What's The Truth About Low Carbohydrate Diets?

Recently the New York Times, as well as many other news organizations, reported on a new study comparing the effects of a low carbohydrate diet to a low fat diet. The study concluded that a low carbohydrate diet is better for weight loss and heart health than a low fat diet. On the surface, the study is very impressive and the general media was quick to praise it, but some subtle problems with the study's design create a critical flaw.

Participants in the study were instructed on how to keep either a low carbohydrate diet or a low fat diet. They had regular counseling with a dietitian and conducted several 24-hour diet recalls to verify that they were following their diets. Participants in both groups lost weight, however those in the low carbohydrate diet lost more.

The first problem was that the low fat diet was defined as less than 30% of their calories from fat. The baseline that dietitians commonly use, the Acceptable Macronutrient Distribution Range is 20-35% of an individual's total calories from fat. This means that the study's "low fat diet" group fell within the generally recommended diet.

So the study compares a low carbohydrate diet to a baseline diet, what's the problem with that? Nothing, if it's done properly, which brings us to the critical flaw. The researchers did not control for the total amount of calories eaten by each group, and as a result the low carbohydrate group ate on average over 100 calories fewer per day than the low fat group. Without having calorically equal diets, it is impossible to say whether the weight loss was due to eating fewer calories, the low carbohydrate component of the diet, or some combination. 

In the end it is very sad because a lot of money was spent on this research, resulting in little insight into weight loss. So do low carbohydrate diets work? Maybe, maybe not, we will have to wait for a better designed study before we know. The one thing that can be concluded is the media regularly makes the wrong conclusions from nutrition studies.

Which Multivitamin Should I Take?

When I tell friends I am pursuing a masters degree in nutrition I often get asked about multivitamins. In this blog entry, I will explore what vitamins are, their history, and give you tools to make an informed decision.

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What are they?
Nutrients are parts of food that are needed for one of many functions in the body. Nutrients can be broken down into two major categories, macronutrients and micronutrients. Macronutrients are carbohydrates, fats, protein, and water. Micronutrients include all vitamins and minerals as well as a newly discovered class of nutrients called phytonutrients or phytochemicals. 

Most of the micronutrients you've heard of are essential, meaning that your body can not make them either at all or in enough quantity to fulfill demand, thus requiring you to eat them. Researchers determine the Recommended Daily Allowance (RDA) based on studies in which the amount of nutrients ingested is compared to the amount found in waste products (feces, urine, etc.) of subjects. Since it would be unsafe to do so, nutrients that are toxic at high levels are not tested this way. Adequate Intake (AI) levels are established based on current research and academic papers. Food labels are based on RDAs established in 1968 and do not indicate if a particular guideline is an RDA or an AI. For example Vitamin C has a RDA and Vitamin D has an AI. Additionally, some nutrients (like cholesterol) may have a "% Daily Value" listed on food labels, but are non-essential, meaning you don't need to eat any at all. The "% Daily Value" is actually the maximum you should eat in a day. In a future blog entry I will dig deeper into reading food labels since it can be such a confusing topic.

Historical context:

To put multivitamins in context I think it is helpful to look at the history of wheat refinement and infant formula. 

During the industrial revolution, refined flour became very popular due to its increased shelf life. When wheat is refined the germ and bran are removed and discarded, removing many important micronutrients. This quickly lead to high numbers of nutrient deficiencies.

Benjamin Jacobs is credited with discovering the link between micronutrient deficiencies and grain refinement. Jacobs later developed methods for reintroducing micronutrients to flour which ultimately became what we now know as enriched wheat flour. The nutrients that are added are in different concentrations than naturally occur. Additionally, a few nutrients that aren't naturally found in wheat are added (e.g., folic acid). 

