Historical changes in the mineral content of fruits
and vegetables
Anne-Marie Mayer
Independent Researcher, Devon, UK
Implies that a balance of the
different essential nutrients is
necessary for maintaining
health. The eight minerals
that are usually analysed are
Na, K, Ca, Mg, P, Fe, Cu, Zn.
A comparison of the mineral
content of 20 fruits and 20
vegetables grown in the
1930s and the 1980s (published in the UK Government’s
Composition of Foods tables)
shows several marked reductions in mineral content.
Shows that there are statistically signifi cant reductions in
the levels of Ca, Mg, Cu and
Na in vegetables and Mg, Fe,
Cu and K in fruit. The only
mineral that showed no signifi cant differences over the
50 year period was P. The
water content increased
signifi cantly and dry matter
decreased signifi cantly in
fruit. Indicates that a nutritional problem associated
with the quality of food has
developed over those 50
years. The changes could
have been caused by anomalies of measurement or
sampling, changes in the food
system, changes in the varieties grown or changes in
agricultural practice. In
conclusion recommends that
the causes of the differences
in mineral content and their
effect on human health be
investigated.
British Food Journal
99/ 6 [ 1997] 207–211
© MCB University Press
[ ISSN 0007-070X]
Th e pu r pose of th is pa per is to a ddr ess th e
qu estion : h a s th e n u tr ition a l qu a lity (pa r ticu la r ly essen tia l m in er a l con ten t) of fr u its a n d
ve geta bles ch a n ged th is cen tu r y du r in g th e
per iod of ch a n ges in th e food system a n d
m oder n iza tion in a gr icu ltu r e? Th e UK Gover n m en t’s Com position of Food s da ta pr ovides
a sou r ce of da ta a t two tim e poin ts sepa r a ted
by a ppr oxim a tely 50 yea r s; by com pa r in g th is
da ta I a ttem pt to a n swer th is qu estion .
The composition of foods tables
Th e fir st edition of th e UK Ch em ica l Com position of Food s[1] a r ose fr om a n eed to pr ovide
in vestiga tor s w ith in for m a tion for a w ide
r a n ge of foods con su m ed in th e UK. Th e da ta
on fr u it a n d ve geta bles wer e com piled fr om
pr eviou s stu dies of th e com position of
foods[2]. Un for tu n a tely, th ese r epor ts wer e
destr oyed in a fir e du r in g th e Secon d Wor ld
Wa r a n d h ave been ou t of pr in t ever sin ce.
Th is m ea n s th a t exa ct da tes or deta ils of th e
a n a lyses a r e n ot k n ow n .
Sin ce th e fi r st edition th er e h ave been fou r
su bsequ en t u pda tes of th e fu ll Com position of
Food s ta bles. It w a sn ’t u n til th e fi fth edition ,
h owever, th a t th e ta bles in clu ded su bsta n tia l
r evision s of th e or igin a l da ta on fr u its a n d
ve geta bles th a t wer e listed in th e fi r st edition .
Th e fifth edition of T h e Com position of
Food s[3] a ddr essed a n eed for u pda tes of th e
old da ta . Th e in tr odu ctor y section sta tes “Th e
n u tr ition a l va lu e of m a n y of th e m or e tr a dition a l foods h a s ch a n ged. Th is ca n h a ppen
wh en th er e a r e n ew va r ieties or n ew sou r ces
of su pply for r aw m a ter ia ls; w ith n ew
fa r m in g pr a ctices wh ich ca n a ffect th e n u tr ition a l va lu e of both pla n t a n d a n im a l
pr odu cts…”
Th e u pda ted com position s of fr u its a n d
ve geta bles a r e ba sed on a n a lytica l stu dies
com m ission ed by th e Min istr y of Agr icu ltu r e, F ish er ies a n d Food (MAF F ). Th e sa m ples wer e design ed to r efl ect th e u su a l pa tter n
of con su m ption in th e UK a t th e tim e of a n a lysis. Th e ta bles a r e n ot design ed to pr ovide
com pa r a tive h istor ica l da ta – th e fr u it a n d
ve geta bles wou ld n ot n ecessa r ily h ave been
gr ow n in sim ila r con dition s, soils, or tim es of
yea r or be of th e sa m e va r ieties. Th e da ta
wer e a lso pr ovided by m ixed sou r ces (see
below ). Mor e con tr olled da ta wou ld h ave been
better, bu t th is da ta n ever th eless pr ovides a
good sta r tin g poin t for th e com pa r ison .
