids, but only 50 or so that we consume in our diets. And only around half of them can be absorbed.
Dietary carotenoids come from things like spinach, kale, butternut squash (a particular favorite of mine), pumpkin (how timely, with Halloween just around the corner!), red bell peppers, carrots, tomatoes, cantaloupe melon and sweet potatoes. As a general rule of thumb, the more intense the color of a fruit or vegetable, the more carotenoids it contains.
These carotenoids have antioxidant properties, which is presumed to be the reason behind their anti-cancer effects. How do they work? Well, they are very efficient at quenching reactive oxygen species (ROS), which are naturally occurring chemically reactive molecules that contain oxygen and are a natural byproduct of many metabolic processes that use oxygen.
Our bodies have many built-in protective mechanisms to mop up these reactive molecules before they can cause any damage, but certain environmental stressors can cause a significant rise in ROS levels. This can cause damage to structures within the cell, including our DNA, and is known as oxidative stress.
Although we don’t fully understand the mechanism, it appears that anti-oxidants work by quenching these reactive molecules. It’s a bit like giving a hyperactive child a “calm-down” jar – anti-oxidants effectively reduce the amount of energy that ROS molecules contain by stabilizing their charged status.
The B-vitamin folate is essential for human health, so much so that the synthetic form, folic acid, is often used to fortify manufactured cereal products, spreads, flour or grains. Pregnant women are also recommended to take folic acid supplements as soon as they find out they are expecting because of the severe effects of folate deficiency in embryogenesis. Dietary sources of folate include liver, beans, spinach, broccoli, romaine lettuce, chicory, oranges and papaya.
Folates are important for synthesizing new DNA building blocks during cell growth and division, and repairing damaged DNA as well. It is thought that this may be the reason behind its anti-cancer properties.
Also known as ascorbic acid, vitamin C is a water-soluble vitamin that we human beings cannot make ourselves, and so it is essential that we are getting it in our diets. This vitamin is needed for making a protein called collagen, which is a key component of our skin, blood vessels, bones and connective tissues. Severe vitamin C deficiency causes scurvy – a relatively rare disease in the modern world that is characterized by loosening of teeth, bleeding gums, weakened bones and impaired wound healing.
Natural dietary sources of vitamin C include red and yellow bell peppers, kiwi fruits, broccoli, papaya, citrus fruits, strawberries and potatoes, but interestingly, it is destroyed by heat and air, so it is lost when vegetables are chopped or cooked.
The anti-cancer properties of vitamin C are thought to be through its anti-oxidant activity, and in fact it is often added to foods in small amounts as an anti-oxidant preservative.
Another potent anti-oxidant is the fat-soluble vitamin E, also known as tocopherol, which can exist in 8 different forms. Alpha- and gamma-tocopherol are the most common forms, and can be found in vegetable oils such as palm, sunflower, corn, soya bean and olive oils, as well in nuts, sunflower seeds, wholegrains, fish and green leafy vegetables.
Pyridoxine is a water-soluble compound that, together with a group of other compounds, makes up vitamin B6. Vitamin B6 is required for making neurotransmitters – the tiny chemical signals released by neurons in our brains to communicate with other parts of the body. It is also needed for making red blood cells, for making another B vitamin called niacin (vitamin B3), for our steroid hormones to work properly, and for making new molecules of DNA during cell growth and division. It is this latter function, DNA synthesis, that is likely to be at the heart of pyridoxine’s anti-cancer properties.
Dietary sources include bananas (I’m actually eating one now as I type!), fish, poultry, liver, potatoes (with the skin on!), leafy green vegetables, beans, pulses, nuts and wholegrains.
Quercetin is a flavonoid, which is a type of polyphenol – without getting too deep into the biochemistry, this basically means it’s a compound with multiple (“poly”) ring-like structures (phenols are rings of carbon molecules bound together).
Although it is not an essential dietary component, many studies (in cells cultured in the lab or in animals, but not yet in humans) suggest that quercetin has anti-oxidant activity which may reduce inflammation (a known cause of cancer).
Dietary sources include apples, green and black tea, onions, raspberries, red wine, red grapes, citrus fruits, leafy green veg, cherries, elderberries, broccoli, blueberries, cranberries and bilberries.
Do you remember I talked briefly about the conflicting studies regarding selenium supplements and cancer risk? Those with low levels of selenium benefited from supplementation by reducing their risk of lung cancer, but those with already normal levels of selenium in their blood saw a slightly increased cancer risk as a result of selenium supplementation.
Selenium is a mineral that is toxic in large quantities but is an essential part of our diets at trace levels. It is present in the soil and taken up by the plants and vegetables we consume. Selenium is a component of some amino acids – the building blocks of the proteins in our bodies – and these selenium-containing amino acids are integrated to form selenoproteins.
Among the selenoproteins that we make are important anti-oxidant enzymes, such as glutathione peroxidases and thioredoxin reductase. Enzymes are specialized proteins that speed up the rate of a reaction, and these particular enzymes are important for DNA synthesis and prevent oxidative injury.
Dietary sources of selenium include brazil nuts, fish, wholegrains, wheatgerm and sunflower seeds.
The bottom line
The more I research this subject area, the more I’m seeing the importance of plant-based foods in our diet, but I’m also noting the presence of fish and poultry on the list of dietary sources of potentially anti-cancer micronutrients.
Interestingly, I came across a page on Cancer Research UK’s website this morning about going vegetarian or vegan for the month of November. I’ve decided to take part in the challenge myself. If anyone fancies joining me, then tag me on social media (@essentialcancereducation on Facebook and Instagram, @mhairimorris on Twitter, and Mhairi (“Vari”) Morris on LinkedIn) and use the hashtag: #VegPledge.
Once again, a wee reminder that October is Breast Cancer Awareness month. I would love it if you could share this post on social media and tag me (as above). The more we can spread the word about making the best possible choices in terms of our own health, the more we can hope to reduce cancer incidence in the future.
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