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Too Much of a Good Thing

Submitted by Amy Sercel MS RD CD

Edited by Marcia Bristow MS RDN CSSD CD

Every health guideline seems to come with the recommendation to increase physical activity levels. It’s widely understood that getting enough activity boosts mental health, can help keep your immune system strong, and decreases your risk of chronic diseases like cancer, diabetes, osteoporosis, and heart disease. Public health officials estimate that 50-80% of the United States population falls short of the guideline to get at least 30 minutes of moderate-intensity exercise each day, for a total of at least 150-300 minutes per week.1 What about the other end of this continuum though? Is it possible to get too much exercise?

Although it is difficult to find a safe maximum amount of exercise recommended in the Physical Activity Guidelines for Americans, one study suggests that this amount may be no more than 60-90 minutes of endurance exercise per day, five days per week. At higher levels than this, the health benefits of being active actually start to decrease.2

Relative Energy Deficiency in Sport (RED-S)

Excessive exercise impacts every system in your body when you are not eating enough to fuel both physical activity and the body’s basic functions. These functions include the immune system, digestion, heart rate, and reproductive system. When RED-S occurs, the body slows down these processes in an effort to reduce overall energy expenditure. As a result, athletes who exercise excessively without eating enough to replace the calories they burn have:3

  • A higher risk of injury (such as stress fracture)
  • Difficulty concentrating due to lack of fuel for the brain
  • Feelings of depression or anxiety
  • Constipation due to slowing of the digestive system
  • Reproductive dysfunction seen as loss of menstrual cycle in females or low testosterone in males

Any athlete who engages in prolonged endurance activity on a regular basis is at risk for RED-S because they may not realize how much more they need to eat in order to make up for the energy burned during activity. Elite athletes and people training for long-distance endurance events, such as marathons or triathlons, are also at a higher risk for RED-S. Fortunately, most of the health impacts of RED-S reverse when an athlete reduces their activity level and/or begins eating enough to fuel their activity.

Cardiovascular Effects

While RED-S is one of the more immediate consequences of excessive exercise, in the long term excessive exercise can increase the risk of heart disease.

Endurance exercise causes the heart to beat more quickly. At high levels, this leads to changes in the heart’s structure that can cause heart arrhythmias, or an irregular heart beat.2,4 This in turn raises the risk of heart attack, stroke, and sudden death. For this reason, it’s suggested that lower amounts of running have the most positive impact on heart health, and researchers advise limiting vigorous endurance exercise to no more than 1 hour per day, 5-6 days per week.2

What’s the Right Amount?

While there are risks of excessive exercise, the health benefits of regular physical activity are indisputable. If you are working on increasing your activity level to promote your own health, aim for about 30 minutes of moderate-intensity activity per day. One study found that this exercise level was associated with the lowest risk of heart disease.2

If you are already highly active as an endurance athlete, make sure you are fueling your body properly by eating enough on a day-to-day basis and including good sources of energy before, during, and after workouts. If you’d like support with this, meet with a registered dietitian who can help you create a nutrition plan to complement your training. If you have a history of intense endurance exercise, it’s also important to have regular check-ups with your doctor, who can monitor your heart health over the long term.


  1. Physical Activity for Everyone: Guidelines: Adults | DNPAO | CDC. http://www.cdc.gov/physicalactivity/everyone/guidelines/adults.html. Accessed June 14, 2015.
  2. Lavie CJ, O’Keefe JH, Sallis RE. Exercise and the Heart — the Harm of Too Little and Too Much. Curr Sports Med Rep. 2015;14(2):104. doi:10.1249/JSR.0000000000000134
  3. Mountjoy M, Sundgot-Borgen J, Burke L, et al. The IOC consensus statement: beyond the Female Athlete Triad—Relative Energy Deficiency in Sport (RED-S). Br J Sports Med. 2014;48(7):491-497. doi:10.1136/bjsports-2014-093502
  4. Kim Y-J, Kim C-H, Park K-M. Excessive exercise habits of runners as new signs of hypertension and arrhythmia. Int J Cardiol. 2016;217:80-84. doi:10.1016/j.ijcard.2016.05.001

A2 Milk: Healthy or Hype?

