A new favourite of mine: Zinc
Zinc (Zn): for HEALTH
ALL micronutrients play an important role in metabolism and the maintenance of tissue function (Shenkin, 2005).
Although muscles and bones contain 90% of the body's zinc, this essential trace element is also found in all areas of the human body where it plays a crucial role to the function of 300 enzymes. This highlights exactly why we really need this micronutrient regularly within our diet.
Particularly high concentrations of zinc are in the prostate gland and semen. Zinc is absolutely necessary for for many different biological functions including:
1. Growth and cell division
2. Fertility; pregnancy, and lactating women
3. Immune System
4. Skin, Hair Nails (healing wounds)
5. Smell taste, appetite
6. Vision
7. Brain development
Where do we get zinc from?
It is best practice to ingest zinc primarily from food sources. You can see from the chart below that, the major sources of this essential trace element are (red) meat, poultry, fish and seafood, (MOST) whilst whole cereals and dairy products contain less (LEAST). The bad news for veggies and vegans is that, the bioavailability of plant-based foods (such as legumes and whole-grains) is generally lower due to dietary fibre and phytic acid which actually bind to zinc and in effect inhibit its absorption.
Vegetarians sometimes require as much as 50% more of the RDA for zinc than non-vegetarians. Interestingly vegetarians may also benefit from using certain food preparation techniques that reduce the binding of zinc by phytates and increase its bioavailability. Techniques to increase zinc bioavailability include soaking beans, grains, and seeds in water for several hours before cooking them and allowing them to sit after soaking until sprouts form.
Vegetarians can also increase their zinc intake by consuming more leavened grain products (such as bread) than unleavened products (such as crackers) because leavening partially breaks down the phytate; thus, the body absorbs more zinc from leavened grains than unleavened grains.
These are the types of people who might benefit from zinc supplementation under professional medical advice.
It must be noted that Large doses of zinc should not be taken over a prolonged period of time without your physician’s direction.
Average Zinc Content in Dietary sources of zinc
(mg/100g)
|
Food Source
|
Zn (mg/100g)
|
|
Oysters
|
25
|
|
Meat (esp red meat)
|
5.2
|
|
Nuts
|
3
|
|
Poultry
|
1.5
|
|
Eggs
|
1.3
|
|
Milk Products
|
1.2
|
|
Cereal
|
1
|
|
Bread
|
1
|
|
Fish
|
0.8
|
|
Green Vegetables
|
0.4
|
|
Potatoes
|
0.3
|
|
Fresh Fruits
|
0.09
|
How much zinc do we need?
Our body regularly needs zinc. Recommended Daily Intakes (RDI) are:
|
Age/status
|
Zinc mg
|
|
Infants
|
5
|
|
Children
|
10
|
|
Women
|
12
|
|
Pregnant Women
|
15
|
|
Lactating Women
|
16
|
|
Men
|
15
|
We know that Zinc has vast functioning within the human body, now we will examine it’s main functions in a little further detail:
ZINC FOR FERTILITY
Why is zinc so important for fertility? In males, zinc is to be considered one of the most important trace minerals to date for male fertility; as it protects the prostate gland from infection (prostates) and ultimately from enlargement (prostatic hypertrophy). Zinc also helps maintain sperm count and mobility and normal levels of serum testosterone.
During a double-blind, placebo-controlled interventional study, Wong et al (2002) studied the effects of folic acid and zinc sulfate treatment on semen variables in 108 fertile and 103 subfertile men. Both groups were randomly assigned to receive one of four treatments for 26 weeks: folic acid and placebo, zinc sulfate and placebo, zinc sulfate and folic acid, and two placebos. Folic acid was given at a
In women, zinc works with more than 300 different enzymes in the body to keep things working well. Without it, cells do not divide properly; essentially estrogen and progesterone levels become imbalanced as a result the reproductive system may not fully function. According to The Centers for Disease Control’s Assisted Reproductive Technology Repor. Low levels of zinc have been directly linked to miscarriage in the early stages of a pregnancy, this could be due to the role of zinc in cell division and growth.
ZINC DURING PREGNANCY AND EARLY CHILDHOOD
Zinc, an essential trace element, plays a critical role in normal growth and development, cellular integrity and many biological functions, including protein synthesis and nucleic acid metabolism. Since all these are involved in cell division and growth, zinc is believed to be important for fetal growth and development. The total amount of zinc retained during pregnancy has been estimated to be 1.5 mmol (100 mg). During the third trimester the physiologic requirement of zinc is approximately twice as high as that in women who are not pregnant
Research strongly indicates that there is a beneficial effect of prenatal zinc supplementation trials, in particular on infant's neurobehavioral development. In the light of the currently available information, zinc supplementation at therapeutic load (30 mg/day) as it is proposed for the treatment of hormonal skin disorders to adolescents, cannot be toxic.
