Food restriction, whether it's fasting, juicing or dieting for weight loss, may lead to nutrient deficiencies. Taking vitamins while fasting can help prevent this and keep you energized. Ideally, choose a formula that provides at least 100 percent of the vitamins and minerals listed on the label.
There are no set rules on how to take vitamins while fasting. Choose a formula with no added sugars and fillers. Make sure it provides close to 100 percent of the nutrients listed on the label.
Look for multivitamin supplements that provide adequate doses of vitamin D, B-complex vitamins, zinc, magnesium and other key nutrients. Consider adding a separate fish oil supplement as well.
Fasting and Nutrient Deficiencies
Different people fast for different reasons. Some are trying to lose a few pounds or improve their overall health. Others resort to fasting in an attempt to prevent cancer, diabetes, skin disorders and other ailments. While this practice isn't a cure-all, it has proven benefits.
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Intermittent fasting (IF), for example, may protect against neurological disorders, reduce inflammation and improve cognition, according to a research paper published in the journal Obesity in October 2017. In clinical trials, it has been shown to facilitate weight loss and decrease insulin resistance. Furthermore, it may help reduce visceral fat mass, which is a major risk factor for diabetes and heart disease.
Read more: 13 DOs and DON'TS of Intermittent Fasting
The journal Obesity defines this dietary pattern as fasting for at least 12 hours per day. Several versions exist and each has different requirements. Alternate-day fasting, for example, involves fasting every other day. Time-restricted feeding alternates between periods of feeding and fasting for eight to 12 hours a day.
Compared to traditional fasting, IF is less restrictive. In fact, you can eat anything you want during the feeding window. However, there is still a risk of nutrient deficiencies.
A May 2013 article posted in the Canadian Medical Association Journal states that intermittent fasting may increase lifespan, improve glycemic control and boost cognition, among other benefits.
The downside is that it can lead to overeating. On top of that, it may cause muscle loss and nutrient deficiencies, especially in those with a poor diet. As the researchers point out, lifting weights and taking multivitamins while fasting may reduce these side effects.
Multivitamins, for example, are unlikely to lower your risk of cardiovascular problems, mental decline, cancer or heart attack. A Mediterranean-style diet, on the other hand, is based on foods that keep your heart healthy, improve blood lipids and protect against chronic diseases.
Taking Multivitamins While Fasting
Fasting is a form of calorie restriction. Therefore, it limits your food choices and energy intake. Extreme fasting protocols, such as water fasting, can lead to malnutrition, moderate organ damage and increased risk of infections. If you're planning to fast for a longer time or go on a water fast, consider taking multivitamins.
Vitamin B12, for example, supports nerve function and helps your body synthesize DNA. This nutrient is found in beef liver, eggs, dairy foods, fortified cereals and most types of meat. Most fasting protocols restrict solid food, especially animal products, which can lead to vitamin B12 deficiency.
According to the National Institutes of Health (NIH), low levels of this nutrient in the bloodstream may cause fatigue, weakness, confusion, poor balance and anemia. One way to prevent deficiencies is to take a daily multivitamin.
Your body also needs vitamin D to absorb calcium from food and keep your bones strong. Low vitamin D intakes have been linked to a higher risk of bone disorders, such as osteomalacia. Few foods contain this nutrient, though, which may explain why more than half of the world's population is deficient in vitamin D. Fasting can further increase the risk of deficiencies.
Another key nutrient is magnesium, which can be found in most multivitamin formulas. This mineral contributes to more than 300 biochemical processes in your body. It plays a crucial role in energy production, muscle function, bone growth, protein synthesis and other functions.
Magnesium deficiency can affect calcium and potassium levels in the bloodstream. You may also experience muscle cramps, fatigue, irregular heartbeat, digestive symptoms and overall weakness. The NIH recommends that you choose a multivitamin that contains magnesium citrate, chloride, aspartate or lactate, as these forms have the highest absorption rates.
Do Vitamins Break a Fast?
