Zinc on a plate

By Professor John H. Beattie
Head of Micronutrients Group, Rowett institute of Nutrition and Health, University of Aberdeen, UK

The importance of zinc

  • Though the actual amount of zinc we need is quite small, its effects on the body are astronomical and scientists are continuing to uncover new roles for this essential trace metal
  • Zinc is found in several foods but many of us get most of our zinc from red meat and poultry
  • Our intake of zinc has fallen in recent years partly because we are eating less red meat
  • A varied diet, with some red meat each week, alongside fruit, vegetable, cereals and pulses will provide sufficient zinc to meet your body’s needs 

Only 0.003% of your body is zinc, but without it, you wouldn’t be able to live. This essential trace metal is used by the body in many inventive ways. One use is structural – zinc atoms hold parts of proteins together, rather like a staple making loops in a ribbon, so the right part of the protein is facing the right way to do its job. A lot of these proteins control the reading of our gene blueprints to make new proteins. For example, the female sex hormone oestrogen has its amazing effect because it activates a zinc-dependent protein involved in creating female characteristics.  Zinc is also used in the activation of enzymes, which convert biochemicals from one form to another. For example, alcohol dehydrogenase, a zinc requiring enzyme, breaks down alcohol, with a consequent return to sobriety! 

Zinc does even more interesting things within cells and this exciting area of research is known as zinc signalling. As the name implies, zinc can trigger changes within cells, starting a rapid chain reaction which helps the cells to survive in response to some kind of stimulus, like stress from free radicals or inflammation. There are many recently discovered zinc “gatekeepers” that control how much zinc gets into and out of cell compartments and into body fluids such as breast milk. The control of zinc signalling is very finely tuned and self-regulated, and scientists are only beginning to understand the complex mechanisms by which this happens. Investigating the malfunction or regulation of zinc “gatekeepers” and other zinc-dependent proteins gives us clues about their role in keeping us healthy, and can reveal how, for example, zinc deficiency affects: 

  • immune function
  • appetite/satiety
  • spatial navigation and memory
  • mood and depression
  • cardiovascular health
  • diabetes

Where to find it

Bad press about cancer and the global warming effects of greenhouse gasses from large farm animals, may have given you the impression that red meat is bad for you and the environment. Additionally, nutritional advice for healthy choices pushes you to eat more fruit and vegetables. As regards zinc however, there is an advice paradox, because red meat contains lots of zinc and fruit and vegetables contain very little. The best compromise is to eat a varied diet, including some lean red meat each week (the Department of Health suggests that up to 90 grams per day is safe), along with fruit and vegetables, cereals and pulses. Some plant foods such as cereals contain a natural compound that can reduce zinc absorption by your gut, so while some of these foods may be reasonably good sources of zinc, the amount of zinc extracted by your body may be lower than with animal foods. 

How much do you need?

The recommended daily intake in the UK is 7.0 and 9.5 mg per day for adult women and men, respectively. You shouldn’t exceed 25 mg a day as very high intakes can be harmful. 

The amount of zinc in an average portion of different foods

 

Zinc in

Percentage of daily

 

food portion*

reference nutrient intake**

Food

(mg)

Men

Women

Beef - Rump Steak & Mince

3.9

41

55

Lamb Loin Chops

2.2

23

31

Pork - Ham

0.4

4

5

Chicken Breast

0.6

6

8

Fish - Oily

0.9

9

13

Fish - White

0.6

7

9

Cheese - Cheddar

1.2

13

18

Eggs

0.8

8

11

Milk

0.4

4

6

Breakfast Cereal – High Bran

0.9

9

13

Nuts

0.7

7

10

Bread - White

0.4

4

5

Bread - Wholemeal

0.7

8

10

Beans

0.4

4

6

Vegetables

0.3

3

4

Fruit

0.2

2

3

*Data were obtained or estimated from published Food Standards Agency tables and retailer statistics. They may vary according to source or variety of food and should be used as a guide only. Values are stated for cooked foods except for fruit.

** UK reference nutrient intakes: daily amount of zinc considered to meet the needs of 97.5% of the adult population

Declining intakes

Our zinc intake has declined over the last 60 years, due to changed eating habits, including a reduction in red meat intake. We are now consuming less zinc than during rationing in World War II. With this in mind, we urgently need to find a good indicator of an individual’s zinc status. Dietary zinc intake can be a guide, but the amount of zinc that is absorbed by the body will depend on the type of foods eaten. The search for a good indicator of zinc status is on-going and could help to identify the 2 billion or so people that the World Health Organisation estimates are of low zinc status Worldwide.

Date: 
Thursday, 29 November, 2012 - 11:48
Thumbnail: 
Zinc on a plate