Le lien crucial entre l’alimentation animale et la santé humaine

 De : https://articles.mercola.com/sites/articles/archive/2024/11/05/animal-feed-human-health.aspx

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The Crucial Connection Between Animal Feed and Human Health

Analysis by Ashley Armstrong  5 novembre 2024

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Story at-a-glance

• The diet of animals we consume directly affects the nutritional quality of meat, dairy, and eggs, which impacts human health
• Modern farming practices have increased PUFA (polyunsaturated fat) levels in chicken and pork, contributing to the overconsumption of omega-6 fats. High PUFA intake can lead to health issues, including liver problems, inflammation, and metabolic disruption
• Conventional chicken is now the highest source of linoleic acid (LA), a problematic omega-6 fat, in the American diet. Pigs fed a high-PUFA diet can have fat concentrations similar to canola oil
• Ruminant animals like cows have a unique digestive system that helps convert PUFAs into more stable saturated fats
• You can reduce PUFA intake by choosing grass fed meat, pasture-raised animal products, and avoiding seed oils

In our modern quest for optimal health, we often focus intensely on what we put on our plates. However, there's a crucial aspect of nutrition that often goes overlooked: the diet of the animals we consume. (What we eat, eats) This oversight can have significant consequences for our health, particularly when it comes to our intake of polyunsaturated fatty acids (PUFAs).

Consider this startling fact: conventional chicken is now the highest source of linoleic acid, an omega-6 PUFA, in the American diet. This means that a food many consider to be a healthy, lean protein source is actually contributing significantly to our overconsumption of PUFAs.

Figure 1. Top source of linoleic acid consumption in the U.S.¹

But it's not just chicken we need to be concerned about. Pork, another staple in many diets, can be equally problematic. When pigs are fed a high-PUFA diet, their fat can have the same PUFA concentration as canola oil — a fact that might make you think twice about having several pieces of conventional bacon every single day for breakfast.

These surprising revelations beg the question: how did we get here, and what does it mean for our health? The answer lies in the intricate relationship between animal feed and the nutritional quality of meat, eggs, and dairy products that end up on our tables. As the saying goes, "You are what you eat." But perhaps more accurately, we are what our food eats.

So, let’s delve into why the diet of the animals we consume matters so much for our health. We'll explore the science behind animal digestion, the problems with high PUFA intake, and how modern farming practices have changed the nutritional profile of our animal products. Most importantly, we'll discuss what you can do to make informed choices and optimize your diet in light of this information.

Understanding Animal Digestive Systems

To comprehend why animal feed is so important, we first need to discuss the fundamental differences in how various animals process their food. Animals are broadly classified into two categories based on their digestive systems: ruminants and monogastric animals.

Ruminants, such as cattle, sheep, goats, and deer, have a specialized digestive system featuring a stomach with four compartments: the rumen, reticulum, omasum, and abomasum. This unique setup allows them to efficiently break down fibrous plant material through a process called fermentation.

The rumen, the largest compartment, is home to a diverse community of microorganisms that play a crucial role in digestion. These microbes break down cellulose and other tough fibers that would be indigestible to most other animals. This process allows ruminants to thrive on a diet of grasses and other plant matter that would provide little nutritional value to other species.

Monogastric animals, including pigs, chickens, dogs, cats, and humans, have a single-chambered stomach. Their digestive process is more straightforward compared to ruminants, with digestion occurring mainly in the stomach and then in the intestines.

Unlike ruminants, monogastric animals cannot efficiently break down cellulose. This means they require a more varied diet and supplemental feed to meet their nutritional needs.

In nature, monogastric animals like pigs and chickens would forage for a diverse range of foods, including insects, seeds, fruits, and small animals. In the conventional system where corn and soy are government subsidized, and thus cheap feed ingredients, their diets are now high in PUFA rich ingredients.

Now that we understand the basic differences in animal digestive systems, let's dive into a critical issue in modern nutrition: the prevalence of polyunsaturated fatty acids (PUFAs) in our diets, particularly linoleic acid, an omega-6 fatty acid.

What Are PUFAs?

Fats are composed of fatty acids, which can be categorized into three main types:

1. Saturated fatty acids (SFAs) — These have no double bonds between carbon atoms.

2. Monounsaturated fatty acids (MUFAs) — These contain one double bond.

3. Polyunsaturated fatty acids (PUFAs) — These contain two or more double bonds.

The number of double bonds in a fatty acid is crucial because it affects the fat's stability and how it behaves in our bodies. PUFAs, with their multiple double bonds, are the least stable and most prone to oxidation.

