Carrots vs Capsules

“Eat your veggies!” You’d have a hard time finding someone who’s never been told this.  We all know that vegetables and fruit are healthy but most of us don’t really know why and aren’t getting the required amount.  Also, there is a notion that if you don’t like vegetables, you can use supplementation to accomplish the same goal. This idea comes from incorrect interpretation of research and although it’s a bit complex, it’s extremely important to understand. 

In the early years of nutritional science, it was discovered that there was a connection between an increased number of servings of fruits and vegetables and lower rates of chronic illnesses like cancer and heart disease.  Massive studies have shown incredible results such as a 44% reduction in cancer and 38% reduction in strokes when comparing  5+ fruit and veggie servings to 1 serving.  This was supported by the finding that patients with the highest blood levels of beta-carotene (a form of vitamin A and an antioxidant) had a 60% lower cancer risks compared to those with the lowest blood levels.  At the same time these benefits were first seen, scientists studying chronic diseases began to understand that oxidation plays a role in disease cause and progression.  This led to the conclusion that the antioxidants in the fruits and vegetables were the “active ingredient” producing the protective health benefits. 

Based on this reductionist perspective, all we need to do to stay healthy is supplement with antioxidants.  Research attempted to prove this by creating large studies in which people were given antioxidant supplements such as beta-carotene, vitamin A and vitamin E.  However, no benefit was seen in these studies and surprisingly, negative outcomes were produced when large doses of these vitamins were given to certain patient populations.  

So how can this be?  Eating fruits and vegetables lowers the risk of disease, and having high blood levels of antioxidants is protective but supplementing with these nutrients shows no benefit and sometimes harm! It took a few more years before researchers identified a possible explanation.  When we measure antioxidant levels in the blood of people who do not take supplements, the antioxidant is acting as a marker for vegetable and fruit intake.  Higher blood levels reflect higher intake of fruits and vegetables.  As a result, the benefits associated with high blood levels of antioxidants can not necessarily be credited to the antioxidants themselves but rather the fruits and vegetables that the antioxidants came from!

In addition to antioxidants, fruits and vegetables provide fibre, a vast range of vitamins and minerals and plant-based compounds called “bioflavonoids” –many of which have not yet been discovered or fully understood.   When we look at the blueberry, we find that vitamin C contributes only 2% of the antioxidant capacity of the fruit. Some of the molecules contributing to the remaining percentage have been identified but others have not, and thus certainly are not present in even the best multivitamin.    

So if you thought that instead of the effort of preparing and eating vegetables you could pop a supplement and get the same benefit, unfortunately this is not the case.  Supplementation can be extremely helpful in the treatment and prevention of illness however it should be done under the supervision of a health care provider who is knowledgeable in the risks and benefits and it certainly should not be a use as a rationale for passing on the kale salad!  Looks like Mom was right all along when she told you to eat your veggies.

References:

Jansen, M.C., Bueno-de-Mesquita, H.B., Feskens, E.J., Streppel, M.T., Kok, F.J. & Kromhout, D. (2004). Quantity and variety of fruit and vegetable consumption and cancer risk. Nutr Cancer, 48(2), 142-8.

Overvad, K., Stripp, C., Tjønneland, A., Husted, S.E. & Sørensen., H.T. (2003). Intake of fruit and vegetables and the risk of ischemic stroke in a cohort of Danish men and women. Am J Clin Nutr, 78(1), 57-64.

Stähelin, H.B., Gey, K.F., Eichholzer, M. & Lüdin, E .(1991). Beta-carotene and cancer prevention: the Basel Study. Am J Clin Nutr, 53(1 Suppl), 265S-269S.

Hennekens, C.H.,  Buring, J.E., Manson, J.E., Stampfer, M., Rosner, B., Cook, N.R., Belanger, C., LaMotte, F., Gaziano, J.M., Ridker, P.M., Willett, W., & Peto, R. (1996). Lack of Effect of Long-Term Supplementation with Beta Carotene on the Incidence of Malignant Neoplasms and Cardiovascular Disease. N Engl J Med, 334, 1145-1149.

The Alpha-Tocopherol Beta Carotene Cancer Prevention Study Group. (1994). The Effect of Vitamin E and Beta Carotene on the Incidence of Lung Cancer and Other Cancers in Male Smokers. N Engl J Med, 330, 1029-1035.