The ketogenic diet (KD), characterized by its low carbohydrate and high fat content, has gained popularity not only for its traditional use in managing epilepsy but also for its potential benefits in addressing obesity and other health conditions. While the KD offers several advantages, it's crucial to understand its impact on vitamin and mineral levels in the body. This article delves into the relationship between the KD and vitamin deficiencies, exploring potential mechanisms, research findings, and strategies to mitigate these risks.
Introduction to the Ketogenic Diet
Ketogenic diets, which are low in carbohydrates and high to normal in fat and protein, have been traditionally used in epilepsy for the last 100 years. 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.
Potential Benefits of the Ketogenic Diet
Studies have demonstrated the efficacy of KDs in patients with drug-resistant epilepsy and certain pediatric epilepsy syndromes under medical supervision. The potential effectiveness of KDs against epilepsy is mainly due to the fact that ketone bodies can act as direct anticonvulsants. KD has received additional interest due to its beneficial effects on several other diseases such as obesity, T2D, cancer, intestinal disorders, respiratory compromise, and cardiovascular disorders. Several mechanisms have been proposed for the beneficial effect of a VLCKD on body weight that include changes in energy expenditure during weight loss and maintenance and appetite suppression (possibly through reductions in insulin levels). Moreover, KDs decrease serum glucose, insulin, and insulin-like growth factor 1 (IFG-1) levels, which are key molecules in carcinogenesis.
Micronutrient Considerations on a Ketogenic Diet
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. 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.
Common Side Effects of Ketogenic Diets
The first side effects of a KD include vomiting, headache, hypoglycemia, and metabolic acidosis. After the first few days, several side effects may appear (gastrointestinal, hepatic, cardiovascular, renal, dermatological, hematologic, and bone effects). Long-term adverse effects of KDs include high cholesterol levels, nephrolithiasis, growth retardation, and decreased bone mineral density.
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Vitamin D and the Ketogenic Diet
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.
The main source of vitamin D is skin synthesis after exposure to UVB light (vitamin D3). Dietary sources of vitamin D are relatively limited and include animal sources such as cod liver oil, fatty fish, liver, and eggs (vitamin D2). 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. 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. Vitamin D binds to its nuclear vitamin D receptor (VDR), which in turn binds to vitamin-D-responsive elements and regulates gene expression.
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.
Research Findings on Ketogenic Diets and Vitamin D
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.
Other Potential Vitamin Deficiencies on a Keto Diet and How to Address Them
The ketogenic diet restricts carbohydrates, limiting the amount of nutrients you may get. You may develop nutrient deficiencies while on the keto diet. Carbohydrates contain many essential nutrients. For example, without enough calcium and vitamin D, your bones may not be as strong. This can increase your risk for osteoporosis (bone loss).
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Fiber
Fiber is essential for digestive health and helps manage weight. Most sources of fiber come from whole grains, fruits, legumes, and vegetables, all of which are carbohydrates. Some fiber-rich foods are lower in carbohydrates. Eating only these low-carb sources of fiber may not be enough, so a daily fiber supplement could help you meet your daily fiber needs. Doctors say that eating up to five servings of low-carb vegetables daily -- foods such as broccoli, cauliflower, and lettuce -- can keep your bowels healthy without interfering with weight loss. If it's still not doing the trick, a fiber supplement -- such as Metameucil or FiberCon can help.
Magnesium
Many high-magnesium foods, like whole grains, bananas, and beans, contain too many carbs to be keto-friendly. Women need 310-320 milligrams (mg) of magnesium daily, while men need 400-420 milligrams. Taking a magnesium supplement can help fill in any nutritional gaps. Talk to a healthcare provider about taking a magnesium supplement. Some of the most absorbable forms of magnesium include magnesium glycinate, magnesium gluconate and magnesium citrate. If you wish to increase your magnesium intake through keto-friendly foods, focus on incorporating these low-carb, magnesium-rich options: Spinach, Avocado, Swiss chard, Pumpkin seeds, Mackerel.
