Garlic, onions, leaks, chives, scallions (also called green or spring onions), and shallots belong to the lily, or Allium family of vegetables. They are used around the world for their pungent flavour as a seasoning, a condiment, or to enhance the flavour of other ingredients. Garlic and onions are certainly a favorite seasoning.  You can use them to spice up most dishes, including pasta sauces, stir fries, curries, soups, omelets, casseroles and marinades.  While they are big on flavour, Allium family vegetables also deliver many health benefits.

Garlic’s healing and medicinal properties have long been known. The herb has been used as both food and medicine in many cultures for thousands of years. Its use dates as far back as to the time the Egyptian pyramids were built. In Biblical times, garlic was thought to preserve strength and was given to slaves to increase their fitness. In ancient Greece, athletes took garlic before competing in the Olympic Games to enhance strength and vigor.  In 1858, Louis Pasteur – the great scientist who invented the pasteurization process – noted garlic’s antibacterial activity, and it was used as an antiseptic to prevent gangrene during Word War I and World War II.

Today scientist are praising garlic’s potential to help treat or protect against certain cancers, heart disease, arthritis, and even diabetes. The disease fighting properties of allium vegetables are attributed to a variety of powerful sulphur containing chemicals, in particular allyl sulphides. (These sulphur compounds are the same chemicals responsible for garlic’s distinctive smell and onion’s ability to make your eyes water.) Allium vegetables also contain flavonoids, phytochemicals linked to disease prevention. Onions are particularly rich in quercetin, a flavonoid thought to guard against cancer and heart disease.

In addition to phytochemicals, allium vegetables are valuable sources of nutrients you would normally expect from more colourful vegetables. Garlic offers vitamin C and B6, manganese, and selenium, while onions are notable for their vitamin C, vitamin B6, chromium and potassium content.

Cancer Prevention with garlic, onions, leeks, chives, scallions and shallots:
Many studies provide compelling evidence that garlic and its sulphur compounds inhibit the cancer process. of 37 observational studies in humans using garlic and its related sulphur compounds, 28 showed some cancer preventative effect. The evidence is particularly strong for digestive tract cancers. A combination analysis of 18 scientific papers concluded people who eat raw or cooked garlic regularly face about half the risk of stomach cancer and two thirds the risk of colorectal cancer as people who eat little or none.

Another study published in the International Journal of Cancer reported that a diet containing 10 grams of garlic and onions (three cloves of garlic or 1 tablespoon of chopped onion) per day was associated with a 30% lower risk of a certain type of stomach cancer.  Another study revealed that amonth the 10,000 subjects studed, the more garlic and opnions consumed, the lower the risk of a wide range of cancers, including cancers of the oral cavity, larynx, esophagus, colon, ovaries and kidneys.

Onions might also help keep lung cancer at bay. A study from the Netherlands that followed over 100,000 men and women between the ages of 55 to 69 discovered that those who consumed the most onions had a 35% lower risk of long cancer than those who ate the least.  Later, when researchers from the Cancer Research Center of Hawaii investigated the relationship between diet and lung cancer risk in 582 patients with lung cancer and 582 controls free of the disease, they too noted significant cancer protection from onions. Compared with people who seldom ate onions, those whose diets contained the most onion were 50% less likely to develope lung cancer.  The researchers also linked a higher intake of the flavonoid quercetin with a lower risk of lung cancer.

Scientists believe that garlic and onions help fight cancer in several ways. Studies show that garlic’s allyl sulphur compounds can slow or prevent the growth of cancer cells. Recently, these compounds proved able to kill leukemia cells in the laboratory.  Allyl sulphides may help rid the body of carcinogens by enhancing the action of certain enzymes in the liver and intestinal tract. It is also thought that natural chemicals in garlic and onions have a direct toxic effect on certain types of tumour cells. Sulphur compounds in allium vegetables also stimulate the body’s immune system, helping the body combat disease.  Finally, onions are a rich source of quercetin, a protent antioxidant that may block carcinogens as well as slow the growth and spread of cancer cells.

The first study that made a news spash was published in 1995 and reported the results of a study from Harvard Medical School in which researchers followed 47,000 healthy men from 1986 to 1992.  At the end of the follow-up period, men who consumed the most lycopene (the bright red carotene and carotenoid pigment and phytochemical found in tomatoes and other red fruits and vegetables) were 21% least likely to have prostate cancer. One of the 46 foods investigated, 4 were significantly associated with protection from prostate cancer; tomato sauce, tomatoes, tomato juice, and pizza. In fact, men who consumed 10 servings of these foods per week had a 35% lower risk of prostate cancer compared with men who ate fewer then 1.5 servings per week.

The researchers followed up again with this large group of men to see if the tomato-prostate cancer relationship persisted.  For the period from 1992 – 1998, frequent tomato or lycopene intake was associated with less prostate cancer. When the researchers analyzed the data for the 12 year period from 1986 to 1998, tomato sauce was found to be the most protective.  Compared with eating tomato sauce less than once per month, eating at least 2 servings each week reduced the risk of disease by 23%.

Men aren’t the only ones who can benefit from eating more tomates. Observational studies hae shown high dietary intakes and high blood levels of lycopene are associated with a lower risk of colon and pancreatic cancers. Preliminary studies also suggest that lycopene-rich vegetables such as tomatoes might guard against cancers of the lung, breast, ovarian, bladder, cervix and skin.

Tomatoes and Heart Disease: Tomatoes might also have cardio-protective properties. In a 7 year study of almost 40,000 women, higher intakes of lycopene rich foods were linked with fewer heart attacks and strokes. Compared with women consuming fewer than 1.5 servings of tomato based products per week, a weekly intake of at least 7 servings reduced the risk of cardiovascular disease by roughly 30%. Among tomato based foods, tomato sauce and pizza offered the most protection.

It is not just the lycopene in tomatoes that provide health benefits.  Researchers are learning that it is the mixture of nutrients and phytochemicals that do the trick, including, lycopene. It appears that all the healthy ingredients in tomatoes work in synergy to confer disease fighting powers. For instance, tomatoes contain many nutrients linked to heart health, such as potassium, folate, and vitamin B6. Diets rich in potassium have been shown to lower blood pressure. Folate and vitamin B6 are needed to convert a potentially harmful compound, homocysteine, to benign molecules. Homocysteine is an amino acid in the bloodstream that can accumulate and damage blood vessels walls. Numerous studies have liked elevated homcysteine levels with a greater risk of heart attack and stroke.

Carotenoids, including beta carotene, have also shown the ability to stimulate cell communication, which is essential for maintaining properly functioning cells.  In cancer, the ability of cells to communicate is impaired, and instead of cells having assigned functions, they proliferate and form tumours.  Normally when a cell senses there is something wrong with a neighbouring cell, it sends a message to that cell instructing it to self destruction. But when cell communication is impaired, this does not occur, and cancerous cells may grow.

A diet rich in beta carotene might also help ward off heart disease. Beta carotene and other carotenoids are fat soluble. That means they circulate in the blood stream along with cholesterol and other fats. Scientist speculate that these phytochemicals prevent LDL (bad) cholesterol from being oxidized, or damaged, by free radicals (oxidized LDL cholesterol is dangerous because it readily sticks to artery walls). A handful of studies have found that eople with higher levels of carotenoids in their bloodstream also have significantly lower levels of carotid artery wall thickness.  The thickness of the carotid arteries (the arteries that supply bood to your brain) can be measured using ultrasound technology; increased thickness is a reliable indicator of heart disease. Also studies have found that higher intake of carotenoid – rich produce is linked with a reduced risk of cardiovascular disease.

It is also thought that beta carotene may aid in female reproductive health.  Although scientists don’t understand the exact role beta carotene plays in reproduction, it is known that the corpus luteum, the area in the ovary where the egg is released at ovulation, has the highest concentration of beta carotene of any organ in the body. 

You need to get your beta carotene from food, not supplements. There is no evidence that getting your beta carotene in pill form reduces the risk of heart disease.  And when it comes to lung cancer, taking a beta carotene supplement may actually boost your risk of the disease.  Two large trials conducted in men at high risk for lung cancer (cigarette smokers, former smokers, or those with a history of occupational asbestos exposure) found that supplemental beta carotene increased lung cancer risk by 16% and 24% respectively.

Even if you have never smoked, it is best to get your beta carotene from bright orange vegetables rather than from supplement.  In addition to beta carotene, these foods provide dietary fibre, vitamins, minerals, and other phytochemicals that guard against disease.