The increasing popularity of low-carbohydrate diets has led many women to adopt them on a regular basis. This raises concerns about their suitability during gestation. While pregnant women are generally advised against extreme diets or weight reduction, some may already adhere to low-carb or gluten-free diets and plan to continue these habits during pregnancy. This article examines the potential risks and benefits of low-carb diets during pregnancy, considering various factors such as neural tube defects, gestational diabetes, fetal development, and the quality of carbohydrates consumed.
Potential Risks of Low-Carb Diets During Pregnancy
Neural Tube Defects
One of the primary concerns associated with low-carb diets during pregnancy is the increased risk of neural tube defects (NTDs). These defects, such as anencephaly and spina bifida, affect the brain, spine, or spinal cord and occur in the first month of pregnancy.
Folate Deficiency: Folate, a B vitamin, plays a crucial role in preventing NTDs. Because folate deficiency in pregnant women has been associated with an increased risk of neural tube defects, including anencephaly and spina bifida, it is recommended that all women take folic acid supplements during pregnancy. The Food and Drug Administration (FDA) has required (since 1998) the addition of folic acid to many enriched breads and cereals in order to increase the amount of folic acid in our diets. However, women on low-carb diets may not benefit from the folate added to grain products like wheat flour, rice, and pasta. A recent study found that gluten-free breads, cereals, and pasta are typically not fortified with folic acid.
A study using data from the National Birth Defects Prevention Study, which included 1,740 mothers of infants with NTDs and 9,545 mothers of live-born infants without birth defects, found that women with restricted carbohydrate intake were slightly more likely to have an infant with a neural tube defect after accounting for potential variables, including use of prenatal vitamins (AOR?=?1.41, 95% CI: 1.11, 1.79). While this is not a huge increase in risk, it is statistically significant and raises concerns about women’s dietary habits during pregnancy. The researchers defined restricted carbohydrate intake as being in the ? 5th percentile. This finding reinforces the importance for women who may become pregnant to talk to their health care provider about any special diets or eating behaviors they routinely practice.
The study authors recommend that women who are pregnant or planning to become pregnant may want to avoid diets that reduce or eliminate carbohydrates, as they could increase the risk of having a child with a neural tube defect.
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Low-Carb Diet and NTDs: A study by researchers at the University of North Carolina at Chapel Hill suggests that following a low-carbohydrate diet during pregnancy may increase a woman’s risk of having a baby with serious birth defects. Compared with pregnant women who didn’t restrict their carbohydrate intake, those on a diet that reduced or eliminated carbs were 30 percent more likely to have babies with neural tube defects.
Gestational Diabetes and Ketone Levels
- Gestational Diabetes: Other research suggests that very low-carb diets around the time of conception may be linked to a higher risk of gestational diabetes. While glucose is important for the successful development of an early pregnancy, too much sugar can cause large spikes in blood sugar and have health consequences.
- Ketone Concerns: Providers also have concerns about high levels of ketones during pregnancy. Some studies have connected long-term ketosis to possible effects on a baby’s development.
Potential Alterations in Embryonic Organ Growth
Animal studies provide additional insights into the potential effects of ketogenic diets during pregnancy.
A study was conducted where CD-1 mouse embryos were imaged from mothers fed either a Standard Diet (SD) or a KD 30 days prior to, as well as during gestation. An anatomical comparison of the SD and KD embryos revealed that at E13.5 the average KD embryo was volumetrically larger, possessed a relatively larger heart but smaller brain, and had a smaller pharynx, cervical spinal cord, hypothalamus, midbrain, and pons, compared with the average SD embryo. The study concluded that a ketogenic diet during gestation results in alterations in embryonic organ growth.
At E13.5, the KD embryo was larger than the SD counterpart by 37% (p < 0.05), while at E17.5 the KD embryo was smaller than the SD one by 20% (p < 0.05). This suggests that the ketogenic diet may influence the growth trajectory of the embryo.
The KD brain occupied a smaller percentage of the embryo volume at E13.5, as compared with the SD brain (p < 0.05), but a larger percentage volume at E17.5 (p < 0.05). Unlike the brain, the KD heart was found to occupy a larger percentage volume compared with the SD heart at E13.5 (p < 0.05), but an equivalent percentage volume at E17.5 (p > 0.05). The KD liver was found to occupy the same percentage volume of the embryo at both time-points (p > 0.05), indicating the KD liver volume grew proportionally to the embryo volume both during as well as post organogenesis. This indicates that the ketogenic diet may affect the proportional development of different organs.
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When compared with the SD embryo, the KD embryo had a decreased relative volume within the pharynx, the cervical spinal cord, and cerebral thalamus region, as well as in the upper hepatic region at E13.5. Increased relative volume was detected in the lateral wall of the left ventricle of the heart as well as in the skeletal muscle. This suggests that the ketogenic diet may lead to localized anatomical changes.