Submitted by Sarah Lange

Edited by Marcia Bristow MS RDN CSSD CD

If you take a trip to your local grocery store, you will likely find A2 milk in the dairy coolers. A half-gallon of A2 milk is 85% more expensive than the conventional milk on the neighboring shelf, so what is all the hype and is it worth the price? There are many different nutrition crazes and fads circulating on the internet, in magazines, and on social media, and A2 milk is just one of the latest trends to hit the market. A2 milk is milk that contains a specific type of protein and is supposedly easier to digest. Who would have guessed that the genetic makeup of the cows your milk comes from would be one of the newest crazes?

Casein, the largest group of proteins in milk, accounts for about 80% of the total protein content. While there are several types of casein found in milk, beta casein is one of the most common forms. Beta-casein exists mainly in the A1 and A2 forms.1 Regular cow milk, that you would find in any grocery store, contains a mixture of both A1 and A2 beta-casein. The ratio of Al to A2 depends on the type of cow the milk comes from, but it is generally about 50/50.1

Before cows were domesticated, they only produced A2 beta-casein protein. At some point after they were domesticated, a natural mutation occurred of a single gene in Holstein cows, resulting in the production of A1 beta-casein.1 While milk from some types of cows, such as Jersey cows, still contains mostly A2 beta-casein, milk from Holsteins contains mostly A1. The most common dairy cow breed in Australia, Northern Europe, and the United States is the Holstein, meaning most milk on grocery stores shelves contains A1 beta-casein.1

Since A1 and A2 proteins are built slightly differently, it is thought that they differ in digestibility. Given the structure of the A2 protein, it may be easier to digest. Scientists believe that the structure of the A2 protein is easier for everyone to digest, but may be especially beneficial for those who are lactose intolerant.2 One of the byproducts of A1 protein, beta-casomorphin (BCM-7), is believed to cause inflammation, which could be a main contributor to gastrointestinal problems.1 While scientists agree on the structural differences between A1 and A2 proteins and that the structure of the A2 protein makes it easier to digest, the research is just beginning on the impact of these variations on the human body and, thus far, the evidence of any health benefits remains unclear.

The a2 Milk Company, and others, have capitalized on the prospects of A2 milk providing gastrointestinal relief for consumers who find regular milk difficult to digest. Many people who have difficulty digesting milk think it is because of the lactose, but it is possible that their symptoms could be from the A1 proteins.2 However, the evidence on this claim is sparse. The a2 Milk Company funded a study in China in which 600 adults who reported lactose intolerance were randomly assigned to drink either regular milk or A2 milk. Participants drinking the A2 milk reported less severe bloating, gas, and abdominal pain, but only slightly less than the participants drinking the A1 milk.2

The bottom line is that the science either isn’t there yet to support the health benefit claims of A2 milk or the benefits simply do not exist. Until more research is conducted, and not funded by A2 milk companies, it is probably not worth doling out the extra cash for A2 milk.


  1. Truswell AS. The A2 milk case: a critical review. Eur JClin Nutr. 2005;59(5):623-631. doi:1038/sj.ejcn.1602104
  2. He M, Sun J, Jiang ZQ, Yang YX. Effects of cow’s milk beta-casein variants on symptoms of milk intolerance in Chinese adults: a multicentre, randomised controlled study. Nutr J. 2017;16(1):72. doi:1186/s12937-017-0275-0
  3. Image from: www.happymilk.in/a1-vs-a2-milk/

Take your Coffee with Cream, Sugar… or Butter?

Submitted By Amy Sercel MS RD CD

Edited By Marcia Bristow MS RDN CSSD CD

You can spot a fad diet by the number of unique products or supplements you need to buy to follow the diet as “completely” as possible. The ketogenic diet is arguably the most popular fad diet right now. You can read more about it in our earlier blog post. In short, the ketogenic diet is a very high-fat diet that involves eating no more than about 3 servings of carbohydrate-rich foods per day. This shifts your body away from burning carbohydrates for fuel, and instead forces your body to convert fats into a compound called ketones that your cells can use for fuel instead of carbohydrates.

Right now, there is no shortage of foods, supplements, and other products you can buy to help “push you into ketosis,” prevent digestive distress, or help you get through the “keto flu” more quickly. One product you may have heard of is called Bulletproof Coffee.