Most multivitamin formulas contain a mix of vitamins, minerals, antioxidants and bioactive compounds. These are known as micronutrients and have zero calories. Protein, carbs and fat are called macronutrients because your body needs them in large amounts. One gram of fat has 9 calories, while protein and carbs provide 4 calories per gram.
Multivitamins are non-caloric, so they won't break your fast. However, some formulas have added sugars and fillers that increase their calorie content. Chewable multivitamins, for instance, may contain maltodextrin, pectin, cane sugar, fruit juice concentrate and other caloric ingredients. If you're fasting, choose a formula with zero calories.
A growing number of brands are offering food-based multivitamins. These usually contain fruit and vegetable extracts, such as raspberry, kale, noni, mangosteen and so on. Some products exceed 50 calories per serving. While there's nothing wrong with these formulas, they can break a fast.
Beware that taking multivitamins on an empty stomach — such as when fasting — may cause digestive discomfort, as reported by the Cleveland Clinic. Additionally, they may worsen gastritis, gastroesophageal reflux disease (GERD) and other digestive disorders. Some dietary supplements, especially those containing fat-soluble vitamins, are best absorbed when taken with food, according to the American Heart Association.
What About Fish Oil?
Fish oil isn't a multivitamin, but it can benefit your health, especially during fasting. This dietary supplement is rich in good fats that can be used as a source of fuel. Your body needs fats to stay warm, absorb some vitamins and get the energy needed to sustain itself, as the American Heart Association points out.
Remember that each gram of fat has 9 calories. The human body can use fat for energy during periods of food restriction, such as fasting. Therefore, fish oil supplements are a welcome addition to low-carb diets and fasting regimens.
There are no set rules on how much fish oil you should take. One teaspoon provides 41 calories and 4.5 grams of fat, while one tablespoon has 123 calories and 13.6 grams of fat. This supplement contains mostly mono- and polyunsaturated fatty acids, which may benefit cardiovascular health. Talk to your doctor about how much fish oil you should take as high doses may increase risk of bleeding and stroke, according to the Mayo Clinic.
According to the experts at Penn Medicine, the omega-3 fatty acids in fish oil, walnuts, salmon, tuna and other foods may lower blood pressure and triglyceride levels, fight inflammation and protect against stroke.
While it's true that most claims require further investigation, these dietary fats seem to be beneficial. One thing is for sure: they are a lot healthier than saturated and trans fats. Plus, they can slightly boost your energy when food is scarce.
If you're fasting, stick to one teaspoon of fish oil per day. A few grams of dietary fats are unlikely to break the fast.
- Obesity: "Flipping the Metabolic Switch: Understanding and Applying Health Benefits of Fasting"
- Harvard Health Publishing: "Abdominal Fat and What to Do About It"
- NCBI: Canadian Medical Association Journal: "Intermittent Fasting: The Next Big Weight Loss Fad"
- Johns Hopkins Medicine: "Is There Really Any Benefit to Multivitamins?"
- Mayo Clinic: "Mediterranean Diet: A Heart-Healthy Eating Plan"
- American Journal of Clinical Nutrition: "Health Effects of Intermittent Fasting: Hormesis or Harm? A Systematic Review"
- National Institutes of Health: "Vitamin B12"
- National Institutes of Health: "Vitamin D"
- NCBI: Journal of Pharmacology & Pharmacotherapeutics: "Vitamin D: The "Sunshine" Vitamin"
- National Institutes of Health: "Magnesium"
- ACE Fitness: "Macronutrients, Micronutrients and Water"
- Cleveland Clinic: "Get Nauseous After Taking Vitamins? 6 Tips to Make Them Easier to Stomach"
- American Heart Association: "Vitamin Supplements: Hype or Help for Healthy Eating"
- American Heart Association: "Dietary Fats"
- University of Utah: "Building, Burning, and Storing: How Cells Use Food"
- USDA: "Cod Liver Oil"
- American Heart Association: "The Facts on Fats Infographic"
- Penn Medicine: "The Truth About Fish Oil, Omega-3 Fatty Acids, and Heart Health"
- Mayo Clinic: "Fish Oil"