Zinc For Human Body
Zinc, an essential mineral in human nutrition, which plays as antioxidants to protect DNA from damage, and assists in its repair. Zinc is also required for producing energy, healing wound, regulating body immune system, and cell metabolism.
Zinc deficiency, due to low dietary intake, may lead to immune dysfunction, impaired growth, diarrhea, infection, neuropathy, loss of appetite, dermatitis, hair loss, bleeding, cold, hypotension, hypothermia, and cancer. Zinc as a dietary intake, could be found in seafoods, meats, nuts, eggs, cheese, grains, cereal, beans, peas, and seeds.
Dietary Intake of Zinc
Below is the tolerable upper intake level for zinc, according to the Food and Nutrition Board, Institute of Medicine:
0 to 6 months = 4 mg/d
6 to 12 months = 4 mg/d
1 to 3 years = 7 mg/d
4 to 8 years = 12 mg/d
- Both Males/Females, and Pregnancy/Lactation:
9 to 13 years = 23 mg/d
14 to 18 years = 34 mg/d
19 to 70 years and above = 40 mg/d
Dietary intake of zinc, whether from foods or zinc supplements, more than the upper level per day, may increase the risk of nausea, fatigue, kidney failure, urinary tract problems, vomiting, headache, infections, anemia, low HDL cholesterol, low immune function, copper deficiency, and the development of prostate cancer in men. Also, pregnant and lactation women should consult to the doctor, or pharmacist, before taking any zinc supplements.
Zinc in Cancer Prevention Studies
High concentration of zinc, in the prostate suggests that, zinc may play a role in prostate health. A 14 years follow up study among 46,974 U.S. men, from 1986 to 2000, was found 2,901 new cases of prostate cancer, of which 434 cases were diagnosed in advanced stage.
The study found that, dietary intake of zinc supplements up to 100 mg/d, was not associated with prostate cancer risk, but an overdose of zinc may play a role in prostate carcinogenesis. (Leitzmann MF, et al. 2003)
Head and Neck Cancer
Head, and neck cancer is a form of cancers of the mouth, nose, sinuses, salivary glands, throat, and lymph nodes, in the neck. A randomized double blind, placebo controlled trial among 144 head, and neck cancer patients, was conducted to determine the efficacy of zinc sulfate supplementation, in reducing radiation induced oral mucositis, and pharyngitis.
The study concluded that, zinc sulfate administered during head, and neck radiation therapy, produced no significant benefit, in relieving radiation induced oral mucositis and pharyngitis with acceptable side effects. (Sangthawan D, et al. 2013)
In 1988, a double blind randomized trial, in Italy, was started to demonstrate the efficacy of a combination of antioxidant supplement (200 μg selenium, 30 mg zinc, 2 mg vitamin A, 180 mg vitamin C, and 30 mg vitamin E), in reducing the incidence of recurrent adenomas (benign tumor) of the large bowel, among 411 patients, on post polypectomy (surgical removal of a polyp) endoscopic.
All patients were assigned to receive either a supplement, or a placebo, daily for five years. After follow up of four years, in range of 1 to 15 years, the study showed significant effect of antioxidant supplementation, on adenoma recurrence. Since the study used a combination of antioxidant supplement all together, it is difficult to determine the role of zinc, in reducing the risk for colorectal cancer. (Bonelli L, et al. 2013)
Recent study managed to develop zinc sulfide nanoparticles (ZnS NPs), to study their cytotoxicity against the KG-1A (human acute myeloid leukemia) cell line. Cell viability study, and flow cytometric analysis, confirmed the potent cytotoxic effects of ZnS NPs, on cancer cells.
The study found that, ZnS NPs had no toxic effects on normal lymphocytes, at doses up to 50 µg ml, and clarified the mechanism of ZnS NPs, in inducing anticancer activities in vitro. More studies were needed to investigate ZnS NPs application to cancer treatment in vivo. (Dash SK, et al. 2014)