COLLARDS

Health benefits and concerns

Asthma

Vitamin C, present in fruits and vegetables, is a powerful antioxidant and anti-inflammatory. This anti-inflammatory activity may influence the development of asthma symptoms. A large preliminary study has shown that young children with asthma experience significantly less wheezing if they eat a diet high in fruits rich in vitamin C.

Bruising

Many Americans eat insufficient amounts of foods containing vitamin C; the disease caused by vitamin C deficiency, scurvy, causes easy bruising. While very few people actually have scurvy, even minor deficiencies of vitamin C can increase the incidence of bruising. People who experience easy bruising may want to try eating more fruits and vegetables—common dietary sources of vitamin C.

Cancer

The strong association between increased intake of beta-carotene from food and a reduced risk of lung cancer does not necessarily mean that supplementation with natural beta-carotene supplements would reduce the risk of lung cancer. Dietary beta-carotene may be a marker for diets high in certain fruits and vegetables that contain other anticancer substances that may be responsible for the protective effects. Until more is known, some doctors advise smokers to avoid all forms of beta-carotene supplementation—even natural beta-carotene.

Foods high in vitamin K, such as vegetables, typically are associated with low cancer risk. Despite the fact that the anti-vitamin K drug warfarin might reduce the risk of cancer under certain circumstances, no evidence suggests that avoidance of vitamin K (from food or from supplements) would in any way help protect against cancer.

Capillary fragility

Eating plenty of flavonoid- and vitamin C-rich fruits and vegetables helps to support the structure of capillaries.

Cataracts

Some but not all studies have reported that eating more foods rich in beta-carotene or vitamin A was associated with a lower risk of cataracts. Synthetic beta-carotene supplementation has not been found to reduce the risk of cataract formation. It remains unclear whether natural beta-carotene from food or supplements would protect the eye or whether beta-carotene in food is merely a marker for other protective factors in fruits and vegetables high in beta-carotene.

High homocysteine

A controlled trial showed that eating a diet high in fruits and vegetables containing folic acid, beta-carotene, and vitamin C effectively lowered homocysteine levels. Healthy people were assigned to either a diet containing a pound of fruits and vegetables per day, or to a diet containing 3 1/2 ounces (99g) of fruits and vegetables per day. After four weeks, those eating the higher amount of fruits and vegetables had an 11 percent lower homocysteine level compared to those eating the lower amount of fruits and vegetables.

Macular degeneration

People who eat plenty of fruits and vegetables high in beta-carotene appear to be at lower risk for macular degeneration than people who do not eat these foods. However, another study found no association between age-related macular degeneration and intake of antioxidants, either from the diet, from supplements, or from both combined. More research is needed to reconcile these differences. In the meantime, beta-carotene-rich vegetables continue to be part of a healthful diet.

Lutein and zeaxanthin are antioxidants in the carotenoid family. These carotenoids, found in high concentrations in spinach, collard greens, and kale, concentrate in the part of the retina where macular degeneration occurs. Once there, they protect the retina from damage caused by sunlight.

Harvard researchers reported that people eating the most lutein and zeaxanthin—an average of 5.8mg per day—had a 57 percent decreased risk of macular degeneration, compared with people eating the least. On the other hand, in another study, blood levels of lutein did not correlate with the risk of macular degeneration. Lutein and zeaxanthin can be taken as supplements; 6mg per day of lutein may be a useful amount.

As expected, spinach and kale eaters have a lower risk of macular degeneration, although blood levels of lutein have not correlated with risk of macular degeneration in one trial.

Multiple sclerosis (MS)

In one survey, researchers gathered information from nearly 400 people (half with MS) over three years. They found that consumption of vegetable protein, fruit juice, and foods rich in vitamin C, thiamine, riboflavin, calcium, and potassium correlated with a decreased MS risk.

Pregnancy

Pregnant women should consume 1,500mg of calcium per day. Food sources of calcium include milk products, dark green leafy vegetables, tofu, sardines (canned with edible bones), salmon (canned with edible bones), peas, and beans.

Stroke

Diets high in fruit and/or vegetables are associated with a reduced risk of stroke, according to most studies. In a large preliminary study, cruciferous and green leafy vegetables, conferred the highest degree of protection. Because it is not clear which components of fruits and vegetables are most responsible for the protective effect against stroke, people wishing to reduce their risk of stroke should rely primarily on eating more fruits and vegetables themselves rather than taking supplements.

Health benefits and concerns for vegetables
Many health benefits and concerns associated with this food are applicable to other vegetables. Read about health benefits and concerns for vegetables for a full description.