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The "carnivore diet" aka carnivore diet? What do scientific studies say about this topic?

Die „Carnivore Diät“ alias Carnivore Diät? Was sagen wissenschaftliche Studien zu diesem Thema?

Having looked at what the carnivore diet is in the first two parts of this article series and begun to examine the extent to which the claimed benefits of this diet are factual, in this third part of this article series we will look at the alleged positive effects of the carnivore diet on testosterone levels and take a closer look at the issue of nutrient deficiencies before coming to a final assessment of this nutritional approach.


People who follow the Carnivore Diet and other high-fat diets often claim that these diets can increase testosterone levels, which in return can lead to a number of benefits ranging from fat loss to muscle gain, increased libido, more energy and stamina and more.

There is some truth in this statement.

Eating more dietary fat can indeed increase testosterone levels - but not as significantly as many followers of high-fat diets would have you believe.

In other words, even though a high-fat diet can increase your hormone production, it's not enough to help you burn fat, build muscle faster or become a male sex god.

To understand why this is the case, let's look at a frequently cited study on this topic conducted by scientists at the National Cancer Institute (57).

The scientists divided 43 men between the ages of 19 and 56 into two groups:

  1. Group one followed a diet that provided 41% of calories in the form of fat, with most of the fat coming from saturated sources.
  2. Group two followed a diet that provided 19% of calories in the form of fat, with most of the fat coming from polyunsaturated sources (polyunsaturated fats such as canola oil are liquid at room temperature).

Both groups consumed the same amount of calories, the same amount of protein and more or less the same types of food, and all meals were provided by the scientists to ensure exact adherence to the dietary guidelines.

After 10 weeks, the scientists found that group one - which consumed more than twice as much fat as group two - had 13% higher testosterone levels than group two.

Another study conducted by scientists at the National Public Health Institute of Finland showed similar results (58).

However, even though a 13% increase looks good on paper, scientific research clearly shows that this is not nearly enough to cause significant changes in terms of fat loss, muscle gain or overall health and well-being.

For example, it is known that training with weights can increase post-workout testosterone levels by up to 15% (59).

But does this lead to greater muscle gains and increased fat loss?

Scientists at McMaster University investigated this relationship in a study conducted with young men experienced in weight training who completed 5 weight training sessions per week and followed a standard "bodybuilding diet" as part of the study (60).

After 12 weeks, the scientists found that training-induced increases in anabolic hormone levels had no effect on muscle growth or strength gains. The magnitude of the hormonal response varied greatly between subjects, but there were no significant changes in muscle and strength gains.

Another notable study was conducted by researchers at Charles R. Drew University of Medicine and Science (61). This study involved manipulating the testosterone levels of 61 young healthy men using a combination of testosterone and drugs that suppress natural testosterone production.

After 20 weeks, the scientists found a dose-dependent relationship between testosterone levels and leg strength (higher levels meant more strength), but the effects were not significant until testosterone levels exceeded the upper limit of the natural range by 20 to 30% (about 1,200 ng/dL).

And to put this in perspective, here's an excerpt from steroid research. Scientists at Maastricht University published a comprehensive study review on the topic in 2004 and found the following (61):

  • Muscle gains in people who train with weights and use steroids range from 4.5 to 11 pounds within a short period of time (less than 10 weeks).
  • The largest amount of muscle gain was 15.5 pounds within 6 weeks

Compare this to the amount of muscle you can build naturally and you'll understand what I'm getting at:

Even if you extremely increase your hormone levels with steroids, it doesn't necessarily mean you'll build shocking amounts of muscle mass. And if this is the case even with the extreme hormone levels that come from using artificial hormones, what does this tell us about minor fluctuations that occur within the normal range?

These minor changes will not make much difference unless they are from the absolute lowest to the highest of the normal range - which would not be achievable through a change in diet.

This is the reason why I recommend a high protein, high carbohydrate diet with moderate fat consumption for muscle building. This diet will allow you to reap the significant muscle building benefits of protein and carbohydrates rather than chasing negligible changes in hormone levels through extreme dietary changes.

The bottom line is that the Carnivore Diet will not make your testosterone levels skyrocket, nor will it help you build more muscle or improve your libido, energy or mood.

Nutrient deficiencies

You've probably heard that a healthy diet is a balanced diet.

Different foods contain different amounts of vitamins and minerals. By eating many different foods and food groups, you can therefore ensure that you get enough of everything your body needs.

That's why one of the first things many people ask about the Carnivore Diet is: "How do I get all the nutrients I need from steak and hamburgers?"

Well, meat is a very nutritious food, but it also contains very low amounts of several important vitamins like vitamin C and it's also low in fiber.

Vitamin C is important because it is involved in many different functions in the body, which include wound healing, immune function, iron absorption and protecting cells from oxidative damage.

If you take very little vitamin C (less than 10 mg per day) for long enough, you can develop scurvy, which can cause inflammation of the gums and tooth loss, fatigue, skin ulcers, joint pain and ultimately death.

Fiber is also important as it is responsible for maintaining regular digestion, regulating cholesterol levels and good digestive health.

The Carnivore Diet provides very little of either, so how can it be considered healthy?

Let's start with vitamin C.

The recommended daily intake of vitamin C for the average adult male is 90 mg and 75 mg for women. Most meats including chicken, turkey, beef, lamb and pork contain little or no vitamin C. The exception is offal such as liver, heart and kidneys, which contain traces of vitamin C.

Beef liver, for example, contains 1 mg of vitamin C per 100 grams, lamb liver contains 4 mg and chicken liver 18 mg. So if you were to try to cover your entire vitamin C requirement with chicken liver alone, you would have to eat over a pound a day. (Which, by the way, is likely to be problematic due to the high content of vitamin A, which accumulates in the body and is toxic in high quantities).

