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Can B12 Shots Help You Lose Weight? 

By Michael Henze, MS

Reviewed by Jinan Banna, PhD, RD

Looking for a “quick fix” for weight loss? There are plenty of companies, websites and infomercials constantly advertising the latest silver bullet “guaranteed” to help you lose weight fast. Be sure to read the fine print! 

B12 injections are an emerging trend in the wellness industry being offered everywhere from doctors’ offices to IV infusion spas. But are they worth the hype… or the price? 

What is B12?

Vitamin B12 is a water soluble vitamin. Formally known as “cobalamin”, the different types of B12 form a ring structure around an atom of the element cobalt, hence the name. 

B12 is found naturally in foods from animal products (meat, eggs, dairy, fish). Read my blog on the components of food to learn more about vitamins. 

What is the Function of B12?

Enzymes are proteins that facilitate chemical reactions in the body and some require the help of another compound called a “coenzyme” to do their job. Humans use vitamin B12 as a coenzyme for many reactions involved with the metabolism of amino acids (the building blocks of proteins). Another important B12 mediated reaction allows us to convert folate (another B vitamin) into its usable form. These chemical reactions ensure that our bodies make healthy DNA and blood cells. 

Like all vitamins, the human body cannot make B12 and therefore we must get it from the diet. Without sufficient supply of B12 we cannot carry out the chemical reactions where it is needed as a coenzyme, which can cause problems in the body.

What are B12 Shots? What are the Claims? 

B12 shots are typically a form of B12 called “cyanocobalamin” given as an injection into a muscle. This will increase levels of B12 circulating in the blood. 

Most places that offer B12 shots claim that they boost energy, improve mood, and can help you lose weight.

Are B12 Shots Safe?

B12 shots given by a health professional in a sterile setting are likely safe. B12 even in large doses as seen in these injections are considered safe and there is very low risk of toxicity. For that reason there is no defined upper limit for B12

Are B12 Shots Effective?

B12 shots are effective at raising the concentration of B12 in the blood, which is beneficial for people with B12 deficiencies. However, B12 deficiencies are actually very rare in healthy adults! 

According to large pools of health data for Americans the average adult woman consumes more than 150% of the recommended daily allowance for B12. According to that same data, only 8% of American women consume less than the estimated average requirement of B12. 

While most adults are at no risk of B12 deficiency, these groups may may be at elevated risk:

  • Older adults over 65: Older adults aren’t as efficient at absorbing B12 from food. 
  • Individuals with inflammatory bowel diseases: They may absorb B12 less effectively.
  • Vegans and vegetarians: B12 naturally occurs in animal foods, not in plant foods. Those following a vegan/ vegetarian diet can easily avoid B12 deficiency by seasoning food with nutritional yeast.
  • People taking stomach acid reducing medications: Stomach acid is vital for digesting B12
  • People diagnosed with pernicious anemia: This is a very rare autoimmune disease that affects only 0.1% of adults 
  • Individuals who have had surgical removal of the stomach or re-routing of intestines: Surgical changes to the anatomy of the gut may affect B12 digestion and absorption.

If you do not fall into one of these categories, there is little chance you are B12 deficient. In fact, unlike other water soluble vitamins, the body can store B12 in the liver. We can store 3-5 years worth of this vitamin, so it would take a very long time for a deficiency to even occur! 

It should also be noted that oral supplementation of B12 has similar benefits in treating deficiencies compared to injections, which is far less invasive and a fraction of the cost.

If you consume sufficient amounts of B12, and have plenty in storage, any additional amounts are simply excreted. Under normal circumstances excess B12 leaves the body in feces, but when a megadose is given through a B12 shot, most of it is excreted in the urine if there is no deficiency present. 

B12 Shots and Weight Loss

While B12 is a coenzyme in several reactions involved with the breakdown of fat molecules for energy, a megadose in the form of an injection does not speed up the rate of fat metabolism when a deficiency is not present. Many other factors, like timing of the last meal, the intensity of physical movement, and hormones in circulation influence the rate of fat breakdown, not B12. 

Think of it like putting gas in your car. Without gas, your car can’t move, but having more gas doesn’t mean your car moves faster. How fast your car moves is based on other factors (foot on the accelerator, aerodynamics, engine power, etc.) unrelated to how much gas is in the tank. It’s the same with vitamin B12 and fat metabolism.

Lack of B12 can inhibit the rate of fat metabolism in the rare cases of a deficiency, but otherwise it has no effect on the rate of fat metabolism when B12 is present in normal or even megadose amounts. 

In fact, the majority of a B12 megadose injection will likely just end up in your urine For these reasons B12 injections would not be effective treatments for weight loss.

Focus on Food Sources of B12 

B12 is abundant in the food supply, especially in animal products of all kinds (meat, fish, dairy, eggs). Individuals following a vegan or vegetarian diet should be mindful that plant foods do not contain B12, but seasoning food with nutritional yeast will provide more than enough B12! Just two tablespoons of nutritional yeast provides 625% of the daily requirement of B12. 

Follow this link to learn more about how to eat a vegetarian/ vegan diet and still get all essential vitamins and minerals. 

FoodB12 Content (micrograms)% Daily Value 
Clams (3oz meat cooked in moist heat)843500%
Nutritional Yeast (2 tbsp)15625%
Salmon (3 oz, sockeye cooked dry heat) 3.8158%
Low fat Yogurt (1 cup)1.3757%
Milk (1 cup, 2% reduced fat)1.3556%
Egg (2 eggs, large)1.0242.5%
Chicken Breast (3 oz, skinless, baked).29212%

Source: USDA FoodData Central 

Not sure what to make with clams? Try this White Kale and Clam Pizza recipe by registered dietitian Kara Lydon RD, LDN for a fun twist on pizza rich in B12 and leafy greens!  

Individuals with the gastrointestinal conditions that limit B12 digestion or absorption can supplement with a B12 spray that is sprayed under the tongue. That bypasses the gut altogether and prevents deficiency! 

Final Thoughts

  • Vitamin B12 acts as a coenzyme for chemical reactions in the body that facilitate amino acid metabolism, DNA and blood cell formation.
  • Most of the B12 from an injection will be excreted in the urine!
  • B12 deficiency is very rare among adults and this vitamin is plentiful in foods from animal sources. 
  • B12-rich foods and over the counter oral supplements are far less expensive than paying for B12 injections and will provide all the B12 your body can use.
  • While vitamin B12 is required for fat breakdown, a megadose B12 injection does not speed up the rate if no deficiency is present. Therefore B12 injections will not help most adults lose weight!

There is no “quick fix” for safe and sustainable weight management. Building healthy nutritional habits and engaging in joyful movement on a regular basis are the most effective way to lose weight and stay healthy! No needles necessary. 
Try some new healthy cooking techniques or introducing more high fiber foods into your routine as a place to start. 

Have questions? Comments? I would love to hear what you think below!

lose weight fast;, Can B12 Shots Help You Lose Weight? 
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