Hypervitaminosis A and sweet potatoes

Can consumption of sweet potatoes cause hypervitaminosis A? The answer is “no”, even if you eat ten or more sweet potatoes per day. Sweet potatoes do have high vitamin A content, more than almost any other food. However, most of it is in the form of β-carotene, which is used by the body to produce the active form of vitamin A, retinal (yes, with an “a”), only if the body’s vitamin A status is low.

The graph below shows the vitamin A content of different foods, together with the recommended daily allowance. It was prepared with information from Nutritiondata.com (), with the horizontal axis in international units (). The graph also takes into consideration some key research findings related to the bioavailability of vitamin A. For example, the sweet potato is assumed to be taken with some fat to facilitate the absorption of vitamin A.

Primarily, vitamin A is available either as retinol, from animal foods; or β-carotene, from plant foods. There are other carotenes available from plant foods, but their vitamin A contribution is relatively small compared with β-carotene. High β-carotene content is “advertised” by plant foods to animals via a characteristic orange color. The main sources of β-carotene throughout human evolution have probably been fruits, which plants “want” animals to eat so that the plants’ seeds are dispersed.

Retinol also needs to be converted by the body to retinal, and when consumed in excess it tends to be stored in body fat reserves – hence lean individuals tend to store less retinol than fat ones. It seems that intake of retinol from sources like beef liver is naturally controlled via satiety. In the case of plant sources, like sweet potatoes, a key control mechanism is limited internal production of retinal. My impression is that most people, if given the chance, would prefer to eat a lot of sweet potato than a lot of beef liver.

Like all of the fat-soluble vitamins, the bioavailability of vitamin A from foods is dependent on whether they are consumed together with fat. For example, a lot more vitamin A will be absorbed from a sweet potato if it is eaten with butter than if it is eaten by itself (again, if the body’s vitamin A status is low). I should note that butter is itself a good source of vitamin A, in addition to providing the fat needed for absorption. Beef liver is low in fat, which means that the vitamin A content in the graph above may be an overestimation.

Hypervitaminosis is a fat-soluble vitamin phenomenon, and it is usually associated with consumption of supplements (e.g., cod liver oil). Generally speaking, one does not develop noticeable hypervitaminosis symptoms from consumption of natural food sources. This is probably due to a combination of satiety and internal regulation of the production of the active forms of the vitamins.

Liver and meatballs separated by a wall of sweet potatoes

A commenter wrote here some time ago that she liked to eat rice because rice can be easily used to separate food items on a plate. One can just as easily use sweet potatoes to do that; preparing the sweet potatoes in much less time than the rice. This post explains how, with a simple recipe.

- Cut up half of a sweet potato as shown on the first photo below, adding coconut oil or butter to prevent the pieces from sticking to a microwave-safe saucepan.
- Microwave the sweet potato pieces in high heat for about 5 minutes.
- Use the sweet potatoes to separate food items as in the second photo below, showing beef liver and meatballs with their respective sauces.
- Cover the dish with a wet paper towel to prevent spilling, and microwave it for as long as needed to heat up the meats. In this case, 2 minutes in high heat was enough. That will further cook the sweet potato, but not to the point of burning it.

The above assumes that the beef liver and meatballs are leftovers that had been cooked before. In this example, we have about ½ lb of meat and ½ of a sweet potato. As far as plant foods are concerned, sweet potatoes are at the very high end of the nutrition density scale. This is a very nutritious and satiating meal (for me) with over 55 g of protein, as well as a great mix of macro- and micro-nutrients.