NWIW Internship 2019
Numerous studies from a health or environmental standpoint have shown how the population can make changes to improve each field of studies’ respective issues. Combining results from several research studies, this paper shows how shifting one’s diet to include fewer animal products positively impacts both health and the environment. This dietary change not only decreases one’s carbon footprints, but also minimizes risks for some of the leading causes of death, in particular cholesterol-related diseases.
In recent years, health and environmental awareness have risen to become a national, or even global, concern. In the U.S., staggering statistics of diet-related conditions confirm that change needs to happen at the individual level. Alongside health awareness, the ramifications of the Greenhouse Effect are also pushing the nation to be more environmentally conscious. Despite seemingly having very different end goals in mind, both environmentalists and nutritionists can join forces and promote an option that benefits everyone. By reducing the intake of animal foods, risks of life-threatening diseases and carbon footprints can be decreased. This will not only help improve health conditions but also lower carbon emissions on a national scale.
Cholesterol and Its Effects on Health
Cholesterol is an organic molecule created by the body or ingested from animal foods. Around 20% of dietary cholesterol is consumed, while the other 80% is made in the body. This waxy substance is synthesized in the liver and requires acetyl-CoA, an essential molecule for regulating fatty acid synthesis. The acetyl-CoA is passed through a variety of complex reactions that ultimately produce cholesterol. 
Although often shunned as an unhealthy molecule, an adequate amount of cholesterol is essential to building cell membranes, making hormones, maintaining metabolism, and producing vitamins and bile acids. However, once blood cholesterol levels rise above 200mg/dL (200 milligrams of cholesterol for every deciliter of blood), the patient increases their risk for high blood cholesterol (diagnosed as hypercholesterolemia). 
A rise in the body’s cholesterol level can be linked to either hereditary diseases or faulty dietary habits. It is estimated that almost 1 in 3 American adults have high cholesterol, but only 1 in 300 cases of high cholesterol is familial hypercholesterolemia, ruling out hereditary diseases as the primary issue. As a result, faulty dietary habits account for the majority of cases. These habits are characterised by eating an excessive amount of animal foods, frequently exceeding the dietary recommendation of 300 milligrams per day. Excessive digestion of cholesterol results in high blood cholesterol levels, a source various potentially fatal diseases.
LDL (low-density lipoproteins) and HDL (high-density lipoproteins) are the two categories of cholesterol in the body. Dubbed as the “bad” cholesterol, high LDL levels result in a buildup of cholesterol on artery walls, blocking or narrowing certain vessels. Blockage or narrowing of vessels hardens the arteries, resulting in a medical condition called atherosclerosis. This puts the body at danger for life-threatening diseases such as coronary heart disease, strokes, Type 2 diabetes, and high blood pressure; some of America’s leading causes of death. On the other hand, HDL, the “good” cholesterol, lowers blood cholesterol levels by absorbing cholesterol in the bloodstream and carrying it back to the liver.
Figure 1: LDL and HDL Cholesterol in Arteries
Figure 2: Atherosclerosis in Arteries
Figure 3: Death Rates for the 10 Leading Causes of Death in the United States (2016,2017)
Risks for Cholesterol-Related Diseases Based on Diets
The impact of ingested cholesterol from animal foods is most notable when comparing the health of those with different diets. These dietary habits range from meat-lovers to vegans and are categorised by the amount of food consumed from each food group. As shown in Figure 4, the amount of energy animals foods account for in a diet decreases from around 35% in a meat lover to 0% in a vegan. Between the two extreme diets (average to vegetarian), animal foods account for 10-25% of the energy expended. Furthermore, as dietary cholesterol ingested decreases with the number of animal foods consumed, eating fewer animal foods will therefore lower cholesterol levels in the body. For example, a vegan diet, which consists of no dietary cholesterol, has no energy expended on animal foods and is also shown to reduce cholesterol levels by 10-30% in comparison to an average diet.
Figure 4: Food Energy Distribution in Different Diets
As cholesterol levels drop in a less animal-food-intensive diet, risks for cholesterol-related diseases decrease concurrently as well[8,9]. A 2015 study released by the Atherosclerosis Risk in Communities (ARIC) followed the health of 11,000 adult males for a median of 22.7 years. They found that the men who were the highest consumers of processed meat (i.e. jerky, bacon, sausage) had a 24% increased chance of stroke, a cholesterol-related disease. Similarly, the highest consumers of red meat (beef, lamb, pork) had a 41% increased chance of stroke. In total, the high consumers of both red and processed meat had a 62% higher chance of stroke than the average male. Since this group often consumes large volumes of food extremely high in dietary cholesterol, their bodies are more at risk for buildup and blockage of blood vessels. Therefore, it comes as no surprise that they are much more susceptible to strokes.
On the other hand, an analysis in 2017 by the Icahn School of Medicine showed that a plant-based diet can decrease the risk of heart disease, another cholesterol-related condition, by 42%. Furthermore, those who maintained a healthy plant-based diet were 25% less likely to develop heart disease in the next twenty years compared to those who did have a healthy plant-based diet.
Figure 5: Probability for Heart Disease of Stroke Based on Diet[8,9]
Reducing Emissions with a Low-Cholesterol Diet
Research shows that eating fewer animal foods also reduces carbon footprints, in addition to reducing the risk of cholesterol-related diseases. Foods containing dietary cholesterol are often the most carbon-intensive in comparison to plant-based foods due to the inefficient transformation of energy. A 2018 study found that food production accounts for 26% of global GHG (greenhouse gas) emissions, and animal foods accounting for a staggering 31% of that number.
Figure 6: Carbon Emissions of Different Types of Food
Therefore, diets consisting of high proportions of animal foods, in particular, beef, inevitably have a high carbon footprint. On the contrary, switching out less carbon-intensive foods can greatly reduce carbon footprints. This requires no dramatic in daily life, as many alternatives, which provide similar nutrition for both less cholesterol and carbon emissions, are available. For example, in the meat lover’s diet in Figure 7, beef accounts for 1.5 of the 3.3 t CO2e. By simply cutting out the beef, one can reduce their carbon emissions by 1.5 tonnes. In addition, these changes will have little impact on their protein intake. For example, in 100 grams of steak, there are 78 mg of cholesterol and 25 grams of protein. Yet, the same quantity of salmon has a similar 20 grams of protein, but only 55 mg of cholesterol. Although both salmon and steak are great sources of protein, one is considerably more harmful to the environment than the other. Therefore, conscious decisions to eat fewer animal foods can both lower intake of dietary cholesterol and reduce carbon footprints, improving both the body’s health and the environment.
Figure 7: Carbon Footprints (t CO2e/person) Based on Different Diets
Figure 8: Relation Between Risk for Disease and Food Carbon Emissions[7,8,9]
Blood cholesterol levels are essential in reducing risks for life-threatening diseases such as strokes, heart diseases, high blood pressure, and Type 2 diabetes. As cholesterol is most often consumed, the number of animal foods, which are carbon-intensive to produce, in a diet plays a large role in determining one’s blood cholesterol levels. Managing these levels is essential in controlling risks for life-threatening diseases such as strokes, heart diseases, high blood pressure, and Type 2 diabetes. Therefore, decreasing the consumption of animal foods, which contain cholesterol, can simultaneously minimize carbon footprints and risk for cholesterol-related disease, combating primary issues of both health and the environment.
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About the Author
Audrey is a junior in high school from California interested in Environmental Studies and Cancer Research. She plays both Varsity squash and tennis for her high school and loves reading and drawing in her free time.