Over the past century, there has been a dramatic increase in PUFA consumption, particularly linoleic acid. This shift is largely due to the widespread use of seed oils (often called vegetable oils) in food production and as a component of animal feed. Common sources of these oils include:

Vegetable oil (which is some combination of the items below)	Soybean oil
Corn oil	Sunflower oil
Safflower oil	Canola oil

These oils are high in omega-6 PUFAs, particularly linoleic acid. While omega-6 fatty acids are essential in small amounts, the modern diet often contains an excessive and potentially harmful level of these fats.

"Prior to the 20th century, the average intake of LA was under 2% of the total daily caloric intake. The biological optimal range is approximately 1% to 2%, but current LA consumption is over 25% of the total calorie intake for the average person."²

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Why PUFAs Are Problematic

1. Instability and oxidation — PUFAs are highly unstable due to their chemical structure. Each double bond in the fatty acid makes it more susceptible to oxidation.³ This instability means that PUFAs can easily form harmful compounds when exposed to heat, light, or oxygen — a process that can occur during cooking or even inside our bodies.

2. Tissue incorporation — The fat we consume is used as a fuel source, but it is also used to make up structures inside of us. So dietary fats have energy, structural and signaling roles — impacting metabolism, gut health, cellular repair, and more. A higher PUFA environment inside of you will lead to different cellular signaling relative to an environment that is low/moderate PUFA and higher in SFA.

When a lot of PUFAs get incorporated into cellular structures, they make cells very fluid, leaky and unstable. Being too fluid impairs proper cellular function⁴ and can increase permeability and leakiness, letting things we do not want to get inside the cell⁵ — like water leaking from a bucket with holes. We of course want some permeability, but too much can allow electron leakage and large sized particles, like calcium, to get inside cells.

The half-life of fats is approximately 2 years, meaning these fats stick around for a while and it can take up to 2 years to improve the fatty acid profile inside of you!

3. Oxidative damage — When PUFAs oxidize, they form lipid peroxides and other breakdown products that can cause significant cellular damage.^6,7,8 These oxidized fats can harm proteins, DNA, and other crucial cellular components, potentially leading to inflammation and various health issues.

4. Disrupt liver function — The liver plays a crucial role in processing fats and detoxifying harmful substances in our bodies. High PUFA intake, especially linoleic acid, has been linked to liver problems. PUFAs can promote liver fibrosis.^9,10 Plus, experimental and epidemiological studies have shown that dietary linoleic acid is required for the development of alcoholic liver damage.¹¹

Even small amounts of linoleic acid (0.7% or 2.5% of diet) combined with alcohol consumption caused fatty liver, necrosis, and inflammation in animal studies. These findings suggest that the high levels of linoleic acid in modern diets, partly from high-PUFA animal products, may be contributing to the rise in liver diseases.

5. Metabolic disruption — High PUFA intake can interfere with thyroid function and metabolism.^12,13,14,15 PUFAs have been shown to block thyroid hormone production, transport, and receptor binding, leading to a slower metabolism and associated health problems. Studies have shown that reducing PUFA consumption can increase metabolic rate (measured by basal respiration).¹⁶

A lower metabolic rate means down regulated systemic function (you won’t function at your best) AND weight gain even with a lower calorie intake — something no one wants or needs.

6. Impaired carbohydrate utilization — PUFAs can inhibit the body's ability to properly use carbohydrates.^17,18,19 They interfere with key enzymes involved in glucose metabolism, potentially contributing to insulin resistance and metabolic syndrome.^20,21

More specifically, studies document that PUFAs Inhibit Cytochrome C Oxidase activity²² and inhibit the function of the PDH enzyme.^23,24 PDH is the rate-limiting complex responsible for the decarboxylation of pyruvate to acetyl-CoA and thus serves as a pivotal role in fuel selection and regulation of carb oxidation.

PUFAs have a reductive effect, pushing the pyruvate towards the lactate, glycolytic pathway instead of the acetyl-CoA and thus full oxidative phosphorylation pathway.

One study noted that "enrichment of the diet with polyunsaturated fatty acids causes changes in adipose tissue metabolism that favour fat deposition."²⁵ Another study demonstrated that consuming a meal high in PUFAs, as opposed to saturated fats, led to lower rates of carbohydrate oxidation after the meal.²⁶

These findings suggest that the high PUFA content in modern diets, including from animal products, may be contributing to the rising rates of Type 2 diabetes and obesity.