Th e u pda ted ve geta ble a n a lyses wer e ca r r ied ou t by th e In stitu te for Food Resea r ch
between 1984 a n d 1987 a n d h ave been u sed for
a ll th e ve geta ble m in er a l da ta . Th e u pda ted
fr u it a n a lyses wer e ba sed la r gely on da ta
fr om th e La bor a tor y of th e Gover n m en t
Ch em ist (LGC). Most of th e twen ty fr u its
listed, h owever, in clu de da ta fr om oth er
sou r ces for on e or m or e of th e m in er a ls. For
in sta n ce, th e en tr y for cook in g a pples m a k es
u se of da ta fr om th e LGC for P, Fe, Cu a n d Zn .
Th e va lu es for N a , K, Ca , Mg a r e a n aver a ge of
LGC da ta a n d th e old Ch em ica l Com position of
food s da ta fr om 1936. Ta ble I lists sou r ces of
da ta for a ll th e twen ty ve geta bles a n d fr u its
th a t wer e selected for th e com pa r ison .
In th is pa per I h ave exa m in ed on ly r aw
fr u its a n d ve geta bles. Th is h a s been don e to
exclu de differ en ces ca u sed by ch a n ges in
m eth ods of pr ocessin g. Th e u pda ted a n a lyses
pr ovide a n oppor tu n ity to com pa r e th e
ch a n ges in pu r ch a sed r aw food over a ppr oxim a tely a 50-yea r per iod.
Methods
I a n a lysed twen ty ve geta bles a n d fr u its u sin g
two ver sion s of th e Com position of Food s
ta bles[3,4]. I u sed th e 1960 ver sion for th e old
da ta beca u se it w a s ea sily ava ila ble a n d
in clu des th e sa m e a n a lyses a s th e fir st a n d
secon d edition s. It a lso r epor ts th e r esu lts to
on e m or e sign ifica n t digit th a n th e fou r th
edition . Th e fr u its a n d ve geta bles selected
h a d to m eet th e follow in g cr iter ia :
• Th e old da ta h a d been u pda ted for th e fifth
edition of th e food ta bles. Som e fr u its h ave
a lso been in clu ded wh en old a n d n ew da ta
wer e aver a ged a s ou tlin ed in Ta ble I.
• Th e descr iption s of th e a n a lysed por tion of
th e food wer e iden tica l. For exa m ple, both
sa m ples wer e peeled.
• On ly r aw sa m ples wer e in clu ded.
• Th e food w a s n ot dr ied or r eh ydr a ted a n d
dr y pu lses wer e n ot in clu ded.
• Th e food w a s n ot a con dim en t (e.g. h or ser a dish r oot).
[ 207 ]
Anne-Marie Mayer
Historical changes in the
mineral content of fruits and
vegetables
Table I
Sources of data for The Composition of Foods tables
Fruits
Sources and dates of data
British Food Journal
99/ 6 [1997] 207–211
Apricots
Bananas
Blackberries
Cherries
Cooking apples
Eating apples
Grapefruit
Grapes
Lemons
Melon cantaloupe
Nectarines
Oranges
Passion fruit
Peaches
Pears
Pineapple
Plums
Raspberries
Rhubarb
Strawberries
LGC 85-86 except Na: average of literature
LGC 85-86 except K, Zn: average of literature
LGC 85-86
LGC 85-86
LGC 85-86 except Na, K, Ca, Mg: average of LGC, MW4
LGC 85-86 except Na, K, Cu: average of literature
LGC 85-86 except Na, K, Ca: average MW4, USDA 86, literature
LGC 85-86 except Na, K, Zn: average of literature
MW4, USDA, literature.
