Immune Health: Why Diet Isn't Enough

Immune Health: Why Diet Isn't Enough

By Andrea Bartels CNP NNCP RNT
Registered Nutritional Therapist

17 Mar 2022

Immune Health: Why Diet Isn't Enough

Does YOUR diet provide the immune support you need to fight infection, allergies and more? Probably not---but it's not your fault. It may still taste good, but today's food just doesn't provide the amounts of micronutrients needed to protect us from stress and ill health. Here are some of the key immune nutrients and the limiting factors that warrant their supplementation.

Modern Farming 101

“Foods grown in depleted soils produce malnourished bodies, and disease preys on malnourished bodies”, wrote Mark Anderson and Bernard Jensen in their book, Empty Harvest.  The agricultural practices of letting the fields lie fallow, as well as rotating crops from year to year have become extinct on today’s large-scale farms, with the net result of mineral depletion of the soil and the plants that are harvested from them.

Zinc deficiency is the most widespread micronutrient deficiency in the world’s crops.  It’s no wonder then that tissue zinc levels have decreased in humans over the decades.  Soils that lack the variety of minerals due to over-farming and the incompleteness of popular soil fertilization from synthetic nitrogen-based fertilizers also result in crops with lower vitamin C content.
In fact The Organic Consumers Association notes that a Kushi Institute analysis of nutrient data from 1975 to 1997 found a 30 percent reduction in vitamin C over this time period when looking at 20 different vegetable types.

Food Storage and Preparation Techniques

Some immune-essential nutrients, like vitamin C, have some inherent weaknesses that make it vulnerable to destruction by air, light and heat. For example, vitamin C exhibits poor heat tolerance, meaning the vitamin disintegrates when orange juice is pasteurized to kill bacteria, and foods are cooked at boiling temperatures or higher. 

Don’t depend on frozen fruits and vegetables to get your vitamin C, either.  Extreme cold is another enemy, as below zero this vitamin will be destroyed by the freezing process. This is made worse over time with long durations in the freezer, and when ice crystals form on the food.  In fact, thawing foods before cooking actually causes more vitamin C loss.  While factors such as length of time stored at freezing temperatures and the cooking method do affect the amount of loss, it’s important to realize that frozen foods are not reliable sources of vitamin C.

Societal Food Trends and Preferences

As a fat-soluble immune nutrient, vitamin D is much more stable than vitamin C, but it’s found in very few foods, and in small quantities, at that. Egg yolks, liver and other organ meats are the highest natural sources—the latter which are hardly popular in most households these days.  Fear of saturated fats, cholesterol and toxins have been cited as reasons for abstinence from these foods.  While mushrooms can synthesize vitamin D, they can only do so when grown under a certain intensity of UV light. Unfortunately, without consulting the farmer there’s no way to tell whether this was the case.  Although the vitamin has been added to fluid milk since the mid-20th century in industrialized nations to reduce incidence of the crippling bone disease, rickets, fewer individuals today are drinking milk and more are choosing lactose-free, low-fat milk substitutes.  It’s important to note that unlike cow’s milk, these milk substitutes are rarely fortified with vitamin D, so these ‘mylks’ are not a reliable way to obtain our daily requirements. 

Absorption Inhibitors

Are you a fiber fan?  Unfortunately, a diet high in phytate—a fibre type found in whole grains, nuts and legumes-- predisposes a person to zinc deficiency. That’s because phytic acids bind to zinc and make it unavailable for uptake by the intestinal tract. This means that vegetarians have to take in about 50% percent more zinc in order to fulfill their zinc requirements.  Oysters are a far more bioavailable source of zinc. But who can obtain, cook and eat those regularly unless you live in a seaside town?

Did you have your gallbladder removed? If you’re missing this handy little bile-storage tank, then you might develop trouble with fats and fat-soluble nutrient absorption.  This means you could be at higher risk for deficiencies in fat-soluble vitamins like vitamin D, E, K and A. That just isn’t fair.

How to Get Enough

Simply put, unless you have access to freshly-picked-off-the-vine produce coming from your own orchards and vegetable gardens, you can’t depend on store-bought fruits and vegetables to fulfil our vitamin C requirements. And, unless you are a big milk-drinker and oyster-eater, you may fall short on your vitamin D and zinc needs, respectively.  These are just a few reasons why nutrient supplementation is a valuable part of immune support.  Not only are encapsulated nutrients less vulnerable to spoilage—they also provide amounts that more adequately address your body’s needs than food alone could.



Alloway BJ. Soil factors associated with zinc deficiency in crops and humans. Environ Geochem Health. 2009;31(5):537-548.

Cardwell G, Bornman JF, James AP, Black LJ. A Review of Mushrooms as a Potential Source of Dietary Vitamin D. Nutrients. 2018;10(10):1498. Published 2018 Oct 13.

Chandel G, Banerjee S, See S, Meena R, Sharma DJ, Verulkar SB. Effects of different nitrogen fertilizer levels and native soil properties on rice grain Fe, Zn and Protein Contents. Rice Sci. 2010;17:213–227.

Jensen, Bernard and Mark Anderson. Empty Harvest: Understanding the Link Between Our Food, Our Immunity, and Our Planet. Avery Publishing, 1995.

MS Society of Canada. “Vitamin D and MS Research”. Accessed online March 10, 2022.

Nursal B, Yücecan S. Vitamin C losses in some frozen vegetables due to various cooking methods. Nahrung. 2000;44(6):451-453.

Office of Dietary Supplements. Vitamin C Fact Sheet for Health Professionals. National Institutes of Health. Accessed online March 10, 2022.

Office of Dietary Supplements. Vitamin D Fact Sheet for Health Professionals. National Institutes of Health. Accessed online March 10, 2022.

Scientific American. “Dirt Poor: Have Fruits and Vegetables Become Less Nutritious?” April 27th, 2011. Accessed online March 10, 2022.

Seymour, Tom. “Are Organ Meats Good for You?” Medical News Today, September 3, 2017. Accessed online March 10, 2022.

Sharma A, Patni B, Shankhdhar D, Shankhdhar SC. Zinc - an indispensable micronutrientPhysiol Mol Biol Plants. 2013;19(1):11-20.

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