Pregnant women, particularly those starting their pregnancy with marginal zinc status, are at increased risk of becoming zinc insufficient due, in part, to high fetal requirements for zinc. Lactation can also deplete maternal zinc stores. For these reasons, the RDA for zinc is higher for pregnant and lactating women than for other women.
Lactation
Zinc concentrations in human milk are high in early lactation, 2-3 mg/l (31-46 mmol/l) in the first month, and fall to 0.9 mg/l (14 mmol/l) after 3 months. From data on maternal milk volume and zinc content, it was estimated that the daily output of zinc in milk during the first 3 months of lactation could amount to 1.4 mg/day (21.4 mmol/l), which would theoretically triple the physiologic zinc requirements in lactating women compared with non-lactating, non-pregnant women. In setting the estimated requirements for early lactation it was assumed that part of this requirement was covered by postnatal involution of the uterus and from skeletal resorption
Breast milk provides sufficient zinc (2 mg/day) for the first 4–6 months of life but does not provide recommended amounts of zinc for infants aged 7–12 months, who need 3 mg/day In addition to breast milk, infants aged 7–12 months should consume age-appropriate foods or formula containing zinc. Zinc supplementation has improved the growth rate in some children who demonstrate mild-to-moderate growth failure and who have a zinc deficiency.
BRAIN FUNCTION AND ZINC
Much science provides evidence which advocates the crucial function which zinc has on healthy and diseased brains. Zinc can be classified as an endogenous modulator of synaptic transmission. According to Takeda (2000) zinc is found in synaptic vesicles, released upon excitation, and has multiple synaptic targets. Zinc, is supplied to the brain via both the blood–brain and blood–cerebrospinal fluid barriers and is most concentrated in the limbic system, i.e. the hippocampus and amygdala, zinc-containing glutaminergic neuron-rich areas. A large portion of zinc serves the function of zinc metalloproteins in neurons and glial cells. In zinc-containing glutaminergic neurons, vesicular zinc, probably ionic zinc, may serve as an endogenous neuromodulator in synaptic neurotransmission. Vesicular zinc is dynamically coupled to the electrophysiological activity of zinc-containing glutaminergic neurons.
Dietary zinc deprivation may influence zinc homeostasis in the brain, resulting in brain dysfunction such as learning impairment. Excessive excitation of zinc-containing glutaminergic neurons causes a decrease in vesicular zinc, and the decrease might be associated with the susceptibility to seizure.
Alteration of zinc levels released into the synaptic cleft may influence neurotransmission in zinc-containing glutaminergic synapses. Therefore, zinc homeostasis in the presynaptic vesicle is important for the function of zinc-containing glutaminergic neurons.
ZINC AND THE IMMUNE SYSTEM
Among all the vitamins and minerals, zinc shows the strongest effect on our all-important immune system as it forms a unique role for T-cells in our body. There is substantial evidence that zinc supplementation may well reduce the impact of many of the aforementioned diseases by preventing the dismantling of the immune system (Fraker et al, 2000). Low zinc levels lead to reduced and weakened T-cells, which are not able to recognize and fight off certain infections. On the contrary, increases of the zinc level has proven effective in fighting pneumonia and diarrhea and other infections. Zinc can also reduce the duration and severity of a common cold.
In a randomized, double blind, placebo-controlled study, Mossad (2003) studied the ability of zinc nasal gel to shorten the duration and reduce the severity of the common cold in 80 subjects.
With administration 24-48hr from the onset of the cold illness, patients received one dose per nostril of a nasal gel spray containing either 33 mmol/l zincum gluconicum, or an identical placebo four times daily until their symptoms resolved, for a maximum of 10 days.
The author found that, median duration of cold symptoms in the zinc group was significantly shorter than in the placebo group (4.3 days vs 6 days). Nasal drainage, nasal congestion, hoarseness, and sore throat were the symptoms most affected. Significant reduction of total symptom scores started from the second day of the study. Adverse effects (mainly nasal stinging) were similar in both groups.
Zincum gluconicum nasal gel shortens duration and reduces symptom severity of the common cold in healthy adults, when started within 24-48 h of the onset of illness.