LGC 85-86
LGC 85-86 except K, Mg: literature
LGC 85-86 except K: literature
Literature sources
LGC 85-86 except K: literature
LGC 90
LGC 85-86, MW4, literature
Recalculated from stewed plums
LGC 85-86
Average of USDA 81, MW4
LGC 85-86
Notes:
LGC Laboratory of the Government Chemist
MW4 McCance and Widdowson’s Composition of Foods 4th edition (1936 data)[6]
USDA United States Department of Agriculture data
First to third editions: The data used in the first four editions of the Chemical Composition of Foods were compiled
from the 1936 data[2]
Fourth edition: The data were compiled from the 1936 data with a few additions from the literature. For example Zn
values were added from literature sources
Fifth edition: The data for vegetables in the fifth edition were all taken from the Institute of Food Research between
1984 and 1987. The data for fruits were obtained from mixed sources
wh eth er ea ch m ea n r a tio w a s sign ifica n tly
differ en t fr om 1. Th e logs of th e r a tios wer e
u sed for th is test.
A tota l of 20 fr u its a n d 20 ve geta bles sa tisfied
th ese cr iter ia a n d th ese a r e listed w ith th eir
m in er a l con ten ts a t both tim e poin ts in Ta ble
III.
I ca lcu la ted th e loga r ith m of th e r a tios
(n ew :old) for ea ch m in er a l for ea ch fr u it a n d
ve geta ble a n d fr om th ese com pu ted th e geom etr ic m ea n s. Stu den ts t-test w a s u sed to test
Findings
Th e aver a ge r a tios a n d r esu lts of th e t -test
a r e listed in Ta ble II. A r a tio of 0.81 for
Table II
Average a ratio of mineral content (new:old) of 20 vegetables and 20 fruitsb
Ca
Mg
Fe
Cu
Na
K
P
Dry matter
H2O
Vegetables ratio
0.81
0.65
0.78
0.19
0.57
0.86
0.94
0.97
1.00
p valuec
0.014* 0.000* 0.088
0.000** 0.013* 0.090
0.487
0.53
0.872
Fruits ratio
1.00
0.89
0.68
0.64
0.90
0.80
0.99
0.91
1.02
p value
0.957
0.016* 0.002** 0.006** 0.561
0.000** 0.903
0.023* 0.006**
Notes: a Geometric mean, the antilogarithm of the mean of the logarithm of the ratio of 1980s to 1930s values
b See text for data sources and Table III for vegetables and fruits included. Analyses of Mn, Se and I were
only added in the 1991 edition. Zn was only added in the 1978 edition. S was omitted from the 1991
tables although it was analysed in previous editions. C1 was not revised in many cases for the 1991
edition. For these reasons comparisons were only possible for the above 7 minerals, water and dry matter.
c Probability that average of logarithm of new:old is statistically different from 0 by t-test. (This is
equivalent to the ratios being different from 1)
* = significant at the 5 per cent level
** = significant at the 2 per cent level
[ 208 ]
Anne-Marie Mayer
Historical changes in the
mineral content of fruits and
vegetables
British Food Journal
99/ 6 [1997] 207–211
ca lciu m , for exa m ple, m ea n s th a t over a n
a ppr oxim a te 50-yea r per iod th e aver a ge con ten t of ca lciu m in ve geta bles h a s declin ed to
81 per cen t of th e or igin a l level.