The mid-brain and pons were smaller in relative volume at E13.5, but larger in relative volume at E17.5 in the KD brain. Additionally, the hypothalamus was smaller in relative volume at E13.5, and the thalamus was enlarged at E17.5, whereas these regions were not statistically different at the other time-points. Overall, this result is consistent with differences in overall brain size found using organ-based analysis. This indicates that the ketogenic diet may affect the development of specific brain regions.
Other Potential Risks
- Nutrient deficiencies: Many high-carb foods, including fruits, whole grains, and legumes, contain essential vitamins and minerals that you and your baby need, like folic acid, which helps prevent neural tube defects.
- The keto flu: The “keto flu” is the name given to a collection of symptoms that you experience as your body starts to transition from burning carbs to burning fat. You’ll feel sick, have headaches, be tired, and suffer from nausea.
- Low birth weight: Research suggests that low-carb diets in pregnancy can increase the likelihood of having a baby with a lower birth weight, which may lead to health complications.
- Ketoacidosis risk: Extreme carbohydrate restriction can push the body into ketosis, which may be harmful during pregnancy, leading to increased acidity in the blood. Increased acidity is linked to significant complications, including fetal hypoxia (not enough oxygen in the body’s tissues), stillbirth, perinatal death, and long-term cognitive problems.
- Reduced energy levels: Pregnancy already demands extra energy, and cutting carbs can leave you feeling fatigued and sluggish.
Potential Benefits of Low-Carb Diets in Gestational Diabetes
While the risks associated with low-carb diets during pregnancy are considerable, there may be some benefits for women with gestational diabetes.
Managing Blood Sugar Levels
- Decreased Glycemia: Low-carb diets may decrease glycemia in gestational diabetes. A 2018 meta-analysis published in Diabetes Care evaluated 18 randomized controlled trials of 1,151 pregnant women with gestational diabetes and found that any nutrition pattern modification after gestational diabetes diagnosis was associated with reduced maternal fasting and postprandial glucose by 4 mg and 8 mg.
- Dietary Advice for Gestational Diabetes: Valent reviewed several major landmark studies demonstrating that gestational diabetes treatment can decrease pregnancy complications such as preeclampsia and large for gestational age infants. She said ACOG guidelines recommended a low-carbohydrate diet for gestational diabetes until the most recently revised edition in January.
- Individualized Dietary Advice: The Australian Carbohydrate Intolerance Study in Pregnant Women (ACHOIS), which individualized dietary advice with a dietitian and assessed individual dietary intakes, demonstrated that this strategy was associated with lower perinatal complications, birth weight, large for gestational age and macrosomia.
- Carbohydrate Percentage and Postprandial Glucose Level: Trial results published in Diabetes in 1991 showed a correlation between carbohydrate percentage and postprandial glucose level at 1 hour. Results also showed that having a carbohydrate target of less than 140 mg/dL was associated with a 45% carbohydrate intake at breakfast, 55% at lunch and 50% at dinner. However, having a carbohydrate target of less than 120 mg/dL was associated with overall lower intakes, with 33% at breakfast, 45% at lunch and 40% at dinner.
Considerations for Low-Carb Diets in Gestational Diabetes
- Nutrient-Dense Foods: The concern with lowering carbohydrates is the risk of consuming lower nutrient-dense foods and resulting in the body to produce ketones, which may be associated with negative effects on the developing baby.
- Ketonuria: A 2013 study published in Diabetes Care compared ketonuria percentage among pregnant women with gestational diabetes following a 55% carbohydrate diet or a 40% carbohydrate diet. According to Valent, findings showed no differences in ketonuria between the two groups.
- Compliance: An Australian study assessing a 6-week intervention with a low-carbohydrate diet (180-200 g) or an absolute low-carbohydrate diet (135 g) found low compliance: 65% of pregnant women in the moderate-carbohydrate group and 20% of pregnant women in the low-carbohydrate group stuck to their assigned eating plan.
- Neonatal Head Circumference: Results demonstrated a difference in neonatal head circumference with smaller heads among the absolute low-carbohydrate group compared with the low-carbohydrate group (33.9 cm vs. 34.9 cm).
The Importance of Carbohydrate Quality and Quantity
Glycemic Index and Glycemic Load
Glycemic Response (GR): When foods containing carbohydrates are ingested, the resulting change in PPG is a glycemic response (GR).
Glycemic Index (GI): The glycemic response induced by a portion of food containing 50 g of available carbohydrates is the glycemic index (GI). Foods with a GI above 70 on the glucose scale are considered high GI foods, indicating rapid digestion, absorption, and metabolism of carbohydrates. Conversely, low GI foods have a GI of less than 55, leading to a slower rise in blood sugar.
