#1 Reason You Shouldn’t Try a Low-Carb Diet

Rates of obesity are rising, and it seems like more people are trying specialized diets, particularly those that cut back on carbohydrates. Currently, more than 40% of adults in the United States experience obesity, and while many aim to lose weight, keeping that weight off remains a significant challenge as obesity rates continue to grow.

According to the International Food Information Council, 43% of people believe carbohydrates or sugars are the main cause of weight gain. But only 25% of folks see calories from all sources as contributing to weight gain. However, scientific studies suggest that cutting carbs doesn’t offer significant weight loss benefits when the total number of calories consumed is the same. And there are downsides to a low-carb diet, too—some research suggests that cutting back on carbohydrates can lead to inadequacies in key vitamins and minerals.

To shed more light on those concerns, a group of researchers analyzed data to help figure out if adults on low-carb diets are missing out on some macronutrients and, if so, which ones. They published their work, which also includes insights about how fat may affect macronutrient intake, in the Journal of the Academy of Nutrition and Dietetics.

How Was This Study Conducted?

This study relies on data collected as part of a large, ongoing health study called the National Health and Nutrition Examination Survey (NHANES), which is conducted by the Centers for Disease Control. These researchers focused on data from adults aged 20 years or older that was collected from 2007 to 2018, which resulted in just over 15,000 participants for the study. On average, the participants were 48 years old.

Participants in the study were divided into two main groups based on the percentage of calories they consumed from carbohydrates, which was determined based on food surveys that participants took. The first group included those with a carbohydrate intake of less than 45% of their total energy, referred to as the “restricted carbohydrate” group. The second group included those whose diets met established guidelines for carbohydrates (45% to 65% of energy), as well as for other nutrients like fats, protein and specific fatty acids. 

Intake of certain nutrients, like vitamins A, B12, C, D and E, as well as folate, iron, calcium, magnesium and zinc, were assessed to see how many people might not be getting enough when following the lower carb dietary pattern. They also checked how many people consume too much sodium. The research analyzed what people get from food alone and, for most nutrients, also included supplements.

To further understand the role of fats, the restricted carbohydrate group was split into smaller subgroups based on how much fat they consumed. These subgroups looked at total fat and the types of fat, such as monounsaturated, polyunsaturated and saturated fats to analyze intakes of certain nutrients. By analyzing these patterns, researchers aimed to identify connections between dietary intake and nutrient deficiencies across the population.

What Did the Study Find?

Compared to the group that followed the recommended dietary ranges, those in the low-carb group were slightly less likely to be women, more likely to have finished college, and had a higher income compared to their household needs. The low-carb group consumed fewer carbohydrates but more protein, more fat and more alcohol compared to the recommended group.

People following a diet low in carbohydrates were more likely to have too little of certain minerals and vitamins compared to those who followed a balanced diet that met all recommended intake ranges. 

Specifically, the low-carb group was more likely to be deficient in:

• Iron 
• Magnesium 
• Vitamin A 
• Folate 
• Vitamin C 
• Vitamin D 

On the brighter side, the low-carb group was less likely to be deficient in zinc and vitamin B12. Those on a lower carb diet were likely to consume more vitamin K and choline than recommended, but they also ate more sodium than recommended.

When people following a low-carb diet were grouped by how much total fat they ate, further patterns emerged regarding their nutrient levels. For instance, those on a low-carb, low-fat diet were more likely to consume less calcium and vitamin E than recommended. 

And different types of fat were linked to different intakes of certain nutrients as well. For example, the research team investigated how monounsaturated fatty acid (MUFA) intake affected nutrient levels in people on low-carb diets. They found that a low-carb, low-MUFA diet often led to overconsumption of sodium and underconsumption of vitamin E, while a high-MUFA diet supported healthy potassium intake. MUFAs are found in foods like olive oil and avocado. 

Researchers also looked into similar relationships between some micronutrients and polyunsaturated fats and saturated fat, finding, for example, that a diet lower in saturated fat was more likely to support healthy calcium intake. 

These findings suggest that the relationship between carbohydrate restriction and micronutrient inadequacy is dependent on the amount and type of fat intake, which has implications for clinical practice.

It’s important to note a few limitations when considering this data. The information about food intake came from self-reports, which can sometimes be inaccurate due to personal bias or errors in recall. Additionally, participants were grouped into the carb-restricted category regardless of whether they were intentionally following this type of diet or not. Lastly, everyone with a carbohydrate intake below 45% of their total energy was grouped together, but it’s possible that varying levels of carbohydrate restriction could lead to different outcomes.

How Does This Apply to Real Life?

For those considering a low-carbohydrate diet, these findings highlight some practical takeaways that can guide healthier choices. While reducing carbohydrates might seem like a straightforward way to manage weight, it’s essential to understand the potential trade-offs.

Cutting back on carbs without carefully planning your diet can lead to deficiencies in essential vitamins and minerals like magnesium, vitamin C and folate. These nutrients play vital roles in energy production, immune function and overall health, so it’s crucial to make adjustments to ensure you’re not missing out on them.

Supplementation can be a useful strategy to address nutrient gaps, especially for individuals following more restrictive diet plans. But it’s important to remember that supplementation isn’t a one-size-fits-all solution. Consulting with a healthcare provider or a dietitian ensures personalized advice tailored to your specific diet, lifestyle and health needs. They can help assess whether supplements are necessary and recommend the right dosage to complement your diet safely and effectively.

A balanced approach to low-carb eating can make all the difference. Incorporating diverse food groups, such as leafy greens, nuts, seeds and lean proteins, can help mitigate the risk of nutrient deficiencies while still reaping the benefits of carbohydrate reduction. By paying attention to dietary quality and seeking professional input when needed, you can pursue your health goals while maintaining optimal nutrition and well-being.

The Bottom Line

A new study in the Journal of the Academy of Nutrition and Dietetics highlights potential nutritional gaps among people who follow a low-carbohydrate diet. While many people turn to these diets to shed excess weight, it comes with potential downsides, including deficiencies in some vitamins, iron, magnesium and folate. Micronutrient deficiencies can compromise energy levels, immune support and long-term health outcomes. These risks emphasize the necessity of a well-structured diet (or even strategic supplementation) to avoid any nutritional gaps while following a low-carb lifestyle.

Ultimately, the takeaway is clear—diet quality matters just as much as diet quantity. For those choosing a low-carb approach, prioritizing nutrient-dense foods is essential to ensure proper health and functionality. This might mean incorporating foods like spinach, avocados, nuts, and berries, which can supply vital vitamins and minerals typically missing from low-carb meal plans. By making informed adjustments, consulting with health professionals and tailoring dietary choices to individual needs, those pursuing low-carb diets can achieve more sustainable and healthful outcomes.