The “Junk Food” Effect
It is well documented that CO2 levels in the atmosphere are steadily rising, and plants depend on CO2 and sunlight to grow. So, what effect might an increase in CO2 have on the nutrient content of our crops? Dr. Irakli Loladze took interest in this topic when he observed that algae grew rapidly when exposed to sunlight, but were suddenly much less nutrient rich and unable to support life. The sugar-to-nutrient ratio in these algae was altered into what he called “junk food algae.” (Loladze 2014) Outside of the lab, Dr. Loladze stated “Every leaf and every grass blade on earth makes more and more sugars as CO2 levels keep rising.” (Evich 2017)
“Rising CO2 revs up photosynthesis, the process that helps plants transform sunlight to food. This makes plants grow, but it also leads them to pack in more carbohydrates like glucose at the expense of other nutrients that we depend on, like protein, iron, and zinc.” (Evich 2017) This process is called CO2 fertilization. So, as time goes on, we cannot help but wonder what these environmental changes are doing to the nutritional quality of our food.
A report from the United Nations’ Intergovernmental Panel on Climate Change discussed the effects that the increasing global temperatures and CO2 concentrations may have on our crops. The report proposes two main routes by which our food quality may be affected.
- Increasing temperatures changing the basic metabolism of plants.
- Increasing CO2 concentrations causing “CO2”
Essentially, greater atmospheric concentrations of CO2 can change the way that plants invest in growth versus reproduction, which may decrease protein and mineral concentrations. (DaMatta et al. 2010)
What if Carbon Dioxide Levels Continue to Increase?
A meta-analysis from seven FACE (Free-Air Carbon Dioxide Enrichment) experiments found that increasing atmospheric CO2 concentration to 546 to 586 parts per million would cause the following changes:
- Wheat grains would see a 9.3% decrease in zinc, a 5.1% decrease in iron, and a 6.3% decrease in protein content.
- Rice grains would have a 7.8% lower protein content.
(Myers et al. 2014)
Another meta-analysis of FACE trials on a range of rice cultivars calculated that with this increase in CO2,
- Protein content decreases by an average of 10%.
- Iron decreases by 8%.
- Zinc decreases by 5%.
- Vitamin B1 decreases by 17%.
- Riboflavin decreases by 17%.
- Pantothenic acid decreases 13%.
- Folate decreases 30%.
(Zhu et al. 2018)
Has the Nutrient Content of Our Food Already Changed?
Researchers at the University of Texas studied the nutrient content of 43 garden crops from 1950 to 1999 and saw the following changes:
- Median calcium content decreased by 16%
- Median phosphorus content decreased by 9%
- Median iron content decreased 15%
- Median ash content (major minerals, mostly potassium) decreased 6%
- Riboflavin content decreased 38%
- Ascorbic acid content decreased 15%
(Davis et al. 2004)
So, we’ve already seen a significant decrease in the micronutrient content of our food. Unless some serious changes are made, this unfortunate trend will only continue.
Is the USDA Reported Micronutrient Content Still Accurate?
If we are seeing these changes in our garden crops, what does that mean about the nutrient content of our food reported by the USDA?
Well, Davis and colleagues set out to answer this question by studying the actual calcium and magnesium content of broccoli as compared to that which was reported by the USDA. They found that the broccoli they studied had an average calcium concentration of 2.6mg/g vs. the USDA reported content of 4.4mg/g, and a magnesium concentration of 2.2mg/g vs. the USDA reported content of 2.0mg/g (as of 2003). “Consumers get nearly the same total amount of Ca and Mg per head, but diluted in a larger amount of water, dry matter, fiber, and energy.” (Davis et al. 2004)
What does this mean for us? Well, you may need to eat more broccoli today to get the same amount of micronutrients that you would have gotten by eating a smaller portion in the past. It is an unfortunate fact that even those of us who are eating a diet rich in fruits, vegetables, nuts, and seeds are probably not getting as many vitamins and minerals as we might expect.
Despite the dismal nature of these statistics, we are in control going forward. To prevent further declines in nutrient composition due to global warming, it is our responsibility as residents of this planet to make a conscious effort to decrease our carbon footprint. Next time you consider driving to your friend's house two blocks down the street, remember that, over time, your carbon emissions could change the nutritional quality of food for all of us.
In the meantime, we can ensure we are getting enough nutrients by supplementing with what we may fall short on. There are many high-quality nutritional supplements out there that can help you maximize your health, despite the uncertainty of these nutrients being delivered from food. I wish you all well in your journey to better health, and may we all make small steps toward reducing our carbon footprint.
DaMatta, F. M., A. Grandis, B. C. Arenque-Musa, and M.S. Buckeridge. 2010: Impacts of climate changes on crop physiology and food quality. Food Research International 43(7):1814–1823. Doi: 10.1016/j.foodres.2009.11.001.
Davis, D. R., M. D. Epp and H. D. Riordan. 2004. Changes in USDA food composition data for 43 garden crops, 1950 to 1999. Journal of the American College of Nutrition 23(6):669–682.
Evich, H. B. 2017.The Great Nutrient Collapse. Poltico Sept 13, 2017. Accessed 6 Nov. 2019.
Loladze, I. 2014. Hidden shift of the ionome of plants exposed to elevated CO2 depletes minerals at the base of human nutrition. eLife 3: e02245. Doi: 10.7554/eLife.02245.
Myers, S. S., A. Zanobetti, I. Kloog, et al. 2014: Increasing CO2 threatens human nutrition. Nature 510:139–142. Doi: 10.1038/nature13179.
Zhu, C., K. Kobayashi, I. Loladze, J. Zhu, Q. Jiang, X. Xu, G. Liu, S. Seneweera, K. L. Ebi, A. Drewnowski, N. K. Fukagawa, and L. H. Ziska. 2018: Carbon dioxide (CO2) levels this century will alter the protein, micronutrients, and vitamin content of rice grains with potential health consequences for the poorest rice-dependent countries. Science Advances 4(5):eaaq1012.
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