The ketogenic (keto) diet, characterized by high fat and very low carbohydrate intake, has gained traction for its potential benefits in managing certain health conditions and promoting weight loss. However, the restrictive nature of the keto diet can increase the risk of nutrient deficiencies. Therefore, understanding which vitamins and minerals may be lacking and how to address these potential gaps is crucial for maintaining overall health while following a keto lifestyle.
Understanding the Ketogenic Diet
The ketogenic diet is a high-fat, low-carb eating plan that continues to grow in popularity. The keto (pronounced KEY-toe) diet was first developed to treat diabetes in the 19th century. Some research suggests that following a keto diet may help manage health conditions like diabetes, heart disease, and obesity. The ketogenic diet (KD), which is low in carbohydrates and high to normal in fat and protein, has been traditionally used in epilepsy for the last 100 years. More recently, its application in obesity has been introduced.
How Keto Works
Glucose is our bodies' main source of energy. When we deprive the body of glucose (found in abundance in carbohydrates), our body's cells turn instead to "ketones," chemical sources of fuel the liver produces from stored fat. You probably guessed that those ketones are where keto gets its name. When you cut out carbohydrates in your diet, or if you've been fasting, your body first takes glucose from stores in the liver. The idea behind keto is that carbohydrates, those easy sources of glucose, are severely restricted and replaced by a higher intake of meats and fats. When health care providers prescribe this diet, they often customize it to each patient.
The name “ketogenic” means that they increase ketone body production (acetoacetate, 3-β-hydroxybutyrate, and acetone), which leads to a ketosis state. In general, KDs have a low carbohydrate content that is limited to 5-10% of total kcal daily intake, which corresponds to 10-50 g of carbohydrates. The fat and protein contents of the KD range from 45 to 90% and from 5 to 43%, respectively. The recommended ratio of fat grams to protein-plus-carbohydrate grams in the KD ranges from 4:1 to 2:1.
When the body is in ketosis, it uses fat as its primary fuel source instead of carbohydrates. This metabolic state is achieved by drastically reducing carbohydrate intake, typically to less than 50 grams per day, and increasing fat consumption.
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Potential Nutrient Deficiencies on Keto
By cutting out fruits and whole grains, a keto diet removes key sources of fiber. Since the keto diet cuts out many food options, it also increases the risk of nutrient deficiencies. The data on the micronutrient content of KDs are scarce. Studies on long-term adoption of KDs point to potential selenium deficits; reduced intakes of calcium, phosphorus, and magnesium; as well as a reduced antioxidant capacity. Moreover, increased levels of vitamin E have been documented, while vitamin A decreases after a classic KD and increases after a KD with medium-chain fatty acids. Common high-fat diet vitamin/mineral deficiencies A high-fat/carb-restrictive diet like keto could lack the following vitamins and minerals necessary for a healthy diet: vitamin B1, vitamin B6, vitamin B7, vitamin B12, calcium, iron, magnesium, and phosphorus. These are all essential nutrients that your body needs to function properly. Our bodies don’t produce these vitamins and minerals, so we must get them daily from food or supplements.
The Importance of Vitamins
From its Latin origin, 'vita,' meaning life, vitamins are crucial for the development and functioning of our bodies. B vitamins are building blocks for our cells. They support brain and heart function, digestion, and hormone production. These vitamins help convert food into fuel and energy.
Specific Vitamins and Minerals of Concern
- B Vitamins: Fortified cereals, fruits, and vegetables can have B vitamins, which is why they are low on ketogenic diets. B vitamins are necessary for turning your food into energy.
- Vitamin C: This helps prevent scurvy, repairs tissues, and fights infections.
- Vitamin D: This vitamin is technically a steroid, made in your skin with sunlight exposure, and helps your body absorb calcium. It is found in fatty fish and eggs, but also added to milk and orange juice, which are not on ketogenic diets. Children with low Vitamin D levels on ketogenic diets are at risk for bone density problems.
- Zinc: This mineral (not a vitamin) helps the immune system and wound healing. Without it you can have hair thinning. It is found in beef, pork, and lamb, but is also in nuts, spinach, oysters, and grains.
- Calcium: This mineral is needed to keep bones healthy and is always supplemented on ketogenic diet. The calcium requirements for adults aged 19-50 are 1000 mg per day.
