Twenty five years ago, It was largely assumed that health benefits came from the vitamin and mineral content of fruits and vegetables. That conclusion turned out to be incorrect because supplementation with specific vitamins and minerals failed to yield the same health benefits as did diets rich in fruits and vegetables. In addition, use of individual vitamin and mineral supplements was found to increase health risks in some studies, but not all. So, what else is in our foods?
Now nutrition and other scientists are investigating the effects of thousands of other substances in food on health. The subjects of many current studies are plant chemicals known as phytochemicals or phytonutrients. Phytochemicals are not considered essential nutrients because deficiency diseases do not develop when we fail to consume them. They are considered to be nutrients however because they are biologically active and perform health promoting functions in the body. Most bioactive food constituents are derived from plants.
Phytochemicals play a variety of roles for plants as they provide protection for the plant against bacterial, viral, and fungal infections; ward off insects; and prevent tissue damage due to oxidation. Some operate as plant hormones or participate in the regulation of gene function, while others provide plants with flavor and color.
More than 2000 types of phytochemicals, that act as pigments, have been identified and give plants a wide variety of colors. Some of these phytochemicals have been identified: beta-carotene (orange), lycopene (red), anthocyanins (blue to purple), allicin (white), and lutein (yellow-green). Many of them function as antioxidants in the human body as well as help us to fight against many chronic diseases in other ways.
The following are examples of vegetables you can buy or plant in the garden (organic not necessary) that provide some specific human health benefits that are thought to be due to either established nutrients or phytochemicals. Keep in mind that some have more research behind their claims; however, many do not and simply rely on presumed health benefits.
- Kale is a member of the cabbage family and is known to contain vitamins A, K, and C, as well as essential minerals like potassium, calcium, and magnesium. It is also rich in fiber and acts as a prebiotic that increases nutrient absorption in the gut. Kale also contains antioxidants that protect against oxidative damage and other aspects of chronic disease. Its nutrient density exceeds that of other vegetables like carrots, sweet potatoes, or those of the onion family.
- Onions have been known for their healing properties for centuries. One study compared wound healing results after the daily application of onion gel and found that scars were significantly less noticeable after just four weeks of use. Recent research has suggested that onions also contain compounds useful for the treatment and prevention of cardiovascular disease, high blood pressure, diabetes and inflammatory diseases. Most of these benefits can be traced to onion’s high concentration of sulfur amino acids, phytochemicals such as flavonoids, phytosterols, and saponins – compounds that have anticancer, antibiotic, and antithrombotic activity.
- Potatoes are a rich source of potassium, fiber, vitamin C. Little attention is paid to potatoes recently due to their high calorie density and their relationship with obesity and diabetes. If they are eaten in whole form and not as French fries or chips, they can be healthy due to their high potassium content. Often, they are the only source of potassium for many people including children. Adequate potassium can protect us from hypertension.
- Tomatoes contain the phytochemical, lycopene, the carotenoid responsible for its red color and acts as an strong antioxidant. An increased intake has been associated with a decreased risk of prostate and breast cancers.
- Cauliflower in both forms, white or purple are high in phenolic compounds (a phytochemical) and antioxidants. Purple cauliflower is especially high in anthocyanins that is a potent anti-inflammatory and antiviral compound.
- Bell Peppers contain antioxidants that may protect against Alzheimer’s disease. Green, yellow, and red peppers are all high in phenolic compounds and vitamin C.
Bottom Line: As you can see, antioxidant activity can collectively have a powerful effect against free radical damage. This is enhanced by the many phytochemicals associated with a variety of vegetables and fruits, not just reliance on one or two of them in the diet.