Strawberries are one of my favorite fruits, whether in an ice-cold smoothie or warm strawberry shortcake. Packed with phytochemicals, the strawberry plant (scientific name Fragaria ananassa) belongs to the family Rosaceae, which includes roses, apple trees and plum trees. Botanically speaking, Fragaria ananassa is not a berry, and not even a fruit. A fruit is defined as a mature, thickened ovary of a seed-bearing plant, along with it’s parts like the fleshy layers of tissue (the pulp).
But why isn’t a strawberry a fruit? To a botanist, it is classified as a false fruit, because the fleshy “fruit” part doesn’t grow from the plant’s ovaries but from the bottom of the bowl-shaped hypanthium that holds the ovaries.(1)
Why is a Strawberry not a Berry?
The definition of a berry is even narrower. It is a fruit derived from a single ovary and has the whole wall as fleshy. (By the way, eggplants, avocados and tomatoes are classified as berries.) But each strawberry is really an aggregate fruit made up of many tiny single fruits embedded in a fleshy receptacle. These are the little yellow or white specks, on the outside of the strawberry, that most people call seeds.
These are known to botanists as “achenes”, and are what make strawberries so high in fiber (1/2 cup of strawberries has more fiber than a slice of whole wheat bread.) Every strawberry has on average about 200 seeds, no matter how big or small it is. So if anyone ever asks you why do strawberries have seeds on the outside, now you know.
Why are Strawberries Red?
The familiar red hues of a ripe strawberry, melded with the sweet aroma and taste, is a part of the enjoyment of eating them, and it comes naturally- no Red Dye No. 3 is used or needed. Just look at any strawberry growing in the wild or a garden. But where does the color actually come from? Strawberries have high levels of anthocyanins, the same pigments that give other purple and red fruits like blueberries, blackberries and raspberries their color.
In addition to providing coloring, which probably evolved as a means of attracting insects and animals in oder to spread the plant’s seeds, they have another interesting property. Anthocyanins are a powerful antioxidant and a type of flavonoid.
Antioxidants are your body’s weapon against free radicals (unstable oxygen compounds made as a natural byproduct of metabolism.) Left unbridled, free radicals degrade the body’s own cells over time.
For those keeping track, the major anthocyanins in strawberries are: cyanidin 3-glucoside, pelargonidin 3-glucoside, pelargonidin 3-rutinoside and pelargonidin 3-acetylglucoside.(2)
Strawberries Nutrition Facts
Not only are they delicious, but strawberries are good for you. They have a wide range of nutrients, including fiber, vitamin C, amino acids and calcium. The antioxidant phytonutrients in strawberries, which include ellagitannins and quercetin are receiving attention from researchers as potential preventatives for cancer, cardiovascular disease and cognitive conditions.(4)
Eight medium strawberries will provide six percent of the daily need for folate, 93 percent of the daily need for Vitamin C, and 20% of your daily required manganese.1 cup of fresh strawberries contains the following-
Water: 138.24 g
Protein: 1.02 g
Carbohydrates: 11.67 g
Fiber: 3.0 g
Cholesterol: 0 mg
Calcium: 24 mg
Iron: 0.64 mg
Magnesium: 20 mg
Phosphorus: 36 mg
Potassium: 233 mg
Sodium: 2 mg
Zinc: 0.21 mg
Vitamin C: 89.4 mg
Thiamin: 0.036 mg
Riboflavin: 0.033 mg
Niacin: 0.587 mg
Pantothenic Acid: 0.190 mg
Vitamin B6: 0.071 mg
Folate: 36 mcg
Vitamin A: 18 IU
Vitamin E: 0.44 mg
Lutein and Zeaxanthin: 40 mcg
Source: USDA Nutritional Database(3)
What are the Signs of a Strawberry Allergy?
If you are one of the unfortunate ones with an allergy to this wonderful fruit, don’t feel too bad; you’re not alone. The strawberry has many different allergenic substances in it, and is one of the most common food allergies.
The classic sign of an allergic reaction to strawberries is the oral allergy syndrome, marked by reactions such as tingling, swelling and itching in the mouth, throat, tongue or lips. You may also experience a runny nose, itchy watery eyes, and sneezing, just like hay fever. In fact, if you suffer from hay fever you have a higher chance than most to be allergic to strawberries, especially if the hay fever allergy is to birch or ragweed.
Other possible reaction symptoms are hives, dermatitis, asthma and itching. The most dangerous symptoms are those that cause swelling in the throat, as a severe reaction can lead to the airway closing.
Research done in 2004 in Sweden(5) revealed the likely cause of the allergic reactions. Biochemists working at Lund University identified the allergen from the thousands of proteins within a strawberry. They then screened to find strawberries with none of the allergen protein. A colourless, white strawberry variety was found to be nearly free from the allergen.(6)
This would indicate that the allergen protein is somehow related to the red pigmentation in the fruit, although the exact mechanism is unknown as yet. More research is needed into the protein. But one thing about it is known: “This protein resembles a previously known allergen in birch pollen,” according to Cecilia Emanuelsson, Professor of Biochemistry.
An allergy to birch pollen can then trigger secondary allergic reactions against some berries, fruit, and vegetables, though not all birch pollen allergy sufferers react against strawberries. If you have a severe allergy to strawberries and decide to try eating the white variety, please use caution and common sense. Not all white varieties may be allergen free. Consider doing a skin reaction test against them, or better yet, avoid them altogether until more is known.
(1) Mauseth, James D. (April 1, 2003). Botany: An Introduction to Plant Biology. Jones and Bartlett. pp. 271–272. ISBN 0-7637-2134-4.
(2) Identification of anthocyanin pigments in strawberry (cv Camarosa) by LC using DAD and ESI-MS detection , Fatima Lopes De Silva et al, European Food Research and Technology, Volume 214, Number 3 / March, 2002, DOI 10.1007/s00217-001-0434-5
(3) U.S. Department of Agriculture, Agricultural Research Service. 2008. USDA National Nutrient Database for Standard Reference, Release 21. Nutrient Data Laboratory Home Page, http://www.ars.usda.gov/ba/bhnrc/ndl
(4) Joseph JA, Shukitt-Hale B, Denisova NA et al. Long-term dietary strawberry, spinach or vitamin E supplementation retards the onset of age-related neuronal signal-transduction and cognitive behavioral deficits. J Neurosci 1998 Oct 1;18(19):8047-55 1998.
(5) Bet v1 homologues in strawberry identified as IgE binding proteins and presumptive allergens, Karlsson A-L, Alm R, Ekstrand B, Fjelkner-Modig S, Schiött Å, Bengtsson U, Björk L, Hjernö K, Roepstorff P and Emanuelsson C (2004), Allergy 59, 1277-1284.
(6) Down-regulation of the strawberry Bet v 1-homologous allergen in concert with the flavonoid biosynthesis pathway in colourless strawberry mutant, Hjernö K, Alm R, Canbäck B, Matthiesen R, Björk L, Trajkovski K, Roepstorff P and Emanuelsson C (2006), Proteomics 6, 1574-87.