In comparison, oranges contain 53 mg of vitamin C per 100 grams - more than half the daily requirement.

How are you supposed to get enough vitamin C without eating plants?

The standard answer from followers of the carnivore diet is that you don't need much vitamin C to stay healthy if you don't eat carbohydrates.

This is exactly what Dr. Shawn Baker said in the interview with Joe Rogan mentioned above, and he gave two reasons for this. Remember the glucose and vitamin C transporter story we looked at earlier?

Well, Baker argues that because vitamin and glucose compete for the same transporter (which in reality they don't) and because low carbohydrate diets generally result in lower insulin levels (63), a reduced carbohydrate intake reduces the need for vitamin C because the body is better able to absorb what it gets. As a result, higher carbohydrate intake is said to increase vitamin C requirements.

This may sound quite scientific, but as I have already pointed out, this is completely wrong (64). Vitamin C can enter cells through transporters that are not affected by glucose (SVCT1 and SVCT2), and therefore your body has no problem absorbing vitamin C regardless of carbohydrate intake.

Baker and others also argue that the recommended daily requirements for vitamin C, manganese and other nutrients are based on research conducted with people who eat large amounts of carbohydrates and therefore do not apply to people who do not eat carbohydrates.

There is, of course, no scientific data to support this theory.

As far as we know, eating fewer carbohydrates does not fundamentally and dramatically change the body's nutritional needs and to assume otherwise is not only speculative but also potentially dangerous.

And this is especially true for the carnivore diet, which is extremely restrictive.

Although we don't know how this style of diet plan will pan out nutritionally, we can venture a rough estimate with the help of a study conducted by scientists at the Department of Nutritional Research and Education that looked at the nutrient density of popular weight loss diets (Atkins Diet, South Beach Diet, Dash Diet and Best Life Diet) (65).

The researchers added up the average amounts of calories and micronutrients consumed over three days on each of these diets and compared these values with the recommended daily intake of each of these micronutrients.

They found that, on average, the four diets only provided adequate amounts of 12 of the 27 micronutrients considered. They also estimated that you would need to eat 3,475 kcal per day to consume adequate amounts of all 27 micronutrients.

I can imagine how much meat, fish and eggs you would have to eat every day to ensure adequate nutrient intake.

"If what you say is true," an enthusiastic carnivore devotee might say, "then why don't you see many carnivore devotees suffering from scurvy?"

That's a good question, and there's a simple answer: The body can live for months with a very low vitamin C intake before it starts to fall apart, and as long as you consume at least 10 mg of vitamin C per day, it's unlikely you'll develop serious problems. In one documented case, it took eight months without vitamin C for scurvy to develop (66).

Of course, this does not mean that so little vitamin C is optimal and such a low intake may well have negative effects in the long term (67).

We should also not ignore the likely possibility that people are secretly cheating on their carnivore diet. This means that even if they claim to eat only animal products, they occasionally eat some fruit, vegetables or meals that contain plant foods.

Let's be realistic: most people cheat on their diets and scientific research shows that the more restrictive a diet is, the more likely this is to be the case (68, 69)

It wouldn't take much plant-based food to make a big difference either. Assuming you don't get any vitamin C from the produce you eat, eating two oranges a week would be enough to prevent scurvy in most people.

So when you consider the fact that humans don't need much vitamin C to prevent scurvy, that animal foods provide small amounts of vitamin C, and that some people may eat an orange or two here and there (or other vitamin C-rich foods like broccoli, peppers and strawberries), it's not surprising that people are able to follow the Carnivore Diet for an extended period of time without falling apart.

Not dying of a third world disease should not be the goal of your diet or lifestyle. Living a long, healthy and vital life - thriving rather than simply surviving - should be the goal.

The story is similar with fiber.

Humans don't need fiber to survive, which means you could theoretically go without fiber for the rest of your life. However, there is also growing evidence that your life is likely to be shorter and more painful if you do go without fiber.

Studies conducted by scientists at various leading universities (70 - 74) and many other studies conducted around the world have shown, for example, that eating more fiber helps to reduce the risk of cancer, heart disease, metabolic syndrome, type 2 diabetes and diverticulitis - to name just a few.

The bottom line is that while it's possible to follow the carnivore diet without real, life-threatening nutrient deficiencies, there's a good chance you'd be healthier if you also ate plants.

The bottom line on the carnivore diet

The carnivore diet involves eating nothing but animal products (mainly meat), water and salt.

As you may have guessed correctly at the beginning, this hyperrestrictive approach can help people lose weight (by naturally reducing calorie intake) and is a good first step towards an elimination diet - but that's where the benefits end.

The potential downsides are as follows:

  • This diet is likely to increase the risk of heart disease.
  • There is little evidence that this approach reduces inflammation and alleviates inflammation-related disease or dysfunction.
  • Eating more fat - as is the case with the carnivore diet - will likely increase your testosterone levels, but not enough to have a significant impact on muscle gain, fat loss, libido or anything else.
  • By eating only animal products, you will also be consuming significantly less than the recommended amounts of vitamin C and fiber, which can greatly reduce the risk of many different ailments.

In the final analysis, the Carnivore Diet is nothing more than a more extreme version of every other low-carb diet out there.

Like most fad diets, the Carnivore Diet has become popular through media exposure of its advocates rather than scientific research. And now it's running its course and securing its share of attention and money.

However, you should know that unless you are suffering from serious digestive issues and need to follow an elimination diet, the Carnivore Diet has nothing to offer.

If all you want is to lose fat, build muscle, get healthier and enjoy your diet, then you're better off following a more flexible approach to dieting.



From: Michael Matthews

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