Author: Jkwchui

Author: Jkwchui

The history of synthetic infant formula parallels the history of the understanding of micronutrients. Formula first started showing up in the second half of the nineteenth century, but was missing most micronutrients. As understanding of the vitamins and minerals in breast milk has improved, infant formula has been updated to more closely match the nutrient content of breast milk. In 1971 the FDA first mandated the nutritional content in infant formula, and has since revised it several times. Currently 38 different nutrients are regulated. Although the nutrition of formula has improved dramatically it is still missing components of breast milk like hormones and antibodies.

 

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Why do you want to take vitamins?

When asked, most people say they take vitamins because they want to improve their health or they are concerned they are missing nutrients from their diet. Since multivitamins are sold over the counter most consumers view them as safe.

If you are reading this, you most likely want to improve your health status, which is commendable. 

The risk in taking vitamins:

Most likely you don't need them. Nutrient deficiencies are extremely rare, and most dietitians only see them when a disease affects absorption of a particular nutrient. Keep in mind that many food staples are fortified, including: enriched wheat flour, milk, salt and even orange juice!

Since your body can only utilize so much of a given nutrient at a time, much of the multivitamins are excreted without being absorbed. Additionally, some nutrients will actually compete with each other, preventing one another from being absorbed.

Your body will store fat soluble vitamins that it does not need immediately. These include Vitamins A, D, E, and K. Additionally some minerals can be toxic in very small amounts. Many popular vitamins provide 100% of the RDA for fat soluble vitamins as well as minerals that can be toxic when taken in excess. This assumes that none of the food you are eating has any micronutrients!

Current research doesn't support conclusively that multivitamin use improves health. Research shows that some synthetic nutrients may even have a negative impact on health. My personal theory is that, through evolution, the human body is more adapted to deal with acute deficiency than a chronic excess of nutrients. 

Additionally, multivitamins give the false sense of a balanced diet, and may influence people to indulge more in junk foods. 

Moving away from reductionist nutrition: 

Reductionist nutrition is when the health attributes of individual nutrients or food components are studied rather than the synergistic role they play in whole foods.

Of course it is important for dietitians to have a clear understanding on the function micronutrients play in the body, but the food industry's focus on micronutrients has left the public with a poor understanding of how to eat healthfully.

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The history of refined grains and infant formula show that we shouldn't rely on getting our nutrients from vitamins, because there is likely much to be discovered about the nutrients in food.

I recommend that, unless directed by a doctor or dietitian, you do not take a multivitamin.  Here are a few tips to eat a more nutrient dense diet instead:

  • Favor whole foods over processed foods (whole foods are generally found in the produce aisle).
  • Fruits and vegetables should make up the majority of your diet. 
  • Eat lots of seeds, nuts, and beans. 
  • Eat a varied diet trying to eat as many different foods as possible (within the parameters described above).
  • Replace boiling vegetables with steaming to retain more vitamins. 
  • When cooking, keep in mind that excessive cooking time reduces nutrient levels in vegetables.
  • If fresh fruits or vegetables aren't available, choose frozen over canned.
  • Eat a colorful diet. Different nutrients are associated with different pigments found in foods, so the more colors you eat, the more nutrients! 
  • Replace enriched wheat products with whole grain products. While whole wheat flour is better than white flour, whole grain flour is best.
  • Avoid "empty" calories like soda or candy bars.
  • Read the ingredients for everything you eat. Avoid products with more than a handful of ingredients or ingredients you don't recognize. 

Vegans and vegetarians should take a Vitamin B12 supplement or eat Vitamin B12 fortified foods, and make sure to get proper Calcium and Vitamin D in their diets. I will address special nutritional needs for vegans in a future blog. Women who are trying to get pregnant or are expecting should make sure to eat foods high in folate

I would also recommend keeping a food journal for a few days using a tool like the super tracker.  It will give you an analysis of your diet, letting you know if you are missing any key nutrients, allowing you to adjust your diet appropriately.

To recap: save your money, and skip the vitamins. You will get much more out of a well-balanced diet.