SKIN HAIR AND NAILS
We all like glowing skin and silky smooth healthy hair, zinc has been shown to be important for both as it accelerates the renewal of skin cells. It has proven effective for the treatment of acne, reduces symptoms of psoriasis and neuro-dermitis, and can be used as an inflammatory agent to help sooth skin tissue for poison ivy, sunburn blisters and gum diseases.
In industrialised countries cases of mild zinc deficiency can be ob
During a a randomised controlled trial investigating treatment with supplementary arginine, vitamin C and zinc in patients with pressure ulcer, Desenev et al (2005) concluded that only patients receiving additional arginine, vitamin C and zinc demonstrated a clinically significant improvement in pressure ulcer healing (9.4±1.2 vs. 2.6±0.6; baseline and week 3, respectively)
Zinc is also important for healthy hair, in fact, insufficient levels may result in loss of hair and/ or hair that looks thin and dull and that goes grey early. There are also a number of shampoos which contain zinc to help prevent dandruff.
PREVENTION OF CHRONIC DISEASES
AJCN, (2009) recommended 45 milligrams of zinc gluconate per day as they found that zinc can provide anti-inflammatory and antioxidant effects and can protect the heart from damage in elderly patients. Zinc supplements have also shown to be beneficial for infectious and chronic diseases such as malaria and HIV. Taking zinc specifically with meals can improve the liver function in people with alcoholic liver disease and hepatitis C.
Interestingly, studies using animal models have shown that Zn supplementation prevents alcohol-induced liver injury under both acute and chronic alcohol exposure conditions. Kang and Zhou (2005) reviewed Zinc in the prevention and treatment of alcoholic liver disease. Alcoholic liver disease (ALD) is associated with decreases in zinc (Zn) and its major binding protein, metallothionein (MT), in the liver.
Approximately 30%–50% of alcoholics have low zinc status because ethanol consumption decreases intestinal absorption of zinc and increases urinary zinc excretion. In addition, the variety and amount of food consumed by many alcoholics is limited, leading to inadequate zinc intake. Zn supplementation attenuates ethanol-induced hepatic Zn depletion and suppresses ethanol-elevated cytochrome activity, but increases the activity of alcohol dehydrogenase in the liver; an action that is likely responsible for Zn suppression of alcohol-induced oxidative stress.
So what happens if we don’t get enough zinc?
Zinc deficiency is a serious problem in many developing countries. Zinc deficiency is ranked as the 5th leading risk factor in causing disease, especially diarrhea and pneumonia in children, which can lead to high mortality rates in these underdeveloped regions. According to Dardeene (2002) low zinc levels in humans severly hinders cellular immunity. For example, Acrodermatitis, a genetic disorder of Zn malabsorption, is characterized by mucocutaneous lesions, diarrhoea, failure to thrive, and frequent severe infections with fungi, viruses and bacteria.
Other severe deficiency symptoms include stunted growth and impaired development of infants, children and adolescents. Early zinc deficiency also leads to impaired cognitive function, behavioral problems, memory impairment and problems with spatial learning and neuronal atrophy. Public health programs involving zinc supplementation and food fortification could help overcome these problems.
Mild zinc deficiency symptoms can usually be corrected by supplying the body with the right amount of zinc each day. Supplemental zinc not exceeding the recommended daily allowance might be taken. Therapies involving larger doses of zinc should always be discussed with your physician. Therapeutical doses typically range from 20 mg – 30 mg, in some rare cases doses might be higher.
SUPPLEMENTATION
Disadvantage: Short-Term Side Effects
Zinc supplements can cause nausea in some people. The upper tolerable limit for zinc is 40 milligrams per day, but much lower doses can cause temporary stomach discomfort, especially if taken on an empty stomach. Higher doses of zinc can lead to vomiting, headaches, diarrhea and exhaustion. Zinc may also interfere with many common prescription medications, including antibiotics, nonsteroidal anti-inflammatory drugs and immunosuppressant drugs.
Disadvantage: Long-Term Side Effects
Minor or moderate amounts of supplemental zinc can be beneficial to wound healing, immune health and heart health, but according to research excessive doses appear to hinder all three. Long-term, high-dose zinc supplementation can also reduce iron and copper absorption, which can lead to anemia and other disorders associated with low levels of those minerals. Supplementing with 15 milligrams of elemental zinc per day is relatively safe, but long-term doses much higher than that should be limited until more information is available.
No comments:
Post a Comment