Th er e wer e sign ifica n t r edu ction s in th e
levels of Ca , Mg, Cu a n d N a , in ve geta bles
a n d Mg, Fe, Cu a n d K in fr u its. Th e gr ea test
ch a n ge w a s th e r edu ction of copper levels in
ve geta bles to less th a n on e-fi fth of th e old
level. Th e on ly m in er a l th a t sh owed n o
sign ifica n t differ en ces over th e 50-yea r
per iod w a s P. Wa ter in cr ea sed sign ifi ca n tly
Table III
Mineral content of vegetables and fruit (mg/ 100mg)
Ca
old
Vegetables
Beetroot
Brussels
Sprouts
Cabbage – winter
Carrots – old
Celery
Lettuce
Mushroom
Mustard and cress
Onions
Parsley
Parsnips
Peas
Potatoes – old
Pumpkin
Runner beans
Radishes
Swedes
Tomatoes
Turnips
Watercress
Fe
old
Fe
new
24.9 20.0 15.0 11.0 0.37
28.7 26.0 19.6 8.0 0.66
1.0
0.7
72.3
48.0
52.2
25.9
2.9
65.9
31.2
325.0
54.8
15.1
7.7
39.0
33.3
43.7
56.4
13.3
58.8
222.0
Ca
new
68.0
25.0
41.0
28.0
6.0
50.0
25.0
200.0
41.0
21.0
5.0
29.0
33.0
19.0
53.0
7.0
48.0
170.0
Mg
old
16.8
12.0
9.60
9.7
13.2
27.3
7.6
52.2
22.4
30.2
24.2
8.2
23.0
11.4
10.8
11.0
7.4
17.0
Mg
new
6.0
3.0
5.0
6.0
9.0
22.0
4.0
23.0
23.0
34.0
17.0
10.0
19.0
5.0
9.0
7.0
8.0
15.0
Cu
old
Cu
new
Na
old
Na
new
K
old
K
new
P
old
Dry
Dry
P Matter Matter H2O% H2O%
new old
new
old new
0.07 0.02 84.0 66.0 303.0 380.0 32.1 51 12.9
0.05 0.02 9.6 6.0 515.0 450.0 78.4 77.0 15.7
1.23 0.6
N 0.02 28.4 3.0 240.0 270.0 64.1 46.0
0.56 0.3 0.08 0.02 95.0 25.0 224.0 170.0 21.0 15.0
0.61 0.4 0.11 0.01 137.0 60.0 278.0 320.0 31.7 21.0
0.73 0.70 0.15 0.01 3.1 3.0 208 220 30.2 28.0
1.03 0.6 0.64 0.72 9.1 5.0 467.0 320.0 136.0 80.0
4.54 1.0 0.12 0.01 19.0 19.0 337.0 110.0 65.5 33.0
0.30 0.30 0.08 0.05 10.2 3.0 137.0 160.0 30.0 30.0
8.00 7.7 0.52 0.03 33.0 33.0 1,080.0760.0 128.0 64.0
0.57 0.6 0.10 0.05 16.5 10.0 342.0 450.0 69.0 74.0
1.88 2.8 0.23 0.05 0.5 1.0 342.0 330.0 104.0 130.0
0.75 0.4 0.15 0.08 6.5 7.0 568.0 360.0 40.3 37.0
0.39 0.4 0.08 0.02 1.3 0.0 309.0 130.0 19.4 19.0
0.74 1.2 0.09 0.02 6.5 0.0 276.0 220.0 25.9 34.0
1.88 0.6 0.13 0.01 59.0 11.0 240.0 240.0 27.1 20.0
0.35 0.1 0.05 0.01 52.2 15.0 136.0 170.0 19.0 40.0
0.43 0.5 0.10 0.01 2.8 9.0 288.0 250.0 21.3 24.0
0.37 0.2 0.07 0.01 58.0 15.0 238.0 280.0 27.5 41.0
1.62 2.2 0.14 0.01 60.0 49.0 314.0 230.0 52.0 52.0
Fruits
Apricots
17.2 15.0 12.3 11.0 0.37 0.5 0.12 0.06
N
2.0 320.0
Bananas
6.8 6.0 41.9 34.0 0.41 0.3 0.16 0.10 1.2 1.0 348.0
Blackberries
63.3 41.0 29.5 23.0 0.85 0.7 0.12 0.11 3.7 2.0 208.0
Cherries
15.9 13.0 9.6 10.0 0.38 0.2 0.07 0.07 2.8 1.0 275
Cooking apples
