Ask Dr. Casey: Larch For Immunity

Hi Dr. Casey, 

With Thanksgiving coming up and other holiday gatherings, I am anticipating viral illness and colds making their rounds in full force. Do you have any recommendations to help me bolster my immune system against the common cold? 

- Tammy H 

Hi Tammy, 

Yes, viruses have as much of a party this time of year as we do - except they usually aren’t spreading holiday cheer. There are seemingly endless options of immune support to choose from, and understanding what to do during times of known or anticipated viral exposure can be overwhelming. I will focus on a few points of what to do and not to do that may not be so commonly talked about. 

Tending to the fundamentals of adequate quality sleep, well-balanced nutrition, exercise (ideally outside - yes, even in the Winter months!), and adequate rest time all help to bolster immune balance. I know I was put in my place earlier this Fall when I was pushing the limits many ways and sacrificed some sleep a couple nights in a row. I paid for it a few days later with a head cold, which I took as a sign to get back to my daily foundational habits. For those whom illness visits frequently (“I always get sick”), it could be a sign that the foundational habits may not be supportive, and the body’s (not-so) subtle invitation and likely annoying sign to prioritize them. For parents with kids in daycare, I won’t sugarcoat it: it can be a tough phase while your little ones bring home anything and everything.  Do what you can and know that your immune system is also getting an education just like your child’s. 

A potential faux pas I see frequently, especially post-COVID, is the intake of higher doses of zinc on a daily basis. Zinc is a necessary micronutrient for bodily processes, and taking it in smaller doses (< 15 mg) daily can ensure adequate levels for enzymatic processes. Lauded for its antiviral activity, zinc multiplies in potency when paired with quercetin as the chaperone into cells to boost its effects. However, there is a bit of a goldilocks effect with zinc: dosing has to be just right, and it is possible to overdo it. Zinc can outcompete another necessary micronutrient, copper, rendering copper deficiency at amounts of 60 mg/day for more than ten weeks (1). Copper deficiency can present much like anemia, and ironically, can lead to increased infection. I personally take anywhere from 3 - 10 mg/day of zinc, and when sick, exposed, traveling or going to large gatherings will do a short burst of 30 mg zinc with 250 mg quercetin once to twice daily. Taking more than 30 mg of zinc daily for the long term, especially without copper supplementation, has the potential to cause more harm than good. 

Of course, as a naturopathic physician, I am constantly inspired and learning from the natural world. This time of year in our region, larch trees, also known as tamarack by some, turn to golden spires amongst the coniferous forest before dropping their needles. I encourage you to get outside to a national forest and witness the phenomenon - it is a good dose of medicine to just behold. Forest bathing aside, larch trees contain a powerful compound known as arabinogalactans that are an underrated tool for immune support, amongst other health benefits. 

The carbohydrate compounds of arabinogalactans are found in a variety of naturally occurring sources, particularly in the fiber of cell walls of plants including carrot, radish pear and others (2). Arabinogalactans are especially abundant in the North American species of larch (Larix occidentalis), native to our neck of the woods. A 2013 study aimed to compare 4.5 g of daily dose of larch arabinogalactan powder to a placebo powder for ten weeks and found the treatment group to have a decreased cold incidence by 23% (3). Studies in animal and non-human studies have also shown an increase in natural killer cells, a part of our immune system necessary to mount a response to infection (4). 

Part of the immune-boosting properties of larch arabinogalactans may be the positive influence it has on the gut microbiome as a fermentable fiber. Now popularized as the general term of prebiotics, arabinogalactans can help to generate a healthy microbiome through production of short chain fatty acids as one mechanism (5). The fibrous nature of arabinogalactans is also theorized to have a stimulating impact on gut-associated lymphatic tissue to upregulate the immune system in the intestines. A 2020 study analyzing the effect of larch arabinogalactans paired with colostrum and lactobacilli probiotics demonstrated an increase in natural killer cells as well as a 65% improvement of IBS symptoms (6). Talk about a winning combo! 

In short, Tammy, consider taking a cue from our own natural surroundings this Fall and utilize a larch arabinogalactan supplement to bolster your immune system as well as give a boost to your gastrointestinal microbiome to help fend off the common cold. Plus, don’t forget your foundational daily basics and use zinc in moderation when needed. Wishing you robust health this holiday season! 

Sources

1. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academies Press; 2001.

2. D'Adamo P. Larch arabinogalactan. J Naturopath Med. 1996;4:32–9.

3. Riede L, Grube B, Gruenwald J. Larch arabinogalactan effects on reducing incidence of upper respiratory infections. Curr Med Res Opin. 2013;29(3):251-258. doi:10.1185/03007995.2013.765837

4. Currier NL, Lejtenyi D, Miller SC. Effect over time of in-vivo administration of the polysaccharide arabinogalactan on immune and hemopoietic cell lineages in murine spleen and bone marrow. Phytomedicine. 2003;10(2-3):145-153. doi:10.1078/094471103321659852

5. Dion C, Chappuis E, Ripoll C. Does larch arabinogalactan enhance immune function? A review of mechanistic and clinical trials. Nutr Metab (Lond). 2016;13:28. Published 2016 Apr 12. doi:10.1186/s12986-016-0086-x

6. Velikova T, Tumangelova-Yuzeir K, Georgieva R, et al. Lactobacilli Supplemented with Larch Arabinogalactan and Colostrum Stimulates an Immune Response towards Peripheral NK Activation and Gut Tolerance. Nutrients. 2020;12(6):1706. Published 2020 Jun 7. doi:10.3390/nu12061706