7. Damage hut health and increase inflammation — The health of our gut is intrinsically linked to our overall well-being, and high PUFA intake may be compromising gut integrity:

• PUFAs can increase the permeability of tight junctions in the gut,²⁷ potentially leading to "leaky gut" syndrome.

• A diet rich in omega-6 PUFAs resulted in increased host inflammation, oxidative stress, and gut barrier dysfunction in one study.²⁸

• High dietary intake of linoleic acid was associated with a significant increase in ulcerative colitis, an inflammatory bowel disease.²⁹

These effects on gut health can have wide-ranging consequences, as gut health is linked to immune function, mental health, and various other aspects of overall well-being.

Diets high in omega-6 PUFAs have been associated with increased inflammation and gut permeability. This can contribute to various inflammatory conditions and potentially compromise gut health.

8. Cholesterol synthesis inhibition — While often vilified, cholesterol plays crucial roles in our bodies, including hormone production and cell membrane integrity. PUFAs can inhibit the body's natural cholesterol production, which may have unintended negative consequences.

We of course do not want super high levels of cholesterol (that is a sign of hypothyroid), but we also don’t want super low cholesterol since cholesterol is protective.^30,31

Moreover, anything that suppresses your cholesterol synthesis increases the risk of cancer.³² Statins are major carcinogens and are linked to diseases like ALS and other muscular dystrophies.

9. Immune suppression — High PUFA intake can suppress immune function.^33,34,35 This immunosuppressive effect is so well-established that there are several established products on the medical market based on a combo of linoleic and linolenic acid that are given to organ transplant patients.³⁶

"Vegetable oil is recognized as a drug for knocking out the immune system. Vegetable oil emulsions were used to nourish cancer patients, but it was discovered that the unsaturated oils were suppressing their immune systems.

The same products, in which vegetable oil is emulsified with water for intravenous injection, are now marketed specifically for the purpose of suppressing immunity in patients who have had organ transplants.

Using the oils in foods has the same harmful effect on the immune system. [E. A. Mascioli, et al.,Lipids 22(6) 421, 1987.] Unsaturated fats directly kill white blood cells. [C. J. Meade and J. Martin, Adv. Lipid Res., 127, 1978.]" — Dr. Ray Peat

The immunosuppressive effects of vegetable oils are not limited to intravenous administration. Consuming vegetable oils in foods has been found to have similar harmful effects on the immune system. This is particularly concerning given the widespread use of vegetable oils (and high linoleic acid levels) in modern diets.

Now that we understand the potential issues with high PUFA intake, let's explore how the feed given to livestock impacts the nutritional composition of the animal products we consume.

The Feed-Food Connection: How Animal Diets Affect Our Health

Ruminants, thanks to their unique digestive system, have a natural mechanism that helps protect against high levels of PUFAs in their tissues. The bacteria in their rumen can convert some of the PUFAs they consume into saturated fats through a process called biohydrogenation.

This means that the fat in beef and milk will still tend to be more saturated. However, it's important to note that modern farming practices can still influence the fat composition of ruminant products. (Scientists are now researching how to bypass this process and have been able to significantly increase PUFA concentration — yuck!) A conversation for another day!

The situation is quite different for monogastric animals like pigs and chickens. These animals do not have the biohydrogenation process that occurs in ruminants. As a result, the fats they consume are more directly reflected in their body fat and other products. Several studies have demonstrated this direct relationship.

In pigs, increasing dietary PUFA led to a significant decrease in saturated fatty acid levels in adipose tissue. The concentration of linoleic acid increased significantly with an increase in dietary PUFA.³⁷ In chickens, the PUFA content of thigh meat increased exponentially as the inclusion of dietary PUFA increased.³⁸

The push to decrease saturated fat content in animal products has led to an increase in PUFA content in our food system, based on the misguided belief that this improves the nutritional quality of the meat.

"Overall, decreasing the content of SFA and increasing the content of UFA have become the trend of improving the nutritional quality of pork."³⁹ The conventional system is trying to manipulate food to fit a false health narrative!

And they contradict themselves all the time in the literature — "It’s well known that although dietary PUFA improves meat nutritional qualities, such meats are more susceptible to lipid oxidation during processing."⁴⁰ It is well documented how unstable these fats are!