Calcium
The keto diet typically limits your carb intake to 20-50 grams daily. Similarly, calcium-fortified orange juice and tofu are both good sources of calcium, but are not keto-friendly. However, adults aged 19-50 need 1,000 milligrams of calcium daily. Calcium serves many purposes. Although there has been some evidence that a low-carb diet can also take its toll on calcium levels, this is usually only on a short-term basis. It's a "smart idea" to take a calcium supplement beginning at the start of your low-carb diet to safeguard against a possible deficiency. Tofu can also be a good source of calcium.
Iron
Iron is the fuel that allows every body cell to function correctly. Iron makes hemoglobin, a protein that delivers oxygen from your lungs to different body parts. Men aged 19-50 need 8 milligrams of iron daily, while women aged 19-50 need 18 milligrams. Many keto-approved foods contain enough iron, such as beef, oysters, kale, and spinach. Eating meat can give you enough iron. However, iron deficiency is still possible, especially for women.
Vitamin B12
Got a jolt of energy after a healthy meal? Vitamin B12 could be responsible. The complex vitamin handles DNA creation, healthy blood vessels and turning food into energy. Fortified cereals and breads, absent in low carb diets, contain lots of B12. One way to protect yourself is to take a B vitamin supplement -- with at least 400 micrograms of folic acid daily.
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Vitamin C
Although the vitamin gained popularity with cold prevention, Vitamin C has several additional upsides. Vitamin C aids in healing wounds, providing antioxidants and preventing cell damage. The natural source comes from carb-rich foods like potatoes, mangoes, and bananas.
Vitamin E
Though uncommon, vitamin E deficiencies are present in low carb diets. Vitamin E prevents tissue damage, organ damage, and repairs cells. Nuts, oils, and fruit like mangoes contain vitamin E and can be absent in low carb diets.
Supplement Recommendations for Keto Dieters
Because the keto diet cuts out a number of food options, it’s a good idea to supplement with specific nutrients. Some supplements can help dieters reduce adverse effects of the keto flu and even enhance athletic performance when training on a low-carb diet.
Magnesium
Those following a ketogenic diet may be at a higher risk of developing a magnesium deficiency. Taking a magnesium supplement or eating more low-carb, magnesium-rich foods can help you meet your daily requirements.
MCT Oil
MCT oil is a type of rapidly digested fat that can be used to help ketogenic dieters boost fat intake and stay in ketosis.
Omega-3 Fatty Acids
Omega-3 fatty acid supplements can reduce inflammation, lower heart disease risk factors and help ensure a healthy balance of omega-3s to omega-6s.
Vitamin D
Since vitamin D deficiency is common, it may be a good idea for people following the ketogenic diet to get their vitamin D levels checked and supplement accordingly.
Digestive Enzymes
Taking a digestive supplement that contains both protease and lipase enzymes, which break down protein and fat respectively, may help relieve digestive symptoms related to transitioning to a keto diet.
Exogenous Ketones
Exogenous ketones may help raise ketone levels, decrease appetite and increase athletic performance. However, more research is needed to establish the effectiveness of these supplements.
Greens Powder
Greens powders contain powdered forms of healthy plants like spinach, spirulina and kale. They can provide a convenient source of nutrients to those following ketogenic diets.
Electrolyte Supplements or Mineral-Rich Foods
People following a ketogenic diet should focus on increasing their consumption of sodium, potassium and magnesium to prevent unpleasant symptoms like headache, muscle cramps and fatigue.
How to Avoid the Pitfalls and Side Effects of a Low-Carb Weight Loss Plan
- Constipation: Increase fiber intake through low-carb vegetables like broccoli, cauliflower, and lettuce. Consider a fiber supplement if needed. Avoid laxatives and focus on adding more fiber to your diet.
- Dehydration: Drink more water, at least 2 quarts daily, to offset dehydration caused by ketone production.
- Bad Breath: Increase water intake to dilute ketones and alleviate bad breath.
- Vitamin and Mineral Deficiencies: Take a multivitamin, particularly one containing folic acid. Consider calcium and potassium supplements as well.
- Gastrointestinal Upset: Read labels carefully to avoid ingredients like sugar alcohol (sorbitol) that can cause gastrointestinal issues.
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