| Dear Dr. Cordain,
I know that potatoes and sweet potatoes are ‘banned’ foods, but what about other root vegetables such as celeriac, turnips and Swedes (rutabagas)?
Thanks,
Anna W.
Design Manager
Hi Anna,
Let me take a round about approach before I directly answer your question. First off, potatoes and sweet potatoes are not necessarily forever and completely banned from the diet. For overweight individuals and for anyone suffering from chronic diseases of insulin resistance, I highly recommend that potatoes and sweet potatoes be eliminated or severely restricted until body weight normalizes and/or disease symptoms ameliorate. Because both sweet potatoes and potatoes are net base yielding vegetables, they represent superior carbohydrate sources compared to cereal grains. Additionally, when fully cooked, these vegetables contain few or no antinutrients (such as dietary lectins) which can adversely affect health. In contrast fully cooked cereals still contain numerous antinutrients including lectins.
In my original book, The Paleo Diet, I spoke of the 85:15 rule – meaning that if one were 85 % compliant with the diet most of the time, significant improvements in health could occur. I still believe this concept, and I believe that minor dietary discretions involving potatoes and sweet potatoes on an occasional basis will have little adverse impact upon health. In fact, for highly fit athletes, or for healthy, normal weight individuals doing significant aerobic exercise on a daily basis, potatoes and sweet potatoes represent a good source of carbohydrate necessary to replenish spent muscle glycogen stores. See (http://www.thepaleodiet.com/paleo_books/) for more information.

There are approximately 96 vegetable crops that are grown world wide which fit under the catch all phrase of “roots and tubers”1. Root and tuber vegetables are actually the underground food storage organs of various plants. These edible underground organs are classified into one of five categories: 1) roots, 2) tubers, 3) rhizomes, 4) corms, and 5) bulbs. Commonly consumed roots are carrots, parsnips, radishes, beets, Swedes (rutabagas), sweet potatoes, cassava and celeriac, whereas commonly consumed tubers include potatoes and yams. Examples of edible rhizomes are the arrowroot, ginger and turmeric. Corms include taros and Chinese water chestnuts whereas common edible bulbs take in onions and garlic. Crops with an enlarged stem (leek and kohlrabi), even when located underground, are generally not classified as roots and tubers2.
The table below shows worldwide production of the top 11 root and tuber crops.
| Crop |
(Metric tons/year) |
| Potato |
307,440,446 |
| Beet (sugar) |
246,475,609 |
| Cassava |
184,852,540 |
| Sweet potato |
136,130,396 |
| Onion (dry) |
51,914,247 |
| Yam |
39,643,170 |
| Carrot |
21,020,436 |
| Garlic |
12,107,007 |
| Taro |
9,220,522 |
| Ginger |
988,182 |
| Chicory root |
960,700 |
Source: FAO, 2003.
It is interesting to see that the world’s top two tuber crops (potatoes and sugar beets) are major contributors to the ubiquitous high glycemic load in the U.S. diet (see Figure 1 below). Note that 41.4 % of the total calories in the typical US diet come from high glycemic foods: 1) refined grains, 2) refined sugars, 3) potatoes. From previous newsletters, eagle eyed Paleo Diet newsletter subscribers will immediately recognize that a high glycemic load is one of the major dietary factors underlying obesity and numerous chronic health problems in westernized countries3, 4.
Figure 1. Per Capita Percentages of Highly Glycemic and Highly Insulinemic Foods in the U.S. Diet (1990-99).

OK, now let’s get down to directly answering Anna’s question, “but what about other root vegetables such as celeriac, turnips and Swedes (rutabagas)?” In the table below I have compiled data for the only 9 root and tuber vegetables listed in the International table of glycemic index and glycemic load values5. I have also compiled data for 5 additional root and tubers whose glycemic indices have not yet been determined, including turnips and celeriac.
My recommendation for overweight subjects or for people with diseases of insulin resistance (type 2 diabetes, hypertension, dyslipidemia [elevated triglycerides, low HDL, elevated small dense LDL], coronary heart disease, gout, and acne) is to not exceed a glycemic load of 10 for any given meal and to keep the days glycemic load under 40. If you look at the table carefully, you can see that a 100g (~1/4 lb) serving of baked potato would provide you with half your daily glycemic load allotment. A similar serving of sweet potato would be a better choice with a glycemic load of 14.8, but better choices still would be beets, Swedes or carrots, which under normal circumstances you can basically eat until you are full, as it would be quite difficult to consume enough of these foods to exceed a daily glycemic load of 40.
Although glycemic index and load values for celeriac have not yet been determined, the amount of carbohydrate per 100g (9.2g) is similar to that for beets, Swedes and carrots. Consequently, it is likely that celeriac has a similar low glycemic load and presents no problems. The same goes for turnips. Enjoy these healthful, net base yielding root and tuber vegetables.
One final note for eagle eyed readers. I have calculated the glycemic load using a standardized 100g serving as this procedure will “level the playing field” when making comparisons between and among various food items. In the International Table of Glycemic Index and Glycemic Load Values (5), glycemic loads are calculated by multiplying the glycemic index by the carbohydrate content of a “standard serving.” Although this practice is widely utilized, the problem is that “standard servings” vary from food item to food item, thereby introducing a bias for the greater serving size.
International Table of Glycemic Index and Glycemic Load Values
| 100 g samples |
kcal |
CHO g |
CHO g/kcal |
Gly Index |
Std Dev |
Gly Load/100 g |
| Cassava, Manioc, Tapioca |
160 |
38.1 |
4.2 |
70 |
10 |
26.6 |
| Potato, Baked |
109 |
25.2 |
4.3 |
85 |
12 |
21.4 |
| Taro |
142 |
34.6 |
4.1 |
55 |
1 |
19.0 |
| Parsnips |
81 |
19.5 |
4.2 |
97 |
19 |
18.9 |
| Sweet Potato, Baked |
103 |
24.3 |
4.2 |
61 |
7 |
14.8 |
| Yam |
116 |
27.6 |
4.2 |
37 |
8 |
10.2 |
| Beets |
44 |
10.0 |
4.4 |
64 |
16 |
6.4 |
| Rutabegas, Swedes |
39 |
8.7 |
4.5 |
72 |
8 |
6.3 |
| Carrots |
45 |
10.5 |
4.3 |
47 |
16 |
4.9 |
| Jerusalem Artichoke |
76 |
17.4 |
4.4 |
na |
na |
na |
| Chicory |
73 |
17.5 |
4.2 |
na |
na |
na |
| Burdock Root |
72 |
17.4 |
4.1 |
na |
na |
na |
| Celeriac |
42 |
9.2 |
4.6 |
na |
na |
na |
| Turnips |
27 |
6.2 |
4.3 |
na |
na |
na |
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Heya i am for the first time here. I found this board and I to find It really useful & it helped me out much. I’m hoping to provide one thing back and help others such as you aided me.
Comment by Water Potential — September 27, 2011 @ 7:43 am |
Welcome Benjamin It is always good to make new friends and people do communicate from all parts of the world. It’s kinda exciting, really. I see what caught your attention is Loren Cordain with his Paleolithic expertise. This man has almost revolutionized our thinking; makes it simple, and fully develops his reasoning which aids us in our own decisions.
This blog is a little big and somewhat cumbersome. I have tried to organize it to help people find what they are looking for, but no matter what – - its complicated. You have to be part detective to find what you’re after. My almost 900 posts go back 4 years and I have tried to whittle it down but people keep showing interest in many of the older ones. Please enjoy your travels here Benjamin. Jan
Comment by Jan Turner — September 27, 2011 @ 12:38 pm |