This direct relationship between livestock feed and fat composition in monogastric animals means that conventional chicken and pork can be significant sources of PUFAs in the modern diet. And as we discussed earlier, the higher PUFA content of modern can have far-reaching effects on human health. High-PUFA diets will negatively impact:

Metabolic health	Thyroid health
Gut health	Liver health
Inflammation	Insulin sensitivity and glucose metabolism
Cholesterol synthesis	DNA and cellular structures

While some papers were presented above, there are more papers outlined in Dr. Mercola’s review article.⁴¹

Taking Control: Five Actionable Steps for Reducing PUFA Intake

Given the potential health implications of high PUFA intake, it's crucial to take steps to reduce our consumption. Here are five practical strategies:

1. Avoid seed oils — The most direct way to reduce PUFA intake is to eliminate or drastically reduce consumption of seed oils:

• Choose healthier, more traditional cooking fats like tallow, ghee, butter, and coconut oil.

• When buying packaged foods, check the ingredient list and avoid products containing vegetable oil, grapeseed oil, soybean oil, corn oil, sunflower oil, safflower oil, or canola oil.

• It is okay to eat out from time to time! But try to prioritize cooking your meals at home, as seed oils are hard to avoid when eating out all the time.

2. Reduce consumption of nuts and seeds (which are high in PUFAs) — It is not ancestrally consistent to consume a diet high in nuts and seeds. They didn’t have access to online websites where they could order an endless supply of nuts and seeds. Instead, their survival relied on saving seeds from the food they consumed to plant in their gardens the following year.

3. Be mindful when dining out — Restaurant meals can be a significant source of hidden PUFAs. However, there are some ways to pick healthier options!

• Choose dishes that contain ruminant meats over chicken or pork when possible. The ruminant meat will contain less PUFA relative to the confinement raised chicken and pork option at the restaurant.

• Ask for sauces on the side, as many are made with seed oils.

• Ask if your food be cooked in butter instead of the usual cooking oil.

• Consider steamed options to avoid added oils altogether.

4. Source grass fed meat and milk to avoid the fatty acid manipulation that some manufacturers are experimenting with in ruminant products using oilseeds and "rumen bypass." Grass fed meat and milk will reliably have a lower omega-6 content.

5. Select pasture-raised for chicken and pork products:

• Look for products from animals raised on pasture from farmers you trust — These animals have a more natural diet that typically results in a better fatty acid profile in their products.

• For eggs, look for "pasture raised" — While not perfect (since they are still on a supplemental feed that is likely rich in PUFAs), these hens typically have more access to their natural diet of insects and plants, which can improve the nutritional profile of their eggs relative to chickens raised in cages where there only food options are PUFA rich feed.

More information on a source that I created to address this PUFA problem in chicken and pork that ships across the U.S. below!

Conclusion: You Are What Your Food Eats

The saying "you are what you eat" extends further than we might initially think. The diet of the animals we consume plays a crucial role in determining the nutritional quality of our own diets. By being mindful of the feed given to livestock, we can make more informed choices about the animal products we consume and potentially improve our health outcomes.

Stay informed, make conscious choices, and don't be afraid to ask questions about where your food comes from and how it was raised. Your health will thank you for it.

And remember, the goal is not zero PUFA, as this is impossible! All animal products and dietary fat sources will have some amount of PUFA. But reducing linoleic acid and omega-6 intake where you can is beneficial for overall health.

Low-PUFA Eggs and Meat

Exciting news for those looking to take control of their PUFA intake: Angel Acres now has limited openings for their custom-formulated, low-PUFA eggs (which are shipped to all 50 states). These nutrient-dense superfood eggs contain 62% less linoleic acid (an omega-6 PUFA) compared to pasture-raised eggs fed a standard diet, and 70% less linoleic acid than 'cage free' eggs.

Act now to take advantage of this opportunity to minimize your PUFA intake while enjoying these exceptional eggs.

Dr. Mercola and Ashley discussed the importance of low-PUFA eggs in a previous interview, embedded above for your convenience.

Armstrong also co-founded the sister organization, Nourish Food Club, which ships the best low-PUFA pork, low PUFA chicken meat, beef, cheese and A2 dairy, and traditional sourdough to all 50 states. They are close to accepting new members to the farm cooperative — join the waitlist here: nourishcooperative.com.

About the Author

Ashley Armstrong is the co-founder of Angel Acres Egg Co., which specializes in low-PUFA eggs, and Nourish Cooperative, which ships low-PUFA pork, beef, cheese, A2 dairy and traditional sourdough to all 50 states.