Diet is the foundation of good nutrition, but supplements can also fill in some major gaps - especially on a diet like keto, where so many food groups are off the menu or restricted to small servings. Keto limits even the portions of low-carb vegetables that you can eat, and it practically eliminates fruit and high-carb vegetables like beets and squash. That level of extreme restriction does come along with a higher risk of nutritional deficiencies and other issues that might respond well to supplementation.
On the other hand, there are some supplements that are commonly recommended but don’t really have any evidence behind their use. Not everything needs a supplement.
Here’s a look at 4 supplements you might be considering for keto, ranked as “definitely consider,” “consider,” or “probably skip,” based on the level of evidence supporting them as an addition to a ketogenic diet.
1. Exogenous Ketones/Ketone Salts
What are they? Exogenous ketones are ketones that you take in supplement form, instead of making them yourself.
What’s the evidence? There’s some preliminary research showing that they might provide the benefits of keto without the need to actually eat a ketogenic diet. For example, recent research in rats has indicated that they might be an alternative to eating keto.
But there’s no published research in humans evaluating the use of exogenous ketones in addition to a ketogenic diet. Some studies, like this one, studied oral ketone salts in people eating a higher-carb diet, but that's not necessarily relevant to people achieving ketosis through food. There’s no real evidence that they don’t help, but there’s also no real evidence that they do help. Until there’s a decent amount of research on exogenous ketones as an addition to a ketogenic diet, and until there’s a lot more safety research in people rather than mice, there’s no strong evidence in favor of adding them to a ketogenic diet.
N.B. In the case of “raspberry ketones” in particular, there’s no evidence that they cause or speed up weight loss - in fact, there's decent evidence that they don't do anything.
The bottom line: probably skip exogenous ketones because there just isn’t strong evidence in favor of them.
What are they? Sodium, potassium, and magnesium - these are minerals that you need for everything from maintaining blood pressure to contracting your muscles.
What’s the evidence? There’s a significant amount of research suggesting that people on keto need more electrolytes.
For one thing, the hormone insulin increases the amount of sodium that you take up from your food. A ketogenic diet is specifically designed to reduce insulin levels, meaning that it reduces the amount of sodium that you take up from your food (read more about insulin and keto here). Keto also increases the amount of electrolytes that your body flushes out. Low-carb diets in general make people excrete more electrolytes, including sodium, potassium, and magnesium.
All of these factors can combine to create electrolyte imbalances that cause muscle cramping, fatigue, poor athletic performance, insomnia, and other issues. To avoid all that, people on ketogenic diets often do well with extra electrolytes. For example, this paper explains how supplemental sodium and potassium is critical to modifying keto for optimal athletic performance.
The bottom line: definitely consider electrolyte supplements. Anecdotally, a lot of keto dieters love them, the evidence supports their effectiveness, and they're super cheap and easy to get.
Many people are fine just adding more sodium and potassium to their food:
- For sodium, you can salt your food more generously or drink bouillon. If you can’t stand the taste, you can buy salt pills (originally made for endurance athletes) online.
- For potassium, dark green leafy vegetables like beet greens and Swiss chard are high in potassium. Another option is “lite salt,” which has a lot of potassium and tastes just like regular salt.
If you’re experiencing constipation, muscle cramps, or insomnia, you might also consider a magnesium supplement (see here for more info). Start low and slowly increase the dose until you hit the right amount: too much magnesium at once can cause diarrhea.
Electrolytes are particularly important during the first few weeks of keto, as your body’s water balance adjusts (read: you lose a bunch of water weight), and for anyone who does a lot of sweaty exercise.
3. Medium-Chain Triglycerides/MCT Oil
What are they? Medium-Chain Triglycerides (MCTs) are fats that are very easy for your body to process and turn into ketones. Basically, eating them is a way to supercharge your ketone production. Both MCT oil and coconut oil (the richest natural source of MCTs) raise blood ketones.
What’s the evidence? Several papers have shown that using MCTs to ramp up ketone production gives you a little more leeway to eat more protein and carbs. The best example of this is the MCT ketogenic diet, which is an alternative to the classic ketogenic diet used for kids with treatment-resistant epilepsy. With the MCT ketogenic diet, these kids eat 50%+ of their daily calories from MCT oil - but then they get the rest from a much wider range of foods, with way more leeway for protein, fruit, and vegetables.
The bottom line: consider MCTs, especially if you struggle with keto limitations on protein and vegetables. If you want to expand your ketogenic diet to include slightly more protein and carbs, MCT oil or just eating a lot of coconut oil might be worth a try. And coconut oil is a delicious source of healthy fat anyway, regardless of keto goals.
Caution: MCTs can cause significant GI problems in people who aren’t used to them - don’t start off by trying to get 60% of calories from MCT oil! Start low and ramp up slowly.
What is it? Fiber is any type of carbohydrate that you can’t digest and use for energy. Some kinds of fiber are food for the good bacteria that live in your gut; other kinds of fiber have a “bulking” effect on stool.
What’s the evidence?Keto tends to be relatively low in fiber, compared to typical high-carb diets. For example, a keto breakfast might be eggs, bacon, and some fried mushrooms and spinach - a total of 1.6 grams of fiber. Meanwhile, if you had 2 pieces of whole-wheat toast with peanut butter instead, you’d get 5 grams of fiber.
For some people the low fiber content of keto is a huge benefit. Some people thrive on a relatively low-fiber keto diet, especially people who are sensitive to FODMAPs or other types of fiber. There’s experimental evidence that a ketogenic diet normalizes gut bacteria in patients with multiple sclerosis, who often have severe gut problems. Keto also reduces diarrhea episodes in patients with irritable bowel syndrome. Both of these studies would suggest that low-fiber keto has some therapeutic effects on the gut, at least in people who are already sick.
On the other hand, other research shows that the low levels of fiber in a typical keto diet might be suboptimal for some people, especially people who don’t have big pre-existing health problem. For example, this study found that low-carbohydrate diets reduced the population of beneficial bifidobacteria and lowered the production of short-chain fatty acids (SCFA) in the gut. Bifidobacteria and SCFA are both generally good for you, so these reductions are worrying. This suggests that it may be helpful to get some supplemental fiber or probiotics on keto, to keep those good gut bugs humming along.
The bottom line: consider a fiber supplement if you’re having gut problems on keto. But remember that everyone’s gut is a little different, so do what works for you:
- If you’re coming from a very high-fiber, high-whole-grain type of diet, and you’re finding yourself really constipated on keto, some psyllium husk or a similar supplement might help you make the transition. You could start out by taking enough to stay regular and then slowly lower the dose until you can eat keto with no worries about fiber supplements.
- If you’re doing a super low-carb version of keto (20 grams or less) and struggling with gut health, a prebiotic supplement (fiber specifically designed to feed your good gut bacteria) might be worth a try.
- If you do just fine on keto with no extra fiber, don’t worry about it!
The Short Version
Keto is a great diet, but you can make it even better with some well-chosen supplements. Electrolytes are worth at least serious consideration, and fiber or nedium-chain triglycerides (MCTs) might be helpful for your particular goals. On the other hand, exogenous ketones still don't have a lot of research in humans backing up their use in addition to a ketogenic diet for better weight loss, easier ketosis, or other benefits.