Bulletproof Coffee is freshly brewed coffee (ideally made in a French press) blended with about two tablespoons of medium chain triglyceride (MCT) oil and 1-2 tablespoons of butter or ghee.1 Altogether, this comes to about 500 calories and 38 grams of saturated fat.2 For comparison, consider that a person who eats 2,000 calories per day is recommended to get no more than 22 grams of saturated fat in one day.

People have been lightening their coffee and tea with butter for hundreds of years, specifically people living in Nepal, India, Ethiopia, Vietnam, and Singapore. In Ayurvedic cultures, butter tea is thought to “improve mental alertness and cognitive capacity.”3 Fortifying coffee and tea with butter may also provide additional fuel required for life in inclement environments or at high altitudes that naturally increase metabolic rate.

In Western culture, butter coffee has taken off due to its compatibility with the ketogenic diet. According to the website, Bulletproof products are intended to enhance cognitive and physical performance. The makers of Bulletproof Coffee argue that adding grass-fed butter to your coffee will provide you with “high-quality fats that help keep you full and fueled.” Their “Brain Octane Oil” contains MCTs derived from coconut oil. According to the website, this is more effective than regular coconut oil at pushing your body into ketosis. You can buy a kit that contains 12 ounces of coffee, a bottle of MCT oil, and a bottle of grass-fed ghee for about $50 to get started.1

The problem is there isn’t any significant evidence proving that supplementing with MCT oil or following the ketogenic diet are more effective for promoting long-term health. The ketogenic diet was originally intended as a treatment for epilepsy. Studies have shown that up to 50% of these people following the ketogenic diet end up with elevated triglycerides and LDL cholesterol (the “bad” kind), increasing the risk of heart disease.4 Other studies suggest that high-fat diets might promote tumor growth, and diets high in saturated fat promote the storage of fat around your organs.5 On the other hand, diets higher in unsaturated fat tend to decrease your risk of heart disease. Diets that contain carbohydrates from whole grains, fruits, and vegetables have been shown to decrease inflammation compared to high-fat diets, and increase satiety.5 In contrast, high-fat diets increase satiety but also increase inflammation.

Many people recommend switching to MCT oil instead of other types of fats to promote weight loss, claiming that it helps promote satiety by increasing ketone formation. This claim is also not proven. One study showed that people supplementing with MCT oil only lost 0.5 kg more over 10 weeks than people on a regular weight loss diet.6 Half a kilogram (about 1 pound) could be attributed to differences in hydration status and does not indicate more success with long-term weight loss.

All in all, Bulletproof Coffee aims to capitalize on a fad diet without any evidence that it will do anything besides keep you in ketosis. While this might promote weight loss in the short term, there are no studies showing the ketogenic diet is any more effective for weight loss after about 1 year. You may be putting yourself at risk for developing heart disease, and also risk nutrient deficiencies by cutting out food groups rich in vitamins, minerals, antioxidants, and fiber. At the very least, you risk wasting money on a fad that is unlikely to make your life better in the long run.


  1. Official Bulletproof Coffee Recipe – With Video. https://www.bulletproof.com/blogs/recipes/official-bulletproof-coffee/. Accessed May 27, 2019.
  2. Can butter coffee jump-start your morning? – Nutrition Action. https://www.nutritionaction.com/daily/brain-health/can-butter-coffee-jump-start-your-morning/. Accessed May 27, 2019.
  3. Tradition Turned Trendy: Exploring the Origins of Butter Beverages – Food & Nutrition Magazine. https://foodandnutrition.org/january-february-2015/tradition-turned-trendy-exploring-origins-butter-beverages/. Accessed May 27, 2019.
  4. CPE Monthly: The Ketogenic Diet for Epilepsy – Today’s Dietitian Magazine. https://www.todaysdietitian.com/newarchives/0516p46.shtml. Accessed May 27, 2019.
  5. Dietary fat: From foe to friend? | Science. https://science.sciencemag.org/content/362/6416/764. Accessed May 23, 2019.
  6. Mumme K, Stonehouse W. Effects of Medium-Chain Triglycerides on Weight Loss and Body Composition: A Meta-Analysis of Randomized Controlled Trials. J Acad Nutr Diet. 2015;115(2):249-263. doi:10.1016/j.jand.2014.10.022