Micronutrients: to supplement, or not to supplement?

Tell a smoker to eat a carrot a day and he'll keep the doctor away, but give him regular beta-carotene supplements — the major antioxidant nutrient found in carrots — and you may increase his risk of developing lung cancer. Why? Doctors aren't entirely sure what the difference is between dietary intake and micronutrient supplementa-tion, but they do know that any diet – cancer association is far more complex than simply supplementing the diet with a few micronutrients. When a person ingests micronutrients as part of a natural everyday diet, he or she receives more than just a single nutrient. A slice of whole-grain bread, for example, might provide fi ber, iron, vitamin E, and folate. The body breaks down and uses all the micronutrients in the slice, which may interact in different biologic pathways and systems. Micronutrients ingested in supplement form are often pharmacologically or synthetically produced. People who ingest a tablet of vitamin E typically in-gest vitamin E in isolation, without the concommitant interactions of other nutrients. Supplement tablets or capsules often contain much higher doses than the level of micronutrients someone would receive in a typical day's diet. Scientists hypothesize that nutrients taken as supplements act differently or activate different biologic pathways in the body than nutrient intake as part of a natural diet. For instance , a certain micronutrient in isolation may have no ability to prevent metastasis, but when combined with other nutrients, it may form a compound that limits metastasis. Also, evidence would suggest that certain nutrients can be benefi cial as cancer preventives or for combating other health risks, but only at specifi c levels. Whereas 5 mg of beta-carotene might increase