3.6 4.0 2.9 3.0 0.29 0.1 0.09 0.02 21.0 2.0 123.0
Eating apples
3.6 3.0 4.7 3.0 0.29 0.1 0.11 0.02 2.4 3.0 118.0
Grapes
11.7 13.0 5.3 7.0 0.34 0.3 0.09 0.12 1.7 2.0 283.0
Grapefruit
17.1 23.0 10.4 9.0 0.26 0.1 0.06 0.02 1.4 3.0 234.0
Lemons
107.0 85.0 11.6 12.0 0.35 0.5 0.26 0.26 6.0 5.0 163.0
Melon cantaloupe
19.1 20.0 20.1 11.0 0.81 0.3 0.04 0.00 13.5 8.0 319.0
Nectarines
3.9 7.0 12.6 10.0 0.46 0.4 0.06 0.06 9.1 1.0 268.0
Oranges
41.3 47.0 12.9 10.0 0.33 0.1 0.07 0.05 2.9 5.0 197
Passion fruit
15.6 11.0 38.6 29.0 1.12 1.3 0.12
N 28.4 19.0 348.0
Peaches
4.8 7.0 7.9 9.0 0.38 0.4 0.05 0.06 2.7 1.0 259.0
Pears
7.5 11.0 7.2 7.0 0.21 0.2 0.15 0.06 2.3 3.0 128.0
Pineapple
12.2 18.0 16.9 16.0 0.42 0.2 0.08 0.11 1.6 2.0 247.0
Plums
12.4 13.0 7.6 8.0 0.33 0.4 0.10 0.10 1.9 2.0 192.0
Raspberries
40.7 25.0 21.6 19.0 1.21 0.7 0.21 0.10 2.5 3.0 224.0
Rhubarb
103.0 93.0 13.6 13.0 0.40 0.3 0.13 0.07 2.2 3.0 425.0
Strawberries
22.0 16.0 11.7 10.0 0.71 0.4 0.13 0.07 1.5 6.0 161.0
Notes: Old: Composition of Foods 3rd edition (1930s data)[4]
New: Composition of Foods 5th edition (1980s data)[3]
N: No data available
Ca, Mg, Fe, Na, K and P were reported to one fewer significant digits in the 1991 tables.
270.0
400.0
160.0
210
88.0
100.0
210.0
200.0
150.0
210.0
170.0
150
200.0
160.0
150.0
160.0
240.0
170.0
290.0
160.0
21.3
28.1
23.8
16.8
16.2
7.7
19.0
15.6
20.7
30.4
23.9
23.7
54.2
18.5
9.7
7.8
15.4
28.7
21.0
23.0
20.0
28.0
31.0
21.0
7.0
8.0
18.0
20.0
18.0
13.0
22.0
21.0
64.0
22.0
13.0
10.0
23.0
31.0
17.0
24.0
12.9
15.7
87.1 87.1
84.3 84.3
9.4
10.2
6.5
4.8
8.5
7.5
7.2
21.3
17.5
21.5
24.2
5.3
8.4
6.7
8.6
6.6
6.7
8.9
10.3
10.2
4.9
4.9
7.4
4.7
11.0
16.9
20.7
25.4
21.0
5.0
8.8
4.6
8.8
6.9
8.8
7.5
90.6
89.8
93.5
95.2
91.5
92.5
92.8
78.7
82.5
78.5
75.8
94.7
91.6
93.3
91.4
93.4
93.3
91.1
89.7
89.8
95.1
95.1
92.6
95.3
89.0
83.1
79.3
74.6
79.0
95.0
91.2
95.4
91.2
93.1
91.2
92.5
13.4
29.3
18.0
18.5
14.4
15.7
20.0
9.3
14.8
6.4
19.8
13.9
26.7
13.8
16.8
15.7
15.4
16.8
5.8
11.1
12.8
24.9
15.0
17.2
12.3
14.6
18.2
11.0
13.7
7.9
11.1
13.9
25.1
11.1
16.2
13.5
16.1
13.0
5.8
10.5
86.6
70.7
82.0
81.5
85.6
84.3
80.0
90.7
85.2
93.6
80.2
86.1
73.3
86.2
83.2
84.3
84.6
83.2
94.2
88.9
87.2
75.1
85.0
82.8
87.7
85.4
81.8
89.0
86.3
92.1
88.9
86.1
74.9
88.9
83.8
86.5
83.9
87.0
94.2
89.5
[ 209 ]
Anne-Marie Mayer
Historical changes in the
mineral content of fruits and
vegetables
British Food Journal
99/ 6 [1997] 207–211
a n d dr y m a tter decr ea sed sign ifica n tly in
fr u its.
What role do the minerals play in human
nutrition?