- Selenium: This mineral also has been shown in several studies to be low on ketogenic diets and, without it, can lead to heart arrhythmias. It is found in brazil nuts, yellowfin tuna, sardines, beef, and halibut.
- Magnesium: Magnesium affects muscles, nerves, your immune system, and many chemical reactions throughout the body. Magnesium is a mineral that helps produce energy, regulate blood sugar levels, and support your immune system. Research suggests that people who follow a keto diet typically consume less magnesium than the recommended daily intake. Many magnesium-rich foods, such as beans, fruits, nuts, and seeds, are high in carbohydrates. The recommended daily amount of magnesium for adults, age 19 and up, is between 310 and 420 mg.
Addressing Vitamin D Deficiency on Keto
The present review aimed to investigate the effects of the KD on vitamin D. In total, five studies were done in healthy adults, one in subjects with type 2 diabetes, and seven in subjects with epilepsy that assessed the levels of vitamin D pre- and post-intervention. In the majority of studies, increases in circulating vitamin D were reported. The relationship of the KD with vitamin D was explained through several mechanisms: ketone bodies, macronutrient intake, the status levels of other fat-soluble vitamins, weight loss, changes in the hormonal milieu, and effects on gut microbiota. Moreover, potential nutrient-gene-related interactions were discussed. There is still a need to conduct multiple arm studies to compare the effects of the KD versus other diets and better decipher the particular effects of the KD on vitamin D levels and metabolism. Several studies in epileptic children have connected the KD to osteopenia; this relationship was first reported in a study by Hahn et al. 1979 in which children who followed a KD for more than 2 years had low serum vitamin D. Obesity has been related to vitamin D deficiency in epidemiological studies; vitamin D concentration was inversely correlated with fat mass. Moreover, data from human and animal studies suggested that the macronutrient content of a KD, the induced increases in ketone bodies and changes in other fat-soluble vitamin status, the concurrent hormonal changes, alterations in adipose tissue depots, and modification of gut microbiome may affect vitamin D status and metabolism. Moreover, genes implicated in cholesterol synthesis, hydroxylation, and vitamin D transport can affect vitamin D status and deficiency, and potential gene-nutrient interactions may apply. Thus, the aim of the present review was to shed light on the relation of KDs to vitamin D levels and metabolism through an in-depth presentation of intervention studies as well as to clarify potential mechanisms and confounding effects such as those of supplementation. Moreover, potential gene-nutrient interactions are addressed. A clear-cut perspective of existing studies is provided, and potential underlying mechanisms for the observed associations are explained.
The main source of vitamin D is skin synthesis after exposure to UVB light (vitamin D3). As shown in Figure 1, dietary sources of vitamin D are relatively limited and include animal sources such as cod liver oil, fatty fish, liver, and eggs (vitamin D2). Main dietary sources of vitamin D. The main steps in the metabolism of vitamin D are shown in Figure 2. Briefly, vitamin D is hydroxylated in the liver by 25-hydroxylases to form 25-hydroxyvitamin D3 (25(OH)D), which is the major circulating form of vitamin D. Although several hydroxylases such as CYP27A1, CYP2J2/3, and CYP3A4 have been identified, evidence suggests that CYP2R1 is the 25-hydroxylase that is responsible for physiological vitamin D hydroxylation in humans. It was noted that the rate of hydroxylation may be slower in cases of high vitamin D intake. Metabolic steps of vitamin D.There, 25(OH)D is further hydroxylated by the 1α-hydroxylase enzyme (CYP27B1 gene) into 1,25-dihydroxy vitamin D [1,25(OH)2D], which is the active form of the vitamin. The kidney is the major organ that expresses CYP27B1, while data regarding the extra-renal expression of the enzyme (skin, gastrointestinal tract, bone, and placenta) are controversial. The kidney can also produce 24,25(OH)2D (inactive molecule) through the action of 25OHD-24 hydroxylase (CYP24A1).
Vitamin D binds to its nuclear vitamin D receptor (VDR), which in turn binds to vitamin-D-responsive elements and regulates gene expression. VDR forms heterodimers with the retinoid X receptors (RXRs), which translocate to the nucleus and increase DNA binding and transcriptional activity (Figure 2). VDR is distributed in several tissues. Although there is no consensus on the target circulating vitamin D levels and differentiations may apply according to disease status (i.e., osteoporosis), levels below 10 ng/mL indicate insufficiency, while levels 10-20 ng/mL indicate risk of inadequacy. Values greater than 50-100 or 100-150 ng/mL are related to the possible onset of toxicity.
