8 nutrients to boost your immune system

1. Protein
People often look for lesser-known nutrients or supplements while paying little attention to protein intakes. But adequate protein -- at least 46 grams per day -- provides a foundation for essential components of the immune system, including white blood cells and antibodies. Go for moderate portions of protein-rich options such as lower-fat dairy products, fish, lean meat and poultry, eggs, soy foods, legumes and nuts.

2. Iron
It's a mineral that young women are often lacking, but dietary shortfalls can occur at any age. Red meat, eggs, legumes, dark leafy greens and whole- and enriched-grain products supply dietary iron. But to boost absorption of iron from plant sources, consume a vitamin C–rich food at the same meal.

3. Selenium
This important player in immune function is needed only in small amounts. Brazil nuts, meat, fish and poultry all supply this mineral.

4. Zinc
Too little or too much of this mineral can lead to a compromised immune system because zinc is significantly involved in immune-system development and reactivity. Meat, seafood, poultry, eggs, legumes, whole grains and milk are all chock-full of zinc. While earlier studies found inconsistent results, the latest on zinc gluconate lozenges shows that they seem to shorten the duration and severity of symptoms of the common cold when administered within 24 hours of the onset of symptoms.

5. Vitamin A
One of the roles of vitamin A in the immune system is to maintain healthy mucous membranes, which provide protective barriers throughout the body to help fight off infection by blocking the viruses or bacteria from entering the blood stream. Sources include meat, dairy products and plant foods rich in the orange pigment beta-carotene, which converts to vitamin A in the body. Carrots, squash and pumpkin are just a few beta-carotene-rich options.

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7. Vitamin E
Also an integral part of a healthy immune system, this vitamin has received some bad press as of late. Moderate your use of supplements: concerns over higher doses may arise in terms of heart health, and there is a lack of research on the effect of higher doses for those with compromised immune systems. Foods rich in vitamin E include vegetable oils, nuts and seeds, avocados and margarine.

8. Omega-3 fatty acids
For those with overactive immune systems, which includes those with autoimmune diseases as well as allergies, scientists have been investigating a number of foods and nutrients that may calm the immune system. Omega-3 fatty acids have been at the centre of much of this research. This group of unsaturated fats, found in foods including cold water fish such as salmon, trout and herring, and nuts and seeds such as walnuts, may have potential as anti-inflammatory compounds that may calm overactive immune systems. Researchers are still trying to determine which of these fatty acids have the most potent effects.

The fact that being obese is linked to a host of illnesses such as heart disease, stroke, diabetes and certain cancers comes as no surprise to most women. But its connection to impaired immune-system function is not well known. And while achieving and maintaining a healthy weight improves immune system performance, yo-yo dieting, in which a significant amount of weight is lost and regained, can do the opposite.

In a study of more than 100 women conducted at the Fred Hutchinson Cancer Research Center in Seattle and published in the Journal of the American Dietetic Association, losing 10 pounds or more and regaining the weight a number of times took a toll on immunity. Women who lost and regained their weight over a number of years had lower natural killer cell counts than those who remained at stable weights. And the more often they dieted in a yo-yo fashion, the lower the killer cell counts.

In an accompanying editorial in the journal, the authors point out that natural killer cells, while only one part of a well-functioning immune system, do play a role in fighting off not only infection but also cancerous cells.

Now that your immune system is the best it can be, make sure your body is getting the other vitamins and nutrients it needs. Check out our slideshow: top 10 vitamins and minerals women need and make sure your diet is balanced.

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