Min er a ls a ll h ave sever a l r oles in h u m a n
bioch em istr y a n d ph ysiology a n d a ll th e
m in er a ls m en tion ed a bove a r e essen tia l in
th e diet of h u m a n s. Ma n y a r e co-fa ctor s for
differ en t en zym es a n d we a r e depen den t on
th em for en er gy efficien cy, fer tility, m en ta l
sta bility a n d im m u n ity. Alth ou gh fr u its a n d
ve geta bles gen er a lly su pply a sm a ll pr opor tion of tota l m in er a l dieta r y r equ ir em en ts,
th e r edu ction s cou ld be im por ta n t to som e
gr ou ps so th e ca u ses of th e r edu ction s n eed
in vestiga tin g. It is n ot clea r wh a t is ca u sin g
th e r edu ction s. Th er e a r e sever a l possibilities
a n d th ese a r e ou tlin ed below.
Are the reductions anomalies of
measurement or sampling?
Th e ea r lier a n a lyses of som e m in er a ls m ay
h ave been in a ccu r a te com pa r ed to m oder n
a n a lytica l m eth ods. E lsie Widdow son , h ow ever, n otes in th e in tr odu ction to T h e Com position of Food s[3] th a t “th ose m eth ods wer e n o
less a ccu r a te th a n th e m oder n a u tom a ted
on es, bu t th ey took a m u ch lon ger tim e”. If
th is is tr u e, we sh ou ld be a ble to r ely on th e
con sisten cy of th e a n a lytica l m eth ods. How ever, th er e h a s been m u ch deba te over th is
qu estion a n d n o clea r con clu sion h a s been
r ea ch ed.
Th e m eth ods of sa m plin g fr u it a n d ve geta bles wer e design ed to r efl ect th e u su a l ch oice
of foods a t th e tim e of th e r esea r ch . Th er e
cou ld be differ en ces in th e m eth ods of sa m plin g. It is n ot possible to com pa r e th e deta ils
of th e m eth ods u sed beca u se th e or igin a l da ta
a r e n o lon ger ava ila ble. Also, th e u se of m ixed
sou r ces of da ta for th e 1991 edition of T h e
Com position of Food s[3] is a n u n k n ow n fa ctor
a n d possible sou r ce of bia s. It is n ot k n ow n
wh eth er th e fir st edition of th e Ch em ica l
Com position of Food s[1] u sed sim ila r m eth ods
of da ta com pila tion .
Food system changes
In th e pa st sixty yea r s th e food su pply system
h a s ch a n ged con sider a bly. For in sta n ce we
n ow ea t m or e “ou t of sea son ” a n d im por ted
foods gr ow n on a w ide va r iety of soils fr om
m a n y differ en t cou n tr ies. Som e of th e fr u its
a n d ve geta bles h ave a lw ays been im por ted
bu t m a n y of th ose pr eviou sly gr ow n in th e
UK a r e a lso n ow im por ted. Stor a ge a n d r ipen in g system s h ave ch a n ged. Gr een h ou se cr ops
a r e “br ou gh t on ” m or e qu ick ly n ow a n d often
gr ow n in soil-less m ixes. Cou ld th ese pr a ctices h ave ch a n ged th e com position of fr u its
a n d ve geta bles?
[ 210 ]
Th e va r ieties of pla n ts cu ltiva ted n ow h a s
a lso ch a n ged. N ow a days we pr a ctise soph istica ted pla n t br eedin g a n d h ave br ed selectively for qu a lities th a t w ill su it th e dem a n ds
of, for exa m ple, h igh yield, post-h a r vest
h a n dlin g qu a lities a n d cosm etic a ppea l. Also
we select va r ieties th a t w ill r espon d well to
th e m eth ods of a gr icu ltu r e cu r r en tly
em ployed. Specific br eedin g to en h a n ce n u tr ition a l qu a lity is r a r e.
Agricultural practices
Du r in g th e ea r ly 1930s a gr icu ltu r a l ch em ica ls
wer e h a r dly u sed. Ma n u r e a n d com post wer e
th e m a in fer tilizer s u sed. After th e w a r pr a ctices ch a n ged a n d fa r m er s beca m e m or e
r elia n t on th e u se of fer tilizer s a n d oth er
a gr och em ica ls a s well a s h eavy fa r m m a ch in er y.