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Glycemic Load (GL): Glycemic load (GL) is a measure of the quality and quantity of the carbohydrate.
Examples: For example, rice, refined white flour, and potatoes can cause rapid spikes in blood sugar levels, while whole grains, vegetables, and certain fruits can result in lower postprandial blood sugar levels.
Types of Carbohydrates
Simple Carbohydrates: Simple carbohydrates usually include monosaccharides and disaccharides. Monosaccharides include glucose and fructose, which have only one aldehyde or ketone unit, and disaccharides can be hydrolyzed into two monosaccharides. In addition to being found in whole foods, the other major source of simple sugars that people consume in their daily diet is added sugars.
Added Sugars: Added sugars is another important category of sugar, which refers to all monosaccharides and disaccharides used in processed foods and beverages, as well as sugars added to foods that do not naturally occur. It does not include natural sugars found in vegetables, fruits, and milk.
Free Sugars: All monosaccharides and disaccharides added to foods, as well as sugars found naturally in honey, syrups, and fruit juices, are also known as free sugars.
Complex Carbohydrates: Complex carbohydrates are either oligosaccharides containing up to 10 monosaccharide units, or polysaccharides containing very long monosaccharide chains. The starch contained in noodles, bread, etc., is a polysaccharide, which is digested and decomposed into glucose by amylase after intake, and then slowly enters the blood without causing a sharp rise in blood sugar.
The Role of Dietary Fiber and Whole Grains
Dietary Fiber: Foods that contain fiber should be chewed before passing through the stomach and into the small intestine, as they affect satiety, glucose and insulin response, and lipid absorption.
Whole Grains: Compared with refined grains, whole grains, in addition to retaining most of the dietary fiber, more importantly, are not deeply processed, retaining the characteristics of whole foods. More than 100 years of research have demonstrated that eating whole grains can effectively increase dietary fiber intake and reduce the risk of non-communicable diseases.
Vegetables and Fruits: Vegetables and fruits are also important sources of dietary fiber intake, and studies reported that eating 200 g of fruits and vegetables per day reduces the risk of death from coronary heart disease, stroke by about 10%, and cardiovascular disease and cancer by smaller, but still significant amounts.
Non-Nutritive Sweeteners: An Alternative to Sugar
Types of Non-Nutritive Sweeteners
FDA Approved: Food and Drug Administration (FDA) currently approves synthetic high-intensity sweeteners such as saccharin, aspartame, acesulfame-K, sucralose, neotame, and advantame.
Natural High-Intensity Sweeteners: Additionally, natural high-intensity sweeteners include steviol glycosides, thaumatin, and Siraitia grosvenorii.
Considerations for Non-Nutritive Sweeteners
Consumption During Pregnancy: Thirty percent of pregnant women intentionally consume foods with added non-nutritive sweeteners. Other women may make a conscious decision to consume non-nutritive sweeteners in an attempt to reduce gestational weight gain (GWG), or while undergoing medical nutritional treatment for pre-pregnancy or gestational diabetes.
Impact on Body Weight: Research indicates mixed findings regarding the impact of saccharin and sucralose on body weight and weight gain in pregnancy and lactation. While some studies suggest a reduction in body weight, others show no significant effect on maternal weight.
Recommendations and Conclusion
While low-carb diets may offer some benefits for managing gestational diabetes, the potential risks, particularly the increased risk of neural tube defects and alterations in fetal development, warrant caution.
General Recommendations
Consult with a Healthcare Provider: Women who are pregnant or planning to become pregnant should consult with their healthcare provider or a registered dietitian before making significant changes to their diet.
Focus on Nutrient-Dense Foods: Instead of drastically restricting carbohydrates, focus on consuming nutrient-dense, complex carbohydrates such as whole grains, vegetables, and fruits.
Ensure Adequate Folate Intake: Take folic acid supplements as recommended by healthcare providers to reduce the risk of neural tube defects. The CDC recommends that all women who may become pregnant take a daily multivitamin with at least 400 micrograms of folic acid every day before and during pregnancy.
Monitor Ketone Levels: If following a low-carb diet for medical reasons, monitor ketone levels and consult with a healthcare provider to ensure they remain within a safe range.
Prioritize a Balanced Diet: Aim for a balanced diet that includes adequate amounts of carbohydrates, proteins, and healthy fats to support both maternal and fetal health.
Specific Recommendations for Gestational Diabetes
Individualized Nutrition Plans: Work with a registered dietitian to develop an individualized nutrition plan that meets your specific needs and blood sugar goals.
Monitor Blood Sugar Levels: Regularly monitor blood sugar levels to assess the effectiveness of the diet and make adjustments as needed.
Consider Carbohydrate Quality: Focus on consuming low glycemic index carbohydrates to minimize postprandial blood sugar spikes.
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