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As presented above, in studies with healthy adults, vitamin D in patients with T2D and patients with epilepsy was increased following a KD. In patients with epilepsy following a KD, the low levels of vitamin D that initially were observed were increased after supplementation. Ketone bodies produced by a KD create an acidic environment in which liver and kidney hydroxylases are inactivated, and thus vitamin D is not converted to its active form. Acidosis also decreases the vitamin D binding protein, and thus the amount of circulating active vitamin D may be reduced. Similarly, low levels of vitamin D have been associated with the occurrence of diabetic ketoacidosis. In line with this theory, one study that measured both 25(OH)D and its active form 1,25(OH)2D in adult patients with epilepsy following a KD reported that 25(OH)D was increased and 1,25(OH)2D was decreased, which suggested an effect of the KD on hydroxylases. However, it was noted that 1,25(OH)2D has a short half-life of (~4 h) and may not be a reliable index of vitamin D status.
Food and Supplementation Strategies
It is very important to make sure your child is getting enough vitamins while on ketogenic dietary therapy. PWNHealth also reviews your test results and will contact you directly if they require prompt attention.
For a high-fat/no-carb diet, high quality meats like grass-fed beef, pastured pork, poultry, and eggs will give your body the necessary B vitamins, iron, and phosphorus. Dark, leafy greens, broccoli, and avocados are good vitamin B2, B6, B7, calcium, and magnesium sources. Full-fat yogurt is a good way to get vitamin B1, calcium, and phosphorus. In addition to dietary adjustments, supplementation may be necessary to meet the recommended daily intakes of certain nutrients.
- Multivitamins: From a clinical perspective, it is recommended that all children with epilepsy under a KD should receive a daily multivitamin supplement as well as calcium and vitamin D (RDA requirements), while supplementations of selenium, magnesium, zinc, phosphorus, iron and copper are optional. However, suboptimal intakes may still be observed despite supplementation, and the restrictive nature of a KD can lead to low intakes of phytochemicals, which are not typically included in multivitamins.
- Magnesium Supplements: Magnesium supplements may be helpful for people following a keto diet, but it’s important to speak with a healthcare professional before starting any new supplements. Some people claim supplementing with magnesium may also help reduce symptoms commonly experienced by those transitioning to a keto diet, such as muscle cramps, difficulty sleeping, and irritability. This is known as the “keto flu.”
- Omega-3 Fatty Acids: Some animal research has also found that fish oil supplements may be particularly beneficial for individuals on keto diets, as they may help regulate cholesterol levels, fat metabolism, and inflammation associated with high fat diets.
Additional Supplements to Consider
Some people claim that supplements like magnesium, MCT oil, and omega-3 fatty acids may have some benefits if you follow a keto diet. However, more research is needed to support these claims.
- MCT Oil: MCT supplementation has also been shown to promote weight loss in several ways, such as by increasing feelings of fullness, which could be helpful if you’re following a keto diet for weight management.
- Digestive Enzymes: Digestive enzyme supplements can help your body break down macronutrients. Look for a digestive enzyme blend that contains enzymes that break down fats (lipases) and proteins (proteases) to help optimize digestion during a keto diet.
- Exogenous Ketones: Exogenous ketone supplements may help increase blood ketone levels and possibly help you reach ketosis more quickly. These may be particularly useful if you’re gradually switching to a keto diet.
Monitoring and Testing
Keto diets are serious undertakings. You may need to monitor your body while on this diet with the guidance of a health care provider to ensure that your body does not go into ketoacidosis. The Quest High Fat Diet Vitamin Deficiency Test Panel is available to purchase online today. No doctor visit is required to buy your own lab test at questhealth.com.
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The Importance of Professional Guidance
It’s important to remember that keto diet recommendations should come from your health care provider and may differ from person to person. A registered dietitian can help you incorporate more low carb vegetables into your keto diet. If you're thinking about discussing this diet with your health care provider be sure to also ask about vitamin considerations. You might need to take certain supplements while on this diet to reach the daily recommended amount of important nutrients.