Agr icu ltu r e wh ich r elies on N P K fer tilizer s
a n d pesticides, th a t a dds little or ga n ic m a tter
to th e soil a n d th a t a lter n a tes between soil
com pa ction a n d plou gh in g, cou ld pr odu ce
food depleted in m in er a ls. Th ese pr a ctices
a ffect th e str u ctu r e, ch em istr y a n d ecology of
th e soil in w ays th a t cou ld a ffect th e ava ila bility of m in er a ls to pla n ts a n d h en ce th e m in er a l con ten t of cr ops. For in sta n ce, m ycor r h iza l fu n gi h ave a sym biotic r ela tion sh ip
w ith pla n t r oots in wh ich su ga r s a n d m in er a ls a r e exch a n ged. Th e fu n gi a r e r edu ced by
h igh levels of ava ila ble ph osph a te a n d n itr ogen , low pH, w a ter loggin g or excessive
dr yn ess[5].
An oth er fa ctor cou ld be th e differ in g levels
of con ta m in a tion of cr ops w ith r esidu es of
pesticides con ta in in g h igh con cen tr a tion s of
m in er a ls – for exa m ple Bor dea u x m ixtu r e
con ta in s h igh levels of copper a n d w a s w idely
u sed a s a pesticide.
In pr in ciple, m oder n a gr icu ltu r e cou ld be
r edu cin g th e m in er a l con ten t of fr u it a n d
ve geta bles. We n eed to fin d ou t if th is, or a n y
of th e oth er expla n a tion s descr ibed a bove, a r e
sign ifica n t fa ctor s in pr a ctice. Con sider in g
th e m a gn itu de of th e r edu ction s th is m a tter
deser ves u r gen t a tten tion .
The following questions arise from the
findings:
•
•
•
•
•
Ar e th e da ta r elia ble?
Is th e a ppa r en t declin e ca u sed by dim in ish ed levels of m in er a ls in th e soil, poor
ava ila bility, th e ch oice of cu ltiva r s or oth er
ch a n ges in th e food system ?
To wh a t exten t is th e declin e in m in er a ls of
im por ta n ce to h u m a n n u tr ition ?
Ar e oth er cou n tr ies exper ien cin g sim ila r
ch a n ges?
Ar e th er e sim ila r r edu ction s in oth er
cr ops – su ch a s cer ea ls?
Anne-Marie Mayer
Historical changes in the
mineral content of fruits and
vegetables
British Food Journal
99/ 6 [1997] 207–211
•
•
•
•
Ar e oth er m in er a ls of equ a l im por ta n ce to
h u m a n n u tr ition , su ch a s Se a n d Cr, a lso
r edu ced?
Ar e oth er n u tr ien ts – for exa m ple, vita m in s – a lso r edu ced?
Ar e som e cu ltiva r s pr odu cin g cr ops th a t
a r e lower in m in er a ls th a n oth er s?
Does soil con ta m in a tion – pa st or pr esen t –
a ffect th e m in er a l con ten t of cr ops?
To a n swer th ese qu estion s existin g liter a tu r e
n eeds to be r eviewed a n d fu r th er r esea r ch
ca r r ied ou t a lon g th e su ggested lin es;
• a n a n a lysis of th e effect of th e la test Com position of Food s da ta on u su a l diets;
• com pila tion of a da ta ba se of h istor ica l da ta
fr om differ en t cou n tr ies, differ en t tim e
sca les a n d differ en t cr ops;
• deta iled a n d con tr olled stu dies of soils a n d
th e effects of m eth ods of a gr icu ltu r e on
pla n t n u tr ition a n d cr op m in er a l con ten t;
• stu dies of th e m in er a l con ten t of fr u it a n d
ve geta bles gr ow n u sin g differ en t cu ltiva r s
in com m on u se n ow a n d 60 yea r s a go;
• r e gu la r m on itor in g of food com position
w ith deta ils on cu ltiva r s, m eth ods of gr ow in g a n d soils.
References
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[ 211 ]
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