- Winter squash
- green beans
- butternut squash
- sweet potatoes
- sunflower seeds
- turnip greens
- butternut squash
- green peppers
- red hot chili peppers
- Brazil nuts
- sunflower seeds
- mushrooms, Shiitake
- sesame seeds
- pumpkin seeds
- flax seeds
- bean sprouts
Bioflavonoids (Vitamin P)
- Red bell peppers
- citrus fruits – oranges, lemons, limes, tangerines
- Brussels sprouts
- tropical fruits – papayas, mangoes
Both alpha- and beta-carotene are pro-vitamin A carotenoids – they can be converted in the body to vitamin A. Obviously, these carotenoids share many similarities; they are both powerful, fat soluble antioxidants. But they are also different in significant ways. Beta carotene has long been recognized as a powerful antioxidant that boosts immunity and protects health, but a Yale Journal of Biology and Medicine study demonstrated that “Vitamin A and its dietary precursor, beta-carotene, increase absolute T helper cell counts as well as indices of T cell function in both human and animal models.”1 The vitamin E and beta-carotene study I mentioned earlier also demonstrated beta-carotene's ability to increase the number of infection-fighting cells, called natural killer cells. And yet, other studies have shown that alpha-carotene may be more potent than beta-carotene because it contains flavonoids and can remove free-radicals from the body before they cause any cell and tissue damage.
Vitamin E also stimulates the production of natural killer cells. One study, conducted by the Department of Biochemistry, at Aga Khan University, showed that vitamin E also improves the production of B-cells, which are immune cells that produce antibodies that destroy bacteria. And there is evidence that vitamin E and beta-carotene work synergistically to keep malfunctioning cells and other biological threats under control.
Vitamin C has always been associated with better immune health. And numerous studies have explored the why and how of vitamin C's ability to boost immunity. For example, a study published in the journal Inflammation & Allergy Drug Targets proved that “Immune competent cells accumulate vitamin C against a concentration gradient, with a close relationship between vitamin C supply and immune cell activity, especially phagocytosis activity and T-cell function. Accordingly, one of the consequences of vitamin C deficiency is impaired resistance to various pathogens, while an enhanced supply increases antibody activity and infection resistance.”2
Selenium is also a well-known immunity booster. In fact, selenium is essential to immune system functioning. It stimulates the production of white blood cells – also known as leukocytes – and improves natural killer cells' ability to respond to viral and bacterial invasion. “one study suggested that when elderly people took zinc and selenium supplements, their immune systems responded better to the flu vaccine than those who took placebo.”3 Selenium also works synergistically with other antioxidants, making them each even more effective against infections. This was first discovered in the early '60s by Dr. Richard Passwater in regards to vitamin C. More recent research has proven that selenium also works synergistically with vitamins A and E.
The mineral Zinc is available in lozenge form in nearly every drugstore in America; so, it should come as no surprise that this nutrient is an excellent cold and flu fighter and preventative. Zinc is another nutrient that boosts immunity by directly affecting (increasing) the production, maturation and function of white blood cells. Zinc has even been shown to make white blood cells more aggressive toward foreign invaders.
Omega-3 is an immunity booster that receives very little fanfare, despite several prominent research studies that have demonstrated Omega-3 fatty acids' ability to act as modulators of the inflammation and immune response. So, omega-3 fatty acids are capable of regulating or altering the activities that lead to inflammation and infection, making them essential for keeping infections and inflammation at bay.
