Does our Summer diet boost our immunity more than Winter foods?

In modern Ireland our summer weather is getting wetter and more unpredictable. Not so good for the farmers and anyone else working outside. My painter is waiting 6 weeks for a break in the showers to paint ours! Does that affect our immunity? Vitamin D's main function is bones strength but it is the body's co-ordinator for gut health, blood sugar balance and cardiovascular health. We know the main source of vitamin D is from the sun but what else is boosted by summer heat and shedding a few layers of clothes?
In summer we tend to eat more raw vegetables and fruit. Lots of salads and cool drinks. One plate of your average salad can have 3 times more fibre (9g) than a bowl of warm vegetable soup (3g). Not that I'm saying a hearty bowl of soup is bad, far from it but it is not a coincidence that colds, flu's respiratory conditions all peak in the winter months.
The average fiber needs can be seen in this chart-

Another thing that happens when we cook food is the nutrient content is reduced. Heat is the enemy of vitamin C. Once you cook your food above 63 degrees this water soluble vitamin is destroyed. Vitamin C is the number 1 nutrient for our immunity. It is an antioxidant which means it goes around 'cleaning up' the body of free radical 'dirt' which causes oxidative stress (1). There was a big trend towards raw food diets a few years back here in Ireland. Raw foodies eat at least 85% raw foods. I suspect a few Irish winters took the wind out of the sails of that particular trend. They were on to something though.If you could have a quarter of your plate raw vegetables throughout the year it would keep your vitamin c levels on a more even keel. We do not have the capacity to store it so a steady supply in your diet or in supplement form is key to a stronger immunity.
Foods highest in vitamin C may not be what you thought-

Foods with the highest sources of vitamin C include:

• Broccoli, Brussels sprouts, and cauliflower.

• Green and red peppers.

• Spinach, cabbage, turnip greens, and other leafy greens.

• Sweet and white potatoes.

• Tomatoes and tomato juice.

• Winter squash.
• Thyme, parsley
• Strawberries
• Oranges
• Lemons
• Lychees
• Papaya or paw paw

Gram for gram thyme contains more vitamin C than 3 oranges! Thyme is used in herbal medicine to speed up recovery from bacterial and viral infections. Parsley also packs a punch of vitamin C so don't leave it as a momento on your plate when you go out, eat it!
Iodine and zinc rich foods play a major part is boosting our immunity too. Shellfish like oysters and prawns have high levels of both and the season peaks in August/September. All fish contain both volumes consumed don't tend to vary by season just the accompaniments for example salad nicoise, sushi, ceviche.
In 2007 a study showed that influenza virus thrived in the cold and low humidity(2). Now that we know the virus likes to hang around in air particles and low temperatures the best immune boost is diet. Increase those immune boosting foods in Winter too and wrap up well.
By Tara Canning
www.taracanning.ie