The body uses an elaborate system of compounds that act cooperatively to protect body cells from free radical-initiated damage. This is known as the antioxidant defense system. Each one works at different points dealing with different reactive molecules. This system includes enzymes, (dependent upon specific minerals for their action), vitamins (vitamin E, C) as well as non-enzymatic compounds such as glutathione and several phytochemicals.

Free radicals are molecules that attack other molecules, such as those in our DNA or in the cell membrane. Damage by free radicals may be involved in the development of heart disease and cancer.

The relationship between food and health is complex. By replacing foods with supplements, beneficial food components and important interactions between food components may be lost. It is important to recognize, however, that eating a well-balanced diet is not always feasible. The Dietary Guidelines, 2005, acknowledges that although consumption of a balanced diet is critical, use of dietary supplements is warranted when nutrients are not or can not be consumed in adequate amounts. The recommendations for specific populations are as follows:

1. Individuals over 50: Consumption of Vitamin B12 in fortified foods or as a supplement (2.4 μg/ day from fortified food and/or supplements)
2. Women who may become pregnant: Consumption of iron fortified foods with an enhancer such as vitamin C (27 mg/ day)
3. Women who may become pregnant or are in their first trimester of pregnancy: Consumption of folic acid from fortified foods or supplements (400 μg/ day synthetic folic acid from fortified food and/or supplements)
4. Older individuals and those with dark skin: Consumption of vitamin D in fortified foods or supplements (25 μg/ day from fortified food and/or supplements).

Phytochemicals are a large group of plant-derived compounds hypothesized to be responsible for much of the disease protection conferred from diets high in fruits, vegetables, beans, cereals, and plant based beverages such as tea and wine.

Consumption of chocolate or cocoa has been associated with a variety of cardiovascular benefits. In one recent investigation, consumption of approximately 30 kcals of dark chocolate daily for eighteen weeks was associated with decreased blood pressure. However, calories from chocolate are still classified as "discretionary" (added fats and sugars) by the Dietary Guidelines for Americans 2005. These findings suggest that in light of current chocolate research, it may be beneficial to include a small piece of dark chocolate (equal to 30 kcals) as part of your daily diet.

Trans fats are unsaturated fatty acids that are used commercially in foods. They are made from regular cooking oils, such as soy oil, but they have been chemically changed to be more shelf-stable, and be able to withstand high cooking temperatures, such as those used in deep-frying. This change in chemical structure also has resulted in trans fats having negative health effects. Trans fats have been shown to lower high-density lipoprotein (HDL) cholesterol, aka "good" cholesterol, and raise low-density lipoprotein (LDL) cholesterol, aka "bad" cholesterol. As a result, they can raise a person´s risk for heart disease.

Fish is a good source of protein, and fatty fish like salmon contain high amounts of omega-3 fatty acids. These kinds of fatty acids have been found to have a protective effect against heart disease. The American Heart Association recommends eating fish, particularly fatty fish at least twice a week to reduce risk of developing heart disease. However, some species of fish are high in mercury. Mercury can damage developing fetuses and children. For this reason, women who are pregnant or of childbearing age, and children under 18 should never eat swordfish, golden bass, king mackerel, or shark. They should also limit the amount of albacore tuna and tuna steaks or fillets to no more than 6 ounces per week.

Energy drinks are beverages containing caffeine in combination with other ingredients. The caffeine content of a single serving ranges from 72 to 150 mg; however, many bottles contain 2 to 3 servings, raising the caffeine content to as high as 294 mg per bottle. In comparison, the caffeine content per serving of brewed coffee, tea, and cola ranges from 22 to 240 mg. Healthy adults can consume up to 400 mg of caffeine daily; however, women of reproductive age, adolescents, and children should limit their daily consumption of caffeine and consumption of energy drinks by these groups is not recommended. Caution is warranted even for healthy adults. Consumption of two or more energy drinks a day may lead to excessive caffeine intake and other stimulants such as guarana and ginseng are often added to energy beverages and can enhance the effects of caffeine. Adverse effects associated with excessive caffeine consumption include nervousness, irritability, sleeplessness, increased urination, abnormal heart rhythms (arrhythmia), decreased bone levels, and stomach upset.