Bioflavonoids, which use to be called vitamin P, are plant pigments responsible for the color of fruits, vegetables and flowering plants. And they are even less recognized for their immunity enhancing abilities than Omega-3s. So far, 4000 different flavonoid compounds have been identified and classified into 4 groups: PCO (Proanthocyanidins), Quercetin, Citrus bioflavonoids and Green Tea Polyphenols. Bioflavonoids are known as "nature's biological response modifiers", because they modify the body's reaction to compounds such as allergens, viruses, and carcinogens. According to Dr. Mark Neveu, “Flavonoids perform two important functions in the body. First, they strengthen the body’s immune response to attacks from allergens, viruses, and carcinogens. Second, they act as powerful antioxidants, protecting the body against the oxidative stress and free-radical damage that underlie many cardiovascular, neurological, and diabetic diseases. … One of the most important attributes of these flavonoids is their ability to enhance the effects of vitamin C. [And these] flavonoids have been shown to improve the concentration and efficacy of vitamin C throughout the body.”4
How Much Do You Need?If you are wondering how much of these nutrients you need to remain cold and flu free, some are easier to quantify than others. Bioflavonoids, alpha-carotene and omega-3s have no official recommended daily allowance (RDA). As for the rest, the RDA for ...
- beta-carotene is 600 mcg (1,000 IU) per day
- vitamin E is 15mg
- vitamin C is 75mg, with smokers requiring an extra 35mg to offset the damage their habit causes
- selenium is 55mcg for adults, 60 mcg for pregnant women and 70mcg lactating mothers
- zinc 11 mg for men and 8 mg for women, 11 mg for pregnant women and 12 mg for lactating mothers
The foods I listed above are not the only foods that contain those particular nutrients, of course. But they are easy to find year round, and contain effective amounts of those nutrients. Some items, like butternut squash, kale, spinach and peppers, contain more than one of the immunity boosting nutrients. Actually, most whole foods contain most of those nutrients. It's just the amounts that vary from one food to the next. That's one of the main benefits of eating a well-planned whole food diet. You never have to worry about becoming malnourished, and you greatly decrease your chances of falling ill when exposed to cold germs and flu viruses.
1 Fryburg DA, Mark RJ, Griffith BP, et al. “The effect of supplemental beta-carotene on immunologic indices in patients with AIDS: a pilot study”. Yale Journal of Biology and Medicine, January-April 1995. Web. January 4, 2016
2 Ströhle A, Wolters M and Hahn A. “Micronutrients at the interface between inflammation and infection – ascorbic acid and calciferol: part 1, general overview with a focus on ascorbic acid.” Inflammation & Allergy Drug Targets, February 2011. Web. January 5, 2016
3 Ehrlich, Steven D. “Selenium”. University of Maryland Medical Center, October 19, 2015. Web. January 5, 2016
4 Neveu MJ, PhD. “Vitamin C and Dihydroquercetin”. Life Extension, December 2006. Web. January 5, 2016
Higdon, Jane, PhD. “Carotenoids”. Linus Pauling Institute/Oregon State University, 2004. Web. January 4, 2016
Murakoshi M, Nishino H, Satomi Y, et al. “Potent preventive action of alpha-carotene against carcinogenesis: spontaneous liver carcinogenesis and promoting stage of lung and skin carcinogenesis in mice are suppressed more effectively by alpha-carotene than by beta-carotene”. Cancer Research, December 1, 1992. Web. January 4, 2016
Ashfaq MK, Zuberi HS and Anwar Waqar M. “Vitamin E and beta-carotene affect natural killer cell function”. International Journal of Food Sciences and Nutrition, 2000. Web. January 4, 2016
Challem, Jack. “Is Selenium Deficiency Behind Ebola, AIDS and Other Deadly Infections?” Dr. Passwater, 1994. Web. January 5, 2016
Horvath PM and Ip C. “Synergistic effect of vitamin E and selenium in the chemoprevention of mammary carcinogenesis in rats”. Cancer Research, November 1983. Web. January 5, 2015
Rink L and Gabriel P. “Zinc and the Immune System”. The Proceedings of the Nutrition Society, November 2000. Web. January 5, 2016
Fritsche, Kevin. “Fatty Acids as Modulators of the Immune Response”. Annual Review of Nutrition, August 2006. Web. January 5, 2016
Guest blog post by holistic writer Andrea Lewis