Today, we know that the role of vitamins and minerals goes way beyond the prevention of deficiency diseases (维生素缺乏症) to actually preventing cancer and heart disease, the most fearsome killers of our time. With this knowledge has come the widespread call for nutritional supplementation (营养补充) — and a confusing group of vitamin, mineral, and supplements lining the supermarket shelves.

    Far from contributing to better health, however, nutritional supplements threaten to turn a scientific breakthrough into a nutritional disaster.

    Promoters of vitamins and minerals — especially vitamins A, C, and E— would have consumers believe that the little vitamin pill in the bottle is all they need for good health. Take your vitamins in the morning, and you're covered. It's okay to eat fast foods for the rest of the day or skip meals to achieve today's fashionably skinny look. But vitamins and minerals are only one part of the nutritional puzzle. A diet rich in fiber (纤维) and balanced in carbohydrates and protein is essential for good health. You can't get these things from a nutritional supplement. The focus on vitamin and mineral supplements may actually be robbing us of the full nutrition we seek.

    And no supplement can compare to the quality of nutrition found in natural sources. For example, our bodies turn carotenes (胡萝卜素) from plant foods into vitamin A. Many supplements contain a single carotene, but natural sources are rich in many different carotenes. Many supplements contain a form of vitamin E that is made from chemicals, when natural vitamin E is more readily absorbed and used by the body. And science is still discovering the wealth of nutrients in foods.

    You'd be hard-pressed to find a supplement as nutritionally comprehensive and powerful as a balanced diet. Even if you could, you'd pay much more than if you got the same nutritional value from natural sources.

    But perhaps the greatest danger presented by nutritional supplements comes from the very real risks presented by self-medication. Anyone can walk into the market and buy as many different supplements as desired. The reported benefits of high dosages of certain nutrients have led some people to believe that the more the better. Many take several vitamin and mineral supplements without regard to possible consequences.

    Surprising new research suggests that vitamin C pills may speed up hardening of the arteries, the underlying cause of heart attacks. Researchers said their findings support the recommendations of health organizations, which urge people to avoid high doses of supplements and to get their nutrients from food instead.

    As appealing as they're made to sound, nutritional supplements are danger in disguise. If you're looking for good health, don't look on the supplement shelves of your supermarket. Look in the produce section instead.

一、二班共有100名学生参加期末体育测试，两班的平均达标率为81%，其中一班的达标率为87.5%，二班的达标率为75%，设一班有学生x名，二班有学生y名，根据题意，可以得到方程组____．