Nutritional Value of Allium Vegetables

Allium family of vegetables have been a part of almost all types of cuisines. In fact, it is difficult to imagine preparing a meal without including allium vegetables. The term “Allium” may sound alien to many of us, however, once we get to know the vegetables included in this category, we will all agree that we have been using these tasty bulbs in our daily diet, both for flavour as well as for nutrition.

“Allium” is a Latin word which means garlic. 

However, apart from garlic, allium family of vegetables also include onion, scallion, shallot, leek and chives. Though some of the allium vegetables make us cry while chopping, they provide great flavor and aroma to our dishes and are also rich in beneficial sulfur compounds which provide great health benefits including antioxidant, antiviral, and antibacterial properties. They are also considered to have anti-inflammatory, immune-boosting and anti-aging properties. 

Most of the allium vegetables contain organo-sulphur compounds as well as different vitamins, minerals and flavonoids such as quercetin. 

Allium vegetables such as onion and garlic contain different vitamins such as Vitamin B1, Vitamin B2, Vitamin B3, Vitamin B6, folic acid, Vitamin B12, Vitamins C and minerals such as iron, magnesium, phosphorus, potassium, sodium and zinc. They also contain proteins, carbohydrates and dietary fiber.

Impact of Yellow Onion on Hyperglycemia (high blood glucose) and Insulin Resistance in Breast Cancer Patients

A clinical trial conducted by the researchers of Tabriz University of Medical Sciences, Iran, evaluated the impact of eating fresh yellow onions on insulin-related indices compared with a low-onion-containing diet among breast cancer patients who were undergoing treatment with doxorubicin. The study included 56 breast cancer patients who were aged between 30 and 63 years. After the second cycle of chemotherapy, the patients were randomly divided into 2 groups- 28 patients supplemented with 100 to 160 g/d of onions, referred to as the high onion group and another 28 patients with 30 to 40 g/d small onions, referred to as the low onion group, for 8 weeks. Out of these, 23 cases were available for analysis.(Farnaz Jafarpour-Sadegh et al, Integr Cancer Ther., 2017) The study found that those with a high daily onion intake may have a significant decrease in the serum fasting blood glucose and insulin levels as compared to those taking low amounts of onion.

Raw Garlic Consumption and Risk of Liver Cancer

In a population based case-control study in Eastern China between 2003 to 2010, the researchers evaluated the association between raw garlic consumption and liver cancer. Data for the study was obtained from interviews with 2011 liver cancer cases and 7933 randomly selected population-controls.(Xing Liu et al, Nutrients., 2019) The study found that eating raw garlic twice or more per week may be associated with a reduced risk of liver cancer. The study also found that high intake of raw garlic may decrease the risk of liver cancer among Hepatitis B surface antigen (HBsAg) negative individuals, frequent alcohol drinkers, those having a history of eating mold-contaminated food or drinking raw water, and those without family history of liver cancer.

Association of Allium Family of Vegetables with Colorectal Cancer

A hospital-based study between June 2009 and November 2011, done by researchers of the Hospital of China Medical University, China, evaluated the association between the intake of allium vegetables and colorectal cancer (CRC) risk. The study included data from 833 CRC cases and 833 controls whose frequency was matched by age, sex, and residence area (rural/urban) with that of the CRC cases.The study found a decreased CRC risk in both men and women with a high consumption of total and several individual allium vegetables including garlic, garlic stalks, leek, onion, and spring onion. The study also found that the association of garlic intake with cancer risk was not significant among those with distal colon cancer. (Xin Wu et al, Asia Pac J Clin Oncol., 2019)
A meta-analysis of observational studies was carried out by the researchers of Italy to evaluate the associations between allium vegetables intake and the risk of colorectal cancer and colorectal polyps. The study included data from 16 studies with 13,333 cases out of which 7 studies provided information on garlic, 6 on onion, and 4 on total allium vegetables. The study found that a high garlic intake may help in reducing the risk of colorectal cancer. They also found that a high intake of total allium vegetables may be associated with a decrease in the risk of colorectal adenomatous polyps. (Federica Turati et al, Mol Nutr Food Res., 2014). Another meta-analysis also found that a high intake of raw and cooked garlic may have a protective effect against stomach and colorectal cancers.(A T Fleischauer et al, Am J Clin Nutr. 2000).

Raw Garlic Consumption and Lung Cancer

In a study published in 2016, the researchers evaluated the association between raw garlic consumption and lung cancer in a case–control study conducted between 2005 and 2007 in Taiyuan, China. For the study, the data was obtained through face-to-face interviews with 399 lung cancer cases and 466 healthy controls. The study found that, in Chinese population, compared to those who did not take raw garlic, ones with high raw garlic intake may be associated with a reduced risk of lung cancer with a dose-response pattern. (Ajay A Myneni et al, Cancer Epidemiol Biomarkers Prev., 2016)
A similar study also found a protective association between consumption of raw garlic and the risk of lung cancer with a dose-response pattern (Zi-Yi Jin et al, Cancer Prev Res (Phila)., 2013)

Garlic and Risk of Esophageal Cancer 
In a study published in 2019, the researchers evaluated the association between garlic and the risk of esophageal cancer in a population-based study with 2969 esophageal cancer cases and 8019 healthy controls. Data was obtained from food frequency questionnaires. Their findings suggested that a high intake of raw garlic may help in reducing the esophageal cancer risk and may also interact with tobacco smoking and alcohol consumption.(Zi-Yi Jin et al, Eur J Cancer Prev., 2019).

In conclusion

Different observational studies suggest that consumption of allium family of vegetables may help in reducing the risk of different types of cancers. However, these protective associations may be specific to the vegetable consumed. Allium vegetables such as garlic may help in reducing the risk of breast cancer, prostate cancer, lung cancer, colorectal cancer (but not distal colon cancer), gastric cancer, esophageal cancer and liver cancer. Hence, always consult your nutritionist to ensure that the right foods and  supplements are included as part of your diet for cancer care or prevention.