Much of the marketing that is used to sell dietary supplements comes from the logic that if something has a favorable effect on your health, then it's base components must be the reason behind it all. Say for example, scientists and doctors notice that green and yellow vegetables help decrease your risk of cancer. And it just so happens that these same green and yellow vegetables also have high levels of beta-carotene. Does this mean that beta-carotene is the magic ingredient responsible for lowering your risk of cancer?
Not necessarily.
Going back to our green and yellow veggie example. Yes, it's true that there has been a noticeable inverse relationship between the consumption of vegetables high in beta-carotene and cancer. But studies focused on just beta-carotene supplements have been conflicted, with some concluding that the supplements had either no effect or a negative effect (1)(2)(3). So then what is it about these mysterious fruits and vegetables?
Whole Foods vs. Supplements
When you take a supplement, you're basically taking a purified form of an element, such as iron, vitamin D, or calcium. When you eat an apple or an onion, however, you're also ingesting thousands of phytochemicals (antioxidants are a form of phytochemical). Phytochemicals are bioactive non-nutrient plant compounds. It's estimated that more than 5,000 have been identified, but a large percentage still remain unknown to us (4). More and more evidence is surfacing in support of their effect on reducing cancer.
In a 1992, an epidemiological review of around 200 studies that examined the link between fruit and vegetable intake and cancers of the lung, colon, breast, cervix, esophagus, oral cavity, stomach, bladder, pancreas, and ovary was conducted (5). Block et al found that out of 156 dietary studies,128 showed that the consumption of fruit and vegetables had a significant protective effect. In addition, the risk of cancer for most cancer sites were twice as high in individuals with low intake of fruit and vegetables compared with those with high intake (5).
Manufacturing An Apple
Now you might be asking, why don't the pharmaceutical companies just manufacture a pill that contains these phytochemicals? They would if it were that simple. First off, phytochemicals come in all sizes, shapes, polarity, and solubility, which may in return affect the bioavailability and distribution to all the different cells, organs, and tissues in your body. It would be near impossible to mimic this sort of interaction and complexity in a pill, even if we did have a full understanding of what these thousands of phytochemicals are and how they interact with one another and your body. An apple might seem simple to you, but its chemistry and make-up are far more complex than you can imagine.
To further support fresh fruits and vegetables as a preventative treatment for cancer, a study of 9,959 men and women (age 15-99 years) in Finland showed an inverse relationship between the intake of flavonoids and the incidence of all combined sites of cancer (6). And in 2003, a article published in the American Journal of Clinical Nutrition proposed that "the additive and synergistic effects of phytochemicals in fruit and vegetables are responsible for their potent antioxidant and anticancer activities, and that the benefit of a diet rich in fruit and vegetables is attributed to the complex mixture of phytochemicals present in whole foods (7)." We might not know exactly how it works, but we know it works.
No Need To Worry About Dosing
When you take a supplement or multivitamin, dosing becomes very important. Even if something is good for you in small doses, a large dose may suddenly become toxic. But when you get your nutrients from food, it's unlikely any negative side effects will occur. At the moment, the naturally low levels of phytochemicals found in fruits and vegetables have a beneficial effect on humans, but what happens at higher doses? There is no set recommended dietary allowance (RDA) for phytochemicals at this point, and as such, It's unclear whether the effects of phytochemicals at high levels is effective or even safe (7).
Whole Foods: The Best Kind Of Multivitamin
Another way to look at fruits and vegetables is by considering them as Mother Nature's multivitamin, perfectly packaged and delicious. Instead of reaching for different bottles containing various nutrients, antioxidants, and vitamins, find a way to lead a balanced and healthy lifestyle full of fresh produce and a varied combination of fruits and vegetables. Sign up for a CSA box, go to a local farmer's market and talk to the people growing your food, and be adventurous. Never had a rutabaga before? It's never too late to try one.
If you have a history of cancer in your family or are going through treatment for cancer, it's absolutely imperative you get your nutrients and antioxidants from whole foods. It's also important to note that should you decide to use dietary supplements as a back-up, please clear it with your oncologist beforehand. Previous research has found that high levels of vitamin C can have pro-oxidant properties (35)!
Supplements can be a great gap-filler for those who find it impossible to eat a balanced diet or have certain medical conditions, but the best option for both cancer patients and healthy individuals is a diet full of fresh fruits and vegetables.
References:
1. Hennekens CH, Buring JE, Manson JE, et al. Lack of effect of long- term supplementation with beta-carotene on the incidence of malignant neoplasms and cardiovascular disease. N Engl J Med 1996;334: 1145-49.
2. Greenberg ER, Baron JA, Stukel TA, Stevens MM, Mandel JS. A clinical trial of beta-carotene to prevent basal cell and squamous cell cancers of the skin. N Engl J Med 1990;323:789-95.
3. The alpha-tocopherol, beta-carotene Cancer Prevention Study Group. The effect of vitamin E and beta-carotene on the incidence of lung cancer and other cancers in male smokers. N Engl J Med 1994;330: 1020-35
4. Shahidi F, Naczk M. Food phenolics: an overview. In: Shahidi F, Naczk M, eds. Food phenolics: sources, chemistry, effects, applica- tions. Lancaster, PA: Technomic Publishing Company Inc, 1995:1-5.
5. Block G, Patterson B, Subar A. Fruit, vegetables, and cancer preven- tion: a review of the epidemiological evidence. Nutr Cancer 1992; 18(1):1-29.
6. Knekt P, Jarvinen R, Seppanen R, et al. Dietary flavonoids and the risk of lung cancer and other malignant neoplasms. Am J Epidemiol 1997;146:223-30.
7. Liu, RH. Health benefits of fruit and vegetables are from additive and synergistic combinations of phytochemicals. Am J Clin Nutr 2003;78(suppl):517S-20S.
8. Podmore ID, Griffiths HR, Herbert KE, Mistry N, Mistry P, Lunec J. Vitamin C exhibits pro-oxidant